US20020038373A1 - Method and system for improving network performance enhancing proxy architecture with gateway redundancy - Google Patents

Method and system for improving network performance enhancing proxy architecture with gateway redundancy Download PDF

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Publication number
US20020038373A1
US20020038373A1 US09/903,780 US90378001A US2002038373A1 US 20020038373 A1 US20020038373 A1 US 20020038373A1 US 90378001 A US90378001 A US 90378001A US 2002038373 A1 US2002038373 A1 US 2002038373A1
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connection
tcp
platform
message
gateway
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US09/903,780
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John Border
Matthew Butehorn
Ken Burrell
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Hughes Network Systems LLC
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Hughes Electronics Corp
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Publication of US20020038373A1 publication Critical patent/US20020038373A1/en
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Assigned to JPMORGAN CHASE BANK, N.A., AS ADMINISTRATIVE AGENT reassignment JPMORGAN CHASE BANK, N.A., AS ADMINISTRATIVE AGENT FIRST LIEN PATENT SECURITY AGREEMENT Assignors: HUGHES NETWORK SYSTEMS, LLC
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • the present invention relates to a communication system, and is more particularly related to a proxy architecture for improving network performance.
  • TCP/IP transmission control protocol
  • IP Internet protocol
  • FIG. 15 The four layers of the TCP/IP protocol suite are illustrated in FIG. 15.
  • the link layer (or the network interface layer) 10 includes device drivers in the operating system and any corresponding network interface cards. Together, the device driver and the interface cards handle hardware details of physically interfacing with any cable or whatever type of media that is being used.
  • the network layer (also referred to as the Internet layer) 12 handles the movement of packets around the network.
  • IP Internet control message protocol
  • IGMP Internet group management protocol
  • TCP which provides a reliable flow of data between two hosts, is primarily concerned with dividing the data passed to it from the application layer 16 into appropriately sized segments for the network layer 12 below, acknowledging received packets, setting timeouts to make certain the other end acknowledges packets that are sent, and so on. Because this reliable flow of data is provided by the transport layer 14 , the application layer 16 is isolated from these details.
  • UDP provides a much simpler service to the application layer 16 . UDP just sends packets of data called datagrams from one host to another, with no guarantee that the datagrams will reach their destination. Any desired reliability must be added by a higher layer, such as the application layer 16 .
  • the application layer 16 handles the details of the particular application. There are many common TCP/IP applications that almost every implementation provides, including telnet for remote log-in, the file transfer protocol (FTP), the simple mail transfer protocol (SMTP) or electronic mail, the simple network management protocol (SNMP), the hypertext transfer protocol (HTTP), and many others.
  • FTP file transfer protocol
  • SMTP simple mail transfer protocol
  • SNMP simple network management protocol
  • HTTP hypertext transfer protocol
  • TCP provides reliable, in-sequence delivery of data between two IP hosts.
  • the IP hosts set up a TCP connection, using a conventional TCP three-way handshake and then transfer data using a window based protocol with the successfully received data acknowledged.
  • FIG. 16 illustrates an example of the conventional TCP three-way handshake between IP hosts 20 and 22 .
  • the IP host 20 that wishes to initiate a transfer with IP host 22 , sends a synchronize (SYN) signal to IP host 22 .
  • the IP host 22 acknowledges the SYN signal from IP host 20 by sending a SYN acknowledgement (ACK).
  • the third step of the conventional TCP three-way handshake is the issuance of an ACK signal from the IP host 20 to the other IP host 22 .
  • IP host 22 is ready to receive the data from IP host 20 (and vice versa).
  • another handshake (similar to the handshake described to initiate the connection) is used to close the TCP connection.
  • TCP was designed to be very flexible and to work over a wide variety of communication links, including both slow and fast links, high latency links, and links with low and high error rates.
  • TCP and other high layer protocols
  • TCP performance in particular, the throughput possible across the TCP connection, is affected by the characteristics of the link in which it is used.
  • not all characteristics can be compensated for by choices in the link layer design.
  • TCP has been designed to be very flexible with respect to the links which it traverses. Such flexibility is achieved at the cost of sub-optimal operation in a number of environments vis-à-vis a tailored protocol.
  • the tailored protocol which is usually proprietary in nature, may be more optimal, but greatly lacks flexibility in terms of networking environments and interoperability.
  • TCP spoofing An alternative to a tailored protocol is the use of performance enhancing proxies (PEPs), to perform a general class of functions termed “TCP spoofing,” in order to improve TCP performance over impaired (i.e., high latency or high error rate) links.
  • PEPs performance enhancing proxies
  • TCP spoofing involves an intermediate network device (the performance enhancing proxy (PEP)) intercepting and altering, through the addition and/or deletion of TCP segments, the behavior of the TCP connection in an attempt to improve its performance.
  • PEP performance enhancing proxy
  • TCP spoofing implementations include the local acknowledgement of TCP data segments in order to get the TCP data sender to send additional data sooner than it would have sent if spoofing were not being performed, thus improving the throughput of the TCP connection.
  • conventional TCP spoofing implementations have focused simply on increasing the throughput of TCP connections either by using larger windows over the link or by using compression to reduce the amount of data which needs to be sent, or both.
  • TCP PEP implementations are based on TCP ACK manipulation. These may include TCP ACK spacing where ACKs which are bunched together are spaced apart, local TCP ACKs, local TCP retransmissions, and TCP ACK filtering and reconstruction. Other PEP mechanisms include tunneling, compression, and priority-based multiplexing.
  • the present invention addresses the above stated needs by providing a system for providing performance enhancing proxy (PEP) functionalities.
  • PEP performance enhancing proxy
  • the system utilizes a redundant platform that minimizes the impact on the network of redundancy switching as the spoofed connections are restarted.
  • An “unspoofed startup delay” process provides for the termination of unspoofed connections for a predetermined period, so that the restart process of spoofed TCP connections is not delayed.
  • a method for performing redundancy switching from a first platform to a second platform includes identifying a message received over a connection according to a prescribed protocol as an unspoofed message. The method also includes terminating, during a predetermined period, the connection based upon the identifying step. Further, the method includes restarting a spoofed connection between the second platform and a host. Under this approach, network performance is enhanced.
  • a communication system includes a first platform that is configured to communicate with a remote platform and a second platform that is configured to communicate with the remote platform upon failure of the first platform to communicate with the remote platform.
  • the second platform is configured to identify a message received from a local host over a connection according to a prescribed protocol as an unspoofed message, wherein the second platform terminates, during a predetermined period, the connection in response to the identified message.
  • a communication gateway for providing redundant communication in a communication system having a remote platform.
  • the gateway includes a communication interface that is configured to receive a message from a host over a connection according to a prescribed protocol. Additionally, the gateway includes a processor that is coupled to the communication interface and is configured to identify the message received as an unspoofed message, and configured to terminate, during a predetermined period, the connection based upon the identified message, the processor being configured to restart a spoofed connection with another host.
  • a communication gateway for providing redundant communication in a communication system having a remote platform.
  • the gateway includes means for identifying a message received over a connection according to a prescribed protocol as an unspoofed message, and means for terminating, during a predetermined period, the connection based upon the identified message.
  • the gateway also includes means for restarting a spoofed connection between the second platform and a host.
  • a computer-readable medium carrying one or more sequences of one or more instructions for performing redundancy switching from a first platform to a second platform.
  • the one or more sequences of one or more instructions include instructions which, when executed by one or more processors, cause the one or more processors to perform the step of identifying a message received over a connection according to a prescribed protocol as an unspoofed message.
  • Another step includes terminating, during a predetermined period, the connection based upon the identifying step.
  • Yet another step includes restarting a spoofed connection between the second platform and a host.
  • FIG. 1 is a diagram of a communication system in which the performance enhancing proxy (PEP) of the present invention is implemented;
  • PEP performance enhancing proxy
  • FIG. 2 is a diagram of a PEP end point platform environment, according to an embodiment of the present invention.
  • FIG. 3 is a diagram of a TCP Spoofing Kernel (TSK) utilized in the environment of FIG. 2;
  • FIGS. 4A and 4B are flow diagrams of the connection establishment with three-way handshake spoofing and without three-way handshake spoofing, respectively;
  • FIG. 5 is a diagram of a PEP packet flow between two PEP end points, according to an embodiment of the present invention.
  • FIG. 6 is a diagram of an IP (Internet Protocol) packet flow through a PEP end point, in accordance with an embodiment of the present invention
  • FIG. 7 is a diagram of PEP end point profiles utilized in the platform of FIG. 2;
  • FIG. 8 is a diagram of the interfaces of a PEP end point implemented as an IP gateway, according to an embodiment of the present invention.
  • FIG. 9 is a diagram of the interfaces of a PEP end point implemented as a Multimedia Relay, according to an embodiment of the present invention.
  • FIG. 10 is a diagram of the interfaces of a PEP end point implemented as a Multimedia VSAT (Very Small Aperture Terminal), according to an embodiment of the present invention
  • FIG. 11 is a diagram of the interfaces of a PEP end point implemented in an earth station, according to an embodiment of the present invention.
  • FIG. 12 is a diagram an architecture of a PEP end point in which redundancy is provided at the hub site, in accordance with an embodiment of the present invention
  • FIGS. 13A and 13B are a flow chart of an unspoofed startup delay processing performed by a gateway, in accordance with an embodiment of the present invention.
  • FIG. 14 is a diagram of a computer system that can perform PEP functions, in accordance with an embodiment of the present invention.
  • FIG. 15 is diagram of the protocol layers of the TCP/IP protocol suite.
  • FIG. 16 is diagram of a conventional TCP three-way handshake between IP hosts.
  • FIG. 1 illustrates an exemplary network 100 in which the performance enhancing proxy (PEP) of the present invention may be utilized.
  • the network 100 in FIG. 1 includes one or more hosts 110 connected to a network gateway 120 via TCP connections.
  • the network gateway 120 is connected to another network gateway 140 via a backbone connection on a backbone link 130 .
  • the backbone link 130 in an exemplary embodiment, is shown as a satellite link that is established over a satellite 101 ; however, it is recognized by one of ordinary skill in the art that other network connections may be implemented. For example, these network connections may be established over a wireless communications system, in general, (e.g., radio networks, cellular networks, etc.) or a terrestrial communications system.
  • the network gateway 140 is further connected to a second group of hosts 150 , also via TCP connections. In the arrangement illustrated in FIG. 1, the network gateways 120 , 140 facilitate communication between the groups of hosts 110 , 150 .
  • the network gateways 120 , 140 facilitate communication between the two groups of hosts 110 , 150 by performing a number of performance enhancing functions. These network gateways 120 , 140 may perform selective TCP spoofing, which allows flexible configuration of the particular TCP connections that are to be spoofed. Additionally, gateways 120 , 140 employs a TCP three-way handshake, in which the TCP connections are terminated at each end of the backbone link 130 . Local data acknowledgements are utilized by the network gateways 120 , 140 , thereby permitting the TCP windows to increase at local speeds.
  • the network gateway 120 , 140 further multiplexes multiple TCP connections across a single backbone connection; this capability reduces the amount of acknowledgement traffic associated with the data from multiple TCP connections, as a single backbone connection acknowledgement may be employed.
  • the multiplexing function also provides support for high throughput TCP connections, wherein the backbone connection protocol is optimized for the particular backbone link that is used.
  • the network gateways 120 , 140 also support data compression over the backbone link 130 to reduce the amount of traffic to be sent, further leveraging the capabilities of the backbone connection. Further, the network gateways 120 , 140 utilize data encryption in the data transmission across the backbone link 130 to protect data privacy, and provide prioritized access to backbone link 130 capacity on a per TCP connection basis. Each of the network gateways 120 , 140 may select a particular path for the data associated with a connection to flow. The above capabilities of the network gateways 120 , 140 are more fully described below.
  • FIG. 2 illustrates a performance enhancing proxy (PEP) 200 as implemented in a network gateway 120 , 140 , according to one embodiment of the present invention.
  • the PEP 200 has a platform environment 210 , which includes the hardware and software operating system.
  • the PEP 200 also includes local area network (LAN) interfaces 220 and wide area network (WAN) interfaces 230 .
  • LAN local area network
  • WAN wide area network
  • the network gateway 120 may establish the TCP connections with the IP hosts 110 , via a local LAN interface 220 and may establish the backbone connection with the network gateway 140 via a WAN interface 230 .
  • the PEP platform environment 210 may also include general functional modules: routing module 240 , buffer management module 250 , event management module 260 , and parameter management module 270 .
  • the network gateway also includes a TCP spoofing kernel (TSK) 280 , a backbone protocol kernel (BPK) 282 , a prioritization kernel (PK) 284 , and a path selection kernel (PSK) 286 .
  • TCP spoofing kernel TCP spoofing kernel
  • BPK backbone protocol kernel
  • PK prioritization kernel
  • PSK path selection kernel
  • the platform environment 210 performs a number of functions.
  • One such function is to shield the various PEP kernels 280 , 282 , 284 , 286 from implementation specific constraints. That is, the platform environment 210 performs functions that the various PEP kernels 280 , 282 , 284 , 286 cannot perform directly because the implementation of the function is platform specific. This arrangement has the advantageous effect of hiding platform specific details from the PEP kernels 280 , 282 , 284 , 286 , making the PEP kernels more portable.
  • An example of a platform specific function is the allocation of a buffer. In some platforms, buffers are created as they are needed, while in other platforms, buffers are created at start-up and organized into linked lists for later use.
  • platform specific functions are not limited to functions generic to all of the kernels 280 , 282 , 284 , 286 .
  • a function specific to a particular kernel for example, the allocation of a control block for TCP spoofing, may also be implemented in the platform environment to hide platform specific details from the kernel.
  • the platform environment 210 may provide the task context in which the PEP kernels 280 , 282 , 284 , 286 run.
  • all PEP kernels 280 , 282 , 284 , 286 can run in the same task context for efficiency. However, this is not required.
  • the platform environment 210 provides an interface between the PEP functionality (embodied in kernels 280 , 282 , 284 , 286 ) and the other functionality of the network gateway 120 , 140 .
  • the platform environment 210 may provide the interface between the PEP functionality and the routing function 240 , as seen in FIG. 2. It is noted that the platform specific functions illustrated in FIG. 2 are examples and are not considered an exhaustive list. It is further noted that the PEP kernels shown touching each other ( 280 , 282 and 284 , 286 ) in FIG. 2 may have a direct procedural interface to each other. Further, the kernels 280 , 282 , 284 , 286 may include direct interfaces to improve performance, as opposed to routing everything through the platform environment 210 (as shown in FIG. 2).
  • the PEP end point platform 210 may utilize a data compression kernel (CK) 290 and an encryption kernel (EK) 292 .
  • CK data compression kernel
  • EK encryption kernel
  • These kernels 280 , 282 , 284 , 286 , 290 , and 292 facilitate communication between the two groups of hosts 110 , 150 , by performing a variety of performance enhancing functions, either singly or in combination.
  • performance enhancing functions include selective TCP spoofing, three-way handshake spoofing, local data acknowledgement, TCP connection to backbone connection multiplexing, data compression/encryption, prioritization, and path selection.
  • Selective TCP Spoofing is performed by the TSK 280 and includes a set of user configurable rules that are used to determine which TCP connections should be spoofed. Selective TCP spoofing improves performance by not tying up TCP spoofing-related resources, such as buffer space, control blocks, etc., for TCP connections for which the user has determined that spoofing is not beneficial or required and by supporting the use of tailored parameters for TCP connections that are spoofed.
  • TCP spoofing-related resources such as buffer space, control blocks, etc.
  • the TSK 280 discriminates among the various TCP connections based on the applications using them. That is, TSK 280 discriminates among these TCP connections to determine which connection should be spoofed as well as the manner in which the connection is spoofed; e.g., whether to spoof the three-way handshake, the particular timeout parameters for the spoofed connections, etc. TCP spoofing is then performed only for those TCP connections that are associated with applications for which high throughput or reduced connection startup latency (or both) is required. As a result, the TSK 280 conserves TCP spoofing resources for only those TCP connections for which high throughput or reduced connection startup latency (or both) is required. Further, the TSK 280 increases the total number of TCP connections which can be active before running out of TCP spoofing resources, since any active TCP connections which do not require high throughput are not allocated resources.
  • TCP port number field contained in the TCP packets being sent.
  • unique port numbers are assigned to each type of application. Which TCP port numbers should and should not be spoofed can be stored in the TSK 280 .
  • the TSK 280 is also re-configurable to allow a user or operator to reconfigure the TCP port numbers which should and should not be spoofed.
  • the TSK 280 also permits a user or operator to control which TCP connections are to be spoofed based on other criteria. In general, a decision on whether to spoof a TCP connection may be based on any field within a TCP packet.
  • the TSK 280 permits a user to specify which fields to examine and which values in these fields identify TCP connections that should or should not be spoofed. Another example of a potential use for this capability is for the user or operator to select the IP address of the TCP packet in order to control for which users TCP spoofing is performed.
  • the TSK 280 also permits a user to look at multiple fields at the same time. As a result, the TSK 280 permits a user or operator to use multiple criteria for selecting TCP connections to spoof. For example, by selecting both the IP address and the TCP port number fields, the system operator can enable TCP spoofing for only specific applications from specific users.
  • the user configurable rules may include five exemplary criteria which can be specified by the user or operator in producing a selective TCP spoofing rule: Destination IP address; Source IP address; TCP port numbers (which may apply to both the TCP destination and source port numbers); TCP options; and IP differentiated services (DS) field.
  • Destination IP address Destination IP address
  • Source IP address Source IP address
  • TCP port numbers which may apply to both the TCP destination and source port numbers
  • TCP options which may apply to both the TCP destination and source port numbers
  • DS IP differentiated services
  • AND and OR combination operators can be used to link criteria together.
  • a rule can be defined to disable TCP spoofing for FTP data received from a specific host.
  • the order in which the rules are specified may be significant. It is possible for a connection to match the criteria of multiple rules. Therefore, the TSK 280 can apply rules in the order specified by the operator, taking the action of the first rule that matches.
  • a default rule may also be set which defines the action to be taken for TCP connections which do not match any of the defined rules.
  • the set of rules selected by the operator may be defined in a selective TCP spoofing selection profile.
  • the TSK 280 also facilitates spoofing of the conventional three-way handshake.
  • Three-Way Handshake Spoofing involves locally responding to a connection request to bring up a TCP connection in parallel with forwarding the connection requests across the backbone link 130 (FIG. 1). This allows the originating IP host (for example, 110 ) to reach the point of being able to send the data it must send at local speeds, i.e. speeds that are independent of the latency of the backbone link 130 .
  • Three-way Handshake Spoofing allows the data that the IP host 110 needs to send to be sent to the destination IP host 150 without waiting for the end-to-end establishment of the TCP connection. For backbone links 130 with high latency, this significantly reduces the time it takes to bring up the TCP connection and, more importantly, the overall time it takes to get a response (from an IP host 150 ) to the data the IP host 110 sends.
  • a specific example in which this technique is useful relates to an Internet web page access application.
  • an IP host's request to retrieve a web page can be on its way to a web server without waiting for the end-to-end establishment of the TCP connection, thereby reducing the time it takes to download the web page.
  • the TSK 280 in the network gateway 120 locally acknowledges data segments received from the IP host 110 . This allows the sending IP host 110 to send additional data immediately. More importantly, TCP uses received acknowledgements as signals for increasing the current TCP window size. As a result, local sending of the acknowledgements allows the sending IP host 110 to increase it TCP window at a much faster rate than supported by end to end TCP acknowledgements.
  • the TSK 280 (the spoofer) takes on the responsibility for reliable delivery of the data which it has acknowledged.
  • the BPK 282 multiple TCP connections are multiplexed onto and carried by a single backbone connection. This improves system performance by allowing the data for multiple TCP connections to be acknowledged by a single backbone connection acknowledgement (ACK), significantly reducing the amount of acknowledgement traffic required to maintain high throughput across the backbone link 130 .
  • the BPK 282 selects a backbone connection protocol that is optimized to provide high throughput for the particular link. Different backbone connection protocols can be used by the BPK 282 with different backbone links without changing the fundamental TCP spoofing implementation.
  • the backbone connection protocol selected by the BPK 282 provides appropriate support for reliable, high speed delivery of data over the backbone link 130 , hiding the details of the impairments (for example high latency) of the link from the TCP spoofing implementation.
  • the multiplexing by the BPK 282 allows for the use of a backbone link protocol which is individually tailored for use with the particular link and provides a technique to leverage the performance of the backbone link protocol with much less dependency upon the individual performance of the TCP connections being spoofed than conventional methods. Further, the ability to tailor the backbone protocol for different backbone links makes the present invention applicable to many different systems.
  • the PEP 200 may optionally include a data compression kernel 290 for compressing TCP data and an encryption kernel 292 for encrypting TCP data.
  • Data compression increases the amount of data that can be carried across the backbone connection. Different compression algorithms can be supported by the data compression kernel 290 and more than one type of compression can be supported at the same time.
  • the data compression kernel 290 may optionally apply compression on a per TCP connection basis, before the TCP data of multiple TCP connections is multiplexed onto the backbone connection or on a per backbone connection basis, after the TCP data of multiple TCP connections has been multiplexed onto the backbone connection. Which option is used is dynamically determined based on user configured rules and the specific compression algorithms being utilized. Exemplary data compression algorithms are disclosed in U.S.
  • the encryption kernel 292 encrypts the TCP data for secure transmission across the backbone link 130 . Encryption may be performed by any conventional technique. It is also understood that the corresponding spoofer (in the example outlined above, the network gateway 140 ) includes appropriate kernels for decompression and decryption, both of which may be performed by any conventional technique.
  • the PK 284 provides prioritized access to the backbone link capacity.
  • the backbone connection can actually be divided into N (N>1) different sub-connections, each having a different priority level. In one exemplary embodiment, four priority levels can be supported.
  • the PK 284 uses user-defined rules to assign different priorities, and therefore different sub-connections of the backbone connection, to different TCP connections. It should be noted that PK 284 may also prioritize non-TCP traffic (e.g., UDP (User Datagram Protocol) traffic) before sending the traffic across the backbone link 130 .
  • UDP User Datagram Protocol
  • the PK 284 also uses user-defined rules to control how much of the backbone link 130 capacity is available to each priority level.
  • Exemplary criteria which can be used to determine priority include the following: Destination IP address; Source IP address; IP next protocol; TCP port numbers (which may apply to both the TCP destination and source port numbers); UDP port numbers (which may apply to both the UDP destination and source port numbers); and IP differentiated services (DS) field.
  • the type of data in the TCP data packets may also be used as a criterion. For example, video data could be given highest priority. Mission critical data could also be given high priority.
  • any field in the IP packet can be used by PK 284 to determine priority. However, it should be noted that under some scenarios the consequence of using such a field may cause different IP packets of the same flow (e.g., TCP connection) to be assigned different priorities; these scenarios should be avoided.
  • AND and OR combination operators can be used to link criteria together.
  • a rule can be defined to assign a priority for SNMP data received from a specific host.
  • the order in which the rules are specified may be significant. It is possible for a connection to match the criteria of multiple rules. Therefore, the PK 284 can apply rules in the order specified by the operator, taking the action of the first rule that matches.
  • a default rule may also be set which defines the action to be taken for IP packets which do not match any of the defined rules.
  • the set of rules selected by the operator may be defined in a prioritization profile.
  • the PSK 286 is responsible for determining which path an IP packet should take to reach its destination.
  • the path selected by the PSK 286 can be determined by applying path selection rules.
  • the PSK 286 also determines which IP packets should be forwarded using an alternate path and which IP packets should be dropped when one or more primary paths fail.
  • Path selection parameters can also be configured using profiles.
  • the path selection rules may be designed to provide flexibility with respect to assigning paths while making sure that all of the packets related to the same traffic flow (e.g., the same TCP connection) take the same path (although it is also possible to send segments of the same TCP connection via different paths, this segment “splitting” may have negative side effects).
  • Exemplary criteria that can be used to select a path include the following: priority of the IP packet as set by the PK 284 (should be the most common criterion): Destination IP address; Source IP address; IP next protocol; TCP port numbers (which may apply to both the TCP destination and source port numbers); UDP port numbers (which may apply to both the UDP destination and source port numbers); and IP differentiated services (DS) field. Similar to selective TCP spoofing and prioritization, the PSK 284 may determine a path by using any field in the IP packet.
  • the AND and OR combination operators can be used to link criteria together.
  • a rule can be defined to select a path for SNMP data received from a specific host.
  • the order in which the rules are specified may be significant. It is possible for a connection to match the criteria of multiple rules. Therefore, the PSK 286 can apply rules in the order specified by the operator, taking the action of the first rule that matches.
  • a default rule may also be set which defines the action to be taken for IP packets which do not match any of the defined rules.
  • the set of rules selected by the operator may be defined in a path selection profile.
  • a path selection rule may select the path based on any of the following path information in which IP packets match the rule: a primary path, a secondary path, and a tertiary path.
  • the primary path is be specified in any path selection rule.
  • the secondary path is used only when the primary path has failed. If no secondary path is specified, any IP packets that match the rule can be discarded when the primary path fails.
  • the tertiary path is specified only if a secondary path is specified. The tertiary path is selected if both the primary and secondary paths have failed. If no tertiary path is specified, any IP packets that match the rule can be discarded when both the primary and secondary paths fail.
  • a backbone connection is established between the PEPs 200 of two network gateways 120 , 140 (i.e., the two spoofers), located at each end of the backbone link 130 for which TCP spoofing is desired.
  • the TSK 280 of the PEP 200 local to the IP host 110 checks its configured selective TCP spoofing rules. If the rules indicate that the connection should not be spoofed, the PEP 200 allows the TCP connection to flow end-to-end unspoofed.
  • the spoofing PEP 200 locally responds to the IP host's TCP three-way handshake. In parallel, the spoofing PEP 200 sends a message across the backbone link 130 to its partner network gateway 140 asking it to initiate a TCP three-way handshake with the IP host 150 on its side of the backbone link 130 . Data is then exchanged between the IP host 110 , 150 with the PEP 200 of the network gateway 120 locally acknowledging the received data and forwarding it across the backbone link 130 via the high speed backbone connection, compressing the data as appropriate based on the configured compression rules.
  • the priority of the TCP connection is determined when the connection is established.
  • the BPK 282 can multiplex the connection with other received connections over a single backbone connection, the PK 284 determines the priority of the connection and the PSK 286 determines the path the connection is to take.
  • the PEP 200 advantageously improves network performance by allocating TCP spoofing-related resources, such as buffer space, control blocks, etc., only to TCP connections for which spoofing is beneficial; by spoofing the three-way handshake to decrease data response time; by reducing the number of ACKs which are transmitted by performing local acknowledgement and by acknowledging multiple TCP connections with a single ACK; by performing data compression to increase the amount of data that can be transmitted; by assigning priorities to different connections; and by defining multiple paths for connections to be made.
  • TCP spoofing-related resources such as buffer space, control blocks, etc.
  • FIG. 3 shows an exemplary stack, which illustrates the relationship between the TCP stack and the PEP kernels 280 , 282 , 284 , 286 of the present invention.
  • the TSK 280 is primarily responsible for functions related to TCP spoofing.
  • the TSK 280 in an exemplary embodiment, includes two basic elements: a transport layer that encompasses a TCP stack 303 and an IP stack 305 ; and a TCP spoofing application 301 .
  • the transport layer is responsible for interacting with the TCP stacks (e.g., 303 ) of IP hosts 110 connected to a local LAN interface 220 of a PEP 210 .
  • the TSK 280 implements the TCP protocol, which includes the appropriate TCP state machines and terminates spoofed TCP connections.
  • the TCP spoofing application 301 rests on top of the transport layer and act as the application that receives data from and sends data to the IP hosts 110 applications. Because of the layered architecture of the protocol, the TCP spoofing application 301 isolates the details of TCP spoofing from the transport layer, thereby allowing the transport layer to operate in a standard fashion.
  • the TCP spoofing application 301 can also interface to the BPK 282 associated with the WAN interfaces 230 .
  • the BPK 282 performs backbone protocol maintenance, implementing the protocol by which the network gateways 120 , 140 (in FIG. 1) communicate.
  • the BPK 282 provides reliable delivery of data, uses a relatively small amount of acknowledgement traffic, and supports generic backbone use (i.e., use not specific to the TSK 280 ); one such example is the reliable data protocol (RDP).
  • RDP reliable data protocol
  • the BPK 282 lies above the PK 284 and the PSK 286 , according to an exemplary embodiment.
  • the PK 284 is responsible for determining the priority of IP packets and then allocating transmission opportunities based on priority.
  • the PK 284 can also control access to buffer space by controlling the queue sizes associated with sending and receiving IP packets.
  • the PSK 286 determines which path an IP packet should take to reach its destination.
  • the path selected by the PSK 286 can be determined applying path selection rules. PSK 286 may also determine which IP packet should be forwarded using an alternate path and which packets should be dropped when one or more primary paths fail.
  • FIGS. 4A and 4B show flow diagrams of the establishment of a spoofed TCP connection utilizing three-way handshake spoofing and without three-way handshake spoofing, respectively.
  • the TCP Spoofing Kernel 280 establishes a spoofed TCP connection when a TCP ⁇ SYN> segment is received from its local LAN or a Connection Request message from its TSK peer. It is noted that the three-way handshake spoofing may be disabled to support an end to end maximum segment size (MSS) exchange, which is more fully described below.
  • MSS maximum segment size
  • the spoofed TCP connection establishment process is described with respect to a local host 400 , a local PEP end point 402 , a remote PEP end point 404 , and a remote host 406 .
  • the TSK 280 within each of the PEP end points 402 and 404 provides the spoofing functionality.
  • the local host 400 transmits a TCP ⁇ SYN> segment to the local PEP end point 402 at a local LAN interface 220 .
  • the platform environment 402 determines whether there is already a TCP connection control block (CCB) assigned to the TCP connection associated with the TCP segment. If there is no CCB, the environment 402 checks whether the TCP segment is a ⁇ SYN> segment that is being sent to a non-local destination.
  • CCB TCP connection control block
  • the ⁇ SYN> segment represents an attempt to bring up a new (non-local) TCP connection, and the environment 402 passes the segment to the TCP Spoofing Kernel 280 to determine the TCP connection's disposition.
  • the TCP Spoofing Kernel 280 first determines if the connection should be spoofed.
  • TSK 280 uses (in an exemplary embodiment) the priority indicated in the selected TCP spoofing parameter profile and the peer index (provided by the environment 210 with the TCP ⁇ SYN> segment) to construct the handle of the backbone connection which should be used to carry this spoofed TCP connection.
  • the peer index is used as the 14 high order bits of the handle and the priority is used as the two low order bits of the handle.
  • the backbone connection handle is then used (via the TSK control block (TCB) mapping table) to find the TCB associated with the backbone connection.
  • TSK 280 of PEP end point 402 then checks whether the backbone connection is up.
  • TSK 280 determines whether the number of spoofed TCP connections that are already using the selected backbone connection is still currently below the CCB resource limit.
  • the CCB resource limit is the smaller of the local number of CCBs (provided as a parameter by the platform environment 210 ) and the peer number of CCBs (received in the latest TSK peer parameters (TPP) message from the TSK peer) available for this backbone connection. If the number of connections is still below the limit, TSK 280 of PEP end point 402 assigns a unique TCP connection identifier (e.g., a free CCB mapping table entry index) to the connection and calls the environment 210 to allocate a TCP connection control block for the connection.
  • TCP connection identifier e.g., a free CCB mapping table entry index
  • TSK 280 of PEP end point 402 returns the TCP ⁇ SYN> segment back to the environment 210 to be forwarded unspoofed if any of the above checks fail.
  • the following conditions result in the TCP connection being unspoofed.
  • the selective TCP spoofing rules indicate that the connection should not be spoofed.
  • there is no backbone connection for the priority at which the TCP connection should be spoofed (indicated by the absence of a TCB for the backbone connection). No spoofing is performed if the backbone connection is down.
  • TSK 280 of PEP end point 402 may also post an event to alert the operator that there is a mismatch between the configured TCP spoofing parameter profiles and the configured set of backbone connections.
  • TSK 280 of PEP end point 402 writes the backbone connection handle into the buffer holding the TCP ⁇ SYN> segment. It is noted that this is not done until a CCB is successfully allocated by the platform environment 402 , because the environment does not count the buffer unless a CCB is successfully allocated. TSK 280 then copies the parameters from the selected TCP spoofing parameter profile into the CCB. Consequently, relevant information (e.g., the maximum segment size that is advertised by the host (if smaller than the configured MSS), the initial sequence number, and etc.) is copied out of the TCP ⁇ SYN> segment and stored in the CCB. It is noted that the source and destination IP addresses and source and destination TCP port numbers will already have been placed into the CCB by the platform environment 402 when the CCB was allocated; the environment 402 uses this information to manage CCB hash function collisions.
  • relevant information e.g., the maximum segment size that is advertised by the host (if smaller than the configured MSS), the initial sequence
  • the TCP Spoofing Kernel 280 of PEP end point 402 constructs a Connection Request (CR) message, per step 403 , and sends it to its TSK peer associated with the remote PEP end point 404 .
  • the CR message basically contains all of the information extracted from the TCP spoofing parameter profile and the TCP ⁇ SYN> segment and stored in the local CCB, e.g., the source and destination IP addresses, the source and destination TCP port numbers, the MSS value, etc., with the exception of fields that have only local significance, such as the initial sequence number.
  • the CR message contains all of the information that the peer TSK of PEP end point 404 requires to set up its own CCB.
  • the TCP Spoofing Kernel 280 of the local PEP end point 402 sends a TCP ⁇ SYN,ACK> segment to the local host 400 in response to the ⁇ SYN> segment received, per step 405 .
  • TSK 280 of PEP end point 402 performs step 405 simultaneously with the step of sending the Connection Request message (i.e., step 403 ), if three-way handshake spoofing is enabled.
  • TSK 280 of 402 waits for a Connection Established (CE) message from its TSK peer of the remote PEP end point 404 before sending the ⁇ SYN,ACK> segment.
  • CE Connection Established
  • TSK 280 of PEP end point 402 selects a random initial sequence number (as provided in IETF (Internet Engineering Task Force) RFC 793 , which is incorporated herein by reference in its entirety) to use for sending data.
  • the MSS value sent in the ⁇ SYN,ACK> segment is set equal to the MSS value received in the CE message. If three-way handshake spoofing is enabled, the MSS value is determined from the TCP spoofing parameter profile selected for the connection (and the configured path maximum transmission unit (MTU)). For this case, TSK 280 of PEP end point 402 then compares the MSS value received in the Connection Established message, when it arrives, to the value it sent to the local host in the TCP ⁇ SYN,ACK> segment. If the MSS value received in the CE message is smaller than the MSS value sent to the local host, a maximum segment size mismatch exists.
  • MTU configured path maximum transmission unit
  • TSK 280 of the local PEP end point 402 is ready to start accepting data from the local host 400 .
  • the local host 400 transmits an ⁇ ACK> segment to the TSK 280 of PEP end point 402 ; thereafter, the local host forwards, as in step 409 data to the TSK 280 of PEP end point 402 as well.
  • TSK 280 does not need to wait for the Connection Established message to arrive from its TSK peer before accepting and forwarding data. As seen in FIG.
  • TSK 280 of the local PEP end point 402 sends an ⁇ ACK> segment to the local host and simultaneously sends the TCP data (TD) from the local host 400 to the peer TSK of PEP end point 404 (per step 413 ) prior to receiving a CE message from the peer TSK of PEP end point 404 .
  • TSK 280 of PEP end point 402 does not accept data from its TSK peer of PEP end point 404 until after the CE message has been received.
  • TSK 280 of PEP end point 402 does not forward any data received from its TSK peer of PEP end point 404 to the local host 400 until it has received the TCP ⁇ ACK> segment indicating that the local host has received the ⁇ SYN,ACK> segment (as in step 407 ).
  • the TCP Spoofing Kernel 280 allocates a CCB for the connection and then stores all of the relevant information from the CR message in the CCB.
  • TSK 280 of PEP end point 404 uses this information to generate a TCP ⁇ SYN> segment, as in step 415 , to send to the remote host 406 .
  • the MSS in the ⁇ SYN> segment is set to the value received from the TSK peer of PEP end point 404 .
  • TSK 280 of PEP end point 402 sends a Connection Established message to its TSK peer of the remote PEP end point 404 (step 419 ), including in the CE message the MSS that is sent by the local host in the ⁇ SYN,ACK> segment.
  • TSK 280 of PEP end point 402 also responds, as in step 421 , with a TCP ⁇ ACK> segment to complete the local three-way handshake.
  • the peer TSK of PEP end point 404 then forwards the data that is received from TSK 280 to the host, per step 423 .
  • the remote host 406 sends data to the peer TSK of PEP end point 404 , which acknowledges receipt of the data by issuing an ⁇ ACK> segment to the remote PEP end point 404 , per step 427 . Simultaneously with the acknowledgement, the data is sent to TSK 280 of PEP end point 402 (step 429 ).
  • TSK 280 is ready to receive and forward data from either direction.
  • TSK 280 forwards the data, as in step 431 to the local host, which, in turn, sends an ⁇ ACK> segment (step 433 ). If the data arrives from its TSK peer before a ⁇ SYN,ACK> segment response is received from the local host, the data is queued and then sent after the ⁇ ACK> segment is sent in response to the ⁇ SYN,ACK> segment (when it arrives).
  • FIG. 4B a spoofed TCP connection is established with the three-way handshake spoofing disabled.
  • the local host 400 transmits a TCP ⁇ SYN> segment, as in step 451 , to the TSK 280 within the local PEP end point 402 .
  • the local PEP end point 402 does not respond to the a TCP ⁇ SYN> segment with a ⁇ SYN,ACK> segment, but merely forwards a CR message to the remote PEP end point 404 (step 453 ).
  • step 455 sends a TCP ⁇ SYN> segment to the remote host 406 .
  • the remote host 406 transmit a TCP ⁇ SYN,ACK> segment back to the remote PEP end point 404 (per step 457 ). Thereafter, the remote PEP end point 404 , as in step 459 , forwards a CE message to the local PEP end point 402 , which subsequently issues a ⁇ SYN,ACK> segment to the local host 400 , per step 461 . Simultaneous with step 459 , the remote PEP end point 404 issues an ⁇ ACK> segment to the remote host 406 (step 463 ).
  • the remote host 406 may begin transmission of data, as in step 465 .
  • the remote PEP end point 404 simultaneously transmits, as in step 467 , the TD message to the local PEP end point 402 and transmits an ⁇ ACK> segment to the remote host 406 to acknowledge receipt of the data (step 469 ).
  • the local host 400 Because the local host 400 has received a ⁇ SYN,ACK> segment from the local PEP end point 402 , the local host 400 acknowledges the message, per step 471 . Thereafter, the local host 400 transmits data to the local PEP end point 402 . In this example, before the local PEP end point 402 receives the data from the local host 400 , the local PEP end point 402 forwards the data that originated from the remote host 406 via the TD message (step 467 ) to the local host 400 , per step 475 .
  • the local PEP end point 402 issues an ⁇ ACK> segment, as in step 477 , and forwards the data in a TD message to the remote PEP end point 404 , per step 479 .
  • the local host 400 responds to the received data of step 475 with an ⁇ ACK> segment to the local PEP end point 402 (step 481 ).
  • the remote PEP end point 404 sends the data from the local host 400 , as in step 483 , upon receipt of the TD message.
  • the remote host 406 acknowledges receipt by sending an ⁇ ACK> segment back to the remote PEP end point 404 , per step 485 .
  • FIG. 5 shows the flow of packets with the PEP architecture, according to one embodiment of the present invention.
  • a communication system 500 includes a hub site (or local) PEP end point 501 that has connectivity to a remote site PEP end point 503 via a backbone connection.
  • PEP end points 501 and 503 handle IP packets.
  • PEP end point 501 includes an internal IP packet routing module 501 a that receives local IP packets and exchanges these packets with a TSK 501 b and a BPK 501 c .
  • the remote PEP end point 503 includes an internal IP packet routing module 503 a that is in communication with a TSK 503 b and a BPK 503 c . Except for the fact that the hub site PEP end point 501 may support many more backbone protocol connections than a remote site PEP end point 503 , hub and remote site PEP processing is symmetrical.
  • the PEP end point 501 receives IP packets from its local interface 220 (FIG. 2). Non-TCP IP packets are forwarded (as appropriate) to the WAN interface 230 (FIG. 2). TCP IP packets are internally forwarded to TSK 501 b . TCP segments which belong to connections that are not be spoofed are passed back by the spoofing kernel 501 b to the routing module 501 a to be forwarded unmodified to the WAN interface 230 . For spoofed TCP connections, the TCP spoofing kernel 501 a locally terminates the TCP connection.
  • TCP data that is received from a spoofed connection is passed from the spoofing kernel 501 a to the backbone protocol kernel 501 c , and then multiplexed onto the appropriate backbone protocol connection.
  • the backbone protocol kernel 501 c ensures that the data is delivered across the WAN.
  • the remote PEP end point 503 receives IP packets from its WAN interface 230 (FIG. 2). IP packets that are not addressed to the end point 503 are simply forwarded (as appropriate) to the local interface 220 (FIG. 2). IP packets addressed to the end point 503 , which have a next protocol header type of “PBP” are forwarded to the backbone protocol kernel 503 c .
  • the backbone protocol kernel 503 c extracts the TCP data and forwards it to the TCP spoofing kernel 503 b for transmission on the appropriate spoofed TCP connection.
  • the backbone protocol connection is used by the TCP spoofing kernel 501 b to send control information to its peer TCP spoofing kernel 503 b in the remote PEP end point 503 to coordinate connection establishment and connection termination.
  • Prioritization may be applied at four points in the system 500 within routing 501 a and TSK 501 b of PEP end point 501 , and within routing 503 a , and TSK 503 b of PEP end point 503 .
  • priority rules are applied to the packets of individual TCP connections at the entry point to the TCP spoofing kernel 501 b . These rules allow a customer to control which spoofed applications have higher and lower priority access to spoofing resources.
  • Upstream prioritization is also applied before forwarding packets to the WAN.
  • prioritization is used to control access to buffer space and other resources in the PEP end point 503 , generally and with respect to TCP spoofing.
  • the PEP end point 501 may be implemented in a network gateway (e.g. an IP Gateway), according to one embodiment of the present invention.
  • the PEP end point 503 may be implemented in the remote site component, e.g. a satellite terminal such as a Multimedia Relay, a Multimedia VSAT or a Personal Earth Station (PES) Remote.
  • a satellite terminal such as a Multimedia Relay, a Multimedia VSAT or a Personal Earth Station (PES) Remote.
  • PES Personal Earth Station
  • TCP spoofing may be accomplished in both upstream and downstream directions. Additionally, the system supports spoofing of TCP connection startup, and selective TCP spoofing with only connections that can benefit from spoofing actually spoofed. Further, system 500 enables prioritization among spoofed TCP connections for access to TCP spoofing resources (e.g., available bandwidth and buffer space). This prioritization is utilized for all types of traffic that compete for system resources.
  • TCP spoofing resources e.g., available bandwidth and buffer space
  • the system 500 is suitable for application to a satellite network as the WAN. That is, the backbone protocol is optimized for satellite use in that control block resource requirements are minimized, and efficient error recovery for dropped packets are provided.
  • the system 500 also provides a feedback mechanism to support maximum buffer space resource efficiency. Further, system 500 provides reduced acknowledgement traffic by using a single backbone protocol ACK to acknowledge the data of multiple TCP connections.
  • FIG. 6 illustrates the flow of IP packets through a PEP end point, according to an embodiment of the present invention.
  • the PEP end point 210 determines (as shown by decision point A), whether the packets are destined for a host that is locally situated; if so, the IP packets are forwarded to the proper local LAN interface 220 . If the IP packets are destined for a remote host, then the PEP end point 210 decides, per decision point B, whether the traffic is a TCP segment. If the PEP end point 210 determines that in fact the packets are TCP segments, then the TSK 280 determines whether the TCP connection should be spoofed.
  • the BPK 282 processes the traffic, along with the PK 284 and the PSK 286 for eventual transmission out to the WAN. It should be noted that the BPK 282 does not process unspoofed IP packets; i.e., the packets flow directly to PK 284 .
  • traffic that is received from the WAN interface 230 is examined to determine whether the traffic is a proper PBP segment (decision point D) for the particular PEP end point 210 ; if the determination is in the affirmative, then the packets are sent to the BPK 282 and then the TSK 280 .
  • Routing support includes routing between the ports of the PEP End Point 210 (FIG. 2), e.g., from one Multimedia VSAT LAN port to another.
  • the functionalities of TCP spoofing, prioritization and path selection fit between the IP routing functionality and the WAN.
  • PEP functionality need not be applied to IP packets which are routed from local port to local port within the same PEP End Point 210 .
  • TCP spoofing, prioritization and path selection are applied to IP packets received from a local PEP End Point interface that have been determined to be destined for another site by the routing function.
  • FIG. 7 shows the relationship between PEP End Points and PEP End Point profiles, in accordance with an embodiment of the present invention.
  • PEP parameters are primarily configured via a set of profiles 701 and 703 , which are associated with one or more PEP end points 705 .
  • PEP parameters are configured on a per PEP End Point basis, such as whether TCP spoofing is globally enabled. These parameters are configured in the PEP End Point profiles 701 and 703 . It is noted that parameters that apply to specific PEP kernels may be configured via other types of profiles.
  • Profiles 701 and 703 are a network management construct; internally, a PEP End Point 705 processes a set of parameters that are received via one or more files.
  • the platform environment compares the new parameters to the existing parameters, figures out which of the PEP kernels are affected by the parameter changes, and then passes the new parameters to the affected kernels.
  • all parameters are installed dynamically. With the exception of parameters that are component specific (such as the IP addresses of a component), all parameters may be defined with default values.
  • the PEP end point 210 may be implemented in a number of different platforms, in accordance with the various embodiments of the present invention. These platforms may include an IP gateway, a Multimedia Relay, a Multimedia VSAT (Very Small Aperture Terminal), and a Personal Earth Station (PES) Remote, as shown in FIGS. 8 - 11 , respectively.
  • the PEP end point 210 defines a local LAN interface 220 an interface through which the PEP End Point 210 connects to IP hosts located at the site.
  • a WAN interface 230 is an interface through which the PEP End Point 210 connects to other sites. It is noted that a WAN interface 230 can physically be a LAN port.
  • FIG. 8 shows the interfaces of the PEP end point implemented as an IP gateway, according to one embodiment of the present invention.
  • an IP Gateway 801 has a single local LAN interface, which is an enterprise interface 803 .
  • the IP Gateway 803 employs two WAN interfaces 805 for sending and receiving IP packets to and from remote site PEP End Points: a backbone LAN interface and a wide area access (WAA) LAN interface.
  • WAA wide area access
  • the backbone LAN interface 805 is used to send IP packets to remote site PEP End Points via, for example, a Satellite Gateway (SGW) and a VSAT outroute.
  • a VSAT outroute can be received directly by Multimedia Relays (FIG. 9) and Multimedia VSATs (FIG. 10) (and is the primary path used with these End Points); however, IP packets can be sent to a PES Remote (FIG. 11) via a VSAT outroute.
  • FIG. 9 shows a Multimedia Relay implementation of a PEP end point, in accordance with an embodiment of the present invention.
  • a Multimedia Relay has two or three local LAN interfaces 903 .
  • a Multimedia Relay 901 has up to two WAN interfaces 905 for sending IP packets to hub site PEP End Points: one of its LAN interfaces and a PPP serial port interface, and four or five interfaces for receiving IP packets from hub site PEP End Points, a VSAT outroute, all of its LAN interfaces, and a PPP serial port interface. It is noted that a PPP (Point-to-Point Protocol) serial port interface and a LAN interface are generally not be used at the same time.
  • PPP Point-to-Point Protocol
  • a Multimedia Relay 901 supports the use of all of its LAN interfaces 903 at the same time for sending and receiving IP packets to and from hub site PEP End Points. Further, a Multimedia Relay 905 supports the use of a VADB (VPN Automatic Dial Backup) serial port interface for sending and receiving IP packets to and from the hub site PEP End Points.
  • VADB VPN Automatic Dial Backup
  • FIG. 10 shows a Multimedia VSAT implementation of the PEP end point, according to one embodiment of the present invention.
  • a Multimedia VSAT 1001 in an exemplary embodiment, has two local LAN interfaces 1003 . Support for one or more local PPP serial port interfaces may be utilized.
  • the Multimedia VSAT 1001 has two WAN interfaces 1005 for sending IP packets to hub site PEP End Points: a VSAT inroute and one of its LAN interfaces.
  • the Multimedia VSAT 1001 thus has three interfaces for receiving IP packets from hub site PEP End Points, the VSAT outroute and both of its LAN interfaces 1003 .
  • a Multimedia VSAT 1003 may support uses of both of its LAN interfaces 1003 at the same time for sending and receiving IP packets to and from hub site PEP End Points.
  • the Multimedia VSAT 1003 further supports the use of a VADB serial port interface for sending and receiving IP packets to and from the hub site PEP End Points.
  • FIG. 11 shows a PES Remote implementation of a PEP end point, according to one embodiment of the present invention.
  • a PES Remote 1101 may have a local LAN interface and/or several local IP (e.g. PPP, SLIP, etc.) serial port interfaces, collectively denoted as LAN interfaces 1103 .
  • the particular LAN interfaces 1103 depend on the specific PES Remote platform.
  • PES Remote 1101 has up to five WAN interfaces 1105 for sending IP packets to hub site PEP End Points, an ISBN inroute, a LAN interface, a VADB serial port interface, a Frame Relay serial port interface and an IP serial port interface, and up to five existing interfaces for receiving IP packets from hub site PEP End Points: an ISBN outroute, a LAN interface, a VADB serial port interface, a Frame Relay serial port interface, and an IP serial port interface.
  • the physical Frame Relay serial port interface may be supporting multiple Permanent Virtual Circuits (PVCs); some of which are equivalent to local interfaces 1103 and some of which are WAN interfaces 1105 .
  • PVCs Permanent Virtual Circuits
  • FIG. 12 shows an architecture of the PEP end point in which redundancy is provided at the local site, in accordance with an embodiment of the present invention.
  • a local site PEP end point 1201 (or gateway), within a communications system 1200 , serves as the primary gateway, whereby a remote site gateway 1203 maintains connectivity with the local site gateway 1201 over backbone connections, as described with respect to FIG. 2.
  • the gateways 1201 and 1203 may employ the Internet Protocol (IP) to communicate.
  • IP Internet Protocol
  • the remote site PEP end point 1203 coordinates with the primary hub site gateway 1201 to establish spoofed TCP connections.
  • another local site gateway 1205 is utilized as the redundant gateway; that is, a gateway redundancy switch is performed.
  • the remote gateway 1203 may not be aware of the redundancy switch; in fact, the remote gateway 1203 does not know that the local gateway 1201 is configured for redundancy.
  • the redundant gateway 1205 assumes the IP addresses of the primary gateway 1201 .
  • the remote site gateway 1203 may be informed of the redundancy switch because the redundant gateway 1205 utilizes different addresses.
  • gateway redundancy switch handling has a bias against unspoofed TCP connections in a network that utilizes a mix of both spoofed and unspoofed connections.
  • unspoofed TCP connections may be blocked (for several minutes) during the initial startup period to allow spoofed TCP connections to recover properly.
  • the present invention addresses this problem by modifying the handling of unspoofed TCP connections such that, during this initial startup period, the TCP Spoofing Kernel 280 uses its selective TCP spoofing rules to determine the particular TCP segments that belong to spoofed versus unspoofed TCP connections. This information may then be used to allow the unspoofed TCP segments to be forwarded, instead of blocked.
  • system 1200 need not support redundancy of the components of the remote site. However, both systems support redundancy of local site components. If a redundancy switch of a local site PEP End Point (i.e. gateway) occurs, there is no requirement that TCP connections currently being spoofed be unaffected. It is noted that all of the backbone connections from all of the remote site PEP End Points 1203 that used the failed gateway are capable of automatically switching to another (redundant) gateway 1205 ; this is accomplished by using PEP End Point IP addresses that are shared by both gateways 1201 , 1205 .
  • a redundancy switch of a local site PEP End Point i.e. gateway
  • the redundant gateway 1205 is capable of performing startup processing, which is designed to expedite restart of the TCP connections, as more fully described below.
  • gateway redundancy switch When a gateway redundancy switch occurs, all of the backbone connections are restarted by the redundant gateway 1205 .
  • the gateway platform environment 1205 opens PBP connections as active, resulting in PBP ⁇ SYN> segments being sent by the PEP Backbone Protocol Kernel 282 for every connection.
  • the remote site PEP End Points 1203 upon receiving the PBP ⁇ SYN> segments, are alerted to the fact that the backbone connections have failed. As a result, a TCP ⁇ RST> segment is sent for every TCP connection that is being spoofed.
  • the above behavior advantageously results in a relatively gracefully shutdown of the remote half of the spoofed TCP connections that are affected by a gateway redundancy switch.
  • the hub half of the spoofed TCP connections remain open.
  • the gateway 1205 does not know that these connections are spoofed TCP connections. Therefore, any TCP segments that are sent by the local host(s) (except ⁇ SYN> segments) may be forwarded unspoofed by the gateway 1205 . Besides wasting bandwidth, sending such unspoofed TCP segments to the remote site hosts is undesirable because the reaction by the receiving hosts is not completely predictable. In many cases, the hosts will respond with a TCP ⁇ RST> segment which will knock down the local site host's TCP connection. But, in other cases, the remote site hosts may just ignore these segments.
  • the gateway platform environment 1205 implements a startup delay function for unspoofed TCP segments.
  • FIGS. 13A and 13B shows a flow chart of the unspoofed startup delay processing performed by a gateway, in accordance with an embodiment of the present invention.
  • the redundancy switch occurs.
  • the redundant gateway 1205 determines whether the TCP spoofing function has been globally enabled, per step 1307 ; if the TCP spoofing function has been enabled, then a delay timer is started, per step 1311 .
  • an IP packet is received by the gateway 1205 , as in step 1319 .
  • the gateway 1205 determines whether the received packets are TCP or non-TCP, as in step 1303 . It is noted that the startup delay, according to an embodiment of the present invention, applies to TCP segments; thus, non-TCP IP packets are forwarded normally without any startup delay processing, regardless of the setting of the global TCP spoofing parameter (as in step 1305 ). If the packets are non-TCP packets, the redundant gateway 1205 checks whether the TCP spoofing function has been globally enabled, per step 1321 .
  • the gateway platform environment 1205 only invokes the “unspoofed startup delay” processing if TCP spoofing is globally enabled. However, if TCP spoofing is globally disabled, all TCP segments are forwarded unspoofed, as in step 1309 , without performing the delay processing.
  • the gateway 1205 examines the delay timer to determine whether the timer has expired, as in step 1315 .
  • the gateway 1205 is configured with an “unspoofed startup delay” timeout value.
  • the delay value is configurable, largely because of its potential impact on unspoofed TCP connections. Accordingly, at startup the gateway 1205 starts the delay timer with this value.
  • the gateway environment 1205 terminates unspoofed TCP connections on the hub side, as in step 1313 , by forwarding all TCP segments—except ⁇ SYN> segments—for which it has no CCB (which will be all segments at first) to a special TCP Spoofing Kernel utility function, as determined per step 1323 .
  • This utility function tsk_reset_tcp_connection( ), responds to any TCP segment provided to it by the environment 1205 by sending a TCP ⁇ RST> segment to the local host, effectively tearing down the TCP connection. In this manner, the unspoofed TCP connections can be terminated (step 1313 ).
  • This reset function is more fully described below.
  • the gateway 1205 continues to forward TCP ⁇ SYN> segments for which no CCB exists to the normal TSK new connection entry point. However, if TSK returns the ⁇ SYN> segment to be forwarded unspoofed (e.g., because the appropriate backbone connection is not up yet) while the delay timer is still running, the environment will discard the segment rather than forward it. After the timer expires, the gateway environment 210 processes TCP segments normally, per step 1317 . The above approach has the benefit that it does not delay restarting spoofed TCP connections. As soon as the backbone connection comes up, TSK 280 of gateway 1205 accepts a TCP ⁇ SYN> segment for spoofing and allocates a CCB for the TCP connection. With a CCB in place, the environment 1205 ceases forwarding TCP segments from that TCP connection to the TCP connection “reset” function.
  • the value of the delay timer may be configurable depending on the mix of traffic. If, in general, all TCP connections are intended to be spoofed, the delay timer can be set to a relatively large value to ensure that all of the hub side spoofed TCP connections that are left over from before a redundancy switch are handled. In the scenario whereby unspoofed TCP connections exist, either because of selective TCP spoofing rules or because of a lack of TCP connection control block resources, a smaller value for the delay timer might be warranted. It is noted that discarding TCP segments for unspoofed TCP connections during the startup delay period results in the tear down of these connections if the startup delay period (i.e., timer value) is too long.
  • TSK 280 provides a utility function that the environment 1205 can use to send TCP ⁇ RST> segments to terminate TCP connections.
  • This utility function which is a reset TCP connection command, is described below.
  • the reset function, tsk_reset_tcp connection( ), is a utility procedure that is provided by the TCP Spoofing Kernel 280 , as called by the platform environment 1205 to request that a TCP ⁇ RST> segment be sent in response to a TCP segment that is received from a local LAN port.
  • the procedural interface of the TSK 280 takes a single parameter, e.g., a pointer, to the received IP packet containing the TCP segment.
  • tsk_reset_tcp_connection( ) is used by the local site PEP End Point platform environment 1205 to tear down spoofed TCP connections after a redundancy switch.
  • the tsk_reset_tcp_connection( ) results in an allocation of a buffer from the environment 1205 , and the building of a TCP ⁇ RST> segment in the buffer (using the IP addresses and TCP port numbers, reversed, extracted from the received TCP segment); this command then forwards the ⁇ RST> segment to the environment 1205 for transmission. Because there is no backbone connection that is associated with the segment being discarded, TSK 280 allocates the WAN to LAN buffer against a generic 0xFFFF “backbone connection”, for example. The original received TCP segment is then discarded.
  • the redundant gateway 1205 may track the state of the primary gateway 1201 .
  • this approach introduces some complexity, as real time tracking of spoofed connection state by the redundant gateway 1205 is required.
  • no matter how fast the communication is between the two gateways 1201 and 1205 there exists a window of opportunity, albeit small, in which a failure can occur in the primary gateway 1201 before the primary gateway 1201 can pass updated state information to the redundant gateway 1205 , leading to a loss of state. Therefore, the redundant gateway 1205 is required to handle connections which the redundant gateway 1205 detects as unspoofed, but which may actually have been spoofed be the primary gateway 1201 .
  • FIG. 14 illustrates a computer system 1401 upon which an embodiment according to the present invention may be implemented.
  • a computer system 1401 may be configured as a server to execute code that performs the PEP functions of the PEP end point 210 as earlier discussed.
  • Computer system 1401 includes a bus 1403 or other communication mechanism for communicating information, and a processor 1405 coupled with bus 1403 for processing the information.
  • Computer system 1401 also includes a main memory 1407 , such as a random access memory (RAM) or other dynamic storage device, coupled to bus 1403 for storing information and instructions to be executed by processor 1405 .
  • main memory 1407 may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor 1405 .
  • TCP spoofing control blocks may be stored in main memory 1407 .
  • Computer system 1401 further includes a read only memory (ROM) 1409 or other static storage device coupled to bus 1403 for storing static information and instructions for processor 1405 .
  • ROM read only memory
  • a storage device 1411 such as a magnetic disk or optical disk, is provided and coupled to bus 1403 for storing information and instructions.
  • Computer system 1401 may be coupled via bus 1403 to a display 1413 , such as a cathode ray tube (CRT), for displaying information to a computer user.
  • a display 1413 such as a cathode ray tube (CRT)
  • An input device 1415 is coupled to bus 1403 for communicating information and command selections to processor 1405 .
  • cursor control 1417 is Another type of user input device, such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processor 1405 and for controlling cursor movement on display 1413 .
  • Embodiments are related to the use of computer system 1401 to perform the PEP functions of the PEP end point 210 .
  • this automatic update approach is provided by computer system 1401 in response to processor 1405 executing one or more sequences of one or more instructions contained in main memory 1407 .
  • Such instructions may be read into main memory 1407 from another computer-readable medium, such as storage device 1411 .
  • Execution of the sequences of instructions contained in main memory 1407 causes processor 1405 to perform the process steps described herein.
  • processors in a multiprocessing arrangement may also be employed to execute the sequences of instructions contained in main memory 1407 .
  • hard-wired circuitry may be used in place of or in combination with software instructions. Thus, embodiments are not limited to any specific combination of hardware circuitry and software.
  • Non-volatile media includes, for example, optical or magnetic disks, such as storage device 1411 .
  • Volatile media includes dynamic memory, such as main memory 1407 .
  • Transmission media includes coaxial cables, copper wire and fiber optics, including the wires that comprise bus 1403 . Transmission media can also take the form of acoustic or light waves, such as those generated during radio wave and infrared data communications.
  • Computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, or any other magnetic medium, a CD-ROM, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave as described hereinafter, or any other medium from which a computer can read.
  • Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to processor 1405 for execution.
  • the instructions may initially be carried on a magnetic disk of a remote computer.
  • the remote computer can load the instructions relating to execution of the PEP functions of the PEP end point 210 into its dynamic memory and send the instructions over a telephone line using a modem.
  • a modem local to computer system 1401 can receive the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal.
  • An infrared detector coupled to bus 1403 can receive the data carried in the infrared signal and place the data on bus 1403 .
  • Bus 1403 carries the data to main memory 1407 , from which processor 1405 retrieves and executes the instructions.
  • the instructions received by main memory 1407 may optionally be stored on storage device 1411 either before or after execution by processor 1405 .
  • Computer system 1401 also includes one or more communication interfaces 1419 coupled to bus 1403 .
  • Communication interfaces 1419 provide a two-way data communication coupling to network links 1421 and 1422 , which are connected to a local area network 14 (LAN) 1423 and a wide area network (WAN) 1424 , respectively.
  • the WAN 1424 may be a satellite network.
  • communication interface 1419 may be a network interface card to attach to any packet switched LAN.
  • communication interface 1419 may be an asymmetrical digital subscriber line (ADSL) card, an integrated services digital network (ISDN) card, a cable modem, or a modem to provide a data communication connection to a corresponding type of telephone line.
  • Wireless links may also be implemented.
  • communication interface 1419 sends and receives electrical, electromagnetic or optical signals that carry digital data streams representing various types of information.
  • Network link 1421 typically provides data communication through one or more networks to other data devices.
  • network link 1421 may provide a connection through local area network 1423 to a host computer 1425 or to data equipment operated by an Internet Service Provider (ISP) 1427 .
  • ISP 1427 in turn provides data communication services through the Internet 505 .
  • LAN 1423 is linked to an intranet 1429 .
  • the intranet 1429 , LAN 1423 and Internet 505 all use electrical, electromagnetic or optical signals that carry digital data streams.
  • the signals through the various networks and the signals on network link 1421 and through communication interface 1419 which carry the digital data to and from computer system 1401 , are exemplary forms of carrier waves transporting the information.
  • Computer system 1401 can send messages and receive data, including program code, through the network(s), network link 1421 and communication interface 1419 .
  • a server 1431 might transmit a requested code for an application program through Internet 505 , ISP 1427 , LAN 1423 and communication interface 1419 .
  • the received code may be executed by processor 1405 as it is received, and/or stored in storage device 1411 , or other non-volatile storage for later execution.
  • computer system 1401 may obtain application code in the form of a carrier wave.
  • Computer system 1401 can transmit notifications and receive data, including program code, through the network(s), network link 1421 and communication interface 1419 .
  • a local PEP end point and a remote PEP end point communicate to optimize the exchange of data through a TCP spoofing functionality.
  • a redundancy switch occurs, whereby the remote PEP end point directs its communication to another local PEP end point that serves as a redundant gateway.
  • the redundant gateway is configured to minimize the blocking of unspoofed TCP connections through the use of a reset function in conjunction with a delay timer.
  • the reset function effectively terminates the unspoofed TCP connections on the local side for the duration of the delay timer period. This approach advantageously avoids delaying the restarting of spoofed TCP connections.

Abstract

A communication gateway for providing redundant communication in a communication system having a remote platform is disclosed. The gateway includes a communication interface that receives a message from a host over a connection according to a prescribed protocol. Additionally, the gateway includes a processor that is coupled to the communication interface and is configured to identify the message received as an unspoofed message, and configured to terminate, during a predetermined period, the connection based upon the identified message. The processor is configured to restart a spoofed connection with another host. The above arrangement has particular applicability to a bandwidth constrained communication system, such as a satellite network.

Description

    CROSS-REFERENCES TO RELATED APPLICATION
  • This application is related to and claims the benefit of priority to: (i) U.S. Provisional Patent Application (Serial No. 60/220,026), filed Jul. 21, 2000, entitled “Performance Enhancing Proxy,” and (ii) U.S. Provisional Patent Application (Serial No. 60/225,630), filed Aug. 15, 2000, entitled “Performance Enhancing Proxy”; all of which are incorporated herein by reference in their entirety.[0001]
    • BACKGROUND OF THE INVENTION
  • 1. Field of the Invention [0002]
  • The present invention relates to a communication system, and is more particularly related to a proxy architecture for improving network performance. [0003]
  • 2. Discussion of the Background [0004]
  • The entrenchment of data networking into the routines of modern society, as evidenced by the prevalence of the Internet, particularly the World Wide Web, has placed ever-growing demands on service providers to continually improve network performance. To meet this challenge, service providers have invested heavily in upgrading their networks to increase system capacity (i.e., bandwidth). In many circumstances, such upgrades may not be feasible economically or the physical constraints of the communication system does not permit simply “upgrading.” Accordingly, service providers have also invested in developing techniques to optimize the performance of their networks. Because much of today's networks are either operating with or are required to interface with the Transmission Control Protocol/Internet Protocol (TCP/IP) suite, attention has been focused on optimizing TCP/IP based networking operations. [0005]
  • As the networking standard for the global Internet, TCP/IP has earned such acceptance among the industry because of its flexibility and rich heritage in the research community. The transmission control protocol (TCP) is the dominant protocol in use today on the Internet. TCP is carried by the Internet protocol (IP) and is used in a variety of applications including reliable file transfer and Internet web page access applications. The four layers of the TCP/IP protocol suite are illustrated in FIG. 15. As illustrated, the link layer (or the network interface layer) [0006] 10 includes device drivers in the operating system and any corresponding network interface cards. Together, the device driver and the interface cards handle hardware details of physically interfacing with any cable or whatever type of media that is being used. The network layer (also referred to as the Internet layer) 12 handles the movement of packets around the network. Routing of packets, for example, takes place at the network layer 12. IP, Internet control message protocol (ICMP), and Internet group management protocol (IGMP) may provide the network layer in the TCP/IP protocol suite. The transport layer 14 provides a flow of data between two hosts, for the application layer 16 above.
  • In the TCP/IP protocol suite, there are at least two different transport protocols, TCP and a user datagram protocol (UDP). TCP, which provides a reliable flow of data between two hosts, is primarily concerned with dividing the data passed to it from the [0007] application layer 16 into appropriately sized segments for the network layer 12 below, acknowledging received packets, setting timeouts to make certain the other end acknowledges packets that are sent, and so on. Because this reliable flow of data is provided by the transport layer 14, the application layer 16 is isolated from these details. UDP, on the other hand, provides a much simpler service to the application layer 16. UDP just sends packets of data called datagrams from one host to another, with no guarantee that the datagrams will reach their destination. Any desired reliability must be added by a higher layer, such as the application layer 16.
  • The [0008] application layer 16 handles the details of the particular application. There are many common TCP/IP applications that almost every implementation provides, including telnet for remote log-in, the file transfer protocol (FTP), the simple mail transfer protocol (SMTP) or electronic mail, the simple network management protocol (SNMP), the hypertext transfer protocol (HTTP), and many others.
  • As mentioned, TCP provides reliable, in-sequence delivery of data between two IP hosts. The IP hosts set up a TCP connection, using a conventional TCP three-way handshake and then transfer data using a window based protocol with the successfully received data acknowledged. [0009]
  • To understand where optimizations may be made, it is instructive to consider a typical TCP connection establishment. FIG. 16 illustrates an example of the conventional TCP three-way handshake between [0010] IP hosts 20 and 22. First, the IP host 20 that wishes to initiate a transfer with IP host 22, sends a synchronize (SYN) signal to IP host 22. The IP host 22 acknowledges the SYN signal from IP host 20 by sending a SYN acknowledgement (ACK). The third step of the conventional TCP three-way handshake is the issuance of an ACK signal from the IP host 20 to the other IP host 22. At this point, IP host 22 is ready to receive the data from IP host 20 (and vice versa). After all the data has been delivered, another handshake (similar to the handshake described to initiate the connection) is used to close the TCP connection.
  • TCP was designed to be very flexible and to work over a wide variety of communication links, including both slow and fast links, high latency links, and links with low and high error rates. However, while TCP (and other high layer protocols) works with many different kinds of links, TCP performance, in particular, the throughput possible across the TCP connection, is affected by the characteristics of the link in which it is used. There are many link layer design considerations that should be taken into account when designing a link layer service that is intended to support Internet protocols. However, not all characteristics can be compensated for by choices in the link layer design. TCP has been designed to be very flexible with respect to the links which it traverses. Such flexibility is achieved at the cost of sub-optimal operation in a number of environments vis-à-vis a tailored protocol. The tailored protocol, which is usually proprietary in nature, may be more optimal, but greatly lacks flexibility in terms of networking environments and interoperability. [0011]
  • An alternative to a tailored protocol is the use of performance enhancing proxies (PEPs), to perform a general class of functions termed “TCP spoofing,” in order to improve TCP performance over impaired (i.e., high latency or high error rate) links. TCP spoofing involves an intermediate network device (the performance enhancing proxy (PEP)) intercepting and altering, through the addition and/or deletion of TCP segments, the behavior of the TCP connection in an attempt to improve its performance. [0012]
  • Conventional TCP spoofing implementations include the local acknowledgement of TCP data segments in order to get the TCP data sender to send additional data sooner than it would have sent if spoofing were not being performed, thus improving the throughput of the TCP connection. Generally, conventional TCP spoofing implementations have focused simply on increasing the throughput of TCP connections either by using larger windows over the link or by using compression to reduce the amount of data which needs to be sent, or both. [0013]
  • Many TCP PEP implementations are based on TCP ACK manipulation. These may include TCP ACK spacing where ACKs which are bunched together are spaced apart, local TCP ACKs, local TCP retransmissions, and TCP ACK filtering and reconstruction. Other PEP mechanisms include tunneling, compression, and priority-based multiplexing. [0014]
  • In addition to optimization mechanisms, network redundancy is imperative for the operation of modem communication systems. However, such redundancy should not degrade or hinder the performance of the system. That is, redundancy needs to be achieved without compromising performance. [0015]
  • Based on the foregoing, there is a clear need for improved approaches to optimizing network performance, while achieving network redundancy. There is also a need to enhance network performance, without a costly infrastructure investment. There is also a need to employ a network performance enhancing mechanism that complies with existing standards to facilitate rapid deployment. There is a further need to simplify the receiver design. Therefore, an approach for optimizing network performance using a proxy architecture is highly desirable. [0016]
    • SUMMARY OF THE INVENTION
  • The present invention addresses the above stated needs by providing a system for providing performance enhancing proxy (PEP) functionalities. The system utilizes a redundant platform that minimizes the impact on the network of redundancy switching as the spoofed connections are restarted. An “unspoofed startup delay” process provides for the termination of unspoofed connections for a predetermined period, so that the restart process of spoofed TCP connections is not delayed. [0017]
  • According to one aspect of the invention, a method for performing redundancy switching from a first platform to a second platform is provided. The method includes identifying a message received over a connection according to a prescribed protocol as an unspoofed message. The method also includes terminating, during a predetermined period, the connection based upon the identifying step. Further, the method includes restarting a spoofed connection between the second platform and a host. Under this approach, network performance is enhanced. [0018]
  • According to another aspect of the invention, a communication system includes a first platform that is configured to communicate with a remote platform and a second platform that is configured to communicate with the remote platform upon failure of the first platform to communicate with the remote platform. The second platform is configured to identify a message received from a local host over a connection according to a prescribed protocol as an unspoofed message, wherein the second platform terminates, during a predetermined period, the connection in response to the identified message. The above arrangement advantageously improves system throughput and system reliability of a communication system. [0019]
  • According to one aspect of the invention, a communication gateway for providing redundant communication in a communication system having a remote platform is provided. The gateway includes a communication interface that is configured to receive a message from a host over a connection according to a prescribed protocol. Additionally, the gateway includes a processor that is coupled to the communication interface and is configured to identify the message received as an unspoofed message, and configured to terminate, during a predetermined period, the connection based upon the identified message, the processor being configured to restart a spoofed connection with another host. The above arrangement advantageously provides improved system performance. [0020]
  • According to another aspect of the invention, a communication gateway for providing redundant communication in a communication system having a remote platform is disclosed. The gateway includes means for identifying a message received over a connection according to a prescribed protocol as an unspoofed message, and means for terminating, during a predetermined period, the connection based upon the identified message. The gateway also includes means for restarting a spoofed connection between the second platform and a host. The above approach minimizes delay associated with redundancy switching. [0021]
  • In yet another aspect of the invention, a computer-readable medium carrying one or more sequences of one or more instructions for performing redundancy switching from a first platform to a second platform is disclosed. The one or more sequences of one or more instructions include instructions which, when executed by one or more processors, cause the one or more processors to perform the step of identifying a message received over a connection according to a prescribed protocol as an unspoofed message. Another step includes terminating, during a predetermined period, the connection based upon the identifying step. Yet another step includes restarting a spoofed connection between the second platform and a host. This approach advantageously provides improved system reliability and performance.[0022]
    • BRIEF DESCRIPTION OF THE DRAWINGS
  • A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: [0023]
  • FIG. 1 is a diagram of a communication system in which the performance enhancing proxy (PEP) of the present invention is implemented; [0024]
  • FIG. 2 is a diagram of a PEP end point platform environment, according to an embodiment of the present invention; [0025]
  • FIG. 3 is a diagram of a TCP Spoofing Kernel (TSK) utilized in the environment of FIG. 2; [0026]
  • FIGS. 4A and 4B are flow diagrams of the connection establishment with three-way handshake spoofing and without three-way handshake spoofing, respectively; [0027]
  • FIG. 5 is a diagram of a PEP packet flow between two PEP end points, according to an embodiment of the present invention; [0028]
  • FIG. 6 is a diagram of an IP (Internet Protocol) packet flow through a PEP end point, in accordance with an embodiment of the present invention; [0029]
  • FIG. 7 is a diagram of PEP end point profiles utilized in the platform of FIG. 2; [0030]
  • FIG. 8 is a diagram of the interfaces of a PEP end point implemented as an IP gateway, according to an embodiment of the present invention; [0031]
  • FIG. 9 is a diagram of the interfaces of a PEP end point implemented as a Multimedia Relay, according to an embodiment of the present invention; [0032]
  • FIG. 10 is a diagram of the interfaces of a PEP end point implemented as a Multimedia VSAT (Very Small Aperture Terminal), according to an embodiment of the present invention; [0033]
  • FIG. 11 is a diagram of the interfaces of a PEP end point implemented in an earth station, according to an embodiment of the present invention; [0034]
  • FIG. 12 is a diagram an architecture of a PEP end point in which redundancy is provided at the hub site, in accordance with an embodiment of the present invention; [0035]
  • FIGS. 13A and 13B are a flow chart of an unspoofed startup delay processing performed by a gateway, in accordance with an embodiment of the present invention; [0036]
  • FIG. 14 is a diagram of a computer system that can perform PEP functions, in accordance with an embodiment of the present invention; [0037]
  • FIG. 15 is diagram of the protocol layers of the TCP/IP protocol suite; and [0038]
  • FIG. 16 is diagram of a conventional TCP three-way handshake between IP hosts.[0039]
    • DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • In the following description, for the purpose of explanation, specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent that the invention may be practiced without these specific details. In some instances, well-known structures and devices are depicted in block diagram form in order to avoid unnecessarily obscuring the invention. [0040]
  • Although the present invention is discussed with respect to the Internet and the TCP/IP protocol suite, the present invention has applicability to other packet switched networks and equivalent protocols. [0041]
  • FIG. 1 illustrates an [0042] exemplary network 100 in which the performance enhancing proxy (PEP) of the present invention may be utilized. The network 100 in FIG. 1 includes one or more hosts 110 connected to a network gateway 120 via TCP connections. The network gateway 120 is connected to another network gateway 140 via a backbone connection on a backbone link 130. As seen in FIG. 1, the backbone link 130, in an exemplary embodiment, is shown as a satellite link that is established over a satellite 101; however, it is recognized by one of ordinary skill in the art that other network connections may be implemented. For example, these network connections may be established over a wireless communications system, in general, (e.g., radio networks, cellular networks, etc.) or a terrestrial communications system. The network gateway 140 is further connected to a second group of hosts 150, also via TCP connections. In the arrangement illustrated in FIG. 1, the network gateways 120, 140 facilitate communication between the groups of hosts 110, 150.
  • The [0043] network gateways 120, 140 facilitate communication between the two groups of hosts 110, 150 by performing a number of performance enhancing functions. These network gateways 120, 140 may perform selective TCP spoofing, which allows flexible configuration of the particular TCP connections that are to be spoofed. Additionally, gateways 120, 140 employs a TCP three-way handshake, in which the TCP connections are terminated at each end of the backbone link 130. Local data acknowledgements are utilized by the network gateways 120, 140, thereby permitting the TCP windows to increase at local speeds.
  • The [0044] network gateway 120, 140 further multiplexes multiple TCP connections across a single backbone connection; this capability reduces the amount of acknowledgement traffic associated with the data from multiple TCP connections, as a single backbone connection acknowledgement may be employed. The multiplexing function also provides support for high throughput TCP connections, wherein the backbone connection protocol is optimized for the particular backbone link that is used. The network gateways 120, 140 also support data compression over the backbone link 130 to reduce the amount of traffic to be sent, further leveraging the capabilities of the backbone connection. Further, the network gateways 120, 140 utilize data encryption in the data transmission across the backbone link 130 to protect data privacy, and provide prioritized access to backbone link 130 capacity on a per TCP connection basis. Each of the network gateways 120, 140 may select a particular path for the data associated with a connection to flow. The above capabilities of the network gateways 120, 140 are more fully described below.
  • FIG. 2 illustrates a performance enhancing proxy (PEP) [0045] 200 as implemented in a network gateway 120, 140, according to one embodiment of the present invention. In this embodiment, the PEP 200 has a platform environment 210, which includes the hardware and software operating system. The PEP 200 also includes local area network (LAN) interfaces 220 and wide area network (WAN) interfaces 230. In the example in FIG. 1, the network gateway 120 may establish the TCP connections with the IP hosts 110, via a local LAN interface 220 and may establish the backbone connection with the network gateway 140 via a WAN interface 230. The PEP platform environment 210 may also include general functional modules: routing module 240, buffer management module 250, event management module 260, and parameter management module 270. As illustrated in FIG. 2, the network gateway also includes a TCP spoofing kernel (TSK) 280, a backbone protocol kernel (BPK) 282, a prioritization kernel (PK) 284, and a path selection kernel (PSK) 286. These four kernels essentially make up the functionality of the performance enhancing proxy 200.
  • The [0046] platform environment 210 performs a number of functions. One such function is to shield the various PEP kernels 280, 282, 284, 286 from implementation specific constraints. That is, the platform environment 210 performs functions that the various PEP kernels 280, 282, 284, 286 cannot perform directly because the implementation of the function is platform specific. This arrangement has the advantageous effect of hiding platform specific details from the PEP kernels 280, 282, 284, 286, making the PEP kernels more portable. An example of a platform specific function is the allocation of a buffer. In some platforms, buffers are created as they are needed, while in other platforms, buffers are created at start-up and organized into linked lists for later use. It is noted that platform specific functions are not limited to functions generic to all of the kernels 280, 282, 284, 286. A function specific to a particular kernel, for example, the allocation of a control block for TCP spoofing, may also be implemented in the platform environment to hide platform specific details from the kernel.
  • Additionally, the [0047] platform environment 210 may provide the task context in which the PEP kernels 280,282, 284, 286 run. In one exemplary embodiment, all PEP kernels 280, 282, 284, 286 can run in the same task context for efficiency. However, this is not required.
  • Furthermore, the [0048] platform environment 210, in an exemplary embodiment, provides an interface between the PEP functionality (embodied in kernels 280, 282, 284, 286) and the other functionality of the network gateway 120, 140. The platform environment 210 may provide the interface between the PEP functionality and the routing function 240, as seen in FIG. 2. It is noted that the platform specific functions illustrated in FIG. 2 are examples and are not considered an exhaustive list. It is further noted that the PEP kernels shown touching each other (280, 282 and 284, 286) in FIG. 2 may have a direct procedural interface to each other. Further, the kernels 280, 282, 284, 286 may include direct interfaces to improve performance, as opposed to routing everything through the platform environment 210 (as shown in FIG. 2).
  • In addition to the [0049] PEP kernels 280, 282, 284, and 286, the PEP end point platform 210 may utilize a data compression kernel (CK) 290 and an encryption kernel (EK) 292. These kernels 280, 282, 284, 286, 290, and 292, as described above, facilitate communication between the two groups of hosts 110, 150, by performing a variety of performance enhancing functions, either singly or in combination. These performance enhancing functions include selective TCP spoofing, three-way handshake spoofing, local data acknowledgement, TCP connection to backbone connection multiplexing, data compression/encryption, prioritization, and path selection.
  • Selective TCP Spoofing is performed by the [0050] TSK 280 and includes a set of user configurable rules that are used to determine which TCP connections should be spoofed. Selective TCP spoofing improves performance by not tying up TCP spoofing-related resources, such as buffer space, control blocks, etc., for TCP connections for which the user has determined that spoofing is not beneficial or required and by supporting the use of tailored parameters for TCP connections that are spoofed.
  • In particular, the [0051] TSK 280 discriminates among the various TCP connections based on the applications using them. That is, TSK 280 discriminates among these TCP connections to determine which connection should be spoofed as well as the manner in which the connection is spoofed; e.g., whether to spoof the three-way handshake, the particular timeout parameters for the spoofed connections, etc. TCP spoofing is then performed only for those TCP connections that are associated with applications for which high throughput or reduced connection startup latency (or both) is required. As a result, the TSK 280 conserves TCP spoofing resources for only those TCP connections for which high throughput or reduced connection startup latency (or both) is required. Further, the TSK 280 increases the total number of TCP connections which can be active before running out of TCP spoofing resources, since any active TCP connections which do not require high throughput are not allocated resources.
  • One criterion for identifying TCP connections of applications for which TCP spoofing should and should not be performed is the TCP port number field contained in the TCP packets being sent. In general, unique port numbers are assigned to each type of application. Which TCP port numbers should and should not be spoofed can be stored in the [0052] TSK 280. The TSK 280 is also re-configurable to allow a user or operator to reconfigure the TCP port numbers which should and should not be spoofed. The TSK 280 also permits a user or operator to control which TCP connections are to be spoofed based on other criteria. In general, a decision on whether to spoof a TCP connection may be based on any field within a TCP packet. The TSK 280 permits a user to specify which fields to examine and which values in these fields identify TCP connections that should or should not be spoofed. Another example of a potential use for this capability is for the user or operator to select the IP address of the TCP packet in order to control for which users TCP spoofing is performed. The TSK 280 also permits a user to look at multiple fields at the same time. As a result, the TSK 280 permits a user or operator to use multiple criteria for selecting TCP connections to spoof. For example, by selecting both the IP address and the TCP port number fields, the system operator can enable TCP spoofing for only specific applications from specific users.
  • The user configurable rules may include five exemplary criteria which can be specified by the user or operator in producing a selective TCP spoofing rule: Destination IP address; Source IP address; TCP port numbers (which may apply to both the TCP destination and source port numbers); TCP options; and IP differentiated services (DS) field. However, as indicated above, other fields within the TCP packet may be used. [0053]
  • As discussed above, in addition to supporting selective TCP spoofing rules for each of these criterion, AND and OR combination operators can be used to link criteria together. For example, using the AND combination operator, a rule can be defined to disable TCP spoofing for FTP data received from a specific host. Also, the order in which the rules are specified may be significant. It is possible for a connection to match the criteria of multiple rules. Therefore, the [0054] TSK 280 can apply rules in the order specified by the operator, taking the action of the first rule that matches. A default rule may also be set which defines the action to be taken for TCP connections which do not match any of the defined rules. The set of rules selected by the operator may be defined in a selective TCP spoofing selection profile.
  • As an example, assuming sufficient buffer space has been allocated to spoof five TCP connections, if four low speed applications (i.e., applications which, by their nature, do not require high speed) bring up connections along with one high speed application, the high speed connection has access to only ⅕ of the available spoofing buffer space. Further, if five low speed connections are brought up before the high speed connection, the high speed connection cannot be spoofed at all. Using the [0055] TSK 280 selective spoofing mechanism, the low speed connections are not allocated any spoofing buffer space. Therefore, the high speed connection always has access to all of the buffer space, improving its performance with respect to an implementation without the selective TCP spoofing feature of the TSK 280.
  • The [0056] TSK 280 also facilitates spoofing of the conventional three-way handshake. Three-Way Handshake Spoofing involves locally responding to a connection request to bring up a TCP connection in parallel with forwarding the connection requests across the backbone link 130 (FIG. 1). This allows the originating IP host (for example, 110) to reach the point of being able to send the data it must send at local speeds, i.e. speeds that are independent of the latency of the backbone link 130. Three-way Handshake Spoofing allows the data that the IP host 110 needs to send to be sent to the destination IP host 150 without waiting for the end-to-end establishment of the TCP connection. For backbone links 130 with high latency, this significantly reduces the time it takes to bring up the TCP connection and, more importantly, the overall time it takes to get a response (from an IP host 150) to the data the IP host 110 sends.
  • A specific example in which this technique is useful relates to an Internet web page access application. With three-way handshake spoofing, an IP host's request to retrieve a web page can be on its way to a web server without waiting for the end-to-end establishment of the TCP connection, thereby reducing the time it takes to download the web page. [0057]
  • With Local Data Acknowledgement, the [0058] TSK 280 in the network gateway 120 (for example) locally acknowledges data segments received from the IP host 110. This allows the sending IP host 110 to send additional data immediately. More importantly, TCP uses received acknowledgements as signals for increasing the current TCP window size. As a result, local sending of the acknowledgements allows the sending IP host 110 to increase it TCP window at a much faster rate than supported by end to end TCP acknowledgements. The TSK 280 (the spoofer) takes on the responsibility for reliable delivery of the data which it has acknowledged.
  • In the [0059] BPK 282, multiple TCP connections are multiplexed onto and carried by a single backbone connection. This improves system performance by allowing the data for multiple TCP connections to be acknowledged by a single backbone connection acknowledgement (ACK), significantly reducing the amount of acknowledgement traffic required to maintain high throughput across the backbone link 130. In addition, the BPK 282 selects a backbone connection protocol that is optimized to provide high throughput for the particular link. Different backbone connection protocols can be used by the BPK 282 with different backbone links without changing the fundamental TCP spoofing implementation. The backbone connection protocol selected by the BPK 282 provides appropriate support for reliable, high speed delivery of data over the backbone link 130, hiding the details of the impairments (for example high latency) of the link from the TCP spoofing implementation.
  • The multiplexing by the [0060] BPK 282 allows for the use of a backbone link protocol which is individually tailored for use with the particular link and provides a technique to leverage the performance of the backbone link protocol with much less dependency upon the individual performance of the TCP connections being spoofed than conventional methods. Further, the ability to tailor the backbone protocol for different backbone links makes the present invention applicable to many different systems.
  • The [0061] PEP 200 may optionally include a data compression kernel 290 for compressing TCP data and an encryption kernel 292 for encrypting TCP data. Data compression increases the amount of data that can be carried across the backbone connection. Different compression algorithms can be supported by the data compression kernel 290 and more than one type of compression can be supported at the same time. The data compression kernel 290 may optionally apply compression on a per TCP connection basis, before the TCP data of multiple TCP connections is multiplexed onto the backbone connection or on a per backbone connection basis, after the TCP data of multiple TCP connections has been multiplexed onto the backbone connection. Which option is used is dynamically determined based on user configured rules and the specific compression algorithms being utilized. Exemplary data compression algorithms are disclosed in U.S. Pat. Nos. 5,973,630, 5,955,976, the entire contents of which are hereby incorporated by reference. The encryption kernel 292 encrypts the TCP data for secure transmission across the backbone link 130. Encryption may be performed by any conventional technique. It is also understood that the corresponding spoofer (in the example outlined above, the network gateway 140) includes appropriate kernels for decompression and decryption, both of which may be performed by any conventional technique.
  • The [0062] PK 284 provides prioritized access to the backbone link capacity. For example, the backbone connection can actually be divided into N (N>1) different sub-connections, each having a different priority level. In one exemplary embodiment, four priority levels can be supported. The PK 284 uses user-defined rules to assign different priorities, and therefore different sub-connections of the backbone connection, to different TCP connections. It should be noted that PK 284 may also prioritize non-TCP traffic (e.g., UDP (User Datagram Protocol) traffic) before sending the traffic across the backbone link 130.
  • The [0063] PK 284 also uses user-defined rules to control how much of the backbone link 130 capacity is available to each priority level. Exemplary criteria which can be used to determine priority include the following: Destination IP address; Source IP address; IP next protocol; TCP port numbers (which may apply to both the TCP destination and source port numbers); UDP port numbers (which may apply to both the UDP destination and source port numbers); and IP differentiated services (DS) field. The type of data in the TCP data packets may also be used as a criterion. For example, video data could be given highest priority. Mission critical data could also be given high priority. As with selective TCP spoofing, any field in the IP packet can be used by PK 284 to determine priority. However, it should be noted that under some scenarios the consequence of using such a field may cause different IP packets of the same flow (e.g., TCP connection) to be assigned different priorities; these scenarios should be avoided.
  • As mentioned above, in addition to supporting selective prioritization rules for each of these criteria, AND and OR combination operators can be used to link criteria together. For example, using the AND combination operator, a rule can be defined to assign a priority for SNMP data received from a specific host. Also, the order in which the rules are specified may be significant. It is possible for a connection to match the criteria of multiple rules. Therefore, the [0064] PK 284 can apply rules in the order specified by the operator, taking the action of the first rule that matches. A default rule may also be set which defines the action to be taken for IP packets which do not match any of the defined rules. The set of rules selected by the operator may be defined in a prioritization profile.
  • As regards the path selection functionality, the [0065] PSK 286 is responsible for determining which path an IP packet should take to reach its destination. The path selected by the PSK 286 can be determined by applying path selection rules. The PSK 286 also determines which IP packets should be forwarded using an alternate path and which IP packets should be dropped when one or more primary paths fail. Path selection parameters can also be configured using profiles. The path selection rules may be designed to provide flexibility with respect to assigning paths while making sure that all of the packets related to the same traffic flow (e.g., the same TCP connection) take the same path (although it is also possible to send segments of the same TCP connection via different paths, this segment “splitting” may have negative side effects). Exemplary criteria that can be used to select a path include the following: priority of the IP packet as set by the PK 284 (should be the most common criterion): Destination IP address; Source IP address; IP next protocol; TCP port numbers (which may apply to both the TCP destination and source port numbers); UDP port numbers (which may apply to both the UDP destination and source port numbers); and IP differentiated services (DS) field. Similar to selective TCP spoofing and prioritization, the PSK 284 may determine a path by using any field in the IP packet.
  • As with the prioritization criteria (rules) the AND and OR combination operators can be used to link criteria together. For example, using the AND combination operator, a rule can be defined to select a path for SNMP data received from a specific host. Also, the order in which the rules are specified may be significant. It is possible for a connection to match the criteria of multiple rules. Therefore, the [0066] PSK 286 can apply rules in the order specified by the operator, taking the action of the first rule that matches. A default rule may also be set which defines the action to be taken for IP packets which do not match any of the defined rules. The set of rules selected by the operator may be defined in a path selection profile.
  • By way of example, a path selection rule may select the path based on any of the following path information in which IP packets match the rule: a primary path, a secondary path, and a tertiary path. The primary path is be specified in any path selection rule. The secondary path is used only when the primary path has failed. If no secondary path is specified, any IP packets that match the rule can be discarded when the primary path fails. The tertiary path is specified only if a secondary path is specified. The tertiary path is selected if both the primary and secondary paths have failed. If no tertiary path is specified, any IP packets that match the rule can be discarded when both the primary and secondary paths fail. Path selection may be generalized such that the path selection rule can select up to N paths where the Nth path is used only if the (N−1)th path fails. The example above where N=3 is merely illustrative, although N is typically a fairly small number. [0067]
  • By way of example, the operation of the [0068] system 100 is described as follows. First, a backbone connection is established between the PEPs 200 of two network gateways 120, 140 (i.e., the two spoofers), located at each end of the backbone link 130 for which TCP spoofing is desired. Whenever an IP host 110 initiates a TCP connection, the TSK 280 of the PEP 200 local to the IP host 110 checks its configured selective TCP spoofing rules. If the rules indicate that the connection should not be spoofed, the PEP 200 allows the TCP connection to flow end-to-end unspoofed. If the rules indicate that the connection should be spoofed, the spoofing PEP 200 locally responds to the IP host's TCP three-way handshake. In parallel, the spoofing PEP 200 sends a message across the backbone link 130 to its partner network gateway 140 asking it to initiate a TCP three-way handshake with the IP host 150 on its side of the backbone link 130. Data is then exchanged between the IP host 110, 150 with the PEP 200 of the network gateway 120 locally acknowledging the received data and forwarding it across the backbone link 130 via the high speed backbone connection, compressing the data as appropriate based on the configured compression rules. The priority of the TCP connection is determined when the connection is established. The BPK 282 can multiplex the connection with other received connections over a single backbone connection, the PK 284 determines the priority of the connection and the PSK 286 determines the path the connection is to take.
  • The [0069] PEP 200, as described above, advantageously improves network performance by allocating TCP spoofing-related resources, such as buffer space, control blocks, etc., only to TCP connections for which spoofing is beneficial; by spoofing the three-way handshake to decrease data response time; by reducing the number of ACKs which are transmitted by performing local acknowledgement and by acknowledging multiple TCP connections with a single ACK; by performing data compression to increase the amount of data that can be transmitted; by assigning priorities to different connections; and by defining multiple paths for connections to be made.
  • FIG. 3 shows an exemplary stack, which illustrates the relationship between the TCP stack and the [0070] PEP kernels 280, 282, 284, 286 of the present invention. The TSK 280 is primarily responsible for functions related to TCP spoofing. The TSK 280, in an exemplary embodiment, includes two basic elements: a transport layer that encompasses a TCP stack 303 and an IP stack 305; and a TCP spoofing application 301. The transport layer is responsible for interacting with the TCP stacks (e.g., 303) of IP hosts 110 connected to a local LAN interface 220 of a PEP 210.
  • The [0071] TSK 280 implements the TCP protocol, which includes the appropriate TCP state machines and terminates spoofed TCP connections. The TCP spoofing application 301 rests on top of the transport layer and act as the application that receives data from and sends data to the IP hosts 110 applications. Because of the layered architecture of the protocol, the TCP spoofing application 301 isolates the details of TCP spoofing from the transport layer, thereby allowing the transport layer to operate in a standard fashion.
  • As shown in FIG. 3, the [0072] TCP spoofing application 301 can also interface to the BPK 282 associated with the WAN interfaces 230. The BPK 282 performs backbone protocol maintenance, implementing the protocol by which the network gateways 120, 140 (in FIG. 1) communicate. The BPK 282 provides reliable delivery of data, uses a relatively small amount of acknowledgement traffic, and supports generic backbone use (i.e., use not specific to the TSK 280); one such example is the reliable data protocol (RDP).
  • The [0073] BPK 282 lies above the PK 284 and the PSK 286, according to an exemplary embodiment. The PK 284 is responsible for determining the priority of IP packets and then allocating transmission opportunities based on priority. The PK 284 can also control access to buffer space by controlling the queue sizes associated with sending and receiving IP packets. The PSK 286 determines which path an IP packet should take to reach its destination. The path selected by the PSK 286 can be determined applying path selection rules. PSK 286 may also determine which IP packet should be forwarded using an alternate path and which packets should be dropped when one or more primary paths fail.
  • FIGS. 4A and 4B show flow diagrams of the establishment of a spoofed TCP connection utilizing three-way handshake spoofing and without three-way handshake spoofing, respectively. The [0074] TCP Spoofing Kernel 280 establishes a spoofed TCP connection when a TCP <SYN> segment is received from its local LAN or a Connection Request message from its TSK peer. It is noted that the three-way handshake spoofing may be disabled to support an end to end maximum segment size (MSS) exchange, which is more fully described below. For the purpose of explanation, the spoofed TCP connection establishment process is described with respect to a local host 400, a local PEP end point 402, a remote PEP end point 404, and a remote host 406. As mentioned previously, the TSK 280 within each of the PEP end points 402 and 404 provides the spoofing functionality.
  • In [0075] step 401, the local host 400 transmits a TCP <SYN> segment to the local PEP end point 402 at a local LAN interface 220. When a TCP segment is received from the local LAN interface 220, the platform environment 402 determines whether there is already a TCP connection control block (CCB) assigned to the TCP connection associated with the TCP segment. If there is no CCB, the environment 402 checks whether the TCP segment is a <SYN> segment that is being sent to a non-local destination. If so, the <SYN> segment represents an attempt to bring up a new (non-local) TCP connection, and the environment 402 passes the segment to the TCP Spoofing Kernel 280 to determine the TCP connection's disposition. When a TCP <SYN> segment is received from the local LAN interface 220 for a new TCP connection, the TCP Spoofing Kernel 280 first determines if the connection should be spoofed. If the connection should be spoofed, TSK 280 uses (in an exemplary embodiment) the priority indicated in the selected TCP spoofing parameter profile and the peer index (provided by the environment 210 with the TCP <SYN> segment) to construct the handle of the backbone connection which should be used to carry this spoofed TCP connection. In the exemplary embodiment, the peer index is used as the 14 high order bits of the handle and the priority is used as the two low order bits of the handle. The backbone connection handle is then used (via the TSK control block (TCB) mapping table) to find the TCB associated with the backbone connection. TSK 280 of PEP end point 402 then checks whether the backbone connection is up. If the backbone connection is up, TSK 280 determines whether the number of spoofed TCP connections that are already using the selected backbone connection is still currently below the CCB resource limit. The CCB resource limit is the smaller of the local number of CCBs (provided as a parameter by the platform environment 210) and the peer number of CCBs (received in the latest TSK peer parameters (TPP) message from the TSK peer) available for this backbone connection. If the number of connections is still below the limit, TSK 280 of PEP end point 402 assigns a unique TCP connection identifier (e.g., a free CCB mapping table entry index) to the connection and calls the environment 210 to allocate a TCP connection control block for the connection.
  • [0076] TSK 280 of PEP end point 402 returns the TCP <SYN> segment back to the environment 210 to be forwarded unspoofed if any of the above checks fail. In other words, the following conditions result in the TCP connection being unspoofed. First, if the selective TCP spoofing rules indicate that the connection should not be spoofed. Also, there is no backbone connection for the priority at which the TCP connection should be spoofed (indicated by the absence of a TCB for the backbone connection). No spoofing is performed if the backbone connection is down. Additional, if the number of spoofed TCP connections that are already using the backbone connection reaches or exceeds a predetermined threshold, then no spoofing is performed. Further, if there is no CCB mapping table entry available or there is no CCB available from the CCB free pool, then the TCP connection is forwarded unspoofed. For the case in which there is no backbone connection, TSK 280 of PEP end point 402 may also post an event to alert the operator that there is a mismatch between the configured TCP spoofing parameter profiles and the configured set of backbone connections.
  • Continuing with the example, if all of the above checks pass, [0077] TSK 280 of PEP end point 402 writes the backbone connection handle into the buffer holding the TCP <SYN> segment. It is noted that this is not done until a CCB is successfully allocated by the platform environment 402, because the environment does not count the buffer unless a CCB is successfully allocated. TSK 280 then copies the parameters from the selected TCP spoofing parameter profile into the CCB. Consequently, relevant information (e.g., the maximum segment size that is advertised by the host (if smaller than the configured MSS), the initial sequence number, and etc.) is copied out of the TCP <SYN> segment and stored in the CCB. It is noted that the source and destination IP addresses and source and destination TCP port numbers will already have been placed into the CCB by the platform environment 402 when the CCB was allocated; the environment 402 uses this information to manage CCB hash function collisions.
  • After allocating and setting up the CCB, the [0078] TCP Spoofing Kernel 280 of PEP end point 402 constructs a Connection Request (CR) message, per step 403, and sends it to its TSK peer associated with the remote PEP end point 404. The CR message basically contains all of the information extracted from the TCP spoofing parameter profile and the TCP <SYN> segment and stored in the local CCB, e.g., the source and destination IP addresses, the source and destination TCP port numbers, the MSS value, etc., with the exception of fields that have only local significance, such as the initial sequence number. (The IP addresses and TCP port numbers are placed into a TCP connection header.) In other words, the CR message contains all of the information that the peer TSK of PEP end point 404 requires to set up its own CCB. To complete the local connection establishment, the TCP Spoofing Kernel 280 of the local PEP end point 402 sends a TCP <SYN,ACK> segment to the local host 400 in response to the <SYN> segment received, per step 405. TSK 280 of PEP end point 402 performs step 405 simultaneously with the step of sending the Connection Request message (i.e., step 403), if three-way handshake spoofing is enabled. Otherwise, TSK 280 of 402 waits for a Connection Established (CE) message from its TSK peer of the remote PEP end point 404 before sending the <SYN,ACK> segment. In an exemplary embodiment, TSK 280 of PEP end point 402 selects a random initial sequence number (as provided in IETF (Internet Engineering Task Force) RFC 793, which is incorporated herein by reference in its entirety) to use for sending data.
  • If three-way handshake spoofing is disabled, the MSS value sent in the <SYN,ACK> segment is set equal to the MSS value received in the CE message. If three-way handshake spoofing is enabled, the MSS value is determined from the TCP spoofing parameter profile selected for the connection (and the configured path maximum transmission unit (MTU)). For this case, [0079] TSK 280 of PEP end point 402 then compares the MSS value received in the Connection Established message, when it arrives, to the value it sent to the local host in the TCP <SYN,ACK> segment. If the MSS value received in the CE message is smaller than the MSS value sent to the local host, a maximum segment size mismatch exists. (If an MSS mismatch exists, TSK may need to adjust the size of TCP data segments before sending them.) After sending the TCP <SYN,ACK> segment (step 405), TSK 280 of the local PEP end point 402 is ready to start accepting data from the local host 400. In step 407, the local host 400 transmits an <ACK> segment to the TSK 280 of PEP end point 402; thereafter, the local host forwards, as in step 409 data to the TSK 280 of PEP end point 402 as well. When three-way handshake spoofing is being used, TSK 280 does not need to wait for the Connection Established message to arrive from its TSK peer before accepting and forwarding data. As seen in FIG. 4A, in step 411, TSK 280 of the local PEP end point 402 sends an <ACK> segment to the local host and simultaneously sends the TCP data (TD) from the local host 400 to the peer TSK of PEP end point 404 (per step 413) prior to receiving a CE message from the peer TSK of PEP end point 404.
  • However, [0080] TSK 280 of PEP end point 402 does not accept data from its TSK peer of PEP end point 404 until after the CE message has been received. TSK 280 of PEP end point 402 does not forward any data received from its TSK peer of PEP end point 404 to the local host 400 until it has received the TCP <ACK> segment indicating that the local host has received the <SYN,ACK> segment (as in step 407).
  • When a Connection Request message is received from a peer TSK (step [0081] 403), the TCP Spoofing Kernel 280 allocates a CCB for the connection and then stores all of the relevant information from the CR message in the CCB. TSK 280 of PEP end point 404 then uses this information to generate a TCP <SYN> segment, as in step 415, to send to the remote host 406. The MSS in the <SYN> segment is set to the value received from the TSK peer of PEP end point 404. When the remote host responds with a TCP <SYN,ACK> segment (step 417), TSK 280 of PEP end point 402 sends a Connection Established message to its TSK peer of the remote PEP end point 404 (step 419), including in the CE message the MSS that is sent by the local host in the <SYN,ACK> segment. TSK 280 of PEP end point 402 also responds, as in step 421, with a TCP <ACK> segment to complete the local three-way handshake. The peer TSK of PEP end point 404 then forwards the data that is received from TSK 280 to the host, per step 423. Concurrently, in step 425, the remote host 406 sends data to the peer TSK of PEP end point 404, which acknowledges receipt of the data by issuing an <ACK> segment to the remote PEP end point 404, per step 427. Simultaneously with the acknowledgement, the data is sent to TSK 280 of PEP end point 402 (step 429).
  • At this point, [0082] TSK 280 is ready to receive and forward data from either direction. TSK 280 forwards the data, as in step 431 to the local host, which, in turn, sends an <ACK> segment (step 433). If the data arrives from its TSK peer before a <SYN,ACK> segment response is received from the local host, the data is queued and then sent after the <ACK> segment is sent in response to the <SYN,ACK> segment (when it arrives).
  • Turning now to FIG. 4B, a spoofed TCP connection is established with the three-way handshake spoofing disabled. Under this scenario, the [0083] local host 400 transmits a TCP <SYN> segment, as in step 451, to the TSK 280 within the local PEP end point 402. Unlike the TCP connection establishment of FIG. 4A, the local PEP end point 402 does not respond to the a TCP <SYN> segment with a <SYN,ACK> segment, but merely forwards a CR message to the remote PEP end point 404 (step 453). Next, in step 455, sends a TCP <SYN> segment to the remote host 406. In response, the remote host 406 transmit a TCP <SYN,ACK> segment back to the remote PEP end point 404 (per step 457). Thereafter, the remote PEP end point 404, as in step 459, forwards a CE message to the local PEP end point 402, which subsequently issues a <SYN,ACK> segment to the local host 400, per step 461. Simultaneous with step 459, the remote PEP end point 404 issues an <ACK> segment to the remote host 406 (step 463).
  • Upon receiving the <ACK> segment, the [0084] remote host 406 may begin transmission of data, as in step 465. Once the PEP end point 404 receives the data from the remote host 406, the remote PEP end point 404 simultaneously transmits, as in step 467, the TD message to the local PEP end point 402 and transmits an <ACK> segment to the remote host 406 to acknowledge receipt of the data (step 469).
  • Because the [0085] local host 400 has received a <SYN,ACK> segment from the local PEP end point 402, the local host 400 acknowledges the message, per step 471. Thereafter, the local host 400 transmits data to the local PEP end point 402. In this example, before the local PEP end point 402 receives the data from the local host 400, the local PEP end point 402 forwards the data that originated from the remote host 406 via the TD message (step 467) to the local host 400, per step 475.
  • In response to the data received (in step [0086] 473), the local PEP end point 402 issues an <ACK> segment, as in step 477, and forwards the data in a TD message to the remote PEP end point 404, per step 479. The local host 400 responds to the received data of step 475 with an <ACK> segment to the local PEP end point 402 (step 481). The remote PEP end point 404 sends the data from the local host 400, as in step 483, upon receipt of the TD message. After receiving the data, the remote host 406 acknowledges receipt by sending an <ACK> segment back to the remote PEP end point 404, per step 485.
  • FIG. 5 shows the flow of packets with the PEP architecture, according to one embodiment of the present invention. As shown, a communication system [0087] 500 includes a hub site (or local) PEP end point 501 that has connectivity to a remote site PEP end point 503 via a backbone connection. By way of example, at the hub site (or local site) and at each remote site, PEP end points 501 and 503 handle IP packets. PEP end point 501 includes an internal IP packet routing module 501 a that receives local IP packets and exchanges these packets with a TSK 501 b and a BPK 501 c. Similarly, the remote PEP end point 503 includes an internal IP packet routing module 503 a that is in communication with a TSK 503 b and a BPK 503 c. Except for the fact that the hub site PEP end point 501 may support many more backbone protocol connections than a remote site PEP end point 503, hub and remote site PEP processing is symmetrical.
  • For local-to-WAN traffic (i.e., upstream direction), the [0088] PEP end point 501 receives IP packets from its local interface 220 (FIG. 2). Non-TCP IP packets are forwarded (as appropriate) to the WAN interface 230 (FIG. 2). TCP IP packets are internally forwarded to TSK 501 b. TCP segments which belong to connections that are not be spoofed are passed back by the spoofing kernel 501 b to the routing module 501 a to be forwarded unmodified to the WAN interface 230. For spoofed TCP connections, the TCP spoofing kernel 501 a locally terminates the TCP connection. TCP data that is received from a spoofed connection is passed from the spoofing kernel 501 a to the backbone protocol kernel 501 c, and then multiplexed onto the appropriate backbone protocol connection. The backbone protocol kernel 501 c ensures that the data is delivered across the WAN.
  • For WAN-to-local traffic (i.e., downstream direction), the remote [0089] PEP end point 503 receives IP packets from its WAN interface 230 (FIG. 2). IP packets that are not addressed to the end point 503 are simply forwarded (as appropriate) to the local interface 220 (FIG. 2). IP packets addressed to the end point 503, which have a next protocol header type of “PBP” are forwarded to the backbone protocol kernel 503 c. The backbone protocol kernel 503 c extracts the TCP data and forwards it to the TCP spoofing kernel 503 b for transmission on the appropriate spoofed TCP connection. In addition to carrying TCP data, the backbone protocol connection is used by the TCP spoofing kernel 501 b to send control information to its peer TCP spoofing kernel 503 b in the remote PEP end point 503 to coordinate connection establishment and connection termination.
  • Prioritization may be applied at four points in the system [0090] 500 within routing 501 a and TSK 501 b of PEP end point 501, and within routing 503 a, and TSK 503 b of PEP end point 503. In the upstream direction, priority rules are applied to the packets of individual TCP connections at the entry point to the TCP spoofing kernel 501 b. These rules allow a customer to control which spoofed applications have higher and lower priority access to spoofing resources. Upstream prioritization is also applied before forwarding packets to the WAN. This allows a customer to control the relative priority of spoofed TCP connections with respect to unspoofed TCP connections and non-TCP traffic (as well as to control the relative priority of these other types of traffic with respect to each other). On the downstream side, prioritization is used to control access to buffer space and other resources in the PEP end point 503, generally and with respect to TCP spoofing.
  • At the hub (or local) site, the [0091] PEP end point 501 may be implemented in a network gateway (e.g. an IP Gateway), according to one embodiment of the present invention. At the remote site, the PEP end point 503 may be implemented in the remote site component, e.g. a satellite terminal such as a Multimedia Relay, a Multimedia VSAT or a Personal Earth Station (PES) Remote.
  • The architecture of system [0092] 500 provides a number of advantages. First, TCP spoofing may be accomplished in both upstream and downstream directions. Additionally, the system supports spoofing of TCP connection startup, and selective TCP spoofing with only connections that can benefit from spoofing actually spoofed. Further, system 500 enables prioritization among spoofed TCP connections for access to TCP spoofing resources (e.g., available bandwidth and buffer space). This prioritization is utilized for all types of traffic that compete for system resources.
  • With respect to the backbone connection, the system [0093] 500 is suitable for application to a satellite network as the WAN. That is, the backbone protocol is optimized for satellite use in that control block resource requirements are minimized, and efficient error recovery for dropped packets are provided. The system 500 also provides a feedback mechanism to support maximum buffer space resource efficiency. Further, system 500 provides reduced acknowledgement traffic by using a single backbone protocol ACK to acknowledge the data of multiple TCP connections.
  • FIG. 6 illustrates the flow of IP packets through a PEP end point, according to an embodiment of the present invention. When IP packets are received at the [0094] local LAN interface 220, the PEP end point 210 determines (as shown by decision point A), whether the packets are destined for a host that is locally situated; if so, the IP packets are forwarded to the proper local LAN interface 220. If the IP packets are destined for a remote host, then the PEP end point 210 decides, per decision point B, whether the traffic is a TCP segment. If the PEP end point 210 determines that in fact the packets are TCP segments, then the TSK 280 determines whether the TCP connection should be spoofed. However, if the PEP end point 210 determines that the packets are not TCP segments, then the BPK 282 processes the traffic, along with the PK 284 and the PSK 286 for eventual transmission out to the WAN. It should be noted that the BPK 282 does not process unspoofed IP packets; i.e., the packets flow directly to PK 284. As seen in FIG. 6, traffic that is received from the WAN interface 230 is examined to determine whether the traffic is a proper PBP segment (decision point D) for the particular PEP end point 210; if the determination is in the affirmative, then the packets are sent to the BPK 282 and then the TSK 280.
  • Routing support includes routing between the ports of the PEP End Point [0095] 210 (FIG. 2), e.g., from one Multimedia VSAT LAN port to another. Architecturally, the functionalities of TCP spoofing, prioritization and path selection, fit between the IP routing functionality and the WAN. PEP functionality need not be applied to IP packets which are routed from local port to local port within the same PEP End Point 210. TCP spoofing, prioritization and path selection are applied to IP packets received from a local PEP End Point interface that have been determined to be destined for another site by the routing function.
  • FIG. 7 shows the relationship between PEP End Points and PEP End Point profiles, in accordance with an embodiment of the present invention. PEP parameters are primarily configured via a set of [0096] profiles 701 and 703, which are associated with one or more PEP end points 705. In an exemplary embodiment, PEP parameters are configured on a per PEP End Point basis, such as whether TCP spoofing is globally enabled. These parameters are configured in the PEP End Point profiles 701 and 703. It is noted that parameters that apply to specific PEP kernels may be configured via other types of profiles. Profiles 701 and 703 are a network management construct; internally, a PEP End Point 705 processes a set of parameters that are received via one or more files.
  • Whenever the [0097] PEP End Point 705 receives new parameters, the platform environment compares the new parameters to the existing parameters, figures out which of the PEP kernels are affected by the parameter changes, and then passes the new parameters to the affected kernels. In an exemplary embodiment, all parameters are installed dynamically. With the exception of parameters that are component specific (such as the IP addresses of a component), all parameters may be defined with default values.
  • As mentioned previously, the [0098] PEP end point 210 may be implemented in a number of different platforms, in accordance with the various embodiments of the present invention. These platforms may include an IP gateway, a Multimedia Relay, a Multimedia VSAT (Very Small Aperture Terminal), and a Personal Earth Station (PES) Remote, as shown in FIGS. 8-11, respectively. In general, as discussed in FIG. 2, the PEP end point 210 defines a local LAN interface 220 an interface through which the PEP End Point 210 connects to IP hosts located at the site. A WAN interface 230 is an interface through which the PEP End Point 210 connects to other sites. It is noted that a WAN interface 230 can physically be a LAN port. FIGS. 8-11, below, describe the specific LAN and WAN interfaces of the various specific PEP End Point platforms. The particular LAN and WAN interfaces that are employed depend on which remote site PEP End Points are being used, on the configuration of the hub and remote site PEP End Points and on any path selection rules which may be configured.
  • FIG. 8 shows the interfaces of the PEP end point implemented as an IP gateway, according to one embodiment of the present invention. By way of example, an [0099] IP Gateway 801 has a single local LAN interface, which is an enterprise interface 803. The IP Gateway 803 employs two WAN interfaces 805 for sending and receiving IP packets to and from remote site PEP End Points: a backbone LAN interface and a wide area access (WAA) LAN interface.
  • The [0100] backbone LAN interface 805 is used to send IP packets to remote site PEP End Points via, for example, a Satellite Gateway (SGW) and a VSAT outroute. A VSAT outroute can be received directly by Multimedia Relays (FIG. 9) and Multimedia VSATs (FIG. 10) (and is the primary path used with these End Points); however, IP packets can be sent to a PES Remote (FIG. 11) via a VSAT outroute.
  • FIG. 9 shows a Multimedia Relay implementation of a PEP end point, in accordance with an embodiment of the present invention. A Multimedia Relay has two or three local LAN interfaces [0101] 903. A Multimedia Relay 901 has up to two WAN interfaces 905 for sending IP packets to hub site PEP End Points: one of its LAN interfaces and a PPP serial port interface, and four or five interfaces for receiving IP packets from hub site PEP End Points, a VSAT outroute, all of its LAN interfaces, and a PPP serial port interface. It is noted that a PPP (Point-to-Point Protocol) serial port interface and a LAN interface are generally not be used at the same time.
  • A [0102] Multimedia Relay 901 supports the use of all of its LAN interfaces 903 at the same time for sending and receiving IP packets to and from hub site PEP End Points. Further, a Multimedia Relay 905 supports the use of a VADB (VPN Automatic Dial Backup) serial port interface for sending and receiving IP packets to and from the hub site PEP End Points.
  • FIG. 10 shows a Multimedia VSAT implementation of the PEP end point, according to one embodiment of the present invention. A [0103] Multimedia VSAT 1001, in an exemplary embodiment, has two local LAN interfaces 1003. Support for one or more local PPP serial port interfaces may be utilized. The Multimedia VSAT 1001 has two WAN interfaces 1005 for sending IP packets to hub site PEP End Points: a VSAT inroute and one of its LAN interfaces. The Multimedia VSAT 1001 thus has three interfaces for receiving IP packets from hub site PEP End Points, the VSAT outroute and both of its LAN interfaces 1003. A Multimedia VSAT 1003 may support uses of both of its LAN interfaces 1003 at the same time for sending and receiving IP packets to and from hub site PEP End Points. The Multimedia VSAT 1003 further supports the use of a VADB serial port interface for sending and receiving IP packets to and from the hub site PEP End Points.
  • FIG. 11 shows a PES Remote implementation of a PEP end point, according to one embodiment of the present invention. A [0104] PES Remote 1101 may have a local LAN interface and/or several local IP (e.g. PPP, SLIP, etc.) serial port interfaces, collectively denoted as LAN interfaces 1103. The particular LAN interfaces 1103 depend on the specific PES Remote platform. PES Remote 1101, in an exemplary embodiment, has up to five WAN interfaces 1105 for sending IP packets to hub site PEP End Points, an ISBN inroute, a LAN interface, a VADB serial port interface, a Frame Relay serial port interface and an IP serial port interface, and up to five existing interfaces for receiving IP packets from hub site PEP End Points: an ISBN outroute, a LAN interface, a VADB serial port interface, a Frame Relay serial port interface, and an IP serial port interface. The physical Frame Relay serial port interface may be supporting multiple Permanent Virtual Circuits (PVCs); some of which are equivalent to local interfaces 1103 and some of which are WAN interfaces 1105.
  • FIG. 12 shows an architecture of the PEP end point in which redundancy is provided at the local site, in accordance with an embodiment of the present invention. A local site PEP end point [0105] 1201 (or gateway), within a communications system 1200, serves as the primary gateway, whereby a remote site gateway 1203 maintains connectivity with the local site gateway 1201 over backbone connections, as described with respect to FIG. 2. In an exemplary embodiment, the gateways 1201 and 1203 may employ the Internet Protocol (IP) to communicate. Under normal operating conditions, the remote site PEP end point 1203 coordinates with the primary hub site gateway 1201 to establish spoofed TCP connections. In the event of some failure (e.g., hardware and/or software failure), another local site gateway 1205 is utilized as the redundant gateway; that is, a gateway redundancy switch is performed. According to one embodiment of the present invention, the remote gateway 1203 may not be aware of the redundancy switch; in fact, the remote gateway 1203 does not know that the local gateway 1201 is configured for redundancy. In this embodiment, the redundant gateway 1205 assumes the IP addresses of the primary gateway 1201. In an alternative embodiment, the remote site gateway 1203 may be informed of the redundancy switch because the redundant gateway 1205 utilizes different addresses.
  • It is recognized that the mechanics of gateway redundancy switch handling has a bias against unspoofed TCP connections in a network that utilizes a mix of both spoofed and unspoofed connections. After a redundancy switch, unspoofed TCP connections may be blocked (for several minutes) during the initial startup period to allow spoofed TCP connections to recover properly. The present invention, according to one embodiment, addresses this problem by modifying the handling of unspoofed TCP connections such that, during this initial startup period, the [0106] TCP Spoofing Kernel 280 uses its selective TCP spoofing rules to determine the particular TCP segments that belong to spoofed versus unspoofed TCP connections. This information may then be used to allow the unspoofed TCP segments to be forwarded, instead of blocked.
  • In an exemplary embodiment, [0107] system 1200 need not support redundancy of the components of the remote site. However, both systems support redundancy of local site components. If a redundancy switch of a local site PEP End Point (i.e. gateway) occurs, there is no requirement that TCP connections currently being spoofed be unaffected. It is noted that all of the backbone connections from all of the remote site PEP End Points 1203 that used the failed gateway are capable of automatically switching to another (redundant) gateway 1205; this is accomplished by using PEP End Point IP addresses that are shared by both gateways 1201, 1205. As a result of the redundancy switch, all of the TCP connections that were being spoofed by the primary gateway 1201 will eventually terminate (because the redundant gateway 1205 has no TCP spoofing state for these connections). This termination of the spoofed TCP connections may take some time to take effect, thereby prolonging the impact on the network as a result of the redundancy switch. Therefore, the redundant gateway 1205, according to an embodiment of the present invention, is capable of performing startup processing, which is designed to expedite restart of the TCP connections, as more fully described below.
  • When a gateway redundancy switch occurs, all of the backbone connections are restarted by the [0108] redundant gateway 1205. The gateway platform environment 1205 opens PBP connections as active, resulting in PBP <SYN> segments being sent by the PEP Backbone Protocol Kernel 282 for every connection. The remote site PEP End Points 1203, upon receiving the PBP <SYN> segments, are alerted to the fact that the backbone connections have failed. As a result, a TCP <RST> segment is sent for every TCP connection that is being spoofed. The above behavior advantageously results in a relatively gracefully shutdown of the remote half of the spoofed TCP connections that are affected by a gateway redundancy switch.
  • However, the hub half of the spoofed TCP connections remain open. As noted above, because the [0109] redundant gateway 1205 has no state stored for the spoofed TCP connections, the gateway 1205 does not know that these connections are spoofed TCP connections. Therefore, any TCP segments that are sent by the local host(s) (except <SYN> segments) may be forwarded unspoofed by the gateway 1205. Besides wasting bandwidth, sending such unspoofed TCP segments to the remote site hosts is undesirable because the reaction by the receiving hosts is not completely predictable. In many cases, the hosts will respond with a TCP <RST> segment which will knock down the local site host's TCP connection. But, in other cases, the remote site hosts may just ignore these segments. This results in the hub side of the TCP connection still being open and more segments being needlessly sent. Other possibilities also exist. For example, if the PBP <SYN> segment for a particular backbone connection is lost, the remote site local host might not yet have had its half of the TCP connection terminated. Then, the TCP segment from the hub arrives on a still open TCP connection. The consequences of this depend on how disjoint the sequence number space is between the two halves of the spoofed connection. In most cases, the segments get discarded. But, it is not impossible that this could lead to the delivery of out of sequence data to the application in the host. To avoid all of the above problems, the gateway platform environment 1205 implements a startup delay function for unspoofed TCP segments.
  • FIGS. 13A and 13B shows a flow chart of the unspoofed startup delay processing performed by a gateway, in accordance with an embodiment of the present invention. In [0110] step 1301, the redundancy switch occurs. Next, the redundant gateway 1205 determines whether the TCP spoofing function has been globally enabled, per step 1307; if the TCP spoofing function has been enabled, then a delay timer is started, per step 1311.
  • As seen in FIG. 3B, an IP packet is received by the [0111] gateway 1205, as in step 1319. The gateway 1205 then determines whether the received packets are TCP or non-TCP, as in step 1303. It is noted that the startup delay, according to an embodiment of the present invention, applies to TCP segments; thus, non-TCP IP packets are forwarded normally without any startup delay processing, regardless of the setting of the global TCP spoofing parameter (as in step 1305). If the packets are non-TCP packets, the redundant gateway 1205 checks whether the TCP spoofing function has been globally enabled, per step 1321. It is noted that the gateway platform environment 1205 only invokes the “unspoofed startup delay” processing if TCP spoofing is globally enabled. However, if TCP spoofing is globally disabled, all TCP segments are forwarded unspoofed, as in step 1309, without performing the delay processing.
  • If the TCP spoofing is globally enabled, then the [0112] gateway 1205 examines the delay timer to determine whether the timer has expired, as in step 1315. The gateway 1205 is configured with an “unspoofed startup delay” timeout value. The delay value is configurable, largely because of its potential impact on unspoofed TCP connections. Accordingly, at startup the gateway 1205 starts the delay timer with this value. While the timer is running, the gateway environment 1205 terminates unspoofed TCP connections on the hub side, as in step 1313, by forwarding all TCP segments—except <SYN> segments—for which it has no CCB (which will be all segments at first) to a special TCP Spoofing Kernel utility function, as determined per step 1323. This utility function, tsk_reset_tcp_connection( ), responds to any TCP segment provided to it by the environment 1205 by sending a TCP <RST> segment to the local host, effectively tearing down the TCP connection. In this manner, the unspoofed TCP connections can be terminated (step 1313). This reset function is more fully described below.
  • The [0113] gateway 1205 continues to forward TCP <SYN> segments for which no CCB exists to the normal TSK new connection entry point. However, if TSK returns the <SYN> segment to be forwarded unspoofed (e.g., because the appropriate backbone connection is not up yet) while the delay timer is still running, the environment will discard the segment rather than forward it. After the timer expires, the gateway environment 210 processes TCP segments normally, per step 1317. The above approach has the benefit that it does not delay restarting spoofed TCP connections. As soon as the backbone connection comes up, TSK 280 of gateway 1205 accepts a TCP <SYN> segment for spoofing and allocates a CCB for the TCP connection. With a CCB in place, the environment 1205 ceases forwarding TCP segments from that TCP connection to the TCP connection “reset” function.
  • As mentioned above, the value of the delay timer may be configurable depending on the mix of traffic. If, in general, all TCP connections are intended to be spoofed, the delay timer can be set to a relatively large value to ensure that all of the hub side spoofed TCP connections that are left over from before a redundancy switch are handled. In the scenario whereby unspoofed TCP connections exist, either because of selective TCP spoofing rules or because of a lack of TCP connection control block resources, a smaller value for the delay timer might be warranted. It is noted that discarding TCP segments for unspoofed TCP connections during the startup delay period results in the tear down of these connections if the startup delay period (i.e., timer value) is too long. [0114]
  • As evident from the above discussion, if a local site PEP End Point (i.e., gateway) redundancy switch occurs, all of the backbone connections of the gateway will restart. Under this condition, only the TCP Spoofing Kernels in the remote site [0115] PEP End Points 1203 is aware of the restart so that they may terminate all of their spoofed TCP connections. The TCP Spoofing Kernel 280 of the now switched in gateway (i.e., redundant gateway 1205) views this as normal connection startup, such that the TSK 280 will not have any state stored for the TCP connections that had been being spoofed by the now switched out gateway 1201. Therefore, to aid the gateway platform environment 1205 in handling this scenario, TSK 280 provides a utility function that the environment 1205 can use to send TCP <RST> segments to terminate TCP connections. The use of this utility function, which is a reset TCP connection command, is described below.
  • The reset function, tsk_reset_tcp connection( ), is a utility procedure that is provided by the [0116] TCP Spoofing Kernel 280, as called by the platform environment 1205 to request that a TCP <RST> segment be sent in response to a TCP segment that is received from a local LAN port. The procedural interface of the TSK 280 takes a single parameter, e.g., a pointer, to the received IP packet containing the TCP segment. tsk_reset_tcp_connection( ) is used by the local site PEP End Point platform environment 1205 to tear down spoofed TCP connections after a redundancy switch. The tsk_reset_tcp_connection( ) results in an allocation of a buffer from the environment 1205, and the building of a TCP <RST> segment in the buffer (using the IP addresses and TCP port numbers, reversed, extracted from the received TCP segment); this command then forwards the <RST> segment to the environment 1205 for transmission. Because there is no backbone connection that is associated with the segment being discarded, TSK 280 allocates the WAN to LAN buffer against a generic 0xFFFF “backbone connection”, for example. The original received TCP segment is then discarded.
  • In an alternative approach, the redundant gateway [0117] 1205 (i.e., backup PEP End Point) may track the state of the primary gateway 1201. However, this approach introduces some complexity, as real time tracking of spoofed connection state by the redundant gateway 1205 is required. Additionally, under this approach, no matter how fast the communication is between the two gateways 1201 and 1205, there exists a window of opportunity, albeit small, in which a failure can occur in the primary gateway 1201 before the primary gateway 1201 can pass updated state information to the redundant gateway 1205, leading to a loss of state. Therefore, the redundant gateway 1205 is required to handle connections which the redundant gateway 1205 detects as unspoofed, but which may actually have been spoofed be the primary gateway 1201.
  • FIG. 14 illustrates a [0118] computer system 1401 upon which an embodiment according to the present invention may be implemented. Such a computer system 1401 may be configured as a server to execute code that performs the PEP functions of the PEP end point 210 as earlier discussed. Computer system 1401 includes a bus 1403 or other communication mechanism for communicating information, and a processor 1405 coupled with bus 1403 for processing the information. Computer system 1401 also includes a main memory 1407, such as a random access memory (RAM) or other dynamic storage device, coupled to bus 1403 for storing information and instructions to be executed by processor 1405. In addition, main memory 1407 may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor 1405. Notably, TCP spoofing control blocks may be stored in main memory 1407. Computer system 1401 further includes a read only memory (ROM) 1409 or other static storage device coupled to bus 1403 for storing static information and instructions for processor 1405. A storage device 1411, such as a magnetic disk or optical disk, is provided and coupled to bus 1403 for storing information and instructions.
  • [0119] Computer system 1401 may be coupled via bus 1403 to a display 1413, such as a cathode ray tube (CRT), for displaying information to a computer user. An input device 1415, including alphanumeric and other keys, is coupled to bus 1403 for communicating information and command selections to processor 1405. Another type of user input device is cursor control 1417, such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processor 1405 and for controlling cursor movement on display 1413.
  • Embodiments are related to the use of [0120] computer system 1401 to perform the PEP functions of the PEP end point 210. According to one embodiment, this automatic update approach is provided by computer system 1401 in response to processor 1405 executing one or more sequences of one or more instructions contained in main memory 1407. Such instructions may be read into main memory 1407 from another computer-readable medium, such as storage device 1411. Execution of the sequences of instructions contained in main memory 1407 causes processor 1405 to perform the process steps described herein. One or more processors in a multiprocessing arrangement may also be employed to execute the sequences of instructions contained in main memory 1407. In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions. Thus, embodiments are not limited to any specific combination of hardware circuitry and software.
  • The term “computer-readable medium” as used herein refers to any medium that participates in providing instructions to [0121] processor 1405 for execution of the PEP functions of the PEP end point 210. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media includes, for example, optical or magnetic disks, such as storage device 1411. Volatile media includes dynamic memory, such as main memory 1407. Transmission media includes coaxial cables, copper wire and fiber optics, including the wires that comprise bus 1403. Transmission media can also take the form of acoustic or light waves, such as those generated during radio wave and infrared data communications.
  • Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, or any other magnetic medium, a CD-ROM, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave as described hereinafter, or any other medium from which a computer can read. [0122]
  • Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to [0123] processor 1405 for execution. For example, the instructions may initially be carried on a magnetic disk of a remote computer. The remote computer can load the instructions relating to execution of the PEP functions of the PEP end point 210 into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to computer system 1401 can receive the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal. An infrared detector coupled to bus 1403 can receive the data carried in the infrared signal and place the data on bus 1403. Bus 1403 carries the data to main memory 1407, from which processor 1405 retrieves and executes the instructions. The instructions received by main memory 1407 may optionally be stored on storage device 1411 either before or after execution by processor 1405.
  • [0124] Computer system 1401 also includes one or more communication interfaces 1419 coupled to bus 1403. Communication interfaces 1419 provide a two-way data communication coupling to network links 1421 and 1422, which are connected to a local area network 14(LAN) 1423 and a wide area network (WAN) 1424, respectively. The WAN 1424, according to one embodiment of the present invention, may be a satellite network. For example, communication interface 1419 may be a network interface card to attach to any packet switched LAN. As another example, communication interface 1419 may be an asymmetrical digital subscriber line (ADSL) card, an integrated services digital network (ISDN) card, a cable modem, or a modem to provide a data communication connection to a corresponding type of telephone line. Wireless links may also be implemented. In any such implementation, communication interface 1419 sends and receives electrical, electromagnetic or optical signals that carry digital data streams representing various types of information.
  • [0125] Network link 1421 typically provides data communication through one or more networks to other data devices. For example, network link 1421 may provide a connection through local area network 1423 to a host computer 1425 or to data equipment operated by an Internet Service Provider (ISP) 1427. ISP 1427 in turn provides data communication services through the Internet 505. In addition, LAN 1423 is linked to an intranet 1429. The intranet 1429, LAN 1423 and Internet 505 all use electrical, electromagnetic or optical signals that carry digital data streams. The signals through the various networks and the signals on network link 1421 and through communication interface 1419, which carry the digital data to and from computer system 1401, are exemplary forms of carrier waves transporting the information.
  • [0126] Computer system 1401 can send messages and receive data, including program code, through the network(s), network link 1421 and communication interface 1419. In the Internet example, a server 1431 might transmit a requested code for an application program through Internet 505, ISP 1427, LAN 1423 and communication interface 1419. The received code may be executed by processor 1405 as it is received, and/or stored in storage device 1411, or other non-volatile storage for later execution. In this manner, computer system 1401 may obtain application code in the form of a carrier wave. Computer system 1401 can transmit notifications and receive data, including program code, through the network(s), network link 1421 and communication interface 1419.
  • The techniques described herein provide several advantages over prior approaches to improving network performance, particularly in a packet switched network such as the Internet. A local PEP end point and a remote PEP end point communicate to optimize the exchange of data through a TCP spoofing functionality. In the event of a failure of the local PEP end point, a redundancy switch occurs, whereby the remote PEP end point directs its communication to another local PEP end point that serves as a redundant gateway. The redundant gateway is configured to minimize the blocking of unspoofed TCP connections through the use of a reset function in conjunction with a delay timer. The reset function effectively terminates the unspoofed TCP connections on the local side for the duration of the delay timer period. This approach advantageously avoids delaying the restarting of spoofed TCP connections. [0127]
  • Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein. [0128]

Claims (35)

What is claimed is:
1. A method for performing redundancy switching from a first platform to a second platform, the method comprising:
identifying a message received over a connection according to a prescribed protocol as an unspoofed message;
terminating, during a predetermined period, the connection based upon the identifying step; and
restarting a spoofed connection between the second platform and a host.
2. The method according to claim 1, further comprising:
invoking a reset function, wherein the reset function transmits a reset message to a local host that forwarded the message to terminate the connection.
3. The method according to claim 1, further comprising:
determining whether the predetermined period has expired; and
forwarding unspoofed messages to a remote platform based upon the determining step.
4. The method according to claim 1, wherein the prescribed protocol is the Transmission Control Protocol, the method further comprising:
determining whether global TCP spoofing is enabled; and
selectively forward TCP segments unspoofed to a remote platform.
5. The method according to claim 1, further comprising:
establishing a backbone connection from the second platform to a remote platform; and
forwarding a spoofed message over the backbone connection to a remote host.
6. The method according to claim 5, wherein the backbone connection in the establishing step includes a space link over a satellite network.
7. The method according to claim 1, further comprising:
forwarding messages associated with another protocol to a remote platform irrespective of the predetermined period.
8. A communication system comprising:
a first platform configured to communicate with a remote platform; and
a second platform configured to communicate with the remote platform upon failure of the first platform to communicate with the remote platform, the second platform being configured to identify a message received from a local host over a connection according to a prescribed protocol as an unspoofed message, wherein the second platform terminates, during a predetermined period, the connection in response to the identified message.
9. The system according to claim 8, wherein the second platform restarts a spoofed connection with another host.
10. The system according to claim 8, wherein the second platform has a timer to measure the predetermined period, the second platform being configured to determine whether the timer has expired and forwarding unspoofed messages to the remote platform.
11. The system according to claim 8, wherein the prescribed protocol is the Transmission Control Protocol, the second platform being configured to determine whether global TCP spoofing is enabled and to selectively forward TCP segments unspoofed to the remote platform.
12. The system according to claim 8, further comprising:
a backbone connection providing connectivity between the second platform and the remote platform, wherein the second platform configured to forward a spoofed message over the backbone connection.
13. The system according to claim 12, wherein the backbone connection is established over a satellite network.
14. The system according to claim 8, wherein the second platform is configured to forward messages associated with another protocol to the remote platform irrespective of the predetermined period.
15. A communication gateway for providing redundant communication in a communication system having a remote platform, the gateway comprising:
a communication interface configured to receive a message from a host over a connection according to a prescribed protocol; and
a processor coupled to the communication interface and configured to identify the message received as an unspoofed message, and configured to terminate, during a predetermined period, the connection based upon the identified message, the processor being configured to restart a spoofed connection with another host.
16. The gateway according to claim 15, wherein the processor is configured to invoke a reset function to transmit a reset message to the host via the communication interface to terminate the connection.
17. The gateway according to claim 15, wherein the processor is configured to determine whether the predetermined period has expired, and to selectively forward unspoofed messages to a remote platform.
18. The gateway according to claim 15, wherein the prescribed protocol is the Transmission Control Protocol, the processor being configured determine whether global TCP spoofing is enabled and to selectively forward TCP segments unspoofed to a remote platform.
19. The gateway according to claim 15, wherein the communication interface communicates to a remote platform over a backbone connection, the processor being configured to forward a spoofed message over the backbone connection to the remote platform.
20. The gateway according to claim 19, wherein the backbone connection includes a space link over a satellite network.
21. The gateway according to claim 15, wherein the processor forwards messages associated with another protocol to a remote platform irrespective of the predetermined period.
22. A communication gateway for providing redundant communication in a communication system having a remote platform, the gateway comprising:
means for identifying a message received over a connection according to a prescribed protocol as an unspoofed message;
means for terminating, during a predetermined period, the connection based upon the identified message; and
means for restarting a spoofed connection between the second platform and a host.
23. The gateway according to claim 22, further comprising:
means for invoking a reset function, wherein the reset function transmits a reset message to a local host that forwarded the message to terminate the connection.
24. The gateway according to claim 22, further comprising:
means for determining whether the predetermined period has expired; and
means for forwarding unspoofed messages to a remote platform based upon the expiration of the predetermined period.
25. The gateway according to claim 22, wherein the prescribed protocol is the Transmission Control Protocol, the gateway further comprising:
means for determining whether global TCP spoofing is enabled; and
means for selectively forward TCP segments unspoofed to a remote platform.
26. The gateway according to claim 22, further comprising:
means for establishing a backbone connection from the second platform to a remote platform; and
means for forwarding a spoofed message over the backbone connection to a remote host.
27. The gateway according to claim 26, wherein the backbone connection includes a space link over a satellite network.
28. The gateway according to claim 22, further comprising:
means for forwarding messages associated with another protocol to a remote platform irrespective of the predetermined period.
29. A computer-readable medium carrying one or more sequences of one or more instructions for performing redundancy switching from a first platform to a second platform, the one or more sequences of one or more instructions including instructions which, when executed by one or more processors, cause the one or more processors to perform the steps of:
identifying a message received over a connection according to a prescribed protocol as an unspoofed message;
terminating, during a predetermined period, the connection based upon the identifying step; and
restarting a spoofed connection between the second platform and a host.
30. The computer-readable medium according to claim 29, wherein the one or more processors further perform the step of:
invoking a reset function, wherein the reset function transmits a reset message to a local host that forwarded the message to terminate the connection.
31. The computer-readable medium according to claim 29, wherein the one or more processors further perform the steps of:
determining whether the predetermined period has expired; and
forwarding unspoofed messages to a remote platform based upon the determining step.
32. The computer-readable medium according to claim 29, wherein the prescribed protocol is the Transmission Control Protocol, the one or more processors further performing the steps of:
determining whether global TCP spoofing is enabled; and
selectively forward TCP segments unspoofed to a remote platform.
33. The computer-readable medium according to claim 29, wherein the one or more processors further perform the steps of:
establishing a backbone connection from the second platform to a remote platform; and
forwarding a spoofed message over the backbone connection to a remote host.
34. The computer-readable medium according to claim 33, wherein the backbone connection in the establishing step includes a space link over a satellite network.
35. The computer-readable medium according to claim 29, wherein the one or more processors further perform the step of:
forwarding messages associated with another protocol to a remote platform irrespective of the predetermined period.
US09/903,780 2000-07-21 2001-07-12 Method and system for improving network performance enhancing proxy architecture with gateway redundancy Abandoned US20020038373A1 (en)

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US09/903,755 Expired - Lifetime US7213077B2 (en) 2000-07-21 2001-07-12 Method and system for providing buffer management in a performance enhancing proxy architecture
US09/903,781 Abandoned US20020010765A1 (en) 2000-07-21 2001-07-12 Method and system for prioritizing traffic in a network
US09/903,779 Expired - Lifetime US6993584B2 (en) 2000-07-21 2001-07-12 Method and system for improving network performance by utilizing path selection, path activation, and profiles
US09/905,215 Active 2025-04-01 US7596802B2 (en) 2000-07-21 2001-07-13 Method and system for providing connection handling
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US09/903,781 Abandoned US20020010765A1 (en) 2000-07-21 2001-07-12 Method and system for prioritizing traffic in a network
US09/903,779 Expired - Lifetime US6993584B2 (en) 2000-07-21 2001-07-12 Method and system for improving network performance by utilizing path selection, path activation, and profiles
US09/905,215 Active 2025-04-01 US7596802B2 (en) 2000-07-21 2001-07-13 Method and system for providing connection handling
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