|Publication number||US20050018600 A1|
|Application number||US 10/924,226|
|Publication date||Jan 27, 2005|
|Filing date||Aug 23, 2004|
|Priority date||Oct 31, 2000|
|Also published as||EP1332587A2, US6829215, US20020186654, WO2002043322A2, WO2002043322A3|
|Publication number||10924226, 924226, US 2005/0018600 A1, US 2005/018600 A1, US 20050018600 A1, US 20050018600A1, US 2005018600 A1, US 2005018600A1, US-A1-20050018600, US-A1-2005018600, US2005/0018600A1, US2005/018600A1, US20050018600 A1, US20050018600A1, US2005018600 A1, US2005018600A1|
|Original Assignee||Massimiliano Tornar|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (15), Referenced by (20), Classifications (12), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a continuation of and claims the benefit under 35 U.S.C. 120 of copending U.S. patent application Ser. No. 09/817,993 entitled “IP Multi-Homing” and filed on Mar. 27, 2001. This application also incorporates copending U.S. patent application Ser. No. 09/817,993 by reference as if fully rewritten here.
The systems and methods described herein are directed toward the field of data communication networks. In particular, systems and methods for providing protected communication paths between a LAN and a carrier network are described.
2. Description of the Related Art
The preferred user LAN 3 is an Ethernet LAN but other LAN types such as token ring, FDDI, etc., could be used. LAN Hosts 7 b preferably are personal computers (“PCs”) but optionally could be servers or other computer or communication equipment. LAN router 7 a preferably comprises computer or communication hardware that forwards data from or to other computer or communication equipment on the LAN 3. LAN router 7 a optionally could be coupled to other subnets (not shown) on the user's premises which interconnect other LAN hosts (not shown).
The network nodes 22 shown in
In the exemplary communication system 2 shown in
The network node 12 d of the exemplary communication system 2 is an internet gateway node and the network device that makes up the gateway node 12 d includes a multiplexor device or concentrator card (“CC”) 16. The CC 16 functions as a switch that multiplexes data packets transmitted by the access nodes 12 a, 12 b & 12 c onto a single data transmission channel 18 for further routing to the internet access device 5. The CC 16 also functions as a switch for forwarding data packets received over the data transmission channel 18 from the internet access device 5 to one or more access nodes 12 a, 12 b or 12 c.
Router ports have been configured for shared use between multiple virtual circuits and sub-interfaces. The concentrator card 16 facilitates the shared use of a router port and has a two-fold role. The concentrator card 16 merges the data from the various LANs 3 and access cards 14 on the ring network into a single pipe for forwarding to the single router port of the BR 5 to which the concentrator card 16 is coupled. In merging the data, the concentrator card 16 couples the data to different interfaces within the router port. The concentrator card's 16 second task is to take data from the BR 5, packet by packet, and forwards the data to the various access nodes 12 on the ring network.
Each access card 14 includes at least one protocol engine 30, as shown in
A method and system for providing a customer network with high speed access to a carrier network is provided. The system comprises an access device for providing a communication path for the customer network, a first concentrator device that is operable to establish a communication path with the carrier network, and a second concentrator device that is operable to establish a communication path with the carrier network. The access device is operable to receive data traffic from the customer network and to forward the data traffic within the system. The access device and the first concentrator device cooperate to form a first virtual channel for allowing data traffic to flow from the customer network to the carrier network and from the carrier network to the customer network and wherein the first virtual channel is the primary communication channel for the customer network. The access device and the second concentrator device cooperate to form a second virtual channel for allowing data traffic to flow from the customer network to the carrier network and from the carrier network to the customer network and wherein the second virtual channel is a backup communication channel for the customer network. The system is operable to switch the primary communication channel from the first virtual channel to the second virtual channel upon detection of a failure in the first virtual channel.
A. Multi-Homed Reference Network
In a preferred embodiment, a user or customer LAN 32 is connected via a ring 34 and a network node device 36 to two Central Offices (CO) 38, 40, as shown in
The ring 34 of the preferred embodiment includes two or more network node devices. Two of the network node devices are COs preferrably having CCs 16 for connecting to a carrier network 42. One of the network node devices is coupled to a user LAN and preferably includes an AC 14 for providing the coupling. The network node device that is coupled to the user LAN preferably is not one of the COs but optionally could be one of the COs. One skilled in the art could configure the ring 34 in a number of configurations.
As shown in
The upstream direction is defined as the direction of transmission running from the user to the carrier network. The downstream direction is defined as the direction of transmission running from the carrier network to the user. The provision of a working PVC and a single protection PVC to a user LAN is referred to hereinafter as dual-homing to two COs. The provision of a working PVC and multiple protection PVCs is referred to hereinafter as multi-homing to multiple COs. For simplicity of presentation, the discussion that follows is made with reference to dual-homing but it is understood that the same principals could be applied to multi-homing.
Optionally, each CO could be connected to separate router devices in the carrier network or alternatively to the same router device. Also, each CO could be connected to separate bridged service devices or alternatively to the same bridged service device.
B. Failure Detection
The multi-homing system is implemented such that switching from a working PVC 60 to a protection PVC 62 has little or no impact on the user LAN 32.
1. Backbone Router Failure Detection
The CC 16 at CO #1 38 implements a number of failure detection mechanisms to detect IP layer failures with the routed service, which preferably is provided by a BR 5. If a failure occurs with the BR 5, the CC at CO #1 38 can detect the failure using an OSPF failure detection mechanism, a RIP failure detection mechanism, and an active detection mechanism. These detection mechanisms are configurable on a PVC basis in the CC. These failure detection mechanism will be described more fully below.
Upon detection of a BR 5 failure at the other end of the working ATM or FR path 50, the CC at CO #1 38 notifies the AC 14 at node 36 that the working PVC 60 is in a faulty condition so that the AC 14 at node 36 can switch traffic to the protection PVC 62. The CC at CO #1 38 preferably notifies the AC 14 at node 36 of the failure via an asynchronous virtual path control protocol (“VPCP”) message to the AC 14 at node 36. The VPCP message is a message used on optical ring networks to transfer status information. The VPCP message provides a digital link channel identifier (“DLCI”) and status information regarding the digital channel identified by the DLCI number. The cause of the fault, in this case, is the failure of the BR 5, and it is not reported by the CC 16 to the AC 14.
a. OSPF Failure Detection
A first failure detection mechanism for detecting BR 5 failures is an Open Shortest Path Protocol (“OSPF”) snooping function that is implemented by the CC 16. When using this function, the CC 16 inspects incoming OSPF messages on the working FR/ATM path 50. This mechanism can be activated/deactivated on a per PVC basis. Upon failure to receive a hello packet from the BR 5 within a configurable timing window called a dead timer, the CC 16 declares a failure of the BR 5.
If the dead timer expires, the CC 16 preferably determines that the BR 5 is down. The BR 5 sends hello packets at designated intervals which are configurable in the BR 5. Therefore, the dead timer preferably should be configurable. Preferably, the default value of the dead timer is four times the value of the Hello interval. That results in a dead timer default of 40 seconds for broadcast networks and two minutes for non-broadcast networks.
The BR 5 can be declared functional and the working path 52 active if three consecutive hellos are received without the timer expiring. The CC 16 can then notify the AC 14 that the PVC 60 is operational via a VPCP message.
b. RIP Failure Detection
A second failure detection mechanism for detecting BR 5 failures is the RIP failure detection mechanism implemented by the CC 16. When using this failure detection mechanism, the CC 16 can declare the BR 5 down and the PVC not active after a configurable time (preferably more than 30 seconds) during which the CC 16 did not receive any RIP messages from the BR 5. To reactivate the PVC, the CC 16 can declare the BR 5 up and the PVC active if a number of consecutive RIP messages are received, preferably three, without the timer expiring. The CC 16 notifies the AC 14 of the status of the PVC via a VPCP message.
c. Active Detection of Router Failure
A third failure detection mechanism available for detecting BR 5 failures is an active detection mechanism. When using this failure detection mechanism, the CC 16 makes use of its IP address. Each CC 16 has a “service entity” with an IP layer address associated with a “service” PVC; several agents can reside at that address such as the DHCP Relay agent. No traffic flows on the service PVC other than traffic that the Service Entity originates.
2. CC1 Failure
The multi-homing system is capable of switching traffic from the working PVC to the protection PVC in the case of a failure with the CC 1 in the working PVC. In this case, the node that contains CC 2 detects the failure of CC 1 and notifies the AC which in turn switches traffic to the protection PVC as illustrated in
Backbone router R1, LAN router LR and the LAN hosts detect dynamically that the link to the working PVC 60 is broken and makes use of normal routing protocols to overcome this failure. For example, backbone router RI may detect CC1 failure from ATM OAM (AIS/RDI cells, Continuity Check) or from LOS at SONET layer. As the default is declared, the working PVC 60 is declared down and the backbone router R1 link to the customer network is no longer valid. Other backbone routers will be informed of the downed link via routing protocols.
a. CC Failure Detection Mechanism
A failure detection mechanism utilized in the multi-homing system for detecting CC failures is described next. When the CC in CO#1 70 fails, the neighbor nodes will detect the failure at SONET level and will trigger the Wrap mechanism illustrated in
TABLE 1 Events associated with CC failure detection Event Description 1 FWN signal on working VC, received from the current forwarding Path 2 FWN signal on working VC, received from the new current forwarding Path (after Path switching) 3 Continuity asserted and WTR TABLE 2
States associated with CC failure detection
Normal operating state for the working PVC
Path switching state
CC failure detected
CC failure has been detected in the AC.
3. Physical and Layer 2 Fault Detection
The multi-homing system has a mechanism for detecting physical and Layer 2 faults. The CC 16 detects Asynchronous transfer mode (“ATM”) layer faults via OAM F4/F5 cells. F4/F5 AIS/RDI faults are preferably detected. The CC 16 responds to received AIS cells by sending RDI cells.
The CC 16 detects frame relay (“FR”) layer PVC faults via LMI. When the working PVC becomes unavailable due to a failure at the ATM, FR or SONET level of the CC 16 interface, the CC 16 alerts the AC 14 by sending a VPCP message. The VPCP messages issued by the CC 16 report the status of the VCs.
C. VC Switching Mechanism
A number of mechanisms for switching traffic from a working PVC 60 to a protection PVC 62 are provided. In a first case, when CC1 80 detects a backbone router R1 failure, CC1 80 configures the PVC 60 with a “continue” cross-connect and passes traffic through to CC2 82 as illustrated in
CC2 82 can detect the failure of backbone router R1 in a number of ways. CC2 82 can be notified of the failure via VPCP messages when it observes that CC1 80 is no longer a transmitter for the PVC coming from backbone router R1. CC2 82 can detect the failure when that PVC “expires” as there are no more nodes which put that PVC in the Status Report message. Also, CC2 82 can be notified of the failure via a new asynchronous message carried by VPCP and sent by the node that contains CC1 80. After notification of the failure of backbone router R1, the CC2 82 configures the PVC with an “add/drop” cross-connect with backbone router R2.
Switching back to the original PVC can also be enabled. When the backbone router R1 becomes operational again, the original path may optionally be automatically restored (a.k.a. “revertive switching”) if CC1 informs CC2 that the backbone router R1 is available. Also, in the case of failure with CC2 and/or BR2 failure, the original path may be restored if CC1 informs CC2 that the backbone router R1 is available.
In a second case, CC1 80 notifies the AC 84 and CC2 82, for example, by means of VPCP or via a wrap mechanism, of the failure. As illustrated in
Revertive switching can be enabled by CC1 80 informing CC2 82 and AC 84 when the backbone router R1 is available in case of CC2/BR2 failure.
Third, CC1 80 notifies the AC 84 and CC2 82, for example, by means of VPCP of the failure. As illustrated in
Revertive switching can be enabled by CC1 80 informing AC 84 when the backbone router R1 is available in case of CC2/BR2 failure.
Alternatively, BR failure detection can reside in the AC 84, and the CC simply propagates indications of low level failures of the ATM (POS) to devices on the ring. In this case it is the AC 84 that notifies the CC2 82 that the working PVC is no longer valid.
1. Switching Mechanism Description
Upon failure of the working path, the AC 84 is notified by means of VPCP and Wrap mechanism and switches traffic to a protection PVC, with a different DLCI number. The CC2 82 is configured to drop traffic from the protection VC.
The AC 84 treatment of packets flowing through the working PVC before switching is normal. If the user LAN 86 is connected to a routed VC, devices on the user LAN 86 preferably learn their IP address from the IRDP mechanism. Before VC switching, downstream traffic coming from protection VC is preferably forwarded but optionally could be discarded. The VC switching preferably is configured on a VC basis as revertive but optionally could be configured as non-revertive.
The state machine shown in
TABLE 3 Events description for VC switching Event Description 1 Lockout of Protection 2 CC failure condition 3 Protection VC failure 4 Forced switch for working VC 5 Working VC failure 6 Manual switch for working VC 7 Manual switch for protection VC 8 No request of switch1
1This event means “there are no events”. that is none of 1-6 event.
States description for VC switching
Upstream traffic is transmitted to working VC, and
downstream traffic is forwarded according to the
parameter Enable downstream traffic from
Upstream traffic is transmitted to protection VC,
and downstream traffic is forwarded according to
the parameter Enable downstream traffic
from protection VC
Wait to restore
Upstream and downstream traffic flows
through protection VC. WTR timer is configurable
Do not Revert
Upstream traffic is transmitted to protection
VC, and downstream traffic is forwarded according to the
parameter Enable downstream traffic from protection VC
The AC 84 can issue the following commands: Lockout of Protection, Forced switch for working VC, Manual switch for protection VC, and manual switch for working VC. The Lockout of Protection command denies all working traffic access to the protection entity. The Forced switch for working VC command switches traffic to the protection VC unless the protection VC is in a faulty condition. The Manual switch for protection VC command switches traffic from protection VC to working VC. Finally, the Manual switch for working VC command switches traffic from working VC to protection VC.
After VC switching, every entity associated to the working VC (such as MAC address, the ARP process and cache, the RIP and IRDP learning processes and DHCP Relay agent) is associated to the protection routed VC. Downstream routed traffic is restored as soon as the Router at CO#2 discovers the topology change and that the LAN can now be reached via protection VC. Bridged service is restored as soon as the PVC is switched. After VC switching IRDP traffic coming from the router shall be snooped, and IP address auto-configuration will assign the IP address to the protection routed VC. If the IP address is different to that of the working VC, a gratuitous ARP shall be sent with the new IP address and the MAC address of the Ethernet Port.
2. Configurable Parameters
A number of parameters are configurable. The wait to restore (“WTR”) timer is preferably set to 60 seconds and preferably has a range of acceptable values from 1-300 seconds.
In the preferred system, the following parameters are configurable in the AC per PVC: (1) VC switching enabled (ON/OFF*); (2) Revertive VC switching(ON/OFF*); (3) DLCI of protection VC (valid DLCI number); and (4) Enable downstream traffic from protection VC (ON*/OFF). The states followed by the asterisk are the default states in the preferred system In the preferred system, the following parameters are configurable in the CC per PVC: (1) ATM layer failure detection enabled (ON/OFF*); (2) IP layer OSPF failure detection enabled (ON/OFF*); (3) OSPF Dead timer (1-255 seconds); (4) IP layer RIP failure detection (ON/OFF*); (5) RIP timer (30-300 seconds, default 75); (6) Ping mechanism enable (ON/OFF*); and (7) Ping interval (1-60 seconds, default 10).
D. Impact on Customer Network Configurations
1. Bridged VC
The protection system can be utilized in a network that uses the common carrier to provide a bridged connection for data traffic from a user network 96 to a remote network 98. Such a network could be have an asymmetric topology or a symmetric topology.
a. Asymmetric Configuration
An exemplary asymmetric configuration is shown in
Before any VC switching, all the traffic passes through the working PVC 91. The L2 switch 94 is working and passing traffic received through the port 95 connected to the working PVC 91, but the port 97 connected to the protection PVC does not receive traffic and no MAC addresses are learned by that port 97. If the ATM switches 99 runs the Spanning Tree Protocol, the bridged port 97 of L2 switch 94 remains in the “block state”: it does not participate in frame relay and discards received frames. The bridge, however, includes the port 97 in the computation of the active topology.
After VC switching due to a detected failure, the switch 94 will receive frames coming from the protection PVC 93, and the port 97 will learn MAC addresses on the remote network 98. The switch 94 forwards frames received from the port 97 that is connected to the protection PVC 93. The primary impact to the hosts and routers on the customer networks 96, 98 due to VC switching is that the devices on the customer networks 96, 98 must learn their new IP addresses using traditional protocols after VC switching occurs.
b. Symmetric Configuration
An exemplary symmetric configuration network is shown in
When a fault occurs in the ATM network 102, the fault will be reported to both the ACs 104 via ATM OAM cells (AIS/RDI) or Frame Relay LMI and VPCP. As a result, The two ACs 104 will switch forwarding of traffic to the protection PVC 108. The primary impact to the hosts and routers on the customer networks 109 due to VC switching is that the devices on the customer networks 109 must learn their new IP addresses using traditional protocols after VC switching occurs.
2. Routed VC
In the case of routed VCs, the impact of VC switching on customer networks is minimal. An exemplary system is illustrated in
After VC switching Backbone router 1 110, LAN router 123 and the hosts 124 detect dynamically that the working PVC 114 is broken and recover from this situation through the routing protocols. When there is a failure of CC #1 120 or of the working ATM/FR PVC, the OAM cells or the LMI will notify the Backbone router 1 110 and it will declare the ATM/FR sub-interface as down. The routing protocols will take appropriate action, and after a re-convergence period of time, the other routers will learn the new topology and send traffic via the backbone router 2 116. Similarly, the LAN router 123 will learn the new topology because of its routing protocol.
a. Flat Customer LAN
Hosts 124 attached to the LAN 112 should detect the failure of Backbone router 1 110 and react dynamically to recover from the situation. There are several options for the configuration and behavior of the hosts 124. In one embodiment, the hosts 124 on the LAN 112 have configured a default gateway. Using this method a host 124 is statically configured to know the IP address of its default router. If that router, however, becomes unavailable, the host 124 will not be able to communicate with devices off of the local LAN segment 112 even if there is another router available through an alternative PVC. In this embodiment, the hosts 124 must be manually re-configured so that the backbone can be reachable.
In a second embodiment, the hosts 124 on the LAN 112 are configured with a list of default gateways. If the primary default gateway fails, the hosts 124 detect the failure and switch automatically to the next default gateway in the list. The default gateway list preferably includes Backbone router 1 110 and Backbone router 2 116. VC switching preferably occurs before hosts 124 begin sending packets to Backbone router 2 116 so that disruption of upstream service is minimized. In this embodiment, the hosts 124, the hosts 124 automatically reconfigure themselves as soon as they learn by IRDP or RIP that Backbone router 2 116 is available.
In a third embodiment, the hosts 124 on the LAN 112 use the ICMP Router Discover Protocol (“IRDP”) to listen to router hellos. This allows a host 124 to quickly adapt to changes in network topology. IRDP may help hosts 124 to update their route cache and default gateway list. To facilitate this, after VC switching has occurred, Backbone router 2 116 preferably transmits unsolicited IRDP advertisements. As a result, the hosts 124 can readily add cache and default gateway list. To facilitate this, after VC switching has occurred, Backbone to their list of default gateways. In this embodiment, the hosts 124, the hosts 124 automatically reconfigure themselves as soon as they learn by IRDP that Backbone router 2 116 is available.
In a fourth embodiment, IP hosts 124 use “silent RIP” to ‘learn’ the available upstream gateways and builds their own default router tables. In this embodiment, the hosts 124, the hosts 124 automatically reconfigure themselves as soon as they learn by RIP that Backbone router 2 116 is available.
To minimize the period of service disruption and operational complexity, The backbone routers may optionally be provisioned with the same IP address on the customer LAN 112, as illustrated in
b. Customer Network with Firewall
In an alternative embodiment, as shown in
This written description uses examples to disclose the invention, including the best mode, and also to enable a person skilled in the art to make and use the invention. The patentable scope of the invention may include other examples that occur to those skilled in the art.
While various features of the claimed embodiments are presented above, it should be understood that the features may be used singly or in any combination thereof. Therefore, the claimed embodiments are not to be limited to only the specific embodiments depicted herein.
Further, it should be understood that variations and modifications may occur to those skilled in the art to which the claimed embodiments pertains. The embodiments described herein are exemplary. The disclosure may enable those skilled in the art to make and use embodiments having alternative elements that likewise correspond to the elements recited in the claims. The intended scope may thus include other embodiments that do not differ or that insubstantially differ from the literal language of the claims. The scope of the example embodiments is accordingly defined as set forth in the appended claims.
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|International Classification||H04L12/56, H04L29/14, H04L12/46|
|Cooperative Classification||H04L69/40, H04L45/28, H04L12/4608, H04L45/00|
|European Classification||H04L45/00, H04L45/28, H04L12/46B1, H04L29/14|
|Aug 23, 2004||AS||Assignment|
Owner name: MARCONI COMMUNICATIONS, INC., A CORP. OF DELAWARE,
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:TOMAR, MASSIMILIANO;REEL/FRAME:015729/0450
Effective date: 20010103
|Jun 14, 2006||AS||Assignment|
Owner name: ERICSSON AB,SWEDEN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MARCONI INTELLECTUAL PROPERTY (RINGFENCE) INC.;REEL/FRAME:018047/0028
Effective date: 20060101