|Publication number||US20050244158 A1|
|Application number||US 09/999,503|
|Publication date||Nov 3, 2005|
|Filing date||Oct 22, 2001|
|Priority date||Dec 30, 2000|
|Also published as||US7209436, WO2002060097A1|
|Publication number||09999503, 999503, US 2005/0244158 A1, US 2005/244158 A1, US 20050244158 A1, US 20050244158A1, US 2005244158 A1, US 2005244158A1, US-A1-20050244158, US-A1-2005244158, US2005/0244158A1, US2005/244158A1, US20050244158 A1, US20050244158A1, US2005244158 A1, US2005244158A1|
|Original Assignee||Siegfried Luft|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (40), Referenced by (13), Classifications (21), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a continuation-in-part of U.S. patent application Ser. No. 09/887,299, titled Method and Apparatus for Variable Rate Pipes, filed on Jun. 22, 2001, which claims priority to U.S. Provisional Patent Application Ser. No. 60/258,765, titled Method and Apparatus for Variable Rate Pipes, filed on Dec. 30, 2000.
1. Field of the Invention
This invention relates to communication networks. More specifically, the present invention relates to communication over optical networks.
2. Description of the Related Art
Current networks must satisfy consumer demand for more bandwidth and a convergence of voice and data traffic. The increased demand of bandwidth by consumers combines with improved high bandwidth capacity of core networks to make edge networks a bottleneck despite the capacity of optical networks.
Multiplexing is used to deliver a variety of traffic over a single high speed broadband line. An optical standard such as Synchronous Optical Network (SONET) or Synchronous Digital Hierarchy (SDH) in conjunction with a multiplexing scheme is used to deliver various rates of traffic over a single high speed optical fiber. SONET/SDH is a transmission standard for optical networks which corresponds to the physical layer of the open standards institutes (OSI) network model. One of the protection schemes for SONET/SDH involves automatic protection switching (APS) in a bi-directional line switched ring (BLSR) architecture. BLSR utilizes linear switching to implement APS.
The ring described in
High speed optical rings offer large amounts of bandwidth, but the protection scheme utilizes 50% of that bandwidth. This 50% of total bandwidth for a protection channel often goes unused while there is not a failure. It is often unused because traffic transmitted in the protection channel would be preempted by the working TDM traffic while a failure occurs.
Extra TDM traffic is problematic to sell to customers because it is preemptable and unprotected. A consumer could purchase the extra traffic service from two network owners or providers and alternate between the two upon failures. While the above is true for a 2 fiber BLSR, the impact to extra TDM traffic in a 4 fiber BLSR depends on the type of failure. In particular, while a ring switch in 4 fiber BLSR operates in a similar manner as described above, a span switch in a 4 fiber BLSR does not impact the extra TDM traffic transmitted on the non-failing spans.
The invention provides a method and apparatus for a variable rate pipe on a linear connections. According to one aspect of the invention, a method is provided which provisions a pipe from a part of a working channel and at least a part of a protection channel of an M:N linear connection. While there is not a failure in the linear connection, the method provides for load balancing layer 2/3 traffic that is transmitted in the pipe. When there is a failure in the linear connection, the pipe's bandwidth is reduced and layer 2/3 traffic is load balanced for the reduced pipe. Furthermore, the method provides for transmitting load balanced layer 2/3 traffic in the reduced pipe while there is a failure.
The invention may best be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention. In the drawings:
In the following description, numerous specific details are set forth to provide a thorough understanding of the invention. However, it is understood that the invention may be practiced without these specific details. In other instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the invention.
A method and apparatus is described that provides a pipe through an optical ring network that includes some bandwidth from the working and protection channels while there is no failure, but that is not completely lost on a failure. In this ring network, network elements are used that can transmit and receive TDM ring traffic. In addition, at least certain of the network elements provide two different switching techniques—TDM and packet. The packet switching provided can support any number of protocols including layer 2 and layer 3 type protocols such as ATM, Ethernet, Frame Relay, etc. In addition to typical operations of a TDM network element, the network elements are implemented to be able to: 1) programmably select on an STS basis certain of the incoming TDM traffic to be extracted and packet switched rather than TDM switched; and/or 2) receive packet traffic in another form and to be packet switched. Regardless of which switching technique is used, the switched traffic going back onto the ring is put in TDM format and transmitted out. However, each time traffic is packet switched, that traffic can be statistically multiplexed (e.g., the packets can be selectively dropped based on various criteria). An exemplary implementation of such hybrid network elements is provided in
The streams of TDM traffic 411 and 419 carry data traffic formatted according to a layer 2/3 protocol such as ATM, Ethernet, Frame Relay, Internet Protocol, etc as payload. The streams of TDM traffic 411 and 419 can be transmitted in a number of scenarios. The streams of TDM traffic 411 and 419 may be switched into the ring through the packet switching mechanism in one node and exit the ring as TDM traffic from another node. The streams of TDM traffic 411 and 419 maybe switched into the ring as layer 2/3 traffic through the packet switching mechanism in one node and exit the ring through the packet switching mechanism in another node in the form of layer 2/3 traffic. These examples are described as illustrations to aid in understanding the invention and not meant to be limiting upon the invention.
As shown in the illustration of
The variability in the pipe size is possible because of the statistical multiplexing capability of the packet switching mechanism in the network elements of the ring. Specifically, the reduction in the amount of available bandwidth for the TDM traffic having layer 2/3 traffic as payload requires the packet switch of the network element to buffer and/or to drop layer 2/3 traffic to make that traffic fit the provided pipe.
As an illustration of the protection switch in relation to end users, assume that traffic from a first, second, and third user enter the ring illustrated in
As illustrated in
To provide an example of the manner in which the layer 2/3 pipe could be sold, assume that the working and protection channel parts of the layer 2/3 pipe 414 are respectively 30 mbps and 90 mbps. Assume, that each of the first, second and third users above want an equal amount of bandwidth of the layer 2/3 pipe 414. Each customer could be offered a guaranteed (in the event of a single failure) 10 mbps and a maximum of 40 mbps. The customers traffic at node 431 would be statistically multiplexed to fit the size of the layer 2/3 pipe currently being provided. The guaranteed 10 mbps per customer would be provided by the working subpipe on span 403 or the protecting layer 2/3 subpipe 435. The maximum 30 mbps per customer would be provided by the protection subpipe on span 403 while there is no failure. In this manner partially BLSR protected layer 2/3 traffic is provided around the ring.
It should be understood that the ability to offer a guaranteed minimum bandwidth requires that the bandwidth of the layer 2/3 pipes on the ring not be oversold. Thus, in the above example, to offer the third user the service identified above, the ring provider would also have at least the needed bandwidth (guaranteed 10 mbps and a maximum of 40 mbps) on the second layer 2/3 pipe from node 441 to node 439 (not shown) because the third users traffic must traverse that span as well as span 403. In other words, if a potential user's traffic must traverse multiple spans of the ring in layer 2/3 pipes, each of these layer 2/3 pipes must have available the necessary bandwidth.
It should also be noted that not every network element in the ring need to be of the type that is capable of both TDM and packet switching (a hybrid network element). Specifically, while node 431 must be a hybrid network element, the node 439 could be a standard TDM network element capable of only performing TDM switching. Thus, compatibility is maintained.
The layer 2/3 traffic can be switched through the CC 509 or a packet mesh 550. The TPCs are programmable to insert and extract particular STSs that carry layer 2/3 traffic to be packet switched. If TDM traffic contains layer 2/3 payload to be switched through the packet mesh 550, then the TPCs 519, 531, 525, and 537 extract the layer 2/3 payload traffic from the TDM traffic and transmit the layer 2/3 traffic to ingress layer 2/3 processing circuitry 523, 535, 529, and 541 respectively. The TPCs 519, 531, 525, and 537 also receive layer 2/3 traffic from egress layer 2/3 processing circuitry 521, 533, 527, and 539 respectively. For a variable rate layer 2/3 traffic pipe, the egress layer 2/3 processing circuitry includes the ability to queue and statistically multiplex layer 2/3 traffic before transmitting it to a TPC. The TPCs 519, 531, 525, and 537 process the layer 2/3 traffic placing it into SONET/SDH frames for transmission in timeslots. The TPCs 519, 531, 525, and 537 are programmable to insert and extract particular STSs that carry the layer 2/3 traffic to be packet switched.
The CC 509 detects failures, maintains a BLSR state machine, and updates the TDM cross connect table in response to changes in the BLSR state machine. The CC 509 also sends a message to update the logical interfaces for packet BLSR protection switching. Typically an interface is a physical interface or port. A logical interface is the logical connection from a first network element to another network element or node which may or may not be adjacent to the first network element. The logical interface refers to a physical port or interface which can be changed. In addition, the CC 509 sends messages to reprogram the TPCs to handle a protection switch (e.g., reorient concatenations, redirect channels to packet mesh and CC, etc.).
To provide an example of the reprogramming of the network elements to handle a ring switch, assume that the ring of
While There is Not a Failure While There is a Failure Node TDM Layer ⅔ Pipe TDM Layer ⅔ Pipe 431 On TPC 519 for On TPC 519 for On TPC 519 for On TPC 519 for transmit fiber transmit fiber transmit fiber transmit fiber 515: X on 515: STS 2C on 515: X on 515: STS 2C on channels 1-4, channels 5-6; channels 1-4; channels 5-6; where X is STS 6C on STS 1 on STS 2C on some particular channels 7-12 channel 7 channels 11-12 arrangement On TPC 525 for protecting protecting layer On TPC 525 for transmit fiber TDM; ⅔ subpipe transmit fiber 506: STS 2C on STS 3C on On TPC 525 for 506: STS 1 on channels 5-6; channels 8-10 transmit fiber channel 1; STS 6C on protecting 506: Nothing STS 3C on channels channels 7-12 TDM 2-4 On TPC 525 for transmit fiber 506: Nothing 441 On TPC 519 for On TPC 519 for On TPC 519 for On TPC 519 for receive fiber receive fiber receive fiber receive fiber 517: STS 1 on 517: STS 2C on 517: Nothing 517: Nothing channel 1; channels 5-6; On TPC 525 for On TPC 525 for STS 3C on STS 6C on receive fiber receive fiber channels 2-4 channels 7-12 508: Y on 508: STS 2C on On TPC 525 for On TPC 525 for channels 1-4; channels 5-6; receive fiber receive fiber STS 1 on STS 2C on 508: Y on 508: STS 2C on channel 7 channels 11-12 channels 1-4, channels 5-6; protecting protecting layer where Y is STS 6C on TDM; ⅔ subpipe some particular channels 7-12 STS 3C on channels arrangement 8-10 protecting TDM 439 On TPC 519 for On TPC 519 for On TPC 519 for On TPC 519 for transmit fiber transmit fiber transmit fiber transmit fiber 515: Y on 515: STS 2C on 515: Y on 515: STS 2C on channels 1-4 channels 5-6; channels 1-4; channels 5-6; On TPC 525 for STS 6C on STS 1 on STS 2C on receive fiber channels 7-12 channel 7 channels 11-12 508: X on On TPC 525 for protecting protecting layer channels 1-4 receive fiber TDM; ⅔ subpipe 508: STS 2C on STS 3C on On TPC 525 for channels 5-6; channels 8-10 receive fiber STS 6C on protecting 508: STS 2C on channels 7-12 TDM channels 5-6; On TPC 525 for STS 2C on receive fiber channels 11-12 508: X on protecting layer channels 1-4; ⅔ subpipe b STS 1 on channel 7 protecting TDM; STS 3C on channels 8-10 protecting TDM
In addition to the reprogramming of the TPCs, the cross connect tables and the logical interfaces are altered accordingly. As in the example described above, traffic for three users enter the ring at node 431 of
In node 439, while there is not a failure, the traffic from the third user is received at the IL2/3PC 521 and switched through the packet mesh to EL2/3PC 541. While there is a failure, the node 439 is modified so that the traffic for the three users received from node 431 on node 439's PCC 503 in the protecting layer 2/3 channel is switched to the protecting layer 2/3 channel to node 441. This switch will go through the cross connect, and is in fact a BLSR pass-through. An additional change for the dropping of the third users traffic is in the next paragraph.
In node 441, while there is not a failure, the traffic from all three users is received at the IL2/3PC 521 and switched through the packet mesh: the first and second users' traffic is switched to EL2/3PC 541, while the third user's traffic is switched to EL2/3PC 529. While there is a failure between two adjacent nodes, the logical interfaces are modified because of the failure so that the traffic for the first and second users received from node 439 on node 441's PCC 503 is switched through the packet mesh 550 from the IL2/3PC 527 to the EL2/3PC 541 and transmitted out of the ring through the PCC 505. The traffic for the third user is switched through the packet mesh from the IL2/3PC 527 to the EL2/3PC 529 and transmitted out the PCC 503 on the working layer 2/3 channel to node 439 by the TPC 525. The traffic from the third user is received at node 439 at the PCC 501 on the working layer 2/3 channel and switched through the packet mesh 550 from the IL2/3PC 521 to the EL2/3PC 541 in accordance with the forwarding tables and transmitted out of the ring by the PCC 505.
To provide another example of the reprogramming of the TPCs to handle a protection switch, assume that the ring of
Thus, while there is a failure requiring a ring switch on the East span of a node: 1) traffic coming in PCC 505 is protection switched to PCC 503; and 2) the redirect/concatenations of the TPCs 519 and 531 must be altered. Whereas while there is a failure requiring a ring switch on the West span of a node: 1) traffic coming in PCC 507 is protection switched to PCC 501; and 2) the redirect/concatenations of the TPCs 525 and 537 must be altered. In addition, while there is a failure requiring a ring switch on a midspan node, the redirect/concatenations of the TPCs 531 and 537 must be altered accordingly. The redirect/concatenations of the TCPs 519 and 525 are not affected because of the assumption that TPCs 519 and 525 correspond to working channels.
To provide a more specific example, assume that while there is not a failure, node 431 transmits TDM traffic as STS-12 c and STS-24 c through the PCC 503 to node 441. The channels used for the STS-12 c and STS-24 c traffic are collectively referred to as the working TDM pipe. Node 431 transmits over the layer 2/3 pipe STS-12 c and STS-48 c of traffic through PCC 503 and PCC 505 respectively to node 441 of
If both spans between nodes 431 and 441 (the span corresponding to PCC 503 and the span corresponding to PCC 505) are lost (e.g. cables 506, 508, 510 and 512 are severed, both cards having PCCs 503 and 505 are pulled, etc.), then a ring switch will occur. The control card 509 will detect a failure of the spans between nodes 431 and 441. The control card 509 will update the BLSR state machine, reprogram TPC 531, and send a message to node 439 indicating the failure. The control card 509 reprograms the TPC 531 to match the concatenations, channel redirects, etc., of TPC 525. Hence, traffic originally transmitted from node 431 to node 441 through PCCs 503 are now transmitted through PCC 507.
On the nodes adjacent to the failure, the logical interfaces will be reprogrammed, but the destinations in the forwarding tables will not be changed (This is an effect of having two switch mechanisms providing alternative paths; as such, this may not be required in other implementations). An alternative embodiment could be implemented with a single path through the cross-connect. In such an alternative embodiment, the packet mesh would be subordinate to the cross-connect since all traffic including packet switched traffic would pass through the cross-connect when entering or exiting the box.
Embodiments of the invention are not limited to application in an optical ring. The previously described load balancing mechanism can support an M:N protection scheme for protecting variable rate pipes carried over linear connections (e.g., the last mile, links between rings, etc.). Various embodiments of the invention can implement load balancing in an M:N protection scheme of a linear connection carrying optical traffic and layer 2/3 traffic over the last mile, between rings, etc., by implementing multi-link PPP on all IL2/3PCs, implementing multi-link PPP on a primary EL2/3PC, introducing additional hardware or circuitry (e.g., an additional cross connect card), etc.
In another embodiment of the invention, the protection interface table is a data structure with a reference to a logical working interface and a logical protection interface. The logical working interface corresponds to a physical port connecting to a transmit fiber to carry traffic destined for a node X going in a preferred direction on the ring. The logical protection interface corresponds to another physical port connected to a transmit fiber destined for the node X, but going in the opposite direction and possibly through other nodes in the ring. A logical interface stored in or referenced by a layer 2/3 forwarding table initially refers to the logical working interface while there is not a failure. While there is a failure, the logical interface refers to the logical protection interface. While the failure is corrected, the logical interface is updated to refer to the logical working interface. In another embodiment of the invention, a routine manages logical interfaces and another routine manages alternate interfaces. A network administrator configures alternate interfaces on a network element. The alternate interface manager will create a data structure to refer to 2 logical interfaces which are managed by the interface manager. One of the interfaces will be the working interface while the other interface will be the protecting interface. In the layer 2/3 forwarding table, a circuit identifier is associated to either a logical interface or an alternate interface. Upon a failure notification, the alternate interface manager will alter the data structure to reference the logical interface acting as the protecting interface. In another embodiment of the invention, the TDM process instead of the layer 2/3 process updates a data structure indicating protection interfaces.
The owner of the optical ring can now offer protected service to multiple customers. Typically, only the traffic traveling in the working channel was sold to customers since consumers did not want to purchase a service which may be interrupted (e.g., for days). Alternatively, a consumer may choose to purchase at a reduced cost, the extra traffic service from 2 providers. This consumer would alternate between these providers as failures occurred. With a layer 2/3 pipe, the owner of the optical ring can offer multiple classes of service. In addition to the traditional constant rate TDM traffic service, the network owner or provider can offer a variable rate TDM traffic service to customers because the payloads are layer 2/3 units of traffic. For example, if bandwidth corresponding to a layer 2/3 pipe transmits at a rate of 100 megabits per second with 20 megabits corresponding to the layer 2/3 subpipes, the owner or provider can offer a service guaranteeing a rate of 20 megabits per second with a maximum of 100 megabits per second. This variable rate service can be offered to multiple people since the TDM payloads are layer 2/3 units of traffic. In addition, the variable rate service can be offered with a BLSR protection time of 50 milliseconds. Furthermore, the owner or provider of the optical network, is not forced to either donate or sell at a reduced cost 50% of their bandwidth. The owner of provider can sell 100% of its bandwidth with the combination of standard TDM service and the variable rate TDM service.
A continuum of embodiments exist for the invention. On one end of the continuum is an embodiment only utilizing BLSR protection. On the other end of the continuum is an embodiment only utilizing layer 2/3 protection. An embodiment utilizing BLSR protection has already been described. Another embodiment of the invention representing the layer 2/3 end of this continuum switches layer 2/3 traffic through the packet mesh of every hybrid network element of a BLSR. An embodiment of the invention in a 2-fiber BLSR representing this other end of the continuum is described herein.
An embodiment of the invention utilizing layer 2/3 protection is able to deliver best-effort service and differentiated service level Quality of Service (QoS). An embodiment of the invention only utilizing BLSR protection for all traffic on a BLSR is able to deliver guaranteed service level QoS. Embodiments of the invention falling between these two extremes are able to deliver a mixture of service level QoS. Best-effort service is basic connectivity without guarantees. Differentiated service does not offer a guarantee, but traffic is treated based on statistical preference. Various embodiments of the invention can be applied to a network depending on the traffic characteristics of the network.
For example, if layer 2/3 traffic traveling over the ring is erratic or occurs in bursts, an embodiment of the invention which provides for guaranteed bandwidth allows bandwidth to remain idle. For example, assume users A and B are guaranteed 10 Mbits/sec of bandwidth. Even though one user may only be using 2 Mbits/sec of bandwidth, the other user cannot go beyond 10 Mbits/sec of bandwidth. Embodiments of the invention similar to that illustrated in
Furthermore, an embodiment of the invention utilizing layer 2/3 protection allows varying pipe sizes around the ring. A network administrator can adjust the amount of working channel bandwidth allocated to the working optical pipe and the working layer 2/3 pipe in accordance with traffic characteristics on a span by span basis. The ability to customize part of the ring increases efficient utilization of the ring.
TABLE 1 Concatenation of Pipes A B C Wt STS-1 STS-3c STS-3c, STS-1, STS-1 Wp STS-3c, STS-3c STS-1 STS-1, STS-1
The concatenations corresponding to the letter A provide for a larger amount of bandwidth to layer 2/3 traffic. The concatenations corresponding to the letter C allot a larger amount of bandwidth to optically switched traffic. The concatenations corresponding to the letter B evenly allocate bandwidth to layer 2/3 traffic and optically switched traffic.
Table 2 identifies the concatenations for each link for both the inner ring and the outer ring. Since only layer 2/3 traffic will travel in the protection channels of the ring, the column with the header “Pt” remains empty.
TABLE 2 Concatenation of Traffic While There Is Not A Failure Wt Wp Pt Pp Inner Ring 701→705 STS-3c STS-3c STS-6c 705→707 STS-3c STS-3c STS-6c 707→709 STS-3c STS-3c STS-6c 709→703 STS-3c, STS-1, STS-1 STS-6c STS-1 703→701 STS-3c, STS-1, STS-1 STS-6c STS-1 Outer Ring 701→703 STS-3c, STS-1, STS-1 STS-6c STS-1 703→709 STS-3c STS-3c STS-6c 709→707 STS-3c STS-3c STS-6c 707→705 STS-1 STS-3c, STS-1, STS-6c STS-1 705→701 STS-1 STS-3c, STS-1, STS-6c STS-1 TABLE 3 Concatenation of Traffic While There Is A Failure Wt Wp Pt Pp Inner Ring 705→707 STS-3c STS-3c STS-1 STS-3c, STS-1, STS-1 707→709 STS-3c STS-3c STS-1 STS-3c, STS-1, STS-1 709→703 STS-3c, STS-1, STS-1 STS-1 STS-3c, STS-1, STS-1 STS-1 703→701 STS-3c, STS-1, STS-1 STS-1 STS-3c, STS-1, STS-1 STS-1 Outer Ring 701→703 STS-3c, STS-1, STS-1 STS-3c STS-3c STS-1 703→709 STS-3c STS-3c STS-3c STS-3c 709→707 STS-3c STS-3c STS-3c STS-3c 707→705 STS-1 STS-3c, STS-1, STS-3c STS-3c STS-1
As illustrated in Table 3, the concatenations for the traffic transmitted over the protection channel are modified. The protection channels of the inner ring are adjusted based on the working traffic switched from the outer ring. The protection channels of the outer ring are adjusted based on the working traffic switched from the inner ring. Since the Wt traffic which previously traveled over the outer ring link between nodes 701 and 705 was transmitted as STS-1, then STS-1 of the protection channel of the inner ring is used for the protection switched traffic. Likewise, since the Wt traffic which previously traveled over the inner ring link between nodes 701 and 705 was transmitted as STS-3 c, then STS-3 c of the protection channel of the outer ring is used for the protection switched traffic from the inner ring. Hence, each node's TPC transmitting traffic in the protection channel through the inner ring is reprogrammed from transmitting STS-3 c of layer 2/3 traffic to transmitting STS-1 of optically switched traffic, 2 STS-1 s of layer 2/3 traffic, and an STS-3 c of layer 2/3 traffic. Each node's TPC transmitting traffic in the protection channel of the outer ring is reprogrammed from transmitting STS-6 c of layer 2/3 traffic to transmitting an STS-3 c of layer 2/3 traffic and an STS-3 c of optically switched traffic.
As indicated above, such an embodiment of the invention can also be applied to a 4-fiber BLSR or n-fiber BLSR.
The techniques shown in the figures can be implemented using code and data stored and executed on computers. Such computers store and communicate (internally and with other computers over a network) code and data using machine-readable media, such as magnetic disks; optical disks; random access memory; read only memory; flash memory devices; electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.); etc. Of course, one or more parts of the invention may be implemented using any combination of software, firmware, and/or hardware.
While the invention has been described in terms of several embodiments, those skilled in the art will recognize that the invention is not limited to the embodiments described. Although the invention has been described with reference to the TDM form of optical switching, the invention can be applied to any form of optical switching including wave division multiplexing, dense wave division multiplexing, etc. In addition, the invention has been described with respect to a 2 fiber and 4 fiber BLSR, but can be scaled to other n-fiber architectures of BLSR.
Furthermore, while the invention has been described in terms of switching the traffic in the layer 2/3 pipe through the packet mesh of each node while there is not a failure, a variety of configurations are possible for an optical ring with a layer 2/3 pipe. In a five node ring, a first node may have a layer 2/3 pipe defined over a direct connection to a second node. The first node may also have a layer 2/3 pipe defined over a logical direct connection to a third node through the cross connect of the second node. The first node may also have a layer 2/3 pipe defined over a logical direct connection to a fifth node through the fourth node's cross connect. An optical ring may have 4 nodes which are hybrid network elements and 2 nodes which are TDM only network elements. The TDM only network elements may only act as regenerators between the hybrid network elements. A first hybrid node may have a layer 2/3 pipe defined to a second layer 2/3 pipe through a TDM only node. The first hybrid node may have a layer 2/3 pipe defined to the TDM only node while a another layer 2/3 pipe is defined from the TDM only node to the second hybrid node. These examples are provided to aid in the understanding of the invention and not meant to be limiting upon the invention.
In addition, although the traffic that is passing through a given node (being provided to that node on a span of the ring and being transmitted by that node out another span of the ring) in layer 2/3 pipes may be switched through the packet mesh of that node, the traffic is not considered to be terminated from the ring at that node, but is rather considered to still be on the ring (similar to the manner in which virtual tributaries (VTs) are considered to not be terminated from the ring). However, since each packet is addressed individually, squelching is not needed as with a VT ring. The method and apparatus of the invention can be practiced with modification and alteration within the spirit and scope of the appended claims. The description is thus to be regarded as illustrative instead of limiting on the invention.
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|International Classification||H04J14/02, H04B10/213, H04L12/437, H04Q11/00, H04B10/00|
|Cooperative Classification||H04J14/0241, H04B10/032, H04Q2011/0086, H04Q2011/0081, H04J14/0291, H04J14/0283, H04J14/0227, H04L12/437, H04Q11/0062|
|European Classification||H04J14/02N4, H04B10/032, H04Q11/00P4, H04J14/02M, H04L12/437, H04J14/02P4S|
|Dec 4, 2001||AS||Assignment|
Owner name: REDBACK NETWORKS INC., CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:LUF, SIEGFRIED;REEL/FRAME:012342/0528
Effective date: 20011019
|Apr 7, 2004||AS||Assignment|
Owner name: SILICON VALLEY BANK,CALIFORNIA
Free format text: SECURITY AGREEMENT;ASSIGNOR:REDBACK NETWORKS INC.;REEL/FRAME:014499/0957
Effective date: 20040310
|Jan 11, 2007||AS||Assignment|
Owner name: REDBACK NETWORKS, INC., CALIFORNIA
Free format text: RELEASE;ASSIGNOR:SILICON VALLEY BANK;REEL/FRAME:018855/0108
Effective date: 20070104