Fault tolerant automatic protection switching for distributed routers

• US 6,956,816 B1
• Filed: 02/15/2001
• Issued: 10/18/2005
• Est. Priority Date: 02/15/2001
• Status: Active Grant

• Current Assignee: Extreme Networks, Inc.
• Original Assignee: Extreme Networks, Inc.
• Inventors: Grosser, Donald B., Alexander, Cedell A.
• Primary Examiner(s): Patel, Ajit
• Application Number:
  US09/784,841
• Time in Patent Office: 1,706 Days
• Field of Search: 370/216, 370/276, 370/352, 370/533, 370/535, 370/539, 370/386, 370/395.51, 370/541, 370/401, 370/217, 370/218, 370/219, 370/220, 370/221, 370/222, 370/223, 370/224, 370/228, 370/227, 714/100, 714/1, 714/2
• US Class Current: 370/222
• CPC Class Codes: H04J 2203/006 Fault tolerance and recovery
• CPC Class Codes: H04J 2203/0083 Support of the IP protocol
• CPC Class Codes: H04J 3/08 Intermediate station arrangements, e.g. for branching, for tapping-off
• CPC Class Codes: H04J 3/14 Monitoring arrangements for SDH/SONET rings H04J3/085
• CPC Class Codes: H04L 45/22 Alternate routing
• CPC Class Codes: H04L 45/28 using route fault recovery
• CPC Class Codes: H04L 45/58 Association of routers
• CPC Class Codes: H04L 45/586 of virtual routers

Abstract

A working router is coupled to a SONET add-drop multiplexor (ADM) through a working line and a protection router is coupled to the ADM through a protection line. The routers are coupled to each other by a separate side-band connection and comprise a virtual router from the perspective of the neighboring router, which communicates with the virtual router over the SONET network using the Point-to-Point Protocol (PPP). The protection router transmits a heartbeat message to the working router over the side-band connection. If the protection router does not receive a response thereto, it initiates a line switch within the add-drop multiplexor. Once the line switch is complete, the protection router exchanges datagrams with the neighboring router, via the ADM and SONET ring to which the ADM is coupled. The protection router establishes a PPP connection between itself and the neighboring router device coupled to the SONET ring, utilizing the Link Control Protocol (LCP). The protection router includes a predetermined identifier value that identifies the originator of the request, in the LCP Identifier field of LCP request datagrams. The neighboring router includes the Identifier value received in a request datagram in the corresponding response datagram transmitted over the SONET ring to the ADM. Because datagrams received by the ADM from the SONET link are transmitted over both the working and the protect lines, the working router receives the same response as the protection router. Thus, by examining the identifier field, and recognizing the identifier value as that assigned to the protection router, the working router determines that the line switch to the protection router has occurred.

Claims

1. In a network having a router coupled to a multiplexor via a first multiplexor line and a redundant router coupled to the multiplexor via a second multiplexor line, the multiplexor further coupled to a network ring, a method comprising:

transmitting by the redundant router a signal to the router through a communications medium coupling the router and the redundant router;

initiating by the redundant router a switch from the router communicating with the multiplexor via the first multiplexor line to the redundant router communicating with the multiplexor via the second multiplexor line based at least in part on the redundant router not receiving a response via the communications medium to the signal; and

transmitting by the redundant router a request signal to a neighbor device coupled to the network ring, the request signal transmitted via the second multiplexor line, the multiplexor and the network ring, the request signal indicating an identifier of the redundant router;

transmitting by the neighbor device a response signal to the redundant router via the network ring and multiplexor, the response signal indicating the identifier of the redundant router;

transmitting by the multiplexor the response signal to the router via the first multiplexor line and the redundant router via the second multiplexor line;

receiving at the router via the first multiplexor line the response signal and detecting a switch to communication with the multiplexor from the router via the first multiplexor line to the redundant router via the second multiplexor line based on the presence of the identifier of the redundant router in the response signal.

2. The method of claim 1, wherein transmitting by the redundant router the request signal to the neighbor device further comprises establishing a point-to-point link between the redundant router and the neighbor device.

3. The method of claim 1, wherein the ring network comprises a SONET-based ring network.

4. The method of claim 3, wherein the multiplexor comprises an add-drop multiplexor coupled to the SONET-based ring network.

5. The method of claim 3, wherein the communications medium comprises a local area network that operates out-of-band with respect to the SONET network.

6. The method of claim 2, wherein the redundant router utilizes a link control protocol (LCP) to establish the point-to-point link between the redundant router and the neighbor device.

7. The method of claim 6, wherein the identifier is provided in an identifier field of a LCP-based datagram.

8. The method of claim 7, wherein the most significant bit of the identifier field in the LCP-based datagram is utilized to indicate a line switch to the redundant router.

9. The method of claim 1, wherein the neighbor device comprises a router.

10. The method of claim 1, further comprising terminating communication between the router and multiplexor based at least in part on the router receiving the response signal.

11. A method comprising:

transmitting a first signal from a protection router to a working router via a side band connection;

if the protection router fails to receive a response to the first signal from the working router, then;

transmitting a second signal from the protection router to a neighbor device via a signal multiplexor to which the protection router is coupled by way of a protection line and the network device is coupled by way of a network ring, the second signal providing an indicator for the protection router;

transmitting a third signal from the neighbor device in response to the second signal, the third signal providing the indicator for the protection router;

receiving the third signal via the network ring at the signal multiplexor and forwarding the third signal to the protection router via the protection line and to the working router via a working line;

receiving the third signal at the working router and terminating communication between the working router and the signal multiplexor on detecting the indicator for the protection router in the third signal.

12. The method of claim 11, wherein transmitting a second signal from the protection router to a neighbor device comprises transmitting a configuration request signal.

13. The method of claim 12, wherein transmitting a configuration request signal from the protection router to a neighbor device comprises transmitting a link control protocol configuration request signal.

14. The method of claim 13, wherein the indicator for the protection router comprises a link control protocol identifier of the protection router.

15. The method of claim 14, wherein transmitting a third signal from the neighbor device in response to the second signal, the third signal providing the indicator for the protection router, comprises transmitting a configuration response signal from the neighbor device in response to a link control protocol configuration request signal.

16. The method of claim 15, wherein transmitting a configuration response signal from the neighbor device in response to a link control protocol configuration request signal comprises transmitting a link control protocol configuration response signal from the neighboring device in response to a link control protocol configuration request signal.

17. The method of claim 16, wherein the third signal providing the indicator for the protection router comprises a link control protocol configuration response signal providing the link control protocol identifier of the protection router obtained from the link control protocol configuration request signal.

18. The method of claim 17, wherein receiving the third signal via the network ring at the signal multiplexor and forwarding the third signal to the protection router via the protection line and to the working router via a working line comprises receiving the link control protocol configuration response signal via the network ring at the signal multiplexor and forwarding it to the protection router via the protection line and to the working router via the working line.

19. The method of claim 18, wherein receiving the third signal at the working router and terminating communication between the working router and the signal multiplexor on detecting the indicator for the protection router in the third signal, comprises receiving the link control protocol configuration response signal at the working router and terminating communication between the working router and the signal multiplexor on detecting the link control protocol identifier of the protection router in the configuration response signal.

20. A method comprising:

transmitting a heartbeat signal from a protection router for receipt by a working router;

if the protection router fails to receive a signal in response to transmitting the heartbeat signal, then;

transmitting a request signal from the protection router for receipt by a neighbor device via a signal multiplexor and a network ring, the request signal providing an indicator for the protection router, the request signal for causing;

the neighbor device to transmit a response signal from the neighbor device in response to the request signal, the response signal to provide the indicator for the protection router;

the signal multiplexor to receive the response signal via the network ring and forward the response signal to the protection router via the protection line and to the working router via a working line;

the working router to receive the response signal and terminate communication between the working router and the signal multiplexor if the indicator for the protection router in the response signal is detected.

21. An article of manufacture, comprising:

a machine accessible medium that provides instructions that when executed by the machine cause the machine to;

transmit a heartbeat signal for receipt by a working router;

if the machine fails to receive a signal in response to the heartbeat signal, then;

transmit a request signal from the protection router for receipt by a neighbor device via a signal multiplexor and a network ring, the request signal providing an indicator for the protection router, the request signal for causing;

the neighbor device to transmit a response signal from the neighbor device in response to the request signal, the response signal to provide the indicator for the protection router;

the signal multiplexor to receive the response signal via the network ring and forward the response signal to the protection router via the protection line and to the working router via a working line;

the working router to receive the response signal and terminate communication between the working router and the signal multiplexor if the indicator for the protection router in the response signal is detected.