Highly-available OSPF routing protocol

• US 20030218982A1
• Filed: 05/23/2002
• Published: 11/27/2003
• Est. Priority Date: 05/23/2002
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Chiaro Networks, Ltd.
• Inventors: Folkes, Ronald P., Visser, Lance A., Watson, Thomas L.
• Granted Patent: US 7,292,535 B2
• Time in Patent Office: Days
• US Class Current: 370/238
• CPC Class Codes: H04L 45/02 Topology update or discovery
• CPC Class Codes: H04L 45/03 by updating link state protocols
• CPC Class Codes: H04L 45/28 using route fault recovery
• CPC Class Codes: H04L 45/586 of virtual routers
• CPC Class Codes: H04L 45/60 Router architectures

Abstract

In highly-available Open Shortest Path First (OSPF) routing in a network, the dynamic state of a backup OSPF instance in a router is synchronized with the dynamic state of an active OSPF instance using explicit message transmission from the active instance to the backup instance. After this, the dynamic state synchronization of the backup OSPF instance is maintained using a combination of explicit message updates from the active OSPF instance together with a message flow-through mechanism. In the event of fail-over of the active OSPF instance, then the router recovers seamlessly without reconfiguring or interrupting traffic among peer routers in the network, by functionally substituting the synchronized backup OSPF instance for the active OSPF instance, such that the backup OSPF instance establishes itself as the new active OSPF instance.

Claims

1. A method of highly-available Open Shortest Path First (OSPF) routing in a network, comprising the steps of:

synchronizing the dynamic state of a backup OSPF instance with the dynamic state of an active OSPF instance using explicit message transmission from said active instance to said backup instance;

maintaining dynamic state synchronization of said backup OSPF instance with said active OSPF instance using a combination of explicit message updates from said active OSPF instance to said backup OSPF instance together with a message flow-through mechanism; and

in the event of fail-over of said active OSPF instance, then seamlessly recovering from said fail-over without reconfiguring or interrupting traffic among peer routers in said network, by functionally substituting said state synchronized backup OSPF instance for said active OSPF instance, such that said backup OSPF instance establishes itself as the new active OSPF instance.

2. The method of claim 1 wherein said explicit message transmission is performed through a highly reliable private protocol processor link.

3. The method of claim 2 wherein said highly reliable private protocol processor link is a highly reliable Transmission Control Protocol (TCP) link.

4. The method of claim 1 wherein said step of synchronizing comprises transmitting a handshake message from said active OSPF instance and receiving at said active OSPF instance a message from said backup OSPF instance in response to said handshake message.

5. The method of claim 1 wherein said step of synchronizing comprises synchronization of global state information.

6. The method of claim 1 wherein said step of synchronizing comprises configuration synchronization of each OSPF area.

7. The method of claim 6 wherein said step of synchronizing comprises synchronization of the state of each configured OSPF interface.

8. The method of claim 7 wherein said step of synchronizing comprises synchronization of the state of each known neighbor.

9. The method of claim 6 wherein said step of synchronizing comprises synchronization of area-specific link state advertisements (LSAs).

10. The method of claim 1 wherein said step of synchronizing comprises confirmation that said backup OSPF instance is synchronized with said active OSPF instance.

11. The method of claim 10 wherein said confirmation is achieved by receiving at said active OSPF instance link state advertisement (LSA) checksums from said backup OSPF instance.

12. The method of claim 1 wherein said step of maintaining using said explicit message updates comprises interface state updates, designated router election results, and link-state advertisement (LSA) and deleted LSA results.

13. The method of claim 1 wherein said step of maintaining using said message flow-through mechanism comprises reading by said backup OSPF instance of every OSPF protocol packet sent from and/or received by said active OSPF protocol processor.

14. The method of claim 1 wherein, to establish itself as the new active OSPF instance in the event of fail-over of said active OSPF instance, said backup OSPF begins sending Hello packets to all known neighbors, based on synchronized state information.

15. The method of claim 1 wherein, to establish itself as the new active OSPF instance in the event of fail-over of said active OSPF instance, said backup OSPF creates refresh timers for all self-originated LSAs that were created by said active instance.

16. The method of claim 1 wherein, to establish itself as the new active OSPF instance in the event of fail-over of said active OSPF instance, said backup OSPF creates dead interval timers for all known neighbors.

17. The method of claim 1 wherein, to establish itself as the new active OSPF instance in the event of fail-over of said active OSPF instance, said backup OSPF creates retransmit timers for LSAs.

18. The method of claim 1 wherein, to establish itself as the new active OSPF instance in the event of fail-over of said active OSPF instance, said backup OSPF runs a designated router (DR) election algorithm for each multi-access OSPF network segment.

19. The method of claim 1 wherein, to establish itself as the new active OSPF instance in the event of fail-over of said active OSPF instance, said backup OSPF performs an evaluation of each area'"'"'s demand-circuit capability.

20. The method of claim 1 wherein, to establish itself as the new active OSPF instance in the event of fail-over of said active OSPF instance, said backup OSPF redistributes routing information (RIB).

21. The method of claim 1 wherein, to establish itself as the new active OSPF instance in the event of fail-over of said active OSPF instance, said backup OSPF performs a complete Shortest Path First (SPF) algorithm calculation.

22. The method of claim 1 wherein, to establish itself as the new active OSPF instance in the event of fail-over of said active OSPF instance, said backup OSPF performs a consistency check for redistributed routes.

23. A system for highly-available Open Shortest Path First (OSPF) routing in a network, comprising a local OSPF router and peer network routers, said local router including:

a control plane containing an active OSPF instance and a backup OSPF instance directly connected with said active OSPF instance through a highly reliable private processor link;

a data plane containing packet forwarding engines using routing tables initialized and updated from said control plane, said data plane operable to distribute protocol and transit traffic among said peer network routers; and

a message flow-through architecture, such that all incoming protocol control traffic from said peer network routers flows first through said backup OSPF instance before flowing to said active OSPF instance, and such that all protocol control traffic originating at said active OSPF instance flows first through said backup OSPF instance before being distributed among said peer network routers.

24. The system of claim 23 wherein said highly reliable private processor link is a highly reliable Transmission Control Protocol (TCP) link.

25. The system of claim 23 wherein said peer network routers in said network are organized logically into OSPF areas.