Fault-tolerant IS-IS routing system, and a corresponding method

• US 20030084371A1
• Filed: 10/18/2002
• Published: 05/01/2003
• Est. Priority Date: 10/25/2001
• Status: Active Grant

• Current Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Original Assignee: Alcatel SA (Nokia Corporation)
• Inventors: Rombeaut, Jean-Pierre, Mongazon-Cazavet, Bruno
• Granted Patent: US 7,155,536 B2
• Time in Patent Office: Days
• US Class Current: 714/13
• CPC Class Codes: H04L 45/04 Interdomain routing, e.g. hierarchical routing
• CPC Class Codes: H04L 45/28 using route fault recovery
• CPC Class Codes: H04L 45/58 Association of routers

Abstract

The invention provides a high availability control method for a router in an autonomous system, the router being in communication with other routers using an IS-IS protocol via interfaces and presenting both an active IS-IS protocol engine and a standby IS-IS protocol engine. The method comprises steps of storing data concerning adjacency, the state of links, and interfaces in a memory of the active protocol engine, updating the data stored in a memory of the standby protocol engine, and activating the standby protocol engine using the updated data. The invention also provides a router implementing the method. The invention serves to increase router availability in the event of a failure or of maintenance actions.

Claims

1. / A method of controlling a router in an autonomous system, the router being in communication with other routers using an IS-IS protocol via interfaces and presenting:

an active IS-IS protocol engine; and

a standby IS-IS protocol engine;

the method comprising the steps of;

the router communicating with other routers via the active protocol engine;

storing the following in a memory of the active protocol engine;

data concerning the adjacency of the other routers;

data concerning the state of links with the other routers; and

data concerning the interfaces;

updating the data stored in a memory of the standby protocol engine on the basis of the data in the active router concerning the adjacency, the state of the links, and the interfaces; and

activating the standby protocol engine with the updated data, by using the IS-IS protocol with the other routers.

2. / The method of claim 1, wherein all of the data is updated at the request of the standby protocol engine.

3. / The method of claim 1, further comprising a step of detecting a modification of the data stored in a memory of the active protocol engine, with updating being performed whenever a modification of said data is detected.

4. / The method of claim 3, wherein the detected modification is selected from the group constituted by:

adjacency activation;

adjacency deactivation;

adjacency data being modified, possibly after receiving a presence declaration packet;

modifications, deletions, and creations relating to the states of links and of interfaces.

5. / The method of claim 1, wherein the step of activating the standby protocol engine includes a step of validating the preserved adjacency and link state data without modifying the IS-IS protocol.

6. / The method of claim 1, wherein, prior to being activated, the standby protocol engine performs a shortest path search on the basis of the updated data.

7. / The method of claim 1, wherein activation of the standby protocol engine includes a step of verifying the validity of its adjacency data.

8. / The method of claim 7, wherein validity verification comprises:

sending an IIH PDU data packet from the standby protocol engine to an adjacent router, the packet containing a request that the adjacent router send a CSNP data packet; and

modifying the adjacency data as a function of the nature of the response from the adjacent router.

9. / A communication method comprising the following steps:

sending an IIH PDU data packet from a first router to an adjacent second router, the packet including a parameter at a predetermined location;

sending a CSNP data packet from the second router to the first router as a function of the value of said parameter of the IIH PDU data packet.

10. / An IS-IS communication protocol in which an IIH PDU data packet contains a request for a CSNP data packet to be sent.

11. / A router presenting a plurality of interfaces via which it is capable of communicating with other routers using an IS-IS protocol, the router comprising:

an active IS-IS protocol engine;

a standby IS-IS protocol engine;

a communications channel between the protocol engines;

a least one data storage memory in communication with the active protocol engine; and

at least one data storage memory in communication with the standby protocol engine.