Method and apparatus for controlling the dissemination of routing information on a communication network

• US 20050152333A1
• Filed: 01/14/2004
• Published: 07/14/2005
• Est. Priority Date: 01/14/2004
• Status: Active Grant

• Current Assignee: Avaya Management L.P. (Avaya Incorporated)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Smith, Peter Ashwood
• Granted Patent: US 7,697,454 B2
• Time in Patent Office: Days
• US Class Current: 370/351
• CPC Class Codes: H04L 45/02 Topology update or discovery
• CPC Class Codes: H04L 45/03 by updating link state protocols

Abstract

The propagation of link state advertisements (LSAs) is limited by defining a propagation radius on the network, measured by sum of link cost, or using another metric. By limiting the distance a LSA will propagate on the network it is possible to limit LSA traffic on the network without defining areas on the network. This eliminates the need to name those areas and designate nodes as belonging to particular areas, which enables the nodes to be added on an ad-hoc basis without a centralized management structure. Additionally, this enables the nodes to be mobile on the network without requiring close monitoring and updating of area affiliation by the nodes. Further, not having areas on the network eliminates the requirement for area border routers to control link state advertisements, reduces or eliminates special intra-area communication protocol exchanges, and avoids potential congestion which may occur in connection with inter-area traffic.

Claims

1. A method of controlling the dissemination of routing information on a communication network, the method comprising the steps of:

receiving a link state advertisement from the network;

ascertaining distance information associated with at least one of the link state advertisement and link state information contained in the link state advertisement; and

selectively forwarding the link state advertisement on the network, the step of selectively forwarding depending on the ascertained distance information.

2. The method of claim 1, wherein the step of selectively forwarding comprises:

forwarding the link state advertisement on the network where the distance information indicates the link state advertisement is likely to be relevant to other nodes on the network and not forwarding the link state advertisement on the network where the distance information indicates the link state advertisement is not likely to be relevant to other nodes on the network.

3. The method of claim 1, wherein the step of selectively forwarding comprises:

forwarding the link state advertisement on the network if the link state advertisement contained link state information that was relevant, and not forwarding the link state advertisement on the network if the link state advertisement contained information that was not relevant.

4. The method of claim 3, wherein the step of ascertaining distance information comprises analyzing whether link state information contained in the link state advertisement is relevant.

5. The method of claim 4, wherein the distance information is contained in the link state advertisement.

6. The method of claim 1, wherein the distance information is measured by the sum of link costs.

7. A network topology, comprising:

a plurality of OSPF routers interconnected in a network and belonging to an OSPF area, said plurality of OSPF routers being configured to limit the dissemination of Link State Advertisements (LSAs) within the OSPF area such that not every OSPF router within the OSPF area receives every LSA.

8. The network topology of claim 7, wherein the plurality of OSPF routers are interconnected in an ad-hoc wireless mesh network.

9. The network topology of claim 7, wherein the network is configured such that LSAs are disseminated only a predefined distance within the OSPF area.

10. The network topology of claim 7, wherein a subset of the OSPF routers are focal nodes.

11. The network topology of claim 10, wherein the network is configured such that LSAs are disseminated only a predetermined distance within the OSPF area.

12. The network topology of claim 11, wherein the predetermined distance is selected such that each LSA is received by at least two focal nodes.

13. The network topology of claim 11, wherein nodes on the network other than focal nodes are configured to maintain a routing table containing information obtained from LSAs, said routing table containing information associated with at least two focal nodes.

14. The network topology of claim 10, wherein the focal nodes are area border routers to an OSPF backbone area.

15. The network topology of claim 14, wherein the focal nodes on the OSPF backbone area are configured to disseminate link state information for nodes in their local area, their local area being defined as that portion of the network from which the focal nodes receive LSAs.

16. A network node, comprising:

control logic configured to inspect a link state advertisement received from a network, ascertain distance information associated with the link state advertisement, and selectively drop the link state advertisement if the distance information exceeds a predetermined metric.

17. The network node of claim 16, wherein the control logic is configured to ascertain the distance information from information contained in the link state advertisement.

18. The network node of claim 16, wherein the metric is a sum of link costs associated with the link state advertisement.

19. The network node of claim 16, further comprising a routing table, and wherein the control logic is further configured to update information in the routing table from link state information contained in the link state advertisement if the information is determined to be relevant.

20. The network node of claim 16, further comprising a routing table, and wherein the control logic is further configured to update information in the routing table from link state information contained in the link state advertisement, and wherein the control logic is configured to selectively drop the link state advertisement if the link state advertisement is not likely to be relevant to another router on the network.