ROUTE DEPENDENCY SELECTIVE ROUTE DOWNLOAD

Abstract

A method of selecting routing tables to include in a network line card consists of determining dependencies of local routes on remote routes using a reference count on prefixes, and selectively downloading remote routes when resolution of a route has a dependency on a remote route. In one embodiment, only remote routes that are needed to forward traffic are downloaded to a network line card.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram of a network according to an example embodiment.

FIG. 1B is a block diagram of an alternative network according to an example embodiment.

FIG. 2 is a flow chart illustrating a method of detecting remote routes to download to a core facing card according to an example embodiment.

FIG. 3 is a flow chart illustrating a further method of detecting remote routes to download to a core facing card according to an example embodiment.

FIG. 4 is a block diagram of a typical computer system for performing one or more of the methods according to an example embodiment.

Claims

1. A method comprising: determining dependencies of local routes on remote routes using a reference count on prefixes; andselectively downloading remote routes when resolution of a route has a dependency on a remote route.

2. The method of claim 1 wherein routes having a non-zero reference count are downloaded.

3. The method of claim 2 and further comprising incrementing the reference count for a prefix if a next hop for a prefix is a remote next hop.

4. The method of claim 2 and further comprising incrementing the reference count as a function of a longest matching prefix.

5. The method of claim 1 wherein the method is implemented in a core facing line card.

6. The method of claim 1 and further comprising removing a route if the reference count is zero.

7. The method of claim 1 and further comprising incrementing a next hop reference count.

8. The method of claim 7 and further comprising creating a Patricia tree of routes.

9. The method of claim 8 wherein reference counts are modified as a result of traversal of the Patricia tree.

10. A provider edge card comprising: means for determining dependencies of local routes on remote routes using a reference count on prefixes; andmeans for selectively downloading remote routes when resolution of a route has a dependency on a remote route.

11. A computer readable medium having instructions for causing a computer to implement a method of updating a network routing table for a core facing line card, the method comprising: downloading local routes to the routing table of the core facing line card;augmenting route entries in the routing table with a reference count;increasing the reference count for routes if either: a local route has a next hop that is remote; ora remote route has a non-zero reference count and longest match; anddownloading remote routes with non-zero reference counts.

12. The computer readable medium of claim 11 wherein the method is implemented in a core facing line card.

13. The computer readable medium of claim 11 wherein the method further comprises removing a route if the reference count is zero.

14. The computer readable medium of claim 11 wherein the method further comprises: creating a Patricia tree of next hops with next hop reference counts;incrementing a next hop reference count when a local route has a next hop N or a remote route with next hop which has a non zero reference count; andmodifying reference counts as a function of a subtree walk of a route.

15. A network line card comprising: a module that determines dependencies of local routes on remote routes using a reference count on prefixes; anda module that selectively downloads remote routes when resolution of a route has a dependency on a remote route.

16. The network line card of claim 15 and further comprising a memory for storing routes.

17. The network line card of claim 16 wherein routes having a non-zero reference count are downloaded into the line card memory.

18. The network line card of claim 17 and further comprising a module that increments the reference count for a prefix if a next hop for a prefix is a remote next hop.

19. The network line card of claim 17 and further comprising a module that increments the reference count as a function of a longest matching prefix.

20. The network line card of claim 15 wherein the line card is a core facing line card.