System and method for improved routing in autonomous systems

1. A method of advertising routes, the method comprising:

identifying a plurality of first edge routers for an autonomous system;

selecting a plurality of second edge routers from the plurality of first edge routers, a first prefix being reachable using the plurality of second edge routers;

determining a third edge router, the third edge router being associated with a first path for reaching the first prefix, the third edge router being selected from the plurality of second edge routers, and the first path being a best path for reaching the first prefix;

forming an edge router list consisting of the plurality of second edge routers except for the third edge router;

forming a first reachability message including the first prefix, the first path, information associated with the first path, and the edge router list, but not including paths for reaching edge routers in the edge router list; and

transmitting the first reachability message.

2. The method of claim 1 wherein the first reachability message is transmitted to a plurality of fourth routers.

3. The method of claim 2 wherein the plurality of fourth routers include the plurality of first edge routers and one or more non-edge routers of the autonomous system.

4. The method of claim 1 wherein the routes are advertised by a route reflector.

5. The method of claim 4 , further comprising determining the first path based on information associated with routing costs between the route reflector and the third edge router.

6. The method of claim 1 , further comprising determining the first path based on information associated with routing costs to reach the third edge router.

7. The method of claim 6 wherein the first path has a lowest routing cost among all routing costs to reach any of the plurality of second edge routers.

8. The method of claim 1 , further comprising:

detecting whether the first path changes; and

when the first path changes:

determining a second path, the second path being a new best path for reaching the first prefix;

forming a second reachability message including information associated with the second path; and

transmitting the second reachability message.

9. The method of claim 8 , further comprising:

when a fourth edge router associated with the second path is different from the third edge router:

updating the edge router list by adding the third edge router to the edge router list and removing the fourth edge router from the edge router list;

wherein the second reachability message further includes the updated edge router list.

10. The method of claim 1 , further comprising:

detecting whether the first path is down; and

when the first path is down:

determining a second path, the second path being a new best path for reaching the first prefix;

forming a second reachability message including information associated with the second path; and

transmitting the second reachability message.

11. The method of claim 10 , further comprising:

detecting whether all paths to the first prefix are down; and

transmitting a route withdrawal message for the first prefix when all paths to the first prefix are down.

12. The method of claim 11 , further comprising:

when all paths to the first prefix are down:

waiting until the first prefix is reachable using a third path;

forming a third reachability message including information associated with the third path; and

transmitting the third reachability message.

13. The method of claim 1 , further comprising:

detecting whether a second path associated with a fourth edge router is down, the edge router list including the fourth edge router; and

when the second path associated with the fourth edge router is down:

updating the edge router list by removing the fourth edge router from the edge router list;

forming a second reachability message including the updated edge router list; and

transmitting the second reachability message.

14. The method of claim 1 , further comprising:

detecting a new path for reaching the first prefix, the new path being associated with a fourth edge router;

when the new path for reaching the first prefix is detected:

detecting whether the new path is better than the first path;

when the new path is better than the first path:

updating the edge router list by adding the third edge router to the edge router list;

forming a second reachability message including information associated with the new path and the updated edge router list; and

transmitting the second reachability message; and

when the new path is not better than the first path:

updating the edge router list by adding the fourth edge router to the edge router list;

forming a third reachability message including information associated with the updated edge router list; and

transmitting the third reachability message.

15. The method of claim 1 , further comprising:

selecting a plurality of fourth edge routers from the plurality of first edge routers, a second prefix being reachable using the plurality of fourth edge routers;

determining a fifth edge router, the fifth edge router being associated with a second path for reaching the second prefix, the fifth edge router being selected from the plurality of fourth edge routers, and the second path being a best path for reaching the second prefix;

forming another edge router list consisting of the plurality of fourth edge routers except for the fifth edge router;

forming a second reachability message including the second prefix, the second path, information associated with the second path, and the another edge router list, but not including paths for reaching edge routers in the another edge router list; and

transmitting the second reachability message.

16. A method of routing, the method comprising:

receiving a first reachability message including a first prefix, a first path for reaching the first prefix via a first edge router, information associated with the first path, and a first edge router list consisting only of edge routers other than the first edge router that are usable to reach the first prefix, but not including paths for reaching edge routers in the first edge router list, each of the first edge router and the edge routers in the first edge router list being part of an autonomous system;

selecting a second edge router from the first edge router and the edge routers in the first edge router list based on information associated with routing costs to the first edge router and the edge routers in the first edge router list;

receiving network traffic for the first prefix; and

routing the network traffic for the first prefix toward the selected second edge router.

17. The method of claim 16 wherein a routing cost to the first edge router is a lowest routing cost among all routing costs to reach any of the first edge router and the edge routers in the first edge router list.

18. The method of claim 16 , further comprising:

receiving a second reachability message including a second prefix, a second path for reaching the second prefix via a third edge router, information associated with the second path, and a second edge router list consisting only of edge routers other than the third edge router that are usable to reach the second prefix, but not including paths for reaching edge routers in the second edge router list, each of the third edge router and the edge routers in the second edge router list being part of the autonomous system;

selecting a fourth edge router from the third edge router and the edge routers in the second edge router list based on information associated with routing costs to the third edge router and the edge routers in the second edge router list;

receiving network traffic for the second prefix; and

routing the network traffic for the second prefix toward the selected fourth edge router.

19. An information handling system comprising:

a communications network, the communications network including:

a router;

wherein the router is configured to:

identify a plurality of first edge routers for an autonomous system;

select a plurality of second edge routers from the plurality of first edge routers, a prefix being reachable using the plurality of second edge routers;

determine a third edge router, the third edge router being associated with a path for reaching the prefix, the third edge router being selected from the plurality of second edge routers, and the path being a best path for reaching the prefix;

form an edge router list consisting of the plurality of second edge routers except for the third edge router;

form a reachability message including the prefix, the path, information associated with the path, and the edge router list, but not including paths for reaching edge routers in the edge router list; and

transmit the reachability message.