Method and apparatus for managing forwarding of data in an autonomous system

1. A method, comprising:

constructing, at a first border router of a first autonomous system (AS), a primary route to a remote AS;

constructing, at the first border router, an alternate route to the remote AS via a second border router in the first AS;

instigating a backup tunnel from the first border router in the first AS to the second border router in the first AS for use by the alternate route, upon failure of an inter-area link used by the primary route from the first AS to the remote AS; and

sending a failure message to one or more other border routers of the first AS to cause the one or more other border routers to forward traffic to the second border router in the first AS.

2. The method as in claim 1 , wherein the border routers in the first AS comprise a Virtual Private Network (VPN).

3. The method as in claim 2 , wherein the VPN comprises a Border Gateway Protocol (BGP)/Multi-Protocol Label Switching (MPLS) VPN and the primary route comprises an MPLS tunnel.

4. The method as in claim 2 , further comprising:

learning the alternate route at the first border router via a VPN route advertisement.

5. The method as in claim 4 , wherein the VPN route advertisement comprises a corresponding route distinguisher.

6. The method as in claim 1 , wherein the failure message comprises a withdrawal message.

7. The method as in claim 1 , further comprising:

tunneling data for the second AS from a third border router in the first AS to the second border router using a second backup tunnel upon receipt of the failure message.

8. The method as in claim 1 , further comprising:

removing the backup tunnel upon expiration of a convergence period.

9. The method as claim 1 , wherein the primary route comprises one of an Internet Protocol (IP) tunnel and a Multi-Protocol Label Switching (MPLS) tunnel.

10. The method as in claim 1 , further comprising:

detecting failure of the primary route;

setting the primary route to a low preference value; and

advertising the low preference value in the failure message.

11. The method as in claim 1 , further comprising:

receiving the advertisement at the one or more other border routers;

deriving an alternate route at the one or more other border routers; and

forwarding data elements previously destined for the primary route to the derived alternate route using a second backup tunnel.

12. The method as in claim 1 , further comprising:

determining that the first border router no longer receives data elements for the primary route; and in response

removing the backup tunnel.

13. The method as in claim 1 , wherein the border routers of the first AS communicate with one or more border routers of the remote AS using an exterior communications protocol, and wherein the border routers of the first AS communicate with one another using an interior communications protocol.

14. A method, comprising:

communicating between a plurality of border routers in a first autonomous system (AS) using primary tunnels;

communicating from the plurality of border routers to one or more remote ASes using inter-domain links from the border routers;

forwarding data elements for a primary inter-AS route from a first border router to a second border router in the first AS;

receiving a failure message advertisement from the second border router in relation to the primary inter-AS route;

deriving an alternate inter-AS route; and

forwarding data elements previously destined for the primary inter-AS route to the derived alternate inter-AS route using a primary tunnel in the first AS in response to an inter-area link failure used by the primary inter-AS route.

15. Software encoded in one or more volatile or non-volatile non-transitory computer-readable media and when executed operable to:

construct, at a first border router of a first autonomous system (AS), a primary route to a remote AS;

construct, at the first border router, an alternate route to the remote AS via a second border router in the first AS;

instigate a backup tunnel from the first border router in the first AS to the second border router in the first AS for use by the alternate route, upon a failure of an inter-area link used by the primary route from the first AS to the remote AS; and

send a failure message to one or more other border routers of the first AS to cause the one or more other border routers to forward traffic to the second border router in the first AS.

16. An apparatus, comprising:

means for constructing, at a first border router of a first autonomous system (AS), a primary route to a remote AS;

means for constructing, at the first border router, an alternate route to the remote AS via a second border router in the first AS;

means for instigating a backup tunnel from the first border router in the first AS to the second border router in the first AS for use by the alternate route, upon a failure of an inter-area link used by the primary route from the first AS to the remote AS; and

means for sending a failure message to one or more other border routers of the first AS to cause the one or more other border routers to forward traffic to the second border router in the first AS.

17. An apparatus, comprising:

one or more processors;

a network interface communicatively coupled to the one or more processors and configured to communicate one or more packet flows among the one or more processors in a network; and

a memory adapted to store one or more sequences of instructions that when executed are operable to i) construct, at a first border router of a first autonomous system (AS), a primary route to a remote AS, ii) construct, at the first border router, an alternate route to the remote AS via a second border router in the first AS, iii) instigate a backup tunnel from the first border router in the first AS to the second border router in the first AS for use by the alternate route, upon a failure of an inter-area link used by the primary route from the first AS to the remote AS, and iv) send a failure message to one or more other border routers of the first AS to cause the one or more other border routers to forward traffic to the second border router in the first AS.