While mechanisms have existed for sometime that can quickly reroute traffic for RSVP established LSPs, fast reroute for IP/LDP based network has proven to be more difficult due to the dynamic nature of IP routing.

To achieve fast reroute in an IP/LDP network, two issues need to be solved: how to calculate the repair paths and how to implement the repair paths. The solutions must be scalable and must be able to handle the dynamics of IP routing. Recent developments in these areas, including Nexthop Fast ReRoute scheme, Alternative Shortest Path repair path calculation, and MPLS Source Route, among several others, have answers for both questions and thus made it possible to fast reroute in an IP/LDP based network in under 50ms.

Nexthop Fast ReRoute constructs repair paths that terminate at nexthop router for link protection or at next-nexthop routers for node protection. In case of link or node failure, traffic that would have traversed the failing link or node will be redirected through the corresponding repair paths. The scheme can protect IP unicast, IP multicast, LDP and RSVP traffic. Since Nexthop Fast Reroute allows all these different traffic types to share the repair paths, it can minimize the number of repair paths that need to be managed.

The repair paths can be calculated using the Alternative Shortest Path scheme, which basically excludes the link or node being protected and recalculates SPF. The scheme can provide 100% repair coverage. The repair paths can be implemented using RSVP TE, or using MPLS Source Route.

Bio:
Albert Jining Tian is a senior member in Redback Networks' IP routing team, working on various IP routing and MPLS related protocols. He has also been a leading software engineer in system/infrastructure area for Redback's SmartEdge 800 router.

Prior to joining Redback in 1998, he was a leading software engineer at Motorola Canada, working on 3G CDMA data infrastructure.

He received his M.S. Computer Science from Univ. of British Columbia, Vancouver, Canada, where his research focus was on IP multicast routing.