On currently deployed IP networks, "convergence" times, or the ability to reroute, is often cited as one of the key issues in providing new services and larger scale. It is, however, possible for link-state routing protocols to converge in link propagation time scales, that is, in tens of milliseconds. Why then are deployments of IS-IS, a link-state routing protocol, not anywhere near this point?

In this talk, we present some analyses of IS-IS convergence by showing its behavior upon link/router failures and repairs, and its scaling properties to large networks, both in terms of number of nodes and links. We then explore changes needed in the IS-IS specification and implementations to reach IGP convergence in milliseconds. Our results are based on experimentation done with IS-IS, but some of the findings may apply to OSPF as well.

About the Presenters
Cengiz Alaettinoglu <cengiz@packetdesign.com> is a member of the Technical Staff at Packet Design Inc. He was previously at the USC Information Sciences Institute, where he worked on the Routing Arbiter project. Cengiz co-defined the Routing Policy Specification Language along with the protocols to enable a distributed, secure routing policy system.

Van Jacobson <van@packetdesign.com> is Chief Scientist at Packet Design Inc. He was previously Chief Scientist at Cisco Systems. Prior to his tenure at Cisco, he spent 25 years at Lawrence Berkeley Laboratory as a Group Leader for the Network Research Group.

Haobo Yu is a member of the Technical Staff at Packet Design. His research interests include web cache consistency protocols and application-level routing. He received his Ph.D. in 2000 from USC, and can be reached at <haoboy@packetdesign.com>.>