A path-finding algorithm for loop-free routing
IEEE/ACM Transactions on Networking (TON)
Mitigating transient loops through interface-specific forwarding
Computer Networks: The International Journal of Computer and Telecommunications Networking
Avoiding transient loops during the convergence of link-state routing protocols
IEEE/ACM Transactions on Networking (TON)
Shadow configuration as a network management primitive
Proceedings of the ACM SIGCOMM 2008 conference on Data communication
SafeGuard: safe forwarding during route changes
Proceedings of the 5th international conference on Emerging networking experiments and technologies
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Under link-state routing protocols such as OSPF and IS-IS, when there is a change in the topology, propagation of link-state announcements, path recomputation, and updating of forwarding tables (FIBs) will all incur some delay before traffic forwarding can resume on alternate paths. During this convergence period, routers may have inconsistent views of the network, resulting in transient forwarding loops. Previous remedies proposed to address this issue enforce a certain order among the nodes in which they update their FIBs. While such approaches succeed in avoiding transient loops, they incur additional message overhead and increased convergence delay. We propose an alternate approach, loopless interface-specific forwarding (LISF), that averts transient loops by forwarding a packet based on both its incoming interface and destination. LISF requires no modifications to the existing link-state routing mechanisms. It is easily deployable with current routers since they already maintain a FIB at each interface for lookup efficiency. This paper presents the LISF approach, proves its correctness, discusses three alternative implementations of it and evaluates their performance.