Forwarding without loops in Icarus

Abstract

Packets trapped in a forwarding loop can rapidly saturate network links and disrupt communications until they are removed by the IP Time-To-Live (TTL) mechanism. This does not pose a significant problem when loops are rare, as is the case with mature routing protocols such as OSPF and BGP. However, in newer and more experimental settings, such as peer-to-peer overlays, active networks and multicast, routing faults are more likely. In these cases, a greater degree of protection against the effects of forwarding loops is desirable. This paper presents Icarus, a framework for detecting forwarding loops in experimental protocols. Our key insight is to add a small Bloom filter to the packet header to probabilistically detect looping behavior. We have implemented Icarus inside the ANTS active network toolkit. We find that the scheme is simple, efficient and widely applicable like a TFL, yet ensures significantly earlier loop detection.