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Multicast and Anycast
Full Paper
Fault Isolation in Multicast Trees
Anoop Reddy (USC/Information Sciences Institute)
Ramesh Govindan (USC/Information Sciences Institute)
Deborah Estrin (USC/Information Sciences Institute)
Fault isolation has received little attention in the Internet research literature. We take a first step towards addressing this deficiency, exploring robust and scalable mechanisms by which multicast receivers can (in some cases, approximately) locate the on-tree router responsible for a route change, or the link responsible for significant packet loss. These mechanisms rely on receivers with overlapped paths to the source sharing the responsibility of monitoring their overlapped path segments. Our mechanisms assume no additional path monitoring capability other than that provided by \emph{multicast traceroute} (mtrace).
We explore the tradeoff between monitoring overhead and fault isolation error for two classes of mechanisms: those that assume some kind of router assist for selectively multicasting the responses to mtrace requests, and those that do not. In the former category fall schemes that use \emph{subcast} or \emph{directed multicast}. In the latter are schemes that use \emph{scoping}, or a limited number of multicasts. The latter two approaches are deployable in today's multicast infrastructure. Our evaluations reveal that while some deployable alternatives have acceptable overhead, schemes that employ router assist have very desirable scaling characteristics.