Network tomography from aggregate loss reports

Abstract

Multicast applications and network monitors can potentially benefit from the ability to infer the loss rates along links within a multicast tree. Estimators, known generically by minc or multicast inference of network characteristics, have been developed to provide this ability. They consider multicast data packets to be probes, and conduct inference based upon reports of which probes reached each receiver. In practice, gathering reports from receivers in real time is a non-trivial task that presents scaling problems as the number of receivers increases. Prior work has led to an extension of the RTP data transport protocol to permit receivers to report per-probe information in packets known as RTCP XR packets. This paper demonstrates how minc inference can, in fact, be conducted using only a default RTP packet format known as RTCP RR. RTCP RR packets contain summary information rather than per-probe information. They thus offer bandwidth savings, although this comes at the expense of an increase in estimator convergence time. Furthermore, this technique can be used by the observer of any standard RTP session, whereas estimation based upon per-probe information is only possible when a session explicitly employs the extended reporting format.