Wide-Area IP Multicast Tra-c Characterization (Extended Version)
Robert Beverly · 2003
IP multicast is gaining acceptance among ser- vice providers as the protocols and infrastructure mature. Yet characteristics of multicast tra-c remain poorly under- stood. Using passive OC-12 monitors we observe multicast tra-c on links connecting aggregated customers and peer networks to our native multicast backbone network. We flrst reflne existing tra-c ∞ow proflling methodologies via an exploration of temporal difierences in multicast packet trains. Based on this framework we collect multicast ∞ow traces from four geographically dispersed nodes in the vBNS network over a one-month period. We present multicast- speciflc tra-c characteristics including packet and ∞ow size distributions, packet duplication and fragmentation, address accumulation and address space distributions. We analyze the distribution of sources per group and the implications on the applicability of emerging single-source protocols. Anal- ysis reveals results contrary to prevailing wisdom, includ- ing: (i) a preponderance of single-packet ∞ows; (ii) a highly variable packet size distribution, with many large packets and strong modes; (iii) the existence of fragmented multi- cast tra-c; and (iv) an insigniflcant number of simultaneous multiple-source groups. Based on our analysis, we recom- mend policies for deployment and improvements to protocol implementations.