Comparative study of MPNT topological models

MPNT (Multicast Proxies NeTwork) is an overlay architecture that provides multicast services to unicast or multicast clients. It is multimedia-oriented, as it implements RTP, RTCP and SIP protocols. Nevertheless, it can be used to broadcast any type of data. MPNT is proxy-based, i.e. its nodes are not end-users but proxies: they act like relays for end-users, providing them standard unicast or multicast access. For scalability and adaptivity reasons, these proxies can be interconnected using different topologies. The first implemented topology is spanning tree based. It is very efficient in terms of switching delay (no routing) but the global delay variance can be important. To remedy this, we implemented an alternate hypercube-based topology. Indeed, hypercubes have several interesting properties that ensure a better scalability. Nevertheless, this logical hypercube optimization is valid provided that interconnecting links are comparable. To adapt the architecture to the network heterogeneity, we implemented a hybrid topology exploiting both spanning tree and hypercube advantages. The objective of this paper is to compare these topologies using HYRPAN, a MPNT-specific network simulator we developed for this purpose.