Server replication and its placement for reliable multicast

A key challenge in reliable multicast is to reduce the retransmission cost due to features such as bandwidth usage and delay. A local recovery approach employing replicated servers has recently been shown to be effective in reducing this cost. The basic idea in the local recovery approach is to perform data replication on a subset of routers, known as replicated servers, inside the network. Each replicated server is attached to a router and responsible for the retransmission requests from receivers within its local area. In a multicast network, packets are forwarded from a source (sender) to group receivers along a distribution tree where the source is the root, the receivers are the leaves and the multicast-capable routers are the internal nodes. In this paper, we consider the problem of placing multiple replicated servers within the multicast-capable routers. We first present the problem formulation and then present a number of heuristics-based algorithms for server replication. Finally, in order to investigate various trade-offs in terms of cost and algorithm complexity, we carry out comparison studies among different heuristic algorithms