Self-organizing Tree Formation Protocol and Adaptive Subcasting for EÆcient Reliable Multicast

We present a self-organizing tree formation protocol, STFP, for one-to-many reliable multicasts. STFP constructs a minimum spanning tree of receivers over the underlying multicast routing tree. Based on the tree built by STFP, we develop eÆcient one-tomany reliable multicast protocols that use unicast and/or subcast for retransmitting lost packets. We also describe two novel adaptive subcasting techniques that enable multicast applications to control bandwidth/latency trade-o s. These mechanisms choose unicast or subcast repair dynamically according to the loss correlation among the receivers. A simulation study using NS shows that, compared to OTERS, our reliable multicast protocol using unicast retransmission reduces the repair bandwidth to a half, and that another protocol using subcast repair achieves similar recovery latency while spending two thirds of OTERS's repair bandwidth. It is also demonstrated that our adaptive subcasting techniques are e ective in avoiding both the cascaded delay of unicast repair and the bandwidth waste of blind subcast repair.