Contractual group membership CGM: a new mechanism for multicast group management

We present a new concept for multicast group management called contractual group membership or CGM. The main idea behind this concept is the division of the receiver group into homogeneous subgroups. This division is based on physical conditions or/and QoS criteria like available bandwidth, delay, loss probability, ... . The sender will carry a separate conversation with each subgroup using the scalable reliable multicast protocol (SRMTP). We define a multidimensional distance factor to evaluate the logical distance between the members of a group in order to split this group into homogeneous subgroups. The dimensions of this distance factor are end-to-end bandwidth, delay, and loss rate. ESRMTP is an extended version of SRMTP that we have developed in order to support our new distance factor. The simulation results that we have obtained using the three dimensional distance factor with ESRMTP show that the bandwidth splitting is very important for increasing the average throughput of the multicast session and to minimize the average end-to-end delay. It shows as well that the delay and loss probability splitting decrease the jitter for each receiver which is very important for real-time applications. In addition to jitter minimization, loss rate splitting plays a key role in minimizing the network load caused by the FEC integrated in ESRMTP, due to the possibility of controlling the amount of FEC overhead as a function of the loss rate.