QDMR: an efficient QoS dependent multicast routing algorithm

Many real time applications, such as video conferencing, require the transmission of messages from a sender to multiple receivers subject to Quality of Service (QoS) delivery constraints (e.g. bounded delay). This requires the underlying multicast protocol to find a QoS constrained minimum cost communication path (tree). However, finding such a tree is known to be computationally expensive. We present a fast heuristic, called QDMR, for generating delay constrained low cost multicast routing trees. A salient feature of QDMR is that it dynamically adjusts its low cost tree construction policy based on how far the current on-tree node is from violating the QoS delay bound. This QoS dependent (adaptive) tree construction, together with the capability to merge least delay paths into the low cost tree in case of stringent delay requirements, lead to the following properties: (1) QDMR guarantees to find a feasible multicast tree if such tree exists; (2) this delay bounded multicast tree is very rapidly generated; and (3) the tree has low cost. Through analysis and extensive simulations, we confirm the premise of QDMR by comparing it to many existing multicast algorithms.