Due to the advent of many new multimedia applications that have QoS (Quality of Service) requiremenst in high-speed networks, the issue of multicast routing has become more and more important. The multicast routing problem is also known as the Steiner Tree Problem which has been shown to be NP-complete. Previous research works just take delay, delay jitter, loss rate, bandwidth and cost into consideration and not view multicasting ability of router as a constrained factor. Limiting degree of switch or router can save information delivering/copying time and keep load balance.

Delay-constrained is a crucial factor in QoS. This paper takes delay and also degree constraints into account and proposes a new multicast routing algorithm based on genetic algorithm (GA) to construct Degree-Delay Constrained least-cost multicast routing Tree (DDCT). Algorithms adopt pr ..fer coding and decoding which is very suitable for crossover and mutation operation and can save runtime, pruning and grafting techniques are employed to adjust node degree and repair tree structure. Two repairing tree structure methods are proposed and named as DDCT1 and DDCT2. Simulations were conducted on a random graph to evaluate the performance of the proposed algorithm. Experimental result shows proposed algorithms perform well than other similar multicasting algorithm such as CSPT and Wang_GA.