Abstract: The paper studies the two layered application layer multicast networks based on Multicast Service Nodes（MSN），presents the degree-delay-constrained minimum spanning tree problem，and provides a heuristic algorithm named DD-Prim algorithm for this problem.In order to further improve the solution to this problem，the authors introduce a bias vector into the DD-Prim algorithm，rename it BDD-Prim algorithm.The authors use it as a decoder for genetic algorithm.Simulation results proof the genetic algorithm’s efficiency.

摘要： 研究了基于组播服务节点（MSN）的两层应用层组播网络，提出了度和时延联合约束的最小生成树问题（DDCMST问题），并给出了求解该问题的启发式算法——DD-Prim算法。为了进一步提高求解的精度，在该算法中引入了偏置向量，得到了BDD-PRIM算法，并将其作为染色体编码的译码器应用到遗传算法中。仿真结果证明了遗传算法的有效性。