Abstract: Proactive scheme have a shorter recovering time than reactive approach.In this paper a modified delay and degree-constrained scheme named DDCP is proposed.Compared with previous one，the new approach ensures the delay requirement is satisfied while the degree constraint is not violated.At the same time a degree pre-reserved initial tree-construction algorithm is also put forward to improve the efficiency of DDCP.Whatever the responsiveness of the recovery process，the quality of the restored tree or the recovery overhead DDCP have improved to some extent.Simulation tests proved it.

摘要： 应用层组播树的主动恢复方案具有比被动恢复方案更小的恢复时延。针对proactive方案只能满足节点连接度限制的不足提出了一种QOS有保证的主动树恢复方案—DDCP。在满足节点连接度限制的同时，保证了端用户的时延性能。与之对应提出了一种预留节点度的初始组播树构建方案。DDCP方案不论是从组播树的恢复时延、重构树的质量还是用于树重建的控制负荷方面考虑，都比其它方案有一定程度的改进，模拟实验证明了这一点。