(A) study on resilient application-layer multicast for real-time services

Abstract

Application layer multicasts (ALM) have become an attractive alternative to the IP ulticasts over internet, to overcome the limited deployment problem of IP multicast routers. ALMs are promising approaches for the resilient services whose service qualities depend on the amount of data delivered in deadline, such as audio and video streaming services from one source to a number of interested members. The research on application layer multicasts for resilient services has evolved for non-real time services and then has been moving for realtime interactive services for the recent several years. However, in application layer multicasts, if a member leaves, its descendants in the multicast tree cannot receive data any more until they rejoin and so their qualities of service are damaged dramatically. Especially, this problem is exacerbated in interactive real-time services, where the lost packets should be recovered in much shorter deadlines. In order to cope with this problem, resilient application layer multicast schemes operate loss recovery schemes with recovery servers that are to retransmit the lost packets. However, existing methods have troubles in recovery in case of bulk loss. This research proposes a data packet forwarding scheme for real-time resilient multicast services, called customized forwarding, which prevents a big portion of bulk loss caused by member leaves. And, the bandwidth management scheme of customized forwarding is proposed and a multicast infrastructure to support customized forwarding is introduced. Finally, this research evaluates it via extensive simulation with network simulator (ns-2). This research demonstrates that the proposed scheme provides better performance in terms of the number of residual loss, the times of play pause, and the number of recovery overload. And, it also shows that the proposed scheme outperforms even in the environments where available bandwidth may not be measured exactly, for example, in wireless networks.