Multicast is an important research topic for the Internet.Recent research shows some intrinsic limitation in IP Multicast
and Application Layer Multicast (ALM) is proposed.In this article we discuss and classify some major algorithms proposed for ALM.The fundamental problems in ALM research are identified and the metrics for evaluation of ALM algorithms are summarized.Some topics (e.g.
Overlay Network
media encoding method) are also discussed for their close relationship with ALM research.Finally
some possible directions for future research are discussed.