Deployment Issues in Scalable Island Multicast for Peer-to-Peer Streaming

Xing Jin, Ho-Shing Tang, S.-H. Gary Chan, Kan-Leung Cheng
2009 IEEE Multimedia  
W ith the prevalence of peerto-peer (P2P) technologies, multimedia streaming has become an important Internet application. In a P2P-streaming system, cooperative peers organize into an overlay network via unicast connections. The peers cache and relay data for each other, eliminating the need for powerful servers. A popular P2Pstreaming system might consist of more than tens of thousands of peers. 1,2 To improve delivery efficiency, some P2P protocols make use of Internet Protocol (IP)
more » ... . Although global IP multicast is not yet available, many local Internet networks are multicastcapable. These local multicast-capable domains, socalled islands, are frequently interconnected by multicast-incapable or multicast-disabled routers. For example, in the Hong Kong area, Hong Kong Broadband Network Limited has deployed a network that covers more than 2,500 corporate buildings and approximately one million residences. It offers digital television service to subscribers via IP multicast. The Scalable Island Multicast protocol, which we introduced in other research reports, integrates IP multicast into P2P overlay delivery. 3, 4 In SIM, hosts within an island communicate with IP multicast and connect across islands through unicast. Each host distributedly joins an overlay tree and detects and joins its multicast island, if possible. Each island in SIM has a unique ingress host that receives media content from outside the island and multicasts within the island. Other hosts in the island receive data via IP multicast from the ingress. In this article, we investigate the practical deployment issues of the SIM protocol. Network address translation In SIM, hosts first form a low-delay overlay tree, then detect multicast islands and use IP multicast if possible. In the following discussion, a parent of a host refers to the host's parent in the overlay tree. We are interested in building a tree with low end-to-end delay. Clearly, the tree-construction mechanism should be distributed and scalable, and the algorithm should be simple, with low setup and maintenance overheads. A practical problem in setting up connections is that some hosts might be behind network address translations (NATs) and have only limited connectivity. These hosts are called restricted hosts. A host that is not behind any NAT is called public. A restricted host can communicate only with public hosts or other restricted hosts behind the same NAT, while a public host can communicate with either a restricted host (with the restricted host being the initiator of the connection) or a public one. Hence, we integrate the traditional Basic Contributor algorithm 5 into our system to achieve NAT traversal. This algorithm allows restricted hosts to upload
doi:10.1109/mmul.2009.6 fatcat:ywl6nqxpuramfhy3q7dvbimrry