UBC Theses and Dissertations
OmniStream : using centralized tree management for incentives-compatible peer-to-peer media streaming Upadhyaya, Ankur
The ability to exploit Internet infrastructure to support the live delivery of streaming media to large audiences would be of significant practical value. Existing approaches to this problem, however, based on the use of IP Multicast, commercial content distribution networks, or costly bandwidth provisioning, are severely limited: IP Multicast has seen only sparse deployment, while the latter two options are prohibitively expensive for many content providers. In recent work, peer-to-peer media streaming has been explored as an interesting alternative solution. Here, a server peer forwards a stream to a number of client peers using basic unicast transmission. Clients receiving the stream can then contribute their unused upstream bandwidth to forward the stream to additional clients, who in turn can do the same and so on. In effect, the bandwidth demands of a streaming session are distributed over the set of receivers; although each of these collaborative end-hosts may have a low-capacity access link, together they essentially “pool” their upstream bandwidth to support large-scale streaming sessions. Unfortunately, this cooperative approach to media streaming is vulnerable to the inherent tension between selfish interests and collective welfare characteristic of peer-topeer systems. The potential prevalence of free-riding, whereby a peer consumes bandwidth without adequate reciprocity, is of particular concern. Given the highly sensitive throughput requirements of media streaming, the scalability of any peer-to-peer approach would be severely limited by such uncooperative behavior. Although a handful of mechanisms have been proposed to address this issue, they are limited either by their reliance on “tamper-proof’ software - whereby they unrealistically assume that peers will correctly follow a prescribed protocol even though it may be in their selfish interest to deviate, or other practical considerations (e.g. slow responsiveness, instability). In this thesis, OmniStream, a solution based on the centralized management of multicast trees, is proposed to address the issue of free-riding in peer-to-peer media streaming, without these limitations. The proposed protocol is evaluated through simulation experiments representative of typical operational scenarios. The results obtained suggest the viability of the proposed approach.
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