However, the increase in the number of viewers, along with the rise in number of other online applications, has made this architecture ineffective because of bandwidth bottleneck issues. One solution introduced to solve this problem is peer to peer (P2P) technology, wherein peers automatically relay streams to other peers. The P2P network they are connected to performs an algorithm that help peers nd a relay for a specied stream to connect to.
In multimedia streaming service, the important factors to observe are playing time and network bandwidth utilization. The purpose of this report is to present a solution to these issues. The proposal is to utilize P2P caching service that exploits the proximity of connected clients, i.e. the temporal and spatial locality of cached streams to the clients. In this scheme, connected peer clients not only receive multimedia streams from a server, but also send cached streams to peer clients like a proxy server upon request. One P2P technology that can support this architecture is called inter-overlay optimization.
Figure 1 shows the different approaches employed in multimedia streaming starting from the centralized client-server topology to decentralized schemes, which includes IP multicast and P2P solutions. P2P can be further sub-divided into mesh-based, tree-based and hybrid overlays.
Each peer can accept media data from multiple parents...
Each peer can accept media data from multiple parents as well as provide services to multiple children (both parent and child are relative terms in place of master-slave relationship). The advantages of this solution are: high resource utilization and fast discovery of fresh peers in a single mesh due to gossiping. The disadvantages are: quality of service cannot be guaranteed due to gossiping among peers and large buffer space needed to reduce impact of autonomy of peers (in a dynamic environment). Example applications are Coolstreaming, Promise and GNUStream.
Each peer communicates only with one parent (per overlay) and provides service to a number of children such that a "tree" topology is always maintained (in an overlay). The advantages of this solution are: closely resembles original IP multicast ideas and low management overhead. The disadvantages are: highly vulnerable to disruption under dynamic environments and low resource utilization. Example applications are ALMI, NICE and ZigZag (single tree protocol) and SplitStream, Bullet and MDC (multiple tree protocol).
Figure 1. Multimedia Streaming Topologies
There were lots of research done in designing efficient streaming overlay multicast scheme based on P2P networks , where connected viewers act as routers for other users. Different from traditional IP multicast systems, streaming overlays concentrates on the following issues: start-up delay, source-to-end delay and playback continuity. These metrics are very important to the user because large start-up delays would exhaust user patience and streaming interruptions would spoil viewing experience. In order to improve the above-mentioned metrics, studies were done on intra-overlay optimization ,