document: P2Cast : peer-to-peer patching scheme for VoD service Providing video on demand ( VoD ) service over the Internet in a scalable way is a challenging problem . In this paper , we propose P2Cast - an architecture that uses a peer-to-peer approach to cooperatively stream video using patching techniques , while only relying on unicast connections among peers . We address the following two key technical issues in P2Cast : ( 1 ) constructing an application overlay appropriate for streaming ; and ( 2 ) providing continuous stream playback ( without glitches ) in the face of disruption from an early departing client . Our simulation experiments show that P2Cast can serve many more clients than traditional client-server unicast service , and that it generally out-performs multicast-based patching if clients can cache more than of a stream 's initial portion . We handle disruptions by delaying the start of playback and applying the shifted forwarding technique . A threshold on the length of time during which arriving clients are served in a single session in P2Cast serves as a knob to adjust the balance between the scalability and the clients ' viewing quality in P2Cast .
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