1. Pay-Per-View (PPV) Service

• simplest type, analogous to existing PPV channels
• time of access for multimedia documents is decided by the server rather than the client
• the server multicasts the program at fixed times and any interested clients tune in to the server at these fixed times
 

• sometimes called: Shared Viewing with Constraints
• motivation: observation that for certain applications, such as on-demand movies, request arrivals exhibit significant temporal and spatial locality
• the client accesses the multimedia documents at any time it decides by sending a request to the MOD server. The server processes and accepts these requests in groups to exploit any clustering properties
• the client can face admission latency after which it becomes part of a group, all members of which are using the same connection
• advantage: the client can access data at any time instance
• disadvantage: difficult to implement for applications that don't exhibit clustering properties
 

• each access request from clients is treated independently at the server
• advantage: personalized, interactive multimedia delivery
• disadvantage: serious implications in throughput