Multimedia Multicast Transport Service for

Reliability carries different meanings for different applications. For example, in a replicated database setting, reliability means that messages are never lost, and that messages arrive in the same order at all sites. In order to guarantee this reliability property, it is acceptable to sacrifice real-time message delivery: some messages may be greatly delayed, and at certain periods message transmission may even be blocked. While this is perfectly acceptable behavior for a reliable database application, this behavior is intolerable for a reliable video server. For a continuous MPEG video player [20, 19], reliability means real-time message delivery, at a certain bandwidth; It is acceptable for some messages to be lost, as long as the available bandwidth complies with certain predetermined stochastic assumptions. Introducing database style reliability (i.e. message recovery and order constraints) may violate these assumptions, rendering the MPEG decoding algorithm incorrect. Many CSCW groupware and multimedia applications require quality of service multicast for most of their messages, and may greatly benefit from reliable multicast for a small portion of “critical ” messages. Furthermore, such applications often need to be fault-tolerant, and need to support smooth reconfiguration when parties join or leave

The ACCOPI Multimedia Transport Service over ATM

This paper discusses some of the issues in mapping the ACCOPI Multimedia Transport Service (AMTS) over the ATM (Asynchronous Transfer Mode) network technology. The AMTS is a transport service mainly designed to support multimedia applications. ATM offers two important characteristics required by multimedia applications (namely QoS and multicast). We first discuss general architectural issues such as multiplexing and QoS negotiation. Then we outline how the main functionalities of the AMTS (call control, data transfer, call join, etc.) can be supported in an ATM environment. This work has been partially supported by the Commission of the European Communities under the RACE M1005 project ACCOPI: Access Control and Copyright Protection for Images