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

QoS negotiation for multicast communications

This paper deals with the Quality of Service (QoS) negotiation for multicast connections. First, we show that in the multicast case, the QoS parameters may be separated into two classes, namely the parameters whose scope is the whole multicast connection and those whose scope is limited to each receiver separately. Then, after a brief presentation of the enhanced QoS defined in the OSI95 transport service, we examine how the QoS negotiation schemes used in the peer-to-peer ISO and OSI95 transport services can be extended to multicast connections. Finally, a practical issue about QoS negotiation for multicast connections is presented