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Recently, some problems related to using the Real-time Control Protocol (RTCP) in very large dynamic groups have arisen. Some of these problems are: feedback delay, increasing storage state at every member, and ineffective RTCP bandwidth usage, especially for receivers that obtain incoming RTCP reports through low bandwidth links. In addition, the functionality of some fields (e.g. packet loss fraction) in the Receiver Reports (RRs) becomes questionable as, currently, an increasing number of real-time adaptive applications are using receiver-based rate adaptive schemes instead of rate adaptation schemes based on the sender. This paper presents the design of a scalable RTCP (S-RTCP) scheme. S-RTCP is based on a hierarchical structure in which members are grouped into local regions. For every region, there is an Aggregator (AG) which receives the RRs sent by its local members. The AG extracts and summarises important information in the RRs, derives some statistics, and sends them to a Manager. The Manager performs additional statistical analysis to monitor the transmission quality and to estimate regions which are suffering ma<>sively from congestion. We believe that our S-RTCP alleviates some of the RTCP scalability problems encountered in very large dynamic groups and makes effective use of RRs with regard to the current changing requirement<> of real-time adaptive applications in the Internet today.

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In this paper, we address some of the problems concerning RTCP scalability in large multicast groups. The problems are summarised as the increased storage state maintained by every member about every other member in the group, the feedback delay, and the bandwidth usage problem especially for receivers that obtain incoming RTCP reports through low bandwidth links. We designed a scheme to tackle these problems and to improve the RTCP scalability. Our scheme is based on a hierarchical structure in which members are grouped dynamically into local regions and Receiver Reports (RRs) are sent with limited scope. As a result, the load is distributed among members in the group. Each region has an aggregator (AG) that receives the RRs feedback, performs some aggregation statistics on this control data, then sends these statistics to a Manager. The Manager performs additional analysis to evaluate the network performance and to estimate regions which are suffering from significant congestion. Finally, we present the benefits of using our scheme.

In this paper, we outline an architecture which enables the real-time delivery of continuous media over the Internet using the Real-time Transport Protocol (RTP). We present our implementation of RTP with its control protocol RTCP. RTCP feedback reports are used by our adaptive rate controller to help reduce congestion. Then, we assess the functionality of RTP and its suitability for the future Internet. This leads us to investigate the resource Reservation Protocol (RSVP) and evaluate RTP and RSVP together with respect to some transport protocols' requirement for the future Internet.