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Status of this Memo This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.

We investigate the performance of TCP connections over ATM networks without ATM-level congestion control, and compare it to the performance of TCP over packet-based networks, For simulations of congested networks, the effective throughput of TCP over ATM can be quite low when cells are dropped at the congested ATM switch. The low throughput is due to wasted bandwidth as the congested link transmits cells from 'corrupted' packets, i.e., packets in which at least one cell is dropped by the switch. This fragmentation effect can be corrected and high throughput can be achieved if the switch drops whole packets prior to buffer overflow; we call this strategy Early Packet Discard. We also discuss general issues of congestion avoidance for best-effort traffic in ATM networks.

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Telepresence conferencing systems seek to create an environment that gives users (or user groups) that are not co-located a feeling of colocated presence through multimedia communication that includes at least audio and video signals of high fidelity. A number of techniques for handling audio and video streams are used to create this experience. When these techniques are not similar, interoperability between different systems is difficult at best, and often not possible. Conveying information about the relationships between multiple streams of media would enable senders and receivers to make choices to allow telepresence systems to interwork. This memo describes the most typical and important use cases for sending multiple streams in a telepresence conference.

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