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RFC 3550 - 10. Congestion Control

  1. Congestion Control

All transport protocols used on the Internet need to address congestion control in some way [31]. RTP is not an exception, but because the data transported over RTP is often inelastic (generated at a fixed or controlled rate), the means to control congestion in RTP may be quite different from those for other transport protocols such as TCP. In one sense, inelasticity reduces the risk of congestion because the RTP stream will not expand to consume all available bandwidth as a TCP stream can. However, inelasticity also means that the RTP stream cannot arbitrarily reduce its load on the network to eliminate congestion when it occurs.

Since RTP may be used for a wide variety of applications in many different contexts, there is no single congestion control mechanism that will work for all. Therefore, congestion control SHOULD be defined in each RTP profile as appropriate. For some profiles, it may be sufficient to include an applicability statement restricting the use of that profile to environments where congestion is avoided by engineering. For other profiles, specific methods such as data rate adaptation based on RTCP feedback may be required.