RTP: Audio and Video for the Internet

A potential denial-of-service threat exists with payload formats using compression that has nonuniform receiver-end computational load. If the payload format has such properties, an attacker might be able to inject pathological packets into a media stream, which are complex to decode and cause the receiver to be overloaded. There is little a receiver can do to avoid this problem, short of stopping processing packets in overload situations.

Another problem that can cause denial of service is failure to implement the RTCP timing rules correctly. If participants send RTCP at a constant rate rather than increasing the interval between packets as the size of the group increases , the RTCP traffic will grow linearly with the size of the group. For large groups, this growth can result in significant network congestion. The solution is to pay close attention to the correct implementation of RTCP.

Similarly, failure to implement the RTCP reconsideration algorithms can result in transient congestion when rapid changes in membership occur. This is a secondary concern because the effect is only transitory , but it may still be an issue.

Network congestion can also occur if RTP implementations respond inappropriately to packet loss. Chapter 10, Congestion Control, describes the issues in detail; for our purposes here, suffice it to say that congestion can cause significant denial of service.