Constrained TCP-Friendly Congestion Control for Multimedia Communication

With the lack of admission control and resource reservation mechanisms in the Internet, overload situations can only be avoided by having the end systems deploying congestion control schemes. That is, the end systems should adjust their transmission and reception behavior in accordance with the available network resources. This is generally achieved by adjusting the transmission behavior of a sender based on feedback information from the receiver about the network congestion situation. Current proposals for rate adaptation assume that the sender can adjust its transmission with arbitrary granularity. However, especially for the case of audio and video communication it is often the case, that the used compression style, application or the user might impose strict limitations as to the maximum and minimum transmission rates, the granularity with which the sender can change its transmission rate and the frequency with which such changes should occur. In this paper, we present a general model for describing a generic constrained multimedia source. Additionally, we describe an control framework called constrained TCP-friendly adaptation framework (CTFAF). CTFAF incorporates the proposed generic multimedia model with TCP-friendly adaptation schemes and hence allows for adapting the transmission rate of multimedia senders in a TCP-friendly way and at the same time takes the restrictions imposed by the source into account. Using simulations we investigate the performance of this approach in terms of bandwidth utilization, stability and fairness.