Designing and implementing a new type of transport-layer socket: the UDTCP socket case

On most operating systems, the UDP and TCP sockets are the two main types of sockets used to provide transport-layer networking services. However, for several reasons, UDP and TCP sockets are unsuitable for transporting delay-sensitive but error-tolerant streaming data such as the data generated by multimedia streaming applications. In this paper, we create a new type of socket that is suitable for transporting such data and propose a novel and simple implementation for it. We have implemented this new type of socket in Free BSD 4.8 and call it the ‘UDTCP socket.’ It has both the UDP and TCP socket properties suitable for delay-sensitive but error-tolerant streaming data but not those UDP and TCP socket properties unsuitable for such data. When transporting a stream of such data whose sending rate needs to be regulated by TCP congestion control, our simulation results show that the UDTCP socket can provide a much better delay and delay-jitter performance than the TCP socket. q 2003 Elsevier B.V. All rights reserved.