Evaluation of transport layer protocols for voice transmission in various network scenarios

Carrying voice over Internet protocol, known as VoIP, is a rapidly growing technology. It is an interesting real-time application which requires constant bit streaming of application data (voice). There are three protocols-TCP, UDP and SCTP-at the transport layer to carry the data between a source node and a destination node in the Internet. TCP is a reliable, byte-oriented protocol with builtin congestion control mechanism. UDP is an unreliable, connectionless protocol without any congestion control mechanism, hence, may cause congestion collapse. SCTP is a reliable message-oriented protocol which has been designed for newer applications, such as voice, which require more sophisticated service than TCP can provide. In this paper, we have made an attempt to evaluate these protocols for voice application under various congestion scenarios. We see that SCTP and UDP compete with each other under the considered quality metrics for voice transmission.