Effects of Interaction between Transport and Application Layers on SIP Signaling Performance

Abstract

Session Initiation Protocol (SIP) is an application-layer protocol to handle sessions between two points. SIP is implemented on the top of the transport protocols, such as user datagram protocol (UDP) or transmission control protocol (TCP). SIP messages are transmitted by UDP or TCP. We focus on an interaction between the application layer (SIP) and the transport layer (UDP or TCP). The paper studies how the interaction affects performance of SIP signaling. A significant performance difference was found to exist because of the interaction. In the case of SIP over UDP, retransmissions of SIP messages decrease throughput. On the other hand, in the case of SIP over TCP, a large TCP buffer causes a large call setup delay although TCP improves throughput.