Stream Control Transmission Protocol as a Transport for SIP: a case study

The dominant signalling protocol both in future wireless and wired networks will be the Session Initiation Protocol (SIP), as pointed out in the 3G IP-based mobile networks specifications, entailing a fully Internet integrated network. The use of SIP in the IP Multimedia Subsytem (IMS) of Release 5 involves the development of servers capable to handle a large number of call requests. The signaling traffic associated to such requests could explode, if an intelligent congestion control were not introduced. Stream Control Transmission Protocol (SCTP) was born to support transport of SS7 signaling messages. However, many of the SCTP features are also useful for transport of SIP messages, as: congestion control mechanism, good separation among independent messages, multihoming. Indeed, adoption of SCTP as transport of SIP signaling might prove useful in some situations where usual transport protocols, like TCP and UDP, suffer performance degradation. In this paper, we analyse the general framework wherein SIP operates and we discuss the benefits of using SCTP as a transport for SIP, toward fair sharing of network resources. This study is carried on in the context of the implementation of an high-performance SIP Proxy Server. We also present some preliminar results of an implementation of SIP over SCTP/UDP in a real LAN environment