Comparison of VOIP signaling protocol H.323 Vs SIP

There are a number of protocols that may be employed in order to provide the VoIP (Voice over IP) communication services. In IP telephony system, H.323 and Session Initiation Protocol (SIP) are the two major standards. The H.323 protocol suite by International Telecommunication Union (ITU-T) and SIP by Internet Engineering Task Force (IETF). Both of these signaling protocols provide mechanisms for multimedia teleconferencing services. Although the two protocol architecture is quite similar, they have many differences. In this paper we will present Voice over IP communication and summarize the differences of two major VOIP protocols, H.323 and SIP according to the service architectures, Complexity, Extensibility, Scalability, Flexibility, Interoperability, Quality of service (QOS) and Ease of Implementation. It is found that both of them are non-interoperable, approaching each other, their focus and applicability is still different. © 2009 WASET.ORG.