| VoIP Standards |
|
|
There are several VoIP standards available today like SIP, H323, MGCP. They all operate slightly different. SIP being the main player and is slowly being recognised as the standard for VoIP communication. • The Session Initiation Protocol (SIP) was produced by the IETF as an IP standard. Although SIP is gaining considerable attention, it will not become the dominant installed protocol for a few years. The attractions of SIP are better interoperability among vendors, easier application development, operation that is close to other existing IP protocols, and easier operation through firewalls. • H.323, the ITU standard that was published in 1995, started the development of VoIP products and services. There are four versions available. V.1 is obsolete and has been discontinued in virtually all products. Versions 2, 3 and 4 are used in today’s products. • MGCP is a protocol used primarily with gateways, although an occasional hard phone may support MGCP. • MEGACO/H.248, another standard protocol, is a combined effort of the ITU and IETF. It can be used with gateways and server-to-server communications. It is not found in hard or softphones. In addition to the standards, nearly every IP PBX vendor has produced a proprietary signaling protocol. The most commonly found protocol is Cisco’s SCCP, or “Skinny,” protocol. These proprietary protocols may be variations of the standards or may be uniquely designed. They each provide the call control found in the standard protocols. An IP PBX vendor usually supports one or more of the standard signalling protocols plus their proprietary protocol. |