SIP trunking is a VoIP Protocol based upon SIP. SIP Trunking allows ITSPs (Internet Telephony Service Providers) to deliver telephony services and unified communications (voice, video and other media) to a SIP based PBX (Private Branch Exchange). It is also possible to provide SIP trunking on a PBX that isn’t SIP based by using a SIP Gateway to convert from ISDN (Q931) to SIP.
The benefits of using SIP trunks include:
Calls that are made over the Internet are far cheaper than calls made from traditional landlines. Furthermore, it is very common for calls made to different sites within the same business to be free as calls are originated and terminated on the same network (on net).
SIP trunks make use of your existing data connection, and as a result can negate the requirement for line rental, saving your business money.