Session Initiation Protocol (SIP) trunking is the use of voice over IP (VoIP) to facilitate the connection of a private branch exchange (PBX) to the Internet.

In effect, the Internet replaces the conventional telephone trunk, allowing an enterprise to communicate with fixed and mobile telephone subscribers worldwide. (SIP is an IETFstandard for initiating interactive multimedia user sessions; a trunk is a line or link that can carry many signals at once, connecting major switching centers or nodes in a communications system.)

In order to take advantage of SIP trunking, an enterprise must have a PBX that connects to all internal end users, an Internet telephony service provider (ITSP) and a gatewaythat serves as the interface between the PBX and the ITSP. One of the most significant advantages of SIP trunking is its ability to combine data, voice and video in a single line, eliminating the need for separate physical media for each mode. The result is reduced overall cost and enhanced reliability for multimedia services. With SIP trunking, subscribers can:

 

• Initiate and receive local calls

• Initiate and receive long-distance calls

• Make emergency calls (000)

• Access directory assistance

• Use fixed and mobile telephone sets

• Employ e-mail and texting

• Browse the World Wide Web.

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  Make use of softphone client or physical SiP telephone linked back to head office.