Posted on: July 12, 2020 Posted by: wulmeradmin Comments: 0

SIP trunking is a service offered by an Internet Telephony Service Provider (ITSP) that converges voice and data onto one communication line, providing seamless access between the Internet and the worldwide Public-Switched Telephone Network.

There are four components necessary to successfully deploy SIP trunking: a PBX with a SIP-enabled trunk side, an enterprise edge device understanding SIP, an Internet telephony or SIP trunking service provider, and the Public Switched Telephone Network.

Four Components

– The PBX

– Enterprise Boarder Element (EDGE)

– The ITSP



PBX stands for Private Branch Exchange. It is a telephone exchange that serves a particular business or office, as opposed to one that a common carrier or telephone company operates for many businesses or for the general public. In most cases, the PBX is an IP-based PBX, communicating with all endpoints over IP, but it may just as well be a traditional digital or analog PBX. The sole requirement is that it is an interface where SIP trunking connectivity is available.

The Enterprise Border Element (EDGE)

EDGE stands for Enterprise Boarder Element. The edge is the term we use to refer to a unified communications device like a digital phone, a wireless digital phone, or a softphone. The PBX on the local area network connects to the Internet via the enterprise border element, or edge.


ITSP stands for Internet Telephony Service Provider. An ITSP offers Internet data service for making telephone calls using Voice over IP technology. Session Initiated Protocal trunking occurs at this level.


Internet Telephony Service Providers supply connectivity to the Public Switched Telephone Network for communication with mobile and fixed phones. SIP trunking is an action taken by the Internet Telephony Service Provider which allows for the connectivity between the Public-Switched Telephone Network and the EDGE.


Trunking is a service offered by an Internet Telephony Service Provider that routes and transfers voice and data from the Public Switched Telephone Network to a PBX. SIP Trunking works by having SIP protocols direct calls as they travel between the PBX and Public Switched Telephone Network. SIP trunking is a vital service of hosted VoIP PBX and its effectiveness is a major reason for the technology’s success.