SIP is a Session Initiation Protocol at application layer which controls creating, modifying, and terminating sessions with multiple participants. A SIP Trunk can be referred to as a logical connection between an IP PBX and a Service Provider’s application servers that allows voice over IP traffic to be exchanged between the two.  While placing a call PBX routes the information to the SIP Trunk provider who establishes the call to the dialed number and acts as an agent for the call. All signaling and voice traffic between the PBX and the provider is exchanged using SIP and RTP protocol packets over the IP network.

To successfully deploy SIP trunk following three components are essential

  • PBX with a SIP-enabled trunk side,
  • An enterprise edge device understanding SIP
  • Internet telephony or SIP trunking service provider