What is a SIP Server?

SIP Server

SIP server is the main component of an IP PBX, and mainly deals with the management of all SIP calls in the network. A SIP server is also referred to as a SIP Proxy or a Registrar.

Although the SIP server can be considered the most important part of a SIP-based IP-PBX phone system, it only handles or manages sessions; more specifically, a SIP Server can:

  • Set up a session between two (or more) endpoints (an audio conference would have more than two endpoints)
  • Negotiate the media parameters and specifications for the session for each endpoint using the SDP protocol
  • Adjust the media parameters and specifications of a session DURING the session (putting a call on hold, for example)
  • Substituting one endpoint with a new endpoint (call transfer)
  • Terminate a session

The SIP server does not actually transmit or receive any media – this is done by the media server in using the RTP protocol. Within the context of an IP-PBX environment, it is almost always true that the SIP server and its Media server companion reside on the same machine.

Do keep in mind, however, that very-high-volume SIP servers (such as a large VoIP Provider, for example), may separate their Media server to a different machine to better handle the workload, and could also possibly distribute the load to multiple Media servers.

3CX is a leader in the SIP Server and Media Server world. Try it out free today!