SIP Servers and Clients

SIP uses 4 major elements to make a session work:

  • SIP Clients ( sometimes called user agents)
    These end user devices include cell phones, PCs PDAs and dedicated devices. The client sets up the message which is sent to a and using a group of servers:
  • The SIP Registrar Server
    This contains the location of all the clients within a domain. This server sends the users IP addresses to the SIP Proxy Server.
  • The SIP Proxy Server
    This connects the SIP request from the user to the recipient, either directly or via the recipients own Proxy server.
  • The SIP Redirect Server is the device that lets the Proxy Server redirect to a proxy server in another domain.

Because the SIP servers are software applications, they can run concurrently on the same physical server hardware.

a router