P-2302HW/HWL-P1 Series User’s Guide

9.1.5.1 SIP User Agent

A SIP user agent can make and receive VoIP telephone calls. This means that SIP can be used for peer-to-peer communications even though it is a client-server protocol. In the following figure, either A or B can act as a SIP user agent client to initiate a call. A and B can also both act as a SIP user agent to receive the call.

Figure 71 SIP User Agent

9.1.5.2 SIP Proxy Server

A SIP proxy server receives requests from clients and forwards them to another server.

In the following example, you want to use client device A to call someone who is using client device C.

1The client device (A in the figure) sends a call invitation to the SIP proxy server (B).

2The SIP proxy server forwards the call invitation to C.

Figure 72 SIP Proxy Server

Chapter 9 SIP

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