ZyXEL VMG8324 User Guide - Page 254

SIP User Agent, SIP Proxy Server, SIP Redirect Server

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Chapter 21 Voice 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 152 SIP User Agent 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. 1 The client device (A in the figure) sends a call invitation to the SIP proxy server (B). 2 The SIP proxy server forwards the call invitation to C. Figure 153 SIP Proxy Server SIP Redirect Server A SIP redirect server accepts SIP requests, translates the destination address to an IP address and sends the translated IP address back to the device that sent the request. Then the client device that originally sent the request can send requests to the IP address that it received back from the redirect server. Redirect servers do not initiate SIP requests. 254 VMG8324-B10A / VMG8324-B30A Series User's Guide

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Chapter 21 Voice
VMG8324-B10A / VMG8324-B30A Series User’s Guide
254
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 152
SIP User Agent
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.
1
The client device (
A
in the figure) sends a call invitation to the SIP proxy server (
B
).
2
The SIP proxy server forwards the call invitation to
C
.
Figure 153
SIP Proxy Server
SIP Redirect Server
A SIP redirect server accepts SIP requests, translates the destination address to an IP address and
sends the translated IP address back to the device that sent the request. Then the client device that
originally sent the request can send requests to the IP address that it received back from the
redirect server. Redirect servers do not initiate SIP requests.