ZyXEL Communications EMG5324-D10A User Manual
Chapter 18 VoIP
EMG5324-D10A User’s Guide
235
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.
user agent to receive the call.
Figure 124
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.
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 125
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.
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.
In the following example, you want to use client device A to call someone who is using client device
C.
C.
A
B
B
A
C
1
2