Chapter 18 Voice over 3G
LTE5366 Series User’s Guide
128
Figure 82
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 83
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.
In the following example, you want to use client device
A
to call someone who is using client device
C
.
1
Client device
A
sends a call invitation for
C
to the SIP redirect server (
B
).
2
The SIP redirect server sends the invitation back to
A
with
C
’s IP address (or domain name).
3
Client device
A
then sends the call invitation to client device
C
.
