User`s guide

Chapter 11 The Service Configuration Screens
User’s Guide
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11.4.5 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.
Figure 68 SIP Redirect Server
11.4.6 NAT and SIP
The WiMAX Modem must register its public IP address with a SIP register server. If there is a
NAT router between the WiMAX Modem and the SIP register server, the WiMAX Modem
probably has a private IP address. The WiMAX Modem lists its IP address in the SIP message
that it sends to the SIP register server. NAT does not translate this IP address in the SIP
message. The SIP register server gets the WiMAX Modem’s IP address from inside the SIP
message and maps it to your SIP identity. If the WiMAX Modem has a private IP address
listed in the SIP message, the SIP server cannot map it to your SIP identity. See
Chapter 9 The
NAT Configuration Screens
for more information.
Use a SIP ALG (Application Layer Gateway), Use NAT, STUN, or outbound proxy to allow
the WiMAX Modem to list its public IP address in the SIP messages.
A
C
B
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3
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