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Chapter 10 The Service Configuration Screens
User’s Guide
126
3 Client device A then sends the call invitation to client device C.
Figure 51 SIP Redirect Server
10.4.6 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 8 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.
10.4.7 DiffServ
DiffServ is a class of service (CoS) model that marks packets so that they receive
specific per-hop treatment at DiffServ-compliant network devices along the route
based on the application types and traffic flow. Packets are marked with DiffServ
Code Points (DSCPs) indicating the level of service desired. This allows the
intermediary DiffServ-compliant network devices to handle the packets differently
depending on the code points without the need to negotiate paths or remember
state information for every flow. In addition, applications do not have to request a
particular service or give advanced notice of where the traffic is going.
A
C
B
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