Amer Networks E5Web GUI User Manual
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This scenario is similar to the previous but the major difference is the location of the local SIP
proxy server. The server is placed on a separate interface and network to the local clients. This
setup adds an extra layer of security since the initial SIP traffic is never exchanged directly
between a remote endpoint and the local, protected clients.
The complexity is increased in this scenario since SIP messages flow across three interfaces: the
receiving interface from the call initiator, the DMZ interface towards the proxy and the
destination interface towards the call terminator. This the initial messages exchanges that take
place when a call is setup in this scenario are illustrated below:
The exchanges illustrated are as follows:
•
1,2 - An initial INVITE is sent to the outbound local proxy server on the DMZ.
•
3,4 - The proxy server sends the SIP messages towards the destination on the Internet.
•
5,6 - A remote client or proxy server replies to the local proxy server.
•
7,8 - The local proxy forwards the reply to the local client.
This scenario can be implemented in a topology hiding setup with DMZ (Solution A below) as
Chapter 6: Security Mechanisms
420