R2511-HP MSR Router Series Voice Configuration Guide(V5)

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Figure 38 Call setup procedures involving a proxy server
This is a simplified scenario where only one proxy server is involved and no registrar is present. A
complex scenario, however, might involve multiple proxy servers and registrars.
Call redirection
As shown in Figure 39, when a SIP redirect server receives a session request, it sends back a response
indicating the address of the called SIP endpoint instead of forwarding the request. The calling and
called endpoints send request and response to each other directly.