IMG 1010 - Supported 3xx Redirect Responses

3xx responses give information about the user's new location, or about alternative services that might be able to satisfy the call. 

3xx Redirect Support is enabled by default on the IMG and is configurable with the SIP Profile (SGP) on a per gateway basis - see IMG 1010 - SIP Profile - 10.5.3 and IMG 1010 - SIP Redirect Server Support

300 Multiple Choices

The address in the request resolved to several choices, each with its own specific location, and the user (or UA) can select a preferred communication end point and redirect its request to that location.

301 Moved Permanently

The user can no longer be found at the address in the Request-URI, and the requesting client SHOULD retry at the new address given by the Contact header field (Section 20.10).  The requester SHOULD update any local directories, address books, and user location caches with this new value and redirect future requests to the address(es) listed.

302 Moved Temporarily

The requesting client SHOULD retry the request at the new address(es), given by the Contact header field (Section 20.10.  The Request-URI of the new request uses the value of the Contact header field in the response.

305 Use Proxy

305 provides information for next hop to reach proxy server. The requested resource MUST be accessed through the proxy given by the Contact field. The Contact field gives the URI of the proxy.  The recipient is expected to repeat this single request via the proxy.  305 (Use Proxy) responses MUST only be generated by UASs.