3.9.5.5 Handling 415 Response

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This section follows the product behavior described in endnote <59>.

If a SIP proxy compliant with this protocol receives a 415 response from one of the targets to which the proxy forked the call, the proxy MUST handle the response as follows:

  1. If the request that was sent to the target did not contain a body with a "multipart/MIME" content type, no special processing is applied and the 415 response MUST be handled as any 4XX response, as described in [RFC3261], section 16.7.

  2. If multipart/MIME retry has been attempted for this target, the 415 response MUST be handled as any 4XX response.

  3. If any Accept header in the response indicates that the UAS supports multipart/MIME, no special processing is applied and the 415 response MUST be handled as any 4XX response.

  4. If any part of a multipart/MIME body has a Content-Disposition header field with an ms-proxy-2007fallback parameter and that part has SDP content with media description for audio media type (SDP content and media descriptions defined in [RFC4566]), the proxy takes the following actions:

    1. The proxy MUST re-send the INVITE to the target with only the SDP body, and

    2. The proxy MUST update its call context for that target to indicate that multipart/MIME retry has been attempted for this target.

The multipart/MIME content type is defined in [RFC2046].