Refer to the exhibit.

Which SIP response message should the TGW send if it cannot process the tunneled QSIG messages
from the OGW?

A.
405 Method Not Allowed

B.
406 Not Acceptable

C.
412 Conditional Request Failed

D.
415 Unsupported Media Type

E.
485 Ambiguous

Explanation:
Fallback from QSIG Tunneling
In some situations, QSIG tunneling will fail or need to fall back:
• Remote party does not support multipart MIME body: In this case, the remote side sends a “415
Media Not Supported” response. Upon receiving this response, OGW will fall back to normal mode
and send an INVITE request without any tunneled content. This procedure helps ensure that at least
the basic call will work normally.
• Remote party does not understand tunneled content: If the remote side does not support the
tunneled content, it should drop the tunneled content and continue as a normal call; because all
essential parameters are present in the original INVITE, the call can go through without the need for
fallback.
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