Which SIP message header is used to tunnel QSIG messages across the SIP network when the OGW receives a call bound for the TGW?

Refer to the exhibit.

Which SIP message header is used to tunnel QSIG messages across the SIP network when the OGW
receives a call bound for the TGW?

A.
Content-TypE. application/sdp

B.
Content-TypE. application/qsig

C.
Content-TypE. message/ISUP

D.
Content-TypE. message/external-body

E.
Content-TypE. application/x-q931

Explanation:
Tunneling over SIP
The Cisco gateway receives QSIG messages from the PBX side and then identifies the destination of
the message (or call). The QSIG messages received from the PBX are encapsulated within SIP
messages as Multipurpose Internet Mail Extensions (MIME) bodies and are sent (tunneled) across
the IP network to the recipient gateway.
When encapsulating a QSIG message (for switch type primary-qsig) inside a SIP message, Cisco
gateways include the QSIG message in a MIME body of the SIP request or response using media type
application/QSIG:
Content-Type: application/QSIG

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