300-815 · Question #68
Refer to the exhibit. While troubleshooting call failures on the Cisco Unified Border Element, an administrator notices that messages are being sent to the service provider, but there is no response T
The correct answer is B. Require: 100rel. The 'Require: 100rel' header in a SIP INVITE tells the remote end that reliable provisional responses (PRACK) are mandatory for this session. If the ITSP does not support PRACK, it cannot comply with this requirement and will typically reject the call or not respond. Removing the
Question
Exhibit
Options
- AContent-Disposition: session:handling=required
- BRequire: 100rel
- CContent-Type: application/sdp
- DContact: sip:[email protected]:5060
How the community answered
(15 responses)- A7% (1)
- B73% (11)
- C13% (2)
- D7% (1)
Explanation
The 'Require: 100rel' header in a SIP INVITE tells the remote end that reliable provisional responses (PRACK) are mandatory for this session. If the ITSP does not support PRACK, it cannot comply with this requirement and will typically reject the call or not respond. Removing the 'Require: 100rel' header (by configuring 'voice-class sip rel1xx disable' on CUBE) allows the call to proceed without PRACK. The Content-Type and Content-Disposition headers relate to the SDP body, and the Contact header is required for proper SIP dialog routing.
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