Which header should be removed from the SIP message to resolve this issue?

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. The administrator later learns that this SIP provider does not support PRACK .

Which header should be removed from the SIP message to resolve this issue?
A . Content-Disposition: session: handling=required
B . Require 100rel
C . Contact <sip: [email protected]:5060>
D . Content-Type: application/sdp

View Answer

Answer: B