Which header field does a SIP User Agent Client use to advertise that it supports Provisional Response Acknowledgement?

3 thoughts on “Which header field does a SIP User Agent Client use to advertise that it supports Provisional Response Acknowledgement?”

1. A
   The following message flow is an example of a Prack transaction.

   UAC sends: INVITE (Supported: 100Rel)

   UAS sends: 180 Ringing (Required: 100Rel, RSeq: 145)

   UAC sends: PRACK (CSeq: 1 PRACK, RAck: 145)

   UAS sends: 200 Ok (CSeq: 1 PRACK)

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2. A

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3. Correct answer is A

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