SSCA SIP Headers 4

Question 1

What is the role of the Referred-By header in SIP REFER?

Accepted Answer

It identifies the party that initiated the transfer

Answer

The Referred-By header identifies the SIP URI of the user who sent the REFER request, providing accountability in call transfer scenarios.

Question 2

Which header in a SIP response provides the address where the client should send future requests for the same user?

Accepted Answer

Contact

Answer

The Contact header in a response provides the direct URI of the UAS, used by the UAC to address subsequent in-dialog requests.

Question 3

What does the SIP History-Info header capture?

Accepted Answer

A record of URI changes that occurred due to retargeting or forwarding

Answer

History-Info records the sequence of Request-URIs used as a request was retargeted, enabling call forwarding history to be conveyed.

Question 4

Which SIP header is used to indicate that a response is final and terminates the transaction?

Accepted Answer

No header — the response code indicates finality

Answer

In SIP, a 2xx–6xx response code itself signals finality; no special header is needed to indicate the response is final.

Question 5

What does the Min-Expires header in a 423 response indicate?

Accepted Answer

The minimum registration duration the registrar will accept

Answer

A registrar returns 423 Interval Too Brief with a Min-Expires header when the client's requested expiration is shorter than the registrar's minimum.

(SSCA) Sip School Certified Associate Practice Test