SSCA Call Flows 2

Question 1

In a SIP re-INVITE scenario, what is the primary purpose of sending a re-INVITE mid-call?

Accepted Answer

To modify session parameters such as codec or media direction

Answer

A re-INVITE is sent during an established session to renegotiate session parameters, such as changing the codec, putting the call on hold, or updating media addresses.

Question 2

Which SIP response code indicates that a call transfer via REFER was accepted and the transfer is in progress?

Accepted Answer

202 Accepted

Answer

202 Accepted is returned by a UA that has accepted the REFER request and will attempt to contact the refer-to URI.

Question 3

During a SIP call hold using RFC 3264, what attribute is placed in the SDP to indicate the hold?

Accepted Answer

a=sendonly

Answer

A UA placing a call on hold sends a re-INVITE with SDP containing a=sendonly, meaning it will send but not receive media.

Question 4

In a SIP forking scenario, what happens when multiple 200 OK responses arrive from different branches?

Accepted Answer

The proxy accepts the first and sends CANCEL to the others

Answer

When the first 200 OK is received from a forked branch, the proxy or UAC accepts it and cancels the remaining pending branches with CANCEL.

Question 5

What SIP method is used by a transferring UA to instruct the transfer target to contact a third party?

Accepted Answer

REFER

Answer

The REFER method is used to instruct the recipient to contact a third-party URI, which is specified in the Refer-To header.

(SSCA) Sip School Certified Associate Practice Test

(SSCA) Sip School Certified Associate Practice Test

SSCA Call Flows 2