SIP Protocol Fundamentals 3

Question 1

What SIP response code indicates that the callee's phone is ringing?

Accepted Answer

180 Ringing

Answer

180 Ringing is sent by the UAS to inform the UAC that the called party's device is alerting the user.

Question 2

Which SIP method is used to query the capabilities of a SIP server or UA?

Accepted Answer

OPTIONS

Answer

OPTIONS allows a UAC to query a server or UA about its supported methods, extensions, codecs, and other capabilities.

Question 3

What is the function of the SIP 'CSeq' header?

Accepted Answer

Orders requests within a dialog and names the method

Answer

CSeq contains a sequence number and method name, used to order transactions and detect retransmissions within a dialog.

Question 4

Which transport protocol is preferred for SIP in environments requiring reliability and large messages?

Accepted Answer

TCP

Answer

TCP is preferred when reliability is needed or when SIP messages exceed the MTU size, though UDP is more common for basic deployments.

Question 5

What does a SIP 302 Moved Temporarily response instruct the UAC to do?

Accepted Answer

Resend the request to an alternate URI provided in the Contact header

Answer

302 Moved Temporarily provides an alternate Contact URI and instructs the UAC to retry the request at that new address.

(SIP) Session Initiation Protocol Practice Test