SSCA SIP Protocols & Call Flow Fundamentals 4

Question 1

What SIP response code indicates that the server understood the request but is refusing to fulfill it, without the client being able to change this by re-sending?

Accepted Answer

403 Forbidden

Answer

403 Forbidden means the server understood the request but will not authorize it, regardless of credentials.

Question 2

In SIP, the To header tag is added by whom and when?

Accepted Answer

The UAS adds it in the response to establish a dialog

Answer

The UAS (called party) adds the 'tag' parameter to the To header in its response, which together with the From tag creates the dialog.

Question 3

Which SIP method is used to end a subscription established with SUBSCRIBE?

Accepted Answer

SUBSCRIBE with Expires: 0

Answer

A subscription is terminated by sending a SUBSCRIBE request with an Expires header value of 0.

Question 4

What is the role of the P-Asserted-Identity header in SIP?

Accepted Answer

To convey the verified identity of the caller within a trusted network

Answer

P-Asserted-Identity carries the authenticated identity of the originating user as determined by a trusted network element.

Question 5

In SIP, what happens when a proxy receives a request with Max-Forwards: 0?

Accepted Answer

It returns a 483 Too Many Hops response

Answer

When a proxy receives Max-Forwards: 0 and cannot process the request itself, it must return 483 Too Many Hops.

(SSCA) Sip School Certified Associate Practice Test

(SSCA) Sip School Certified Associate Practice Test

SSCA SIP Protocols & Call Flow Fundamentals 4