SSCA Session Management 4

Question 1

What is the significance of the 'tag' parameter in the From and To headers of a SIP session?

Accepted Answer

It serves as part of the dialog identifier and differentiates multiple calls from the same UA

Answer

Tags are random strings added to From and To headers that, combined with the Call-ID, uniquely identify a dialog and distinguish parallel calls from the same address.

Question 2

Which SIP method is used to query the capabilities of a remote UA without establishing a session?

Accepted Answer

OPTIONS

Answer

The OPTIONS method allows a UA or proxy to query the capabilities (supported methods, codecs, extensions) of a remote UA without initiating a call.

Question 3

In SIP session management, what does the Record-Route header accomplish?

Accepted Answer

It ensures that subsequent mid-dialog requests traverse the same proxy path

Answer

Proxies insert themselves into the Record-Route header so that subsequent in-dialog requests (like re-INVITEs and BYEs) continue to be routed through them.

Question 4

What is the function of the Route header in a SIP request sent within an established dialog?

Accepted Answer

It contains the list of proxies the request must traverse, built from the Record-Route header

Answer

The Route header is populated from the stored route set (derived from Record-Route headers) and directs mid-dialog requests through the previously established proxy path.

Question 5

A SIP UA sends a BYE with no prior INVITE having been answered. What is the likely outcome?

Accepted Answer

The remote UA responds with 481 Call/Transaction Does Not Exist

Answer

A BYE sent outside of an established dialog will receive a 481 Call/Transaction Does Not Exist response because no matching dialog is found.

(SSCA) Sip School Certified Associate Practice Test

(SSCA) Sip School Certified Associate Practice Test

SSCA Session Management 4