SIP Protocol Fundamentals 2

Question 1

Which SIP method is used to modify an existing session, such as changing the media parameters?

Accepted Answer

RE-INVITE

Answer

A re-INVITE (sending INVITE within an established dialog) is used to modify session parameters like codec or media direction.

Question 2

What does the SIP 'To' header field represent in an initial request?

Accepted Answer

The logical recipient or callee of the request

Answer

The 'To' header identifies the logical recipient of the request, typically the callee's address-of-record (AOR).

Question 3

What is the purpose of the SIP 'Contact' header?

Accepted Answer

Provides a direct URI for reaching the UA in subsequent requests

Answer

The Contact header provides a direct SIP URI (typically with an IP address) where the UA can be reached, bypassing the AOR.

Question 4

Which SIP response code class indicates a successful request?

Accepted Answer

2xx

Answer

2xx responses indicate success; for example, 200 OK signals that an INVITE was accepted.

Question 5

What is the role of a SIP Registrar?

Accepted Answer

Accepts REGISTER requests and maps AORs to device locations

Answer

A Registrar accepts REGISTER requests and stores the binding between a user's AOR and their current contact URI in a location service.

(SIP) Session Initiation Protocol Practice Test