Question: What format does a Session Transfer Identifier for CS to PS Single Radio Voice Call Continuity (STI-rSR) utilize, according to 3GPP standards, to facilitate media path transfer requests by the User Equipment (UE)?
Option 1: An IP Address with Port Number
Option 2: A Dedicated Short Code (DSC)
Option 3: A Unique Mobile Subscriber ISDN (MSISDN) Variation
Option 4: A Session Initiation Protocol (SIP) Uniform Resource Identifier (URI)
Explanation: The correct answer is Option 4 because, as per the provided context from 3GPP standards, a Session Transfer Identifier for CS to PS Single Radio Voice Call Continuity (STI-rSR) specifically utilizes a SIP URI. This format is crucial for enabling the User Equipment (UE) to request the transfer of a media path efficiently in single radio voice call continuity scenarios, leveraging the capabilities outlined in IETF RFC 3261 for SIP protocols.