Question: What is the primary purpose of the MBMS Detach procedure initiated by the Serving Radio Network Controller (SRNC) towards the Drift Radio Network Controller (DRNC) in a UTRAN Iur interface context?
Option 1: To establish new MBMS bearer services for a User Equipment (UE) in an existing UE Link.
Option 2: To modify the Quality of Service (QoS) parameters for ongoing MBMS sessions within a stored URA Link.
Option 3: To request resource allocation for a UE handover from DRNC to SRNC.
Option 4: To either delete a UE/URA Link in the DRNC or inform the DRNC about the removal of one or several MBMS bearer services from an existing link.
Explanation: The correct answer, Option 4, aligns with the specified purpose of the MBMS Detach procedure as defined for UTRAN Iur interface RNSAP signalling. This procedure is utilized for two main objectives: firstly, to remove a UE Link or URA Link from the DRNC, and secondly, to notify the DRNC of the removal of specific MBMS bearer services within an already established UE or URA Link, ensuring synchronization between SRNC and DRNC regarding resource allocation and service provision.