Question: Under what condition is the termination of all UE (User Equipment) contexts in DRNC (Drift Radio Network Controller) triggered for a specific SRNC (Serving Radio Network Controller), as per RNSAP (Radio Network Subsystem Application Part) signalling?
Option 1: When a UE transitions from idle to active state, requiring resource reallocation.
Option 2: Upon successful handover of all UEs to a different SRNC.
Option 3: If the DRNC experiences a scheduled maintenance period.
Option 4: When RNSAP Signalling Bearer failure is detected according to specific procedures.
Explanation: The correct answer, Option 4, reflects the condition where the termination of all UE contexts in DRNC for a specific SRNC is triggered due to the detection of RNSAP Signalling Bearer failure. This is crucial because the signalling bearer's integrity is essential for maintaining and managing UE contexts across different network controllers. Failure in this bearer would necessitate the termination of affected UE contexts to maintain network stability and functionality, impacting both dedicated and common channel resources allocated to UEs under that specific SRNC.