Question: What happens when a UE in RRC_CONNECTED with activated AS security initiates an RRC connection re-establishment procedure, but the network cannot retrieve or verify the UE context?
Option 1: The network attempts to re-activate AS security with changed algorithms.
Option 2: The UE is instructed to move directly to RRC_IDLE with a release cause 'other'.
Option 3: The network discards the stored AS Context, releases all RBs and RLC channels, and falls back to establish a new RRC connection.
Option 4: The UE's SRB1 is re-established without resuming its previous state.
Explanation: According to the RRC connection re-establishment procedure, if AS security has been activated but the network cannot retrieve or verify the UE context, it will discard the stored AS Context, release all Radio Bearers (RBs) and associated RLC channels, and then fall back to establishing a new RRC connection instead of continuing with the re-establishment. This ensures security and consistency in the network by not proceeding with potentially outdated or compromised context.