Question: Upon detecting a signalling (SCTP) connection unavailability to a Home eNodeB ((H)eNB), what action does the X2 Gateway (X2 GW) take towards the affected (H)eNB's peers?
Option 1: The X2 GW sends an alert to all connected eNodeBs in the network, regardless of prior associations.
Option 2: The X2 GW initiates a re-routing procedure for ongoing sessions through an alternative (H)eNB.
Option 3: The X2 GW waits for a predefined timeout before taking any corrective action towards associated (H)eNBs.
Option 4: The X2 GW initiates the X2 Release procedure to inform relevant (H)eNBs that had an "X2AP association" with the unavailable (H)eNB via the X2 GW.
Explanation: This is correct because, as per the described telecom protocol, when a signalling connection to a (H)eNB is detected as unavailable, the X2 Gateway's immediate response is to notify the relevant peers of this (H)eNB. These "relevant" (H)eNBs are specifically those that maintained an X2AP association with the now-unavailable (H)eNB through the X2 GW at the time of disconnection. This targeted notification via the X2 Release procedure ensures efficient network management and minimizes unnecessary disruptions to unaffected parts of the network.