Base station apparatus and inter-base-station gateway apparatus

A base station apparatus comprising:

• a memory;
• and
• at least one processor coupled to the memory, wherein
• the at least one processor is configured to send a first information element to an inter-base-station gateway,
• the first information element explicitly or implicitly indicates whether a relay operation is necessary, the relay operation being an operation in which the inter-base-station gateway relays a data packet destined for or sent from a radio terminal between the base station apparatus and an other base station, and
• the at least one processor is configured to, when generating the first information element, consider whether it is necessary to conceal a transport-layer address of the base station apparatus from the other base station.