Question: In E-UTRAN, when an X2 Gateway (X2 GW) is utilized to connect one eNB to multiple specific eNB(s), how are SCTP associations established for X2-C interface instances?
Option 1: A single SCTP association is used end-to-end from the originating eNB through the X2 GW to each of the destination eNBs.
Option 2: Separate SCTP associations are used from the originating eNB to the X2 GW and then a single SCTP association is shared among all connections from the X2 GW to the multiple destination eNBs.
Option 3: Each X2-C interface instance from the originating eNB to the X2 GW, and from the X2 GW to each of the destination eNBs, uses its own separate SCTP association.
Option 4: No SCTP associations are used when an X2 GW is involved; instead, a different transport protocol is employed.
Explanation: When an X2 Gateway (X2 GW) is used to connect one eNB to one or more specific eNB(s), all X2-C interface instances from that eNB to the relevant eNB(s) are carried over the same SCTP association from that eNB to the X2 GW, and then over separate SCTP associations from the X2 GW to each of the relevant eNB(s). This ensures efficient management of signaling traffic while maintaining the integrity of communications between multiple eNBs via the gateway. Option 3 accurately reflects this setup, emphasizing separate SCTP associations for each leg of the connection involving the X2 GW.