Question: What is the purpose of the Operator Identifier in the ePDG Fully Qualified Domain Name (ePDG FQDN) and how does it uniquely identify a PLMN?
Option 1: The Operator Identifier is used to identify the UE's location, and it uniquely identifies the PLMN based on the UE's IP address.
Option 2: The Operator Identifier contains the MNC and MCC of the PLMN where the ePDG is located, and it uniquely identifies the PLMN by combining these values in a specific format.
Option 3: The Operator Identifier is used to authenticate the UE, and it uniquely identifies the PLMN based on the UE's authentication credentials.
Option 4: The Operator Identifier is not necessary for identifying a PLMN, as the ePDG FQDN can be constructed without it.
Explanation: According to the 3GPP specification, the Operator Identifier in the ePDG FQDN contains the MNC and MCC of the PLMN where the ePDG is located. This information uniquely identifies the PLMN by combining these values in a specific format ("epdg.epc.mnc<MNC>.mcc<MCC>.pub.3gppnetwork.org").