Question: How does a target MME or SGSN node identify a specific SGSN within an operator's network?
Option 1: Using the Mobile Country Code (MCC) and Mobile Network Code (MNC)
Option 2: Using the Location Area Code (LAC) and Routing Area Code (RAC)
Option 3: Using the Serving GPRS Support Node (SGSN) ID
Option 4: Using the RAI FQDN and Network Resource Identifier (NRI)
Explanation: A specific SGSN within an operator's network is identified using the RAI FQDN and the Network Resource Identifier (NRI). The NRI is a unique identifier for the SGSN, which can be derived from the MME Code received in the GUTI from the UE. This allows the target MME or SGSN node to connect to the source SGSN node.