Question: What is the primary purpose of the Reroute NAS Request procedure in the UTRAN Iu interface Radio Access Network Application Part (RANAP) signalling?
Option 1: To enable the Serving GPRS Support Node (SGSN) to request rerouting of the INITIAL UE message to a specified Destination Charging Network (DCN), particularly in Multi-Operator Core Network (MOCN) configurations.
Option 2: To facilitate direct communication between User Equipment (UE) and the SGSN for initial attach procedures in all network configurations.
Option 3: To manage handover of UE from one RNC to another within the same SGSN's serving area, ensuring seamless connectivity.
Option 4: To handle congestion control in the radio access network by dynamically adjusting the number of active UEs.
Explanation: The correct answer is Option 1 because the Reroute NAS Request procedure is specifically designed to allow an SGSN, which can serve a UE (especially in MOCN configurations), to request that an INITIAL UE message be rerouted to a specified DCN. This highlights the procedure's role in managing network signaling for initial UE messages in complex network setups, ensuring efficient communication routing.