Question: What is the purpose of the network performing a PEI check with 5G-EIR during the establishment of a NAS signalling connection with the UE?
Option 1: To authenticate the UE's identity.
Option 2: To verify the UE's equipment identity and prevent non-authorized access to the network.
Option 3: To establish an IPsec tunnel between the UE and the network.
Option 4: To negotiate ciphering algorithms for NAS signalling messages.
Explanation: The PEI (P-TMSI, P-TMSI Signature, and PEI) check is performed by the network to verify the UE's equipment identity and prevent non-authorized access to the network. This check is done in conjunction with the 5G-EIR (5G Equipment Identity Register), which stores information about authorized UE equipment.