Question: What action should the Serving GPRS Support Node (SGSN) take if the received P-TMSI Signature from the Mobile Station (MS) does not match the stored signature in the SGSN during a Routeing Area Update Request or Attach Request?
Option 1: Ignore the mismatch and proceed without authentication.
Option 2: Use security functions to authenticate the MS, but only if ciphering is supported by the network.
Option 3: Send an error message to the MS and terminate the request.
Option 4: Use security functions to authenticate the MS.
Explanation: According to the procedure for handling P-TMSI Signatures, if the SGSN receives a mismatched P-TMSI Signature from the MS, it should utilize security functions to authenticate the MS, ensuring network integrity and security by verifying the MS's identity when discrepancies are detected.