Patent ID: 7116668

Claim:
A method of authenticating registration reply messages received by a PCF that are purportedly responsive to registration messages previously sent by the PCF to a PDSN, said method comprising: determining a verification threshold for validating time stamps in registration reply messages; generating a sequence of message numbers for sequential use in a series of successive registration messages sent by said PCF to said PDSN, said sequence of message numbers having a repeat interval greater than said verification threshold; inserting said sequential message numbers into successive registration messages sent by said PCF to said PDSN; receiving a registration reply message at said PCF presumptively sent by said PDSN in response to a registration message previously sent by said PCF, said registration reply message containing a time stamp and a message number; validating said message number in said registration reply message by comparing said message number in said registration reply message to the message number in a corresponding registration message sent by said PCF; if said message number is valid, validating said time stamp in the said registration reply.