A method of locating NAS context relating to a network access server session in a communication network is provided, the method comprising receiving an Accounting Stop Request for a PDP context associated to a network access server session, comparing an Accounting Session ID implemented in the Accounting Stop Request with Accounting Session IDs associated with active network access server sessions, in case that no matching Accounting Session ID is found, determining whether a value of an identification parameter implemented in the received Accounting Stop Request matches a value of a corresponding identification parameter associated with an active network access server session, and locating a NAS context based on the result of matching identification parameters.