The invention proposes a system for authenticating and authorizing network services comprising: a mobile device being adapted to, upon receipt of an information message indicating at least one network access type, determine the network access type, to create a start message containing at least a user identity, and to encapsulate the start message in an authentication message compatible with the access network identified in the information message, and an access controller for reading the encapsulated message from the mobile and forwarding the encapsulated message to an authentication server identified in the encapsulated message. The invention also proposes a corresponding method for authenticating and authorizing network services, and an access control device, a subscriber device and a router device.