If an ISP is set up to provide roaming services, a traveling user can dial in a network-access request from nearly any telephone line. Network operators may cooperate through bilateral agreements, or they may participate in a consortium that clears their requests for authentication and billing. To provide roaming services, a network operator either configures all of the realms of its roaming partner or configures its proxy servers to forward all authentication requests that are unknown to the other party to its roaming partner or consortium.