AAA roaming management for PPP and Mobile IP services

In recent years, the means of communication available to mobile users have evolved considerably, enabling them to access their company's Internet and Intranet from anywhere in the world. Typically, a user has access to the Public Switched Telephone Network (PSTN) via PPP (Point-to-Point Protocol) using a modem, particularly if connected from home or a hotel room. Users must then request network access from their Internet Service Provider (ISP) and authenticate themselves, usually with a password. Depending on the type of subscription, the ISP then restricts access to its network to certain services. All these checks are, of course, mandatory if the ISP is to be sure of being paid for the network resources consumed by the user.

To facilitate subscription management, ISPs centralize all subscriber data (password, subscription type, invoice) on secure access servers. Each time a connection is requested, one of these servers is interrogated. The protocols used by ISPs to carry out authentication, authorization and accounting operations are known as AAA (Authentication, Authorization, Accounting).

While AAA protocols are particularly well-suited to subscribers connecting to an ISP via the PSTN, they are expected to be used in a mobile context based on the Mobile IP protocol. These two fields of application are described in this article, confining ourselves to the authentication and authorization aspects of AAA, i.e., leaving aside the billing (Accounting) aspects. Other natural AAA applications are also presented, such as Wi-Fi access protection, VPNs...