If a Network Access Server (NAS) is configured to do so, it sends accounting information to the server at the beginning and end of each dial-in session. The data in these packets vary by NAS vendor but typically include the user’s name, IP address, session time, and the number of characters or packets transferred. The server stores this information for billing and statistical reporting purposes. The accounting packets contain information that enables the ISP to bill either by system-time use or by the amount of data transferred during the session.
ISPs can also forward accounting information on to IAS where it can be collected for auditing purposes.