Networks

I am a Jr. Sys Admin in an ISP. I am using Linux Operating System as Server.

Now i need a software or tool which will tell me the User Usage Details. Not only that i want to give USER ACCOUNTS to our Customers from that software or tool so that the customers will know their usage details minute by minute, hourly and daily, monthly and yearly Just like BSNL has given web interface to the Customers.

I need the supporting ones for that software or tool.
If any body knows such type of software or tool, please give me the details for Linux and Windows Servers.