Well lets give you a simple example. First thing, every ISP buys a large pipe of bandwidth. What they essentially do is that they sell smaller parts of this big pipe and make money. Now what a dial-in ISP will do is this..
They will have a modem pool, and a hunting number. They will calculate how many customers they expect on at any given time and accordingly plan so many customers per modem.. as an ISP gets more popular, the number of customers per modem increases and you start getting busy signals since the modems are tied up..
The modems will interface with some sort of authentication system, most likely a RADIUS or TACACS server that will validate your username and password. There will also be some sort of system to monitor your account balance and log your connections. You will be given a DHCP IP address as well. After this you are essentially just on the network.. any packets you send will go to your default gateway (router) which will know how to pass them up the big pipe that the ISP owns, and from there they will get routed across the Internet.
If you talk about a cable / DSL ISP its a different matter as they will have some other form of WAN link to your house other than using the existing telephone network.
I think Sahir has just given a wonderful explanation in a nutshell about how an ISP works , but that is true for a relatively small ISP . If you move on to the big players , well there's a lot more stuff happening over there. I happened to do my training in a medium sized ISP and really got to learn a lot.Quite a lot of things that take place over there are really fascinating.So if you wanna know anything more , feel free to ask
Re: How does an ISP work and how si it configured?
14 years 5 months ago #4679