I think ISP should be able to provide several kinds of internet connection service. For example, at the ISP edge router, as long as ISP just provide with its own ip address and a link, which is connected to client’ router, the client can use the NAT at the clients router to access the internet. In the large enterprise, the ISP can provide with whole routing table to client, etc.
So, any experts can tell me or send a link, which give an overview on all kinds of internet connection service that ISP can provide ? Thank you.