To tell anybody ‘I AM ISP A’ you will have to connect physically to some ISP C. C will then (hopefully) check you and if you go ‘I AM ISP A’ he’ll ignore you an

To tell anybody ‘I AM ISP A’ you will have to connect physically to some ISP C. C will then (hopefully) check you and if you go ‘I AM ISP A’ he’ll ignore you and don’t tell anyone unless you’re really ISP A and he determined you to be this guy. There are rather obvious limits, however, for example you will likely have to believe your ISP C if he says ‘I AM ISP B NOW, TOO’. If you then connect to another ISP D, and tell him ‘I KNOW ISP B’, D will have to decide whether to trust you (likely if you are a large telecom company) or not (if you just happen to have two 10 MBit/s lines to C and D each).