Routers talk to routers and add them to the tables. Bridge uses MAC address, Router uses network address. Gateways change format of the data to make it conform to the application program at the receiving end. Strips packet and rebuilds with new protocol info I.e. PC connectivity to mainframe. Gateway strips PC packet and rebuilds it in mainframe form.
Proxy server is gateway to the Internet.
Analog phone lines can't carry voice and data simultaneously. Voice, data and video. Provides bandwidth as needed. 53 byte cells instead of packets. Like Token-Ring only many frames can go on the token, not just one.