An internet gateway is your modem or router or any other periphial which allows you to access the internet. Which DSL first hit the market, companies called their modem gateways instead of modems. Most computers in the 70’s and 80’s had internal modems which were connected to a phone line. The wonderful time of dial-up. As technology grew and the need for speed grew with it, DSL provided users with speed from a basic telephone line via their modem (gateway). Simply put, a gateway is a door to which allows access to the internet.