17. DNS: The Domain Name System

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Zillions of hosts are connected to the Internet. How do we keep track of them all when they belong to so many different countries, networks, and administrative groups? Two key pieces of infrastructure hold everything together: the Domain Name System (DNS), which keeps track of who the hosts are, and the Internet routing system, which keeps track of how they are connected.

Although DNS has come to serve several different purposes, its primary job is to map between hostnames and IP addresses. Users and user-level programs like to refer to machines by name, but low-level network software understands only IP addresses ...

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