Java Projects - Second Edition

DNS

The TCP protocol creates a channel using the IP addresses of machines. When you type a URL in the browser, it usually does not contain IP numbers. It contains machine names. The name is converted to IP numbers using a distributed database called Domain Name System (DNS). This database is distributed, and when a program needs to convert a name to an address, it sends a DNS request to one of the DNS servers it knows. These servers send queries to one another, or tell the client whom to ask, until the client knows the IP address assigned to the name. The servers and the client also cache the recently requested names, so answering is fast. On the other hand, when the IP address of a server changes this name, not all clients will immediately ...