There must be a way to translate from alphabetic addresses to numerical numbers, so that people can express recipients of email and remote hosts by easily remembered names, while the underlying protocols can continue to rely on the more economical numerical "names." For a while, each host had a file that was essentially a translation table, matching alphabetic names of hosts with their IP numerical equivalents. After the number of hosts began to climb into the thousands, this got ridiculous. Nowadays, special software and protocols exist to translate alphabetic names dynamically upon request, calling upon distributed database servers for translation. This is called the DNS or Domain Naming System. When somebody says that they want to remotely log in gandalf.net17.att.com, their host computer first consults its own private cache of recently translated names in case that particular name was looked up recently. If not, it consults another computer, using a protocol, which acts as the root server for all com addresses. This computer directs the translation request to a machine that translates just att addresses, and then this one looks up gandalf in net17 and sends the IP address for that machine back to the original recipient. |