The TCP/IP Guide  9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)       9  Name Systems and TCP/IP Name Registration and Name Resolution            9  TCP/IP Name Systems: Host Tables and Domain Name System (DNS)

Overview and History of TCP/IP Host Names and Name Systems 1 2 3 4 TCP/IP Domain Name System (DNS)

The pioneers of the modern Internet made the first name system for the suite when they created simple files containing the names and addresses of the machines in the early ARPAnet. This system was so simple that it originally wasn't even formally specified as a “name system” per se. Since the files contained names for network hosts, the process for relating names to addresses was simply called the “host name” mechanism. Later, these files were called host tables, and for this reason I call this technology the TCP/IP host table name system.

As a system, it is extremely simple, since it consists of nothing more than a text file maintained on each machine on the network. This file is normally called “/etc/hosts” on a UNIX system, or HOSTS on a Windows system (usually residing in the main Windows directory). The file usually begins with some comment lines and then lists pairs of IP addresses and host names. A very simplified example (using the modern table structure, which is slightly different than the original host table format) is shown in Table 161.

The name space and architecture for this system is theoretically flat, with each name being able to take any form without any real structure. Despite this, certain rules were eventually put in place regarding how names should be created, for consistency. As we will see later in this topic, it's also possible to use host tables to support the implementation of a hierarchical name space, which would obviously mean the names would have to be created using that name space’s structural rules.

Overview and History of TCP/IP Host Names and Name Systems 1 2 3 4 TCP/IP Domain Name System (DNS)