Automating System Administration with Perl, 2nd Edition

Chapter 5. TCP/IP Name and Configuration Services

The majority of the conversations between computers these days take place using the Transmission Control Protocol running over a lower layer called the Internet Protocol.^[27] These two protocols are commonly lumped together into the acronym TCP/IP. Every machine that participates in a TCP/IP network must be assigned at least one unique numeric identifier, called an IP address. IP addresses are usually written using the form N.N.N.N (e.g., 192.168.1.9).

While machines are content to address each other using strings of dot-separated numbers, most people are less enamored of this idea. TCP/IP would have fallen flat on its face as a protocol if users had to remember unique 12-digit sequences for every machine they wanted to contact. Mechanisms had to be invented to manage and distribute IP addresses to human-friendly name mappings. Also needed was a way to let a machine automatically determine its own TCP/IP configuration (i.e., IP address) without requiring a human to drop by and type in the information by hand.

This chapter describes the evolution of the network name services that allow us to access data at www.oog.org instead of at 192.168.1.9, and what takes place behind the scenes. We’ll also look at the most prevalent configuration service that allows a machine to retrieve its TCP/IP configuration information from a central server. Along the way we’ll combine a dash of history with a healthy serving of practical advice on how Perl ...