Name Resolution - Novell LINUX ENTERPRISE SERVER 10 - INSTALLATION AND ADMINISTRATION 11-05-2007 Installation Manual

IPv6 Essentials
A book describing all the important aspects of the topic is IPv6 Essentials by Silvia
Hagen (ISBN 0-596-00125-8).

30.3 Name Resolution

DNS assists in assigning an IP address to one or more names and assigning a name to
an IP address. In Linux, this conversion is usually carried out by a special type of soft-
ware known as bind. The machine that takes care of this conversion is called a name
server. The names make up a hierarchical system in which each name component is
separated by dots. The name hierarchy is, however, independent of the IP address hier-
archy described above.
Consider a complete name, such as earth.example.com, written in the format
hostname.domain. A full name, referred to as a fully qualified domain name
(FQDN), consists of a hostname and a domain name (example.com). The latter also
includes the top level domain or TLD (com).
TLD assignment has become quite confusing for historical reasons. Traditionally, three-
letter domain names are used in the USA. In the rest of the world, the two-letter ISO
national codes are the standard. In addition to that, longer TLDs were introduced in
2000 that represent certain spheres of activity (for example, .info, .name, .museum).
In the early days of the Internet (before 1990), the file /etc/hosts was used to store
the names of all the machines represented over the Internet. This quickly proved to be
impractical in the face of the rapidly growing number of computers connected to the
Internet. For this reason, a decentralized database was developed to store the hostnames
in a widely distributed manner. This database, similar to the name server, does not have
the data pertaining to all hosts in the Internet readily available, but can dispatch requests
to other name servers.
The top of the hierarchy is occupied by root name servers. These root name servers
manage the top level domains and are run by the Network Information Center (NIC).
Each root name server knows about the name servers responsible for a given top level
domain. Information about top level domain NICs is available at
.internic.net.
DNS can do more than just resolve hostnames. The name server also knows which host
is receiving e-mails for an entire domain—the mail exchanger (MX).
http://www
Basic Networking 559