The Domain Name System, or DNS, is one of the Internet's
fundamental building blocks. It is the global, hierarchical, and
distributed host information database that's responsible for translating
names into addresses and vice versa, routing mail to its proper
destination, and many other services.
(Another fundamental building block of the Internet is BGP routing, the routing protocol
used to exchange routing information across the Internet. It is
discussed in depth on our companion website about BGP4).
To understand what DNS does, let's take this small example. You'd
like to visit a website, www.example.com.
After entering the website location, the browser has to find out the IP
address of the host www.example.com. Therefore it makes a query to the
local DNS resolver, which in turn queries the local DNS
server. The DNS server does some more work - quickly finds out the
matching IP address - and returns this answer back to the
resolver.
In DNS jargon, this lookup is called a query for the "A record". This
record describes the relation between a hostname and the corresponding
IP address in DNS.
Your web browser is now able to contact the host www.example.com using
its IP address. Further information retrieval takes place using the HTTP protocol, which is not discussed
here.
Of course, the complete DNS resolving process is slightly more
complicated. But finding the corresponding IP address for a hostname -or
vice versa- is one of the basic tasks of DNS. The DNS protocol
however has a lot more features and applications. For a complete
understanding of the workings of the Domain Name System, you're
encouraged to visit the DNS
links section on this website.
The original DNS protocol is described in RFC 1034 and
RFC 1035.
- RFC 1034 - Introduces domain style names,
their use for Internet mail and host address support, and the protocols
and servers used to implement domain name facilities.
- RFC 1035 - Describes the details of the domain
system and protocol, and assumes that the reader is familiar with the
concepts discussed in a companion RFC 1034.
 Related Reading
 DNS RFCs
DNSSEC RFCs
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BIND (Berkeley Internet Name Domain) is an implementation of the DNS protocols and provides an
openly redistributable reference implementation of the major components of
the Domain Name System, including:
- Domain Name System server
- Domain Name System resolver library
- Tools for managing and verifying the proper operation of the DNS server
The BIND DNS Server, named, is used on the vast majority of name serving machines on
the Internet, providing a robust and stable architecture on top of which an
organization's naming architecture can be built.
The resolver library included in the BIND distribution provides the
standard APIs for translation between domain names and Internet addresses
and is intended to be linked with applications requiring name
service.
BIND version 9 is a major rewrite of nearly all aspects of the
underlying BIND architecture. Some of the important features of BIND9
are DNS Security (DNSSEC, TSIG), IPv6, DNS Protocol Enhancements (IXFR, DDNS, DNS Notify, EDNS0), Views, Multiprocessor Support, and an Improved
Portability Architecture.
Today, BIND versions 4 and 8 are officially deprecated. No bug or security
related patches are available. ISC encourages all BIND users to upgrade to the latest version 9 at
their earliest convenience.
In the BIND Nameserver links
section you'll find a lot of BIND howtos, notes and links related to
configuring the BIND nameserver. And there's an online version of the
BIND Manual where you can
learn how to configure your BIND nameserver.
Related Reading
DNSSEC (DNS Security Extensions)
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