DNS and IPv6
By Alex Lightman
CEO, Innofone.com, Inc.
DNS, or the Domain Naming System, has been around for many years. The
existing Internet would not be able to scale by adding nodes through people with
such varying skills without it. The basic function of DNS is to map hierarchical
domain names (e.g. www.usipv6.com) onto IP addresses (e.g. 188.8.131.52, for
IPv4), which is what is actually used in packet headers for addressing on the wire
(See Figure 1). You can think of DNS as the Internet’s (automated) telephone
book, as a start.
Figure 1 – Domain Naming System
DNS also does IP address to domain name mapping (like a “reverse phone
book,” available to business users), and allows you to publish certain things that
must be known to others, such as the nodename of your preferred mail server(s),
which is done with MX records. Few people realize that you can also advertise
the preferred LDAP server for your domain name and other such things, or use it
to map a universal telephone number to one or more URLs (using ENUM), for e-
mail, IM, VoIP with SIP, etc.
There are a number of widely used DNS servers, the most popular of which is a
public domain program originally developed at UC Berkeley, known as the
Berkeley Internet Naming Daemon, or BIND. Microsoft also created their own,
now included with Windows Server. Other folks have created free ones and
commercial ones (e.g. Nominum, headed by Paul Mockapetris, who invented
Every network has to have a DNS server, or else the nodes in your network can
only be addressed by others using numeric IP addresses. In a purely Microsoft
network (or other SMB/CIFS based system such as SAMBA), it is possible to
instead deploy WINS (Windows Internet Naming System), which is used to
automatically register and publish “NetBIOS” names (an alternative namespace
that can map onto various network addressing schemes, including TCP/IP).
However, this system does not scale very well beyond the LAN, and is not used
by most widely used Inte