Domain Name System
(DNS) Introduction
Introduction
DNS is a very well known
protocol. It is used for resolving host names and domain
names to IP addresses. The fact is that when you type
www.firewall.cx it is
translated into an IP address via special queries that
take place from your PC, but I'll explain how that works
later on.
Because
there is a fair bit of material to cover for the DNS
protocol, and I don't want to confuse you with too much
information on one page, I have broken it down into 5
sections, each covering a specific part of the protocol.
People who
want specific information on the DNS protocol can go
straight to the section they need, the rest of us who
just want to learn it all can start reading in the order
presented:
Section 1:
The DNS Protocol. How and
why the DNS protocol was born. Page contains a bit of
historical information and also compares DNS with the
OSI Reference model, where you will see the layers on
which DNS works. Internet DNS hierarchy is also analysed
here, giving you the chance to understand how domains on
the Internet are structured.
Section 2:
The DNS Resolution Process.
What really happens when a host requests a DNS
resolution. Full analysis of the whole resolution
process using a real life example. Understand Name
Servers and the role they play in the DNS system.
Section 3:
The DNS Query Message Format.
This section, along with the next one gives you the DNS
packet format in all its glory. Learn how DNS queries
are generated and formatted. See, learn and understand
the various fields within the packets as your taken
through a full detailed analysis of the packet structure
using the cool
3D diagrams.
Section 4:
The DNS Response Message Format.
This is the continuation of the section above,
dealing with the DNS response that's received. You will
learn how the response packet is generated, formatted
and sent to the resolver. Again, you're taken through a
full detailed analysis of the packet structure using the
cool
3D diagrams.
Section 5:
The DNS Server (BIND).
Based on BIND for Linux, this section is broken into a
futher 6 pages:
-
Section 5.1:
Introduction to the DNS
Server. Learn how a DNS server is
setup on a Linux machine. Over 85% of DNS servers on
the Internet run on Linux and Unix based systems
while Microsoft and Novell DNS servers follow the
same structure. DNS
Zones and
Domains are
also covered on this page, this is essential for
understanding how DNS Servers work.
-
Section 5.2:
The db.DOMAIN file.
Complete analysis of the zone data file for a
Primary DNS server. See what is contains and
understand how its structured.
-
Section 5.3:
The db.ADDR file.
Complete analysis of the zone data file for a
Primary DNS server. See what is contains and
understand how its structured.
-
Section 5.4:
Other common files.
Analysing the rest of the files which are
common to all DNS servers.
-
Section 5.5:
Slave DNS Server.
Instructions on setting up a secondary DNS
server.
-
Section 5.6:
DNS Caching. The
key to an efficient DNS server. This is a must for
any DNS Administrator. Learn how DNS caching helps
improve performance and reduce traffic. Includes
analysis of specific parameters within the DNS
packet, which helps make DNS caching a reality, and
find out how to avoid problems that come with Domain
redelegation or website transfers.
As you can
see, there's plenty of stuff to cover. But don't despair
because is all cool stuff ! Grab something to drink and
let's dive into the DNS waters ! You will be amazed at
the stuff you'll find :)
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