IP Addressing

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As explained previously, humans work with names & computers work with numbers. To identify a specific machine, a unique number called an ´IP address´ is assigned to it.

For example the IP address for the Web server which hosts the Google search engine web site is 216.239.39.100

What's the relationship between IP Address & Domain name?

When your browser makes a HTTP request for the Web site www.google.com the IP address is looked up in a database of IP addresses Versus Domain Names this system is call DNS.

About the DNS

The Domain Name System (DNS) is a distributed Internet directory service. DNS is used mostly to translate between domain names and IP addresses, and to control Internet email delivery. Most Internet services rely on DNS to work, and if DNS fails, web sites cannot be located and email delivery stalls. The domain name system is a distributed database arranged hierarchically. Its purpose is to provide a layer of abstraction between other Internet services (web, email, etc.) and the numeric addresses (IP addresses) used to uniquely identify any given machine on the Internet.

This has several advantages:

It permits use of names instead of numbers to identify hosts (usually servers). Names are much easier to remember.
It permits a server to change numeric addresses without requiring notification of everyone on the Internet, by simply retargeting a name to the new numeric address.
One name can refer to multiple hosts, to share the load.

The DNS directory service consists of DNS data, DNS servers, and Internet protocols for fetching data from the servers. The billions of resource records in the DNS directory are split into millions of files called zones. Zones are kept on authoritative servers distributed all over the Internet, which answer queries according to the DNS network protocols. In contrast, caching servers simply query the authoritative servers and cache any replies. Most servers are authoritative for some zones and perform a caching function for all other DNS information. Most DNS servers are authoritative for just a few zones, but larger servers are authoritative for tens of thousands of zones.

Example

The IP address for the Web server which hosts the Google search engine web site is 216.239.39.100

Neotrace Google Neotrace Google Node

Try putting the URL http://216.239.39.100/ into your browser Address Bar.

Whois

Whois allows you to find the physical locations of, and other information about, IP domains. An easy way to use this tool is to access a Whois Gateway, such as http://www.networksolutions.com/cgi-bin/whois/whois with your browser.

Whois Server Version 1.3
Domain names in the .com, .net, and .org domains can now be registered
with many different competing registrars. Go to http://www.internic.net
for detailed information.

Domain Name: GOOGLE.COM
Registrar: NETWORK SOLUTIONS, INC.
Whois Server: whois.networksolutions.com
Referral URL: http://www.networksolutions.com
Name Server: NS2.GOOGLE.COM
Name Server: NS1.GOOGLE.COM
Name Server: NS3.GOOGLE.COM
Name Server: NS4.GOOGLE.COM
Updated Date: 13-jun-2001

>>> Last update of whois database: Wed, 26 Sep 2001 02:25:22 EDT <<<
The Registry database contains ONLY .COM, .NET, .ORG, .EDU domains and Registrars.

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Christopher Ward London Limited