To understand the Internet you need to understand three main areas:
the fundamental transport protocol i.e. how data is moved around the Internet
domain names and domain name resolution i.e. how things are named or referenced on the Internet
servers, routers and clients i.e. the hardware of the Internet
Transport Protocol - TCP/IP
The fundamental means of moving data around the Internet is controlled by a protocol called TCP/IP,
or transmission control protocol/internet protocol. TCP/IP is also used on private networks, like your office LAN
or home network. As the name suggests, TCP/IP is the combination of TCP and IP protocols working together.
Under TCP/IP a file is broken into smaller parts called "packets"
by the file server. Each packet is assigned an IP (Internet protocol) address of the computer it has to travel to. As the
packet moves through the global network it is "switched" by a number of servers and routers along the way toward
its destination... the requesting computer or "client" computer.
The IP address tells those servers which way to switch the packet. Each time the packet is switched a "wrapper"
is added to the packet this way we can tell how many computers and which computer handled the file while it was in
transit. You can do this with the command "tracert" at the command line of your computer (e.g. tracert dynamicwebs.com.au).
Tracert stands for "trace route".
In Australia, a file coming from the United States can be switched up to 15-20 times, that is fifteen computers passing
on the data like a hot potato toward the destination computer.
The packets do not necessarily travel together on the Internet. Packets from the same file may travel via different paths
through different servers, but toward the same destination.
Packaging technology allows us to use limited bandwidth most efficiently. It means parts of a file can be shared across
a number of phone lines instead of having to find one phone line to put a large file into. It is also hard to break the
network, as the data will be routed around the trouble spot. In this respect TCP/IP can be likened to a group of 10 hitchhikers
(packets) who can not get a lift all together, but easily get lifts if they break up, going by different cars and maybe
by different roads but agree to meet up at a particular point in the future.
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A domain name is a business' or an organisation's name on the Internet. It is the part of the email address after the "@"
sign or part of the web address after the "www.". e.g. dynamicwebs.com.au is the domain name of this web site.
It is also an abbreviation of "Dynamic Web Solutions Pty Ltd"... a business name.
In Australia domain names are registered by licensed registrars of the Australian Domain
Name Authority, the AUDA. Large registrars include: Enetica, Netregistry
and MelbourneIT. These companies are authorised by the AUDA to license domain
names. They also operate reseller programs to allow smaller companies to register domain names on behalf of their customers.
In Australia you need an ABN, ACN or RBN to register a domain name.
Once a domain name is registered, it is "delegated" to a server. Delegation means pointing the domain name at
the server. That server then answers file transfer protocol requests, receives email and serves web pages for that domain.
To delegate a domain name you need to know the name servers of the company
that will maintain your web site and email. This company is referred to as the "host".
The host maintains a DNS server, or "domain name server". This is generally a software server running continuously
answering calls for your domain (and others) that are delegated to that server and directing the requests and inbound data
to different facilities of the host's server. You can think of a DNS server as a table that helps the server route traffic
to different IP addresses.
So why do domain names have to have an IP anyway? An IP address looks like 201.517.635.124... I think you will agreed,
that is not very memorable. That IP address has a letter equivalent... one that humans can easily recall. Therefore the
domain name system is designed to say:
1. which server will answer requests for which domain name i.e. which server is "authoritative" for which domain
2. which IP addresses "resolve" to which domain names".
Broadly speaking the Internet is comprised of servers, routers and clients.
1. Servers are powerful computers that run 24 hours a day, 7 days a week, without stopping and hopefully without failing.
Servers are specially constructed with redundant hard drives (this is called a RAID
array), extra cooling and are generally "rack optimised", which means they are very flat and deep and are
intended to slip into a rack of 32 similar machines.
Most servers are housed in "data centres". The datacentre offers physical security, redundant power supply
(with back up diesel generators), redundant air-conditioning, special fire retarding systems, anti static mats... and
the list goes on. In other words, short of an earthquake or nuclear strike, datacentres are designed to handle many contingencies.
The objective of a datacentre is to keep those servers cool and running continuously. During hurricane Katrina only one
New Orleans datacentre was able to
2. Routers pass data onwards to its destination IP. They aren't all that smart, but they do their job quickly and efficiently.
3. Client machines, that is the end user, the person requesting a web page or downloading email. The client machine uses
a browser and an email client to perform these functions. The server waits for a request from a client, then grabs
the requested data and serves it back.
4. Cables and conduits. The physical connections between servers, routers and clients vary enormously. Between you and
your telephone exchange, it is likely you are using twisted pair copper wire. Between your exchange and your ISPs network,
it is likely you are using fibre optic cables. Between ISP and ISP it is likely you are using T1 carriers, the main trunk
routes of the Internet.
Today, there are good arguments to include VoIP phones, some mobile phones
and Blueberry-styled PDAs as "Internet hardware" as all of these devices are connecting to the Internet for various