2. By the end of this unit you will know
•The basic components of a network system
•Characteristics of networks
•The use of communication networks
•The importance of standards in networking
A lot of this overlaps (sorry!)
3. Basic components of a communications network
A basic network comprises a number of computers and other hardware devices
such as printers, scanners or other facilities such as the internet that are linked
together so that they can communicate and share data with each other.
These are two examples of how this might work in a typical home
4. What equipment do you need to build a network?
•Computers – PC’s or Mac’s or whatever you want to run
•Attached devices – Printers, additional storage, scanner
•Wireless devices – Laptops, iPod, iPad etc
•Gaming devices – Xbox, PS3 etc. Not always needed but many use them.
•Connection devices – Switch or hub to join the devices either via cables or wirelessly
•Cables – Usually use CAT5 or CAT6 UTP (unshielded twisted pair) cables
You can also use a router / homehub to connect your home network to the internet.
This will allow you to access the www via your ISP (internet service provider)
Top tip – never, ever, ever tell the examiner that your network is connected by wires.
They don’t like it and tells them that you don’t know what you’re on about.
Also make sure you know the difference between the internet and the www.
6. Do I really need cables?
No, you could go completely wireless if you want but I would still have at
least 1 wired connection to the router/switch/hub just in case…
The use of Wi-Fi has taken off dramatically over the past few years. Many
coffee shops, pubs, airports, trains now offer free or “cheap” wireless access.
All Wi-Fi needs is a wireless transmitter/receiver to broadcast a signal and
then your wireless device to connect to it. You can then access any resources
that the network provider will let you which is usually web access.
Advantages Can be setup anywhere within reason
Can work anywhere that you can receive the signal
It’s a global standard!
Disadvantages High power consumption especially if the signal is weak
Security issues with the wireless signal
Limited range (still)
Interference where wireless signals overlap
7. Network terminology
Networks can be divided into two types dependant on size:
Local Area Network (LAN) and Wide Area Network (WAN)
In general LAN’s are much smaller than a WAN.
A company can have LAN’s at each site connected together to create a WAN.
A WAN can cover an area from a town with many sites up to a global company.
What you use on a daily basis at home or in school is a LAN.
8. Local Area Network (LAN)
•A LAN occupies a single building or site (a small geographical area)
•The organisation using the LAN normally owns all the kit.
•Connections are usually cables or wireless.
•Your home network and the school network are LAN’s.
9. Wide Area Network (WAN)
•A WAN covers more than one site and possibly many countries
•Connections might be rented from a telecoms provider e.g. BT.
•Can use a range of communication types including telephone, microwave and satellite
10. Network topologies (shapes)
Networks can be linked in many ways dependant on what they will be used for.
A BUS network is arranged along a single cable. It is quick and
easy to install and doesn’t use a lot of cable.
BUT if there are more than 10 active computers the network will
slow down and if the cable is broken the network will crash
This network is rarely found today
A STAR network uses a central connection point
(hub, switch, router). It is easy to add computers and the network
doesn’t tend to slow down. Also if 1 connection fails the other
computers are not affected.
BUT it uses more cable to connect all the machines and if the
central connection fails…
This is the commonest network shape
11. A RING network has its machines arranged in a circle. Data
is transmitted from one machine until it reaches the correct
machine and you can predict how long it will take data to
arrive.
BUT if the connection or cable fails the network will crash
and you cannot add machines whilst the network is active.
This network is rare but is usually found in manufacturing
businesses.
A MESH network has many connections per device and so is
fault tolerant.
BUT it uses a lot of cable and can be a pain to troubleshoot if
a fault occurs.
Implemented as a wireless network this can be found in
many locations
12. Network operations
At its most basic a network can be two computers linked together. They can
share files, programs and a printer. No one computer is in charge and as the
machines have equal rights this is called a PEER-TO-PEER network.
As the network gets bigger it is useful to have one machine to control the
network, to store data and programs and to control access to a printer. This is
a CLIENT-SERVER network where the controlling computer is the SERVER
and the others are CLIENTS.
13. Peer-to-Peer Networks
Advantages
•Cheap and easy to set up
•Great for simple home use such as sharing a printer
•No network manager needed
•No reliance on a central server
•Lower operating costs
Disadvantages
•No central backup of files
•Poor security as each machine/user is responsible for what they do.
•Machines that are hosting often used resources might run slower
•Not really suitable for office use
14. Client-Server Networks
Advantages
•Data is held centrally so everyone can access it
•Only need one copy of software + a multi-user or site licence
•Centralised backup of data and program files
•Easy to enforce security such as usernames, passwords, disc quotas etc
•Often has a professional network manager/administrator to oversee it
Disadvantages
•You usually need specialist knowledge to set up and run it efficiently
•Can be more expensive due to specialist network software
15. The Internet & the www
Contrary to popular belief these are NOT the same!
The terms internet, www, the web, t’interweb etc have all become synonymous
with accessing remote resources via a browser. They are not the same thing. You
might talk about “being on the ‘net” or “surfing the web” but they are
completely different things.
16. The Internet
The history of the internet goes back over 50 years. This is the basic infrastructure
that underlies the web.
1950’s US Govt wants a secure communications system that can withstand a
nuclear “first strike”. RAND Corporation suggests a packet switched
network where messages are broken down into packets of data that
can be routed in many ways from their source to their destination.
1960’s ARAPANET is created in the US linking universities, initially in California.
1970’s Project work to standardise a growing world of packet switched networks.
1974 The first mention of the term “internet” short for internetworking.
1980’s As a result of standardisation TCP/IP is the only communication
protocol allowed on the fledgling internet. All attached devices will
have a unique IP address.
17. The www
The www is a bit more up to date but has still been around over 20 years. The web
is basically the content that sits on the internet.
1989 Tim Berners-Lee working at CERN demonstrates how data can be
indexed and linked using hypertext.
1990 First hypertext browser LYNX.
1994 Marc Andreessen releases the first web browser MOSAIC (his PhD
project) later to become Netscape Navigator.
1995 First web search engines appear (Lycos, AltaVista, Yahoo)
1995 Bill Gates gets a bit worried and releases Internet Explorer as an add on
to the newly released Windows 95.
Mr Brooks makes his first online purchase to demonstrate possible uses
of the web at an IT conference in Bedfordshire ( a QPR football shirt!)
18.
19. Definitions!
The internet a large group of interconnected computers that allow the
sending and retrieval of data/information from one
machine to another. Often called “a network of networks”.
The www a collection of multimedia resources that are accessed
via the internet using browsers using http, https, html,
etc to read and download information.
20. Other internet content
Apart from the web the internet gives you access to the following:
•email
•instant messaging
•usenet to provide newsgroups
•FTP for file sharing
•P2P for file sharing
All of these require different protocols to the http and https that runs the www
21. Intranets & extranets
An intranet is a private network using internet technology within a business.
It is designed to be used for sharing information and resources but only
within the business. Only company employees can access the network either
on or off the company site.
An extranet is similar in concept to an intranet but has some major differences.
• It can be used by the business and by its customers and suppliers.
• It uses usernames and passwords to ensure that the general public do not
have access.
• As access is required from outside of the business, communication links are
important and must be kept secure.
