Networks

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Networks

• And Networking

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Networks and Networking

• Why do we need networks ?

• What are networks ?

• What type of networks are there ?

• How are networks created and managed ?

• Are networks secure ?

• What are the advantages and disadvantages of
• using networks ?

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Why do we need Networks ?

• to share information between users,

• to centrally store information so it can be
  kept safe and secure,

• so that we can easily access the same
  information,

• so that we can share expensive resources (such
  as printers),

• so that we can communicate with each other.

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What is a Network ?

• 2 or more computers connected together,

• there will usually be other devices connected
  to the network (printers, switches etc),

• all the devices need some form of connection
  between each other which can be either physically
  seen (such as a cable or telephone connection) or
  unseen (such as in a wireless network or
  infra-red connection),

• a network needs special equipment (such as
  network cards, switches, etc) to support the
  connections between computer and peripheral
  device.

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Network configurations

• can be a LAN (Local Area Network) or WAN (Wide
  Area Network),

• the choice depends upon the size of the network
  and the purpose it is designed for,

• a LAN is always a permanent network which has a
  known size and is typically in the same building
  or group of buildings close together,

• a WAN is used when the computers are in
  completely different places, such as in large or
  multinational companies or for connecting to
  unknown computers,as in the Internet.

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Network Topologies

• a network topology is the way the computers are
  connected together - their configuration,

• the choice depends upon many factors, such as

- number of network stations and peripherals,
- speed of access and processing needs,
- the cost of installation of cables and
specialist network devices (switches, hubs etc),
- performance requirements of the network,
- the sensitivity and security needs of the
information they hold.
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1. A very simple LAN

• typically used in a very small school, business
  or even in the home,

• a peer-to-peer network with no server,

• each computer can access information from each
  other or share peripherals like printers,

• cheap to set up, easy to manage but NOT secure.

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2. A small LAN

• typically will be an older server-based
  network,

A) a LINE or BUS network with data flowing along
a single cable which connects each computer,
B) a RING network with each computer linked
together in a circle,

• both are cheap to install, but slow and prone
  to network failure.

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3. A modern LAN

• suitable for even the biggest school or a
  company based in a single location,

• typically a STAR server-based network,

• Stations connected in small groups directly to
  the server,

• Allows the network to easily grow as more
  stations and peripherals are added,

• allows for developments such as INTRANETS,

• much more secure in that any loss or damage to
  the cabling only affects some of the network
  stations.

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A typical school LAN
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Wide Area Networks (WAN)

• not usually permanently wired together and so
  have to make use of temporary connections such as
  telephone lines, satellites and microwaves,

• allows networks to operate between different
  towns, countries and continents,

• may consist of a number of different networks
  connected together and able to talk to each
  other by using special hardware devices (Routers),

• Large companies will have each of their offices
  communicating to the Head Office via a WAN,

• The Internet is a WAN, since we communicate
  with our Internet Service Provider (ISP) and
  other web sites via a telephone.

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WANs continued
WANS use either - a standard telephone cable
together with a MODEM, OR - a faster
connection such as an Integrated Services Digital
Network (ISDN) line and a Terminal adapter, OR
- a fibre-optic cable managed by a cable
company OR - more typically a mixture of these !
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A sample WAN
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Using the Internet

• when using the Internet you are part of a WAN,

• connecting to the Internet at home is known as
  dial-up networking and your connection to the WAN
  is via your ISP (e.g. AOL),

• the Internet is connecting lots of different
  computers and networks temporarily together and
  so we need a standard way of communicating called
  Transmission Control Protocol/Internet Protocol
  (TCP/IP),

• each computer on a network has a unique name
  or identifier known as its IP address so that
  requests for data and replies can go to the
  correct computer.

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Creating a Network
We need to consider a number of factors

• the HARDWARE equipment needed to ensure the
  network can run,

• the OPERATING SYSTEM SOFTWARE needed to manage
  the processing and control the data flow around
  the network.

• The needs and demands of the users of the
  network,

• how to maintain the security and integrity of
  the data.

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Hardware considerations

• We need 1 or more powerful servers, usually
  with 2 fast Processors, a number of Network
  Interface Cards (NICs), a number of separate
  fast Hard Disk Drives and an awful lot of RAM !

• additional devices are needed to connect each
  part of the network and ensure efficient data
  flow around the network, such as

- Hubs in individual rooms,
- Switches linking the hubs to the servers,
- Power Supply Units (PSU) to ensure the network
operates in a power cut,

• sufficient computers and peripheral devices.

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Network Operating System

• is far more sophisticated than a simple
  operating system (OS) needed to run a PC (such as
  Windows98),

• a network operating system has to

- share its time between all the users (hence a
Multi-user OS) and all the tasks it has to do
(hence a Multi-task OS),
- monitor who is using the network by keeping a
log of everything users do and tasks completed,
- monitor and control all the shared resources
such as printers,
- maintain network security by controlling User
Id, Passwords and Access Rights.
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Network Security

• we need to protect the physical security of the
  network by practical methods, such as locking the
  server in a secure area, recording serial numbers
  of equipment and alarming ICT areas,

• we need to protect the data from accidental or
  wilful damage using virus checking software,
  controlling user access rights and firewalls to
  stop people hacking into our network,

• regular back-ups need to be taken to protect
  against hardware failure

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Advantages of Networks

• Expensive resources can be shared between
  computers,

• Users can share information and access common
  data,

• Users can access the information from any
  connected network station,

• Users can communicate with each other
  electronically via e-mail and video-conferencing,

• Organisations can easily control what users are
  allowed to see and do and which applications they
  are allowed to use.

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Disadvantages of Networks

• Because of the specialist hardware, software
  and cabling networks are expensive to set up,

• Depending upon the type of network, failure of
  some of the network equipment (hubs, cables etc)
  could stop the network operating fully,

• There is a regular cost in keeping networks
  running such as employing network managers,
  paying for specialist network support and
  telephone charges,

• Making networks secure from damage caused by
  viruses and hacking is difficult and expensive,

• Some software will not easily run over a
  network.

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Networks and Networking
You need to understand both what networks are and
how they can be used in a variety of situations.
You must incorporate some of the information
about networks when explaining how different
organisations use ICT efficiently and
effectively. Try to remember a suitable example
of each type of network so you can discuss the
differences between them.
Good Luck
Networks and Networking