Module 5.1.5

1
Module 5.1.5

• The Role of Communications and Networking

2
The Need for Communication

• Communication between devices is necessary to
• Share information
• Use shared devices (peripherals)
• Communication requires
• Appropriate hardware
• Suitable software
• Compatibility
• Communication can also be necessary between
  software applications on the same system
• Transferring a set of calculations in a
  spreadsheet into a table in a word processor.

3
The Need for Communication

• For effective communication protocols are needed
• A protocol is a set of rules used to ensure the
  proper transfer of information between computers
  and between application packages
• If information is being exchanged between
  applications then a compatible format can be
  found.
• For example, to import data from a database into
  a spreadsheet, the format CSV could be used.
  This would be compatible as an export from the
  Database and as an import into the Spreadsheet.

4
Networks

• A Network is a linked set of computer systems
  capable of sharing computer power, resources and
  data.
• Sometimes network is used to mean the arrangement
  of links between the equipment that forms the
  network
• LAN
• A network in which the computer systems are all
  situated relatively close to each other. Direct
  physical connection is possible.
• WAN
• A network where the computers are geographically
  remote. Makes use of a range of communication
  methods include communication satellites.

5
Networks - VLAN

• VLAN
• Virtual LAN
• A VLAN is a network of computers that behave as
  if they are connected to the same network cable
  even though they may actually be physically
  located on different segments of a LAN
• It is a subdivision of a LAN and can have its own
  settings separate from the LAN
• When a computer is physically moved to another
  location it can stay on the same VLAN without any
  hardware reconfiguration
• Machines on a VLAN can be grouped together
  regardless of physical location
• In a school, all the admin machines can be on a
  VLAN even if they are located all over the school
  and not in a single area

6
Networks - WLAN

• WLAN
• Wireless LAN
• Devices are not physically connected all the time
  connect for a specific purpose
• Printing
• Sharing Files
• E-mail/internet
• Issues of security if physical connection is not
  required
• Speed of connection multiple machines
  connecting to single access point

7
Networks - VPN

• VPN
• Virtual Private Network
• a virtual private network is a group of two or
  more computer systems, typically connected to a
  private network (a network built and maintained
  by an organization solely for its own use) with
  limited public-network access, that communicates
  "securely" over a public network.
• VPNs may exist between an individual machine and
  a private network (client-to-server) or a remote
  LAN and a private network (server-to-server).

8
Types of VPN

• Hardware-based VPNs
• Most hardware based VPN use Encrypting routers
• Hardware based VPNs provide the highest network
  throughput of all VPN systems
• However, they may not be as flexible as software
  based systems
• Firewall-based VPNs
• Take advantage of the firewall's security
  mechanisms, including restricting access to the
  internal network
• They also perform address translation satisfy
  requirements for strong authentication and serve
  up real-time alarms and extensive logging
• OS protection is a major plus
• Performance may be a concern, especially if the
  firewall is already loaded
• Software-based VPNs
• Ideal in situations where both endpoints of the
  VPN are not controlled by the same organization
• At the moment, standalone VPNs offer the most
  flexibility in how network traffic is managed

9
Topologies

• Star
• All the network devices connected to a central
  computer which is often used as the file server
• Ring
• Each of the devices on the network is connected
  in a ring or a loop. (Each machine has a
  connection to the one previous and the one after
  it in the loop)
• Bus
• Each of the devices is connected directly to a
  main communications line, called a bus
• MESH
• All the computers connected to each other

10
Star
11
Star Advantages and Disadvantages

• Advantages of a Star
• If one cable fails the other stations are not
  affected
• Consistent performance even under heavy use
• Reliable market proven system
• No problems with collisions of data since each
  station has its own cable to the server
• Easy to add new stations without disrupting the
  network
• Disadvantages of a Star
• May be costly to install because of the cable
  lengths required

12
Ring
13
Ring Advantages and Disadvantages

• Advantages of a Ring
• No dependence on a central computer or file
  server and each node controls communication to
  and from itself
• Transmission around the network is one way only
• High data transmission rates are possible
• Disadvantages of a Ring
• If one node breaks down transmission is disrupted

14
Bus
15
Bus Advantages and Disadvantages

• Advantages of a Bus
• Easy and inexpensive to install as it requires
  the least amount of cable of the network types
• Easy to add more stations without disrupting the
  network
• Disadvantages of a Bus
• The whole network goes down if the main cable
  fails at any point
• Cable failure is difficult to isolate
• Network performance degrades under a heavy load 
• Information can be transmitted in either
  direction and occasionally there is data
  collision.

16
MESH
17
MESH Advantages and Disadvantages

• Advantages of a MESH
• Communication is not disrupted
• Alternative routes to node points/machines
• Security packages can arrive/be sent via many
  different routes
• Backup with multiple connections it is easier
  to distribute the data in case of disaster
• Disadvantages of a MESH
• Cost
• of cables required to link machines together
• Of machines similar spec machines required at
  each location to be able to take over
• Difficult to install and reconfigure

18
Networks Odds

• Distributed Star
• Also known as structured star
• Star network with other star networks coming from
  each node
• Hybrid
• A combination of any two or more network
  topologies
• A hybrid network exists only when two basic
  networks are connected and the resulting network
  topology fails to meet one of the basic topology
  definitions.
• A hybrid topology always exists when two
  different basic network topologies are connected.

19
Analogue to Digital Conversion

• Computers use binary data (0s and 1s) - digital
• Binary data cannot be transmitted down long
  lengths of cable as pulses, it needs to be
  converted to tones (sent as waves) - analogue
• This is done by modulation. The conversion of
  tones to pulses is demodulation

20
Bandwidth

• Officially, a measure of the capacity of a
  communications channel
• It is how much data a communications channel can
  handle at one time. (Transmission rate in Bits
  per Second)
• The greater the bandwidth the more information
  the channel can carry, and/or the faster the
  information can travel to its destination

21
Networking Hardware

• In the computer, possible components include
• Network Interface Card (NIC)
• Modem
• Additional hardware (possible components)
• Cabling
• Router
• Hub
• Switch
• Gateway
• Repeaters
• External line (Phone Line, ISDN, ADSL, Leased
  Line)
• Servers mail server, web server

22
Networking Software

• Software includes
• Operating system capable of handling a network
  connection
• Communication protocol
• TCP/IP, IPX, Net BEUI etc.
• Internet Browser
• Netscape, Internet Explorer, Opera
• E-mail package
• Outlook, Pegasus, AOL Mail
• Mail server package in a network
• Exchange Server
• Application Software
• Compression software, FTP software, chat
  software, video conferencing software

23
Advantages of Networking

• Sharing of expensive resources
• Share data and ability to backup data centrally
• Accounting and monitoring of resources
• Electronic communication/meeting possible
• Virus checking from a central location

24
Disadvantages of Networking

• Reliant on other resources working
• Virus on a single machine can spread to the rest
  of the network
• Load on the network can slow it to an
  unacceptable speed
• A network station is dependant on a network being
  present
• Require additional employees to run the network

25
Passwords

• Need and Purpose
• To keep personal work safe
• Effectiveness of password maintained by
• Network Manager
• Force password change frequently
• Make minimum length password
• Make unrecognisable words only
• Must contain numbers and letters
• Cannot reuse passwords
• Three password attempts and account is locked
• User
• Not writing password down
• Make it something no one else can guess not
  personal
• Make sure no one is looking when you type it in

26
User IDs

• Required
• To make individual user embers of groups
• To allow access to resources printers, files,
  software, etc.
• To monitor user
• Effectiveness of user ID maintained by
• Must be unique so can be sure who is doing what
• When user is away on holiday, sabbatical, user
  ID can be suspended
• User ID can be linked to an individual machine
  and times of use

27
Forms of Communication

• Many forms of communication, examples include
• Fax
• E-Mail
• Bulletin Boards
• Tele/Video Conferencing
• WWW
• FTP
• Telephone
• Courier

28
Relative Merits

• Discussion of Merits should be based on
• Download Speed / Speed of delivery
• Access to Resource
• Hardware requirements
• Software Requirements
• Security
• Quality of end product

29
Fax

• The use of voice quality telephone lines to send
  copies of documents, which may include drawings
  as well as text
• Needs a fax machine and an available line
• Not secure
• Quality is variable
• Document is not editable
• Can be colour if sending and receiving equipment
  is capable of colour and compatible

30
E-Mail

• Sending a message from user to user through
  computer communication.
• Multiple recipients, carbon copies (CC), blind
  carbon copies (BCC)
• Digital signatures giving security
• Documents are editable
• 24 hours service not location or machine
  dependent
• Depends on hardware working

31
Bulletin Boards

• Equivalent of a short term notice-board carrying
  items that may be of interest to a wide number of
  people.
• Not secure
• Many recipients
• Always available
• Documents are editable
• Accessible from anywhere in the world

32
Tele/Video Conferencing

• The use of communication links to conduct
  meetings between at least two people who are
  geographically separate
• Pictures static and moving, text and voice
• Can transfer files
• Very secure
• Need specialist software and hardware for full
  video conferencing
• Netmeeting is a cheaper alternative but not
  secure or fast.

33
WWW

• The facility to link computers worldwide and
  share information both graphics and text.
• Can be made secure
• Available worldwide
• Documents editable
• Download speed is variable

34
FTP

• Movement of files from one location to another
• Secure passwords required
• Documents are editable
• Specialist software
• Available worldwide

35
Future Developments

• Comparison of various communication media is not
  finite
• New developments occurring all the time
• Need to keep up to date.