1. Networking and connectivity

2. Course Content stand-alone or networked LAN or internet
National 4
National 5
stand-alone or networked
LAN or internet
Wired or wireless
peer-to-peer, client/server
media: wired, optical, wireless.

3. Stand-alone or networked
A stand-alone computer is not part of a network
A network is a linked set of computers
Capable of :-
sharing programs and data
Sending messages
Two types of network (depending on the distance between the computers) :-
Local Area Network
Wide Area Network – the internet

4. Local area network Covers a small area e.g. a room or building
Owned by a person or organisation e.g. our school

5. LAN features Computers called stations
Has a special station called the file server
File server stores :-
shared programs
user’s data files
list of authorised users

6. What is the Internet?
A wide area network that lets computers all over the world communicate
Lots of networks connected together
Made up of :-
Large, well-organised networks e.g. Governments, universities, multi-national corporations
Small company networks networks e.g. schools and little companies
People at home using Internet Service Providers

7. What is an Internet Service Provider?
A company that provides a host computer that subscribers connect to.
The host computer:-
sends and receives data for the subscriber to they can use the internet to communicate
Stores the following for the subscribers:-
electronic mail
web pages
files

8. Questions 1 Describe a network of computers
Why does our school have a network
Where would you find a local area network (apart from at school)?
Which ISP do you use at home?
Carry out some research and write a note about the key features and monthly cost of your ISP.

9. Graphic of the Internet
How does it work?

10. Connectivity Transmission media – carries data on a network
E.g. Wired (cables) or wireless (WiFi)
Bandwidth –
the amount of data that can be carried by a communications channel at any one time.
On a network – “data transfer speed” means the same as “bandwidth”
Measured in Mbps – Megabits per second – or Gbps – Gigabits per second.

11. Transmission media for LAN
Wires or wireless technology (owned by the organisation) can connect stations
Two types of cable may be used:-
Unshielded twisted pairs of copper wires (UTP)
Optical fibre

12. UTP cable facts Carries electrical signals Cheaper than optical fibre
Interference can affect electrical signals
Can be tapped i.e. someone else can read the signals carried by the cable
Can corrode (rust)
Can carry power to a device along with data
Lower bandwidth than optical fibre – carries less data at a time
Carry data over a shorter distance than optical fibre

13. Optical fibre cable facts
Made of lots of very fine stands of glass
Beams of light travel along cable
More expensive than UTP
Secure data transmission – no-one else can read the signal
Does not corrode
Higher bandwidth than UTP
Can carry data over a longer distance than UTP

15. Questions 2 What type of cables are used in our classroom?
Answer “UTP” or “Optical Fibre” for each of the following:-
Higher bandwidth
More secure
Can carry power and data
Carries data over longer distance
Affected by interference
Less expensive

16. Wired transmission for LANs
Bandwidth - 1 Gbps (Gigabit Ethernet)
At 1 Gbps a DVD-quality, full-length Hollywood movie it could take 30 seconds to download
This would take several hours over a typical internet broadband connection

17. Wireless transmission for LANs - Bluetooth
Uses radio waves that pass through walls so devices don’t need to point at each other
Temporary short-range link between personal devices e.g.
mobile phones and headsets
Palmtop
Laptop
Range 10m
Bandwidth is between 1 and 3 Megabits per second (Mbps)
Wireless mice and keyboards typically use Bluetooth® transmission.

18. Wireless transmission for LANs - WiFi
Wireless Fidelity Alliance - allows an electronic device to exchange data wirelessly over a Local Area Network
Used in:-
laptop computers
wireless routers
mobile phones
some games consoles
Minimum range (inside) 60m, (outside) 200m
Data transfer rate – at least 600 Mbps

19. WiFi security
Protect your home WiFi with a hard-to-guess password, to prevent other people from using your bandwidth
Using someone else’s bandwidth may lead to prosecution
Someone else using your internet connection to do something illegal may result in you being held responsible - unless you can prove otherwise

20. Advantages and Disadvantages of Wireless Technology
Easy to install
Easy to add more computers
Portability – a laptop can be used anywhere that the signal can be received
Not as secure as a network with wires

21. Questions What units are used to measure bandwidth?
Give an example of where blue tooth transmission is used.
Why is WiFi not used for a home network?
Give an example of where WiFi is used.
Describe how can someone “use your bandwidth” and how you can prevent it from happening.

22. Network Interface Card
NIC
Circuit board in computer to let it communicate with the network
wired
wireless

23. Transmission media for Wide Area networks
Transmission media in a WAN are own by many different organisations
Three types of media are used :-
Copper cable
Optical fibre
Wireless – including microwave and satellite

24. Transmission media for WANs - Microwave transmission
Used by the public phone service
Organisations may use private installations to send data between important locations
Dish aerials used – directional i.e. the dishes point in the direction that they send and receive on

25. Transmission media for WANs - Satellite links
Public phone services use satellite links for international calls
One channel carries lots of separate transmissions
Use highly directional, narrow beam, two-way transmissions

26. Transmission media for WANs - Optical fibre
Described earlier
Remember – not affected by interference so optical fibre provides a reliable link

28. WAN and the internet: bandwidth
Low bandwidth compared to a LAN
Most common method of connecting a home computer to the internet is ADSL or Asymmetric Digital Subscriber Line
A typical home computer may connect to a WAN such as the internet, at a data transfer speed of 8 Mbps using ADSL via a standard home telephone line
This bandwidth is download (receiving data) only. Sending data (uploading) is at a much slower rate, for example 512 Kbps
The bandwidth of a WAN connection may be greatly improved if your locality or home has a dedicated cable or optical fibre connection, rather than just a standard telephone line.
Many urban areas have optical fibre connected to the cabinet in the street (Fibre To The Cabinet: FTTC), typically allowing bandwidth of between 40 and 100 Mbps. Higher bandwidth may be expected if your home has a direct optical fibre connection (Fibre To The Home: FTTH or Fibre To The Premises: FTTP)

29. Questions Why does a computer require a Network Interface Card?
Describe a difference between microwave transmission and satellite links.

30. What is a peer-to-peer network
Each computer has same status
Each computer has its own set of application programs and backing storage devices i.e. hard disk and optical drives
The user may log but the user’s data is stored locally, on the hard disk so...
... each user must always use the same computer
Each user must back up their own data
Resource sharing is available to users – e.g. can share a printer to avoid buying one for each computer

31. What is a client and server network?
Clients (network stations) use resources available on server(s)
Most clients are desktop computers
Each client has a Network Interface Card that allows it to connect to the network

32. What is a server?
A computer that deals with requests from other computer for data, and file transfers e.g. documents, programs and webpages

33. File server - hardware
Central disk storage - holds programs and user’s data on a network
Compared to a client it has:-
faster processor or many processors to respond quickly to many users
More hard disk space
More RAM
Better quality components as it runs 24 hours a day / 7 days a week
A backup of files is essential – e.g. on magnetic tape

34. File server software
Software organises user’s files and provides security for them
Manages usernames and passwords to control access to files – users must log on to access their files
Each user is given access permissions to control what files and software they can use
Each user can be given a disk quota to control how much disk space they are allowed to use

35. Protecting the file server
A File server should have an Uninterruptable Power Supply (UPS)
This battery allows it to operate a short time when there is a power cut
The file server will safely shut down if the power does not restart quickly

36. Printer Server Controls a printer so many client stations can use it
Puts requests for hard copies in a queue
Often large monochrome laser printers – as they are fast
Colour laser are becoming common too
Network printer has a processor and RAM to store the print jobs

37. Background printing
If there is no printer server on a LAN print jobs are spooled to the workstation’s own local hard disk
This allows the user to continue working while the print job is dealt with by background printing
Background printing - the processor is shared between the user’s commands and sending the print job to the printer when it is ready for more data

38. Other servers
CD-ROM server – client stations access a number of CD-ROMs (e.g. Encarta)
Database server – centrally stores a database for client stations to access
Web server – stores webpages that it provides to provides computers

39. Other servers Internet server – lets stations access the Internet
Mail servers – transfers between computers e.g. POP3 or SMTP

40. Advantages of LAN Share data and programs
Share peripherals e.g. Printers. Called “resource sharing”
Passwords keep data secure
Workgroup computing – many users can access a file at the same time
Client server network advantages:-
Flexible access – users access files from any station
Different levels of access for users
Central backups ensure all user’s data is safe

41. Client server disadvantages
If the file server is not working no-one can access their files
The file server and software are expensive

42. Questions 5 Which topology is used in our school network?
Suggest two places that a multi-access computer system consisting of a mainframe computer and terminals be used
How does a printer server cope when lots of users want a hard copy at the same time?
Describe a client and a server in our network.