Transcript Lesson 4

Unit 2.4
Transfer of Data in ICT Systems
(Networks)
You will cover…
- Basic elements of a network
– What is the difference between a LAN and a WAN?
– What are the advantages of networks over standalone systems?
– What do we mean by peer to peer and client / server
networks?
– The Internet and the World Wide Web
– Extranet and intranet
– Protocols
– Standards (De facto and De jure)
– Network topologies (star, bus and ring)
Basic elements of an ICT Network…
• There are 4 basic elements:
– Communication devices (hardware needed to turn stand-alone
computers into networked computers)
• Network Interface card (prepares and sends the data, controls flow of data)
• Hub (joins computers so they can share files and an internet connection)
• Switches (similar to a hub, but more intelligent – it inspects a data packet and sends it to the
intended computer)
• Routers (act as gateways so that small home computers can connect to the internet)
– Networking software (tells the connected devices how to
communicate with each other)
• Network Operating software (e.g. UNIX, Linux, Novell Netware)
• Network Management software
–
How will this software help a network manager?
– Data transfer media (material through which data travels from one
computer to another)
• Metal wires – (offer high transmission but expensive to be installed)
• Fibre Optic Cable – (high speed, small, lack of electrical interference but are expensive)
• Wireless – (ideal for people who travel)
– Standards and procedures (data sent can be understood)
What is an ICT Network?
• A computer network consists of two or more
computers and peripherals that are linked together
• These links can be made through cables or wirelessly.
• A wireless network uses radio waves in the same way as
TV’s, radios and mobile phones to make links.
• A wireless network following a common protocol is called
Wi-Fi
Advantages & Disadvantages?
Comment on the following…
•
•
•
•
•
•
Where the data is stored?
Client – Server
Vs
Back ups
Peer to Peer
Installation and update of s/w
Maintenance
Security
Administration (allocation of user names and passwords)
What are the disadvantages of
networks?
• Lack of access when file server fails
– If a file server fails the entire network may fail, so
users may not be able to access files and data
• Cost
– Although a network may save money over time, there
is the initial high cost of all the network equipment
and training needed
• Technical knowledge needed
– More IT knowledge is needed to run a network
– Specialist staff are needed
Characteristics of Networks…
• The internet and the world wide web are DIFFERENT things!
• Write down the definition of:
– Internet – A large group of interconnected computers around the
world that allow the sending and retrieval of information from one
computer to another.
– World wide web – A collection of multimedia resources accessible via
the internet
• Other than accessing webpages what other services can the Internet
provide?
–
–
–
–
–
Email facilities
Instant messaging
Forums
FTP (exchanging of files between different computers)
P2P
Characteristics of Networks…
• The intranet and Extranet are DIFFERENT things!
• Write down the definition of:
– Intranet – A private network used within an organisation that makes
use of internet technology. Access is restricted to employees using
passwords.
– Extranet – A private network that restricts access to employees of an
organisation and also external people / organisations.
• What security measures can be put in place to keep data secure in an
extranet?
–
–
–
–
Gateways
Firewalls
Encryption
User authentication
Star Topology…
• A star topology has a central computer with
each device connected directly to it. The
central computer serves as a switch.
• Star topology requires extra cabling.
• If one device or cable is broken, the network
can still operate. However, if the central
computer fails, then the network fails.
Star topology
•
•
•
•
Advantages
Each node has its own cable and does not need to share
the line with any other node.
If the cable to a node is broken, then only that node is
affected. The rest of the network can operate normally.
New links to the central node can be easily added, or
existing links removed, without affecting the rest of the
network.
It is easy to identify a faulty cable because it will only
affect a single link.
Star topology
Disadvantages
• If the central node fails then the entire
network will cease to operate.
• More cabling is needed than for the other
network topologies.
Ring Topology
• A ring topology is an arrangement where all devices
are attached so that the path is in the shape of a
continuous circle.
• Data flow is in one direction, moving from device to
device until the data arrives at its destination.
• There is not necessarily a main computer acting as a
server, if there is a server it is just 1 computer in the ring.
• Less secure – as all data passes through all computers.
• Need to close down network to add another computer
Ring topology…
Advantages
• A single cable is used to connect all the nodes.
Disadvantages
• The ring must be broken (and the network
stopped) to add new nodes or remove existing
ones.
• If the ring is broken, or the cable is faulty, then
the entire network will cease to work.
Bus Topology
• A bus topology is where all the devices are attached to
a direct line called the bus.
• Each device is considered to be connected to every
other device
• A Bus Topology is one of the easiest to set up and can
still operate if one node fails.
• Data is transferred in both directions and the receiving
computer picks up the response.
• If main cable fails all computers are affected.
Bus topology
•
•
•
•
Advantages
They are easy and cheap to set up.
Nodes can be easily added and removed.
Disadvantages
Because the one cable carries all the data, collisions
(data traffic jams) become more common as more nodes
are added.
A fault in the cable can be difficult to locate because it
will usually stop all the nodes from transmitting or
receiving.
Standard & Procedures
• A standard is a common way of doing something, for
example storing data in a particular format or transferring
data in a pre-determined way
• There are hardware standards such as USB (universal
serial bus) ports which can connect a wide range of
peripherals like cameras, phones scanners, printers.
• You need to be aware of:
– De Facto Standards
– De Jure Standards
• Explain what each standard means with examples to
support your explanation
De facto standard
• No formal agreement is in place
• Has become the most commonly used in
practice
• Example GIF format used for pictures placed on
the internet – widely used on the web by
developers
• Example WINDOWS operating system used in
PCs
De jure standard
• Legally binding industry standard
• Restrictions are in place, some people feel
this stifles and slows creativity and
development
• Example WI-FI – wireless standard
Benefits & Limitations of Standards
Benefit
Limitation
Users not restricted to one
manufacturers equipment
Standards and protocols are
difficult to change as getting
universal agreement is time
consuming
Competitive markets better for
consumers
In fast changing areas, standards
may not be able to keep up with
technological developments.
Can communicate with people /
organisations using different
hardware
Having to follow standards may
mean that in some cases the full
power of a machine might not be
available therefore there may be
reduced functionality or
performance
Protocols
• What are protocols?
– Is a standard set of rules that define how communications take
place between computers.
– The use of protocols means that a network does not have to be
restricted to one manufacturers equipment. It allows for the
existence of OPEN SYSTEMS
• This means that several disparate pieces of equipment can be
connected together and communicate effectively.
Protocols cont…
•
Detail the features of FTP, WAP and HTTP
–
FTP
•
–
WAP
•
•
–
–
–
Wireless Application Protocol
Is a standard for wireless communication networks used by mobile phones to access the internet
HTTP
•
•
–
Allows a file to be transferred from one computer to another; it is often used to upload files to the
web
HyperText Transfer Protocol
Is a standard for transferring web pages to a client computer
POP
•
•
Post Office Protocol
Is a standard for transferring e-mail between computers
•
•
Internet Protocol
A protocol that directs data from one computer to another
IP
TCP
•
•
Transmission Control Protocol
A protocol to manage the assembly (and reassembly) of data into packets transmitted between
computers over the internet no matter what hardware is used.
Use of Communication
Technologies
• A high percentage of homes now have one or more computers
which are used in a variety of ways not related to business.
• For example:
– Keeping in contact with friends and family using email and VoIP (e.g.
Skype)
– Accessing the web for information and services
– Online shopping and banking
– Downloading, modifying and sharing photos
– Accessing social networking sites such as Face book
– Instant messaging and web blogs
– Video conferencing
– Forums
The Internet & Business
• Across the globe there are millions of people using the
Internet.
• This technology offers new opportunities for many
businesses. For example they can:
–
–
–
–
–
Market their products to a worldwide audience through a website
Carry out research
Sell products directly over the internet (e-commerce)
Use video conferencing for virtual meetings
Use EDI (electronic data interchange) to communicate with
suppliers
– Use email to communicate quickly
– Use intranets and extranets to get up to the minute information
Virtual Learning Environments
• Many schools and colleges have a Virtual Learning
Environment (VLE Software)
• This allows students and their teachers to interact online.
• Features include access to course materials and
learning resources
• Students can work through the resources at their own
pace
• Progress can be tracked through online assessments
• Communication between students can be conducted via
discussion forums and chat rooms