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Transcript
Networking
A group of computers linked together to share
resources. Common types are Local Area Networks
(LAN), Wide Area Networks (WAN) and intranets.
Local Area Network (LAN)
Is a high-speed data network that covers a relatively
small geographic area. It typically connects
workstations, personal computers, printers, servers,
and other devices.
LANs offer computer users many advantages
including:
shared access to peripheral devices and
applications
file exchange between connected users
communication between users via electronic mail
and other applications
Network Interface Card
Allows a computer to communicate within a network.
Small circuit board fitted inside the computer system.
Desktop computers are most likely to be connected to
a LAN. Although laptops now come with network
interface cards.
How does it work?
The NIC provides the computer with a unique
address, made up of 6 bytes.
Wireless Network Interface (WiFi)
Allows a computer to communicate within a network
from any where in the immediate vicinity of a wireless
base.
Wireless Hotspot
Area where wireless network signals may be received
and computers can connect to the network.
• Universities
• Hotels
• Trains
LAN - Cabling Used
Cable is the medium through which information
usually moves from one network device to another.
There are several types of cable which are commonly
used with LANs.
Twisted-pair copper cable
Bandwidth
(10 Mbps (Ethernet) 100 Mbps (Fast Ethernet))
Co-axial Cable
Bandwidth
(ranges up to 1 Gbps)
Fibre Optic Cable
Transmits light rather than electronic signals
eliminating the problem of electrical interference.
Optical Fibre is fibres of glass, usually about 120
micrometres in diameter, which are used to carry
signals in the form of pulses of light over distances up
to 50 km without the need for repeaters.
In looking at the four categories of networks we will compare
them using the following four characteristics:
a. Transmission media
Refers to the type of cabling or wireless method used to
transfer data.
b. Bandwidth
Relates to the speed at which data can be transferred
throughout the network.
c. Geographical spread
Looks at the size of the area which the network covers.
d. Functions
Considers what tasks the network can carry out for the users.
1. LAN
2. WAN
3. Internet
http://fcit.usf.edu/network
4. Intranet
a. Transmission media
Fibre-optic cable, Unshielded twisted pair(UTP) cable, co-axial
cable (as used in a tv aerial.)
b. Bandwidth
This depends on the cabling and hardware used. UTP cable
allows data transfer at 10 – 100 Mbps
c. Geographical spread
Physical cabling is laid to connect the network. Usually one
building, school, office, factory.
d. Functions
Peripheral sharing, electronic mail, data sharing.
1. LAN
2. WAN
3. Internet
4. Intranet
a. Transmission media
Telecommunications systems covering large areas.
b. Bandwidth
Slower than LAN. Depends on the link used. Modem dial-up up
to 56 Kbps. ADSL up to 9 Mbps, dedicated line up to 45 Mbps.
c. Geographical spread
WANs can cover any size of area. They use
telecommunications which covers most of the earth.
d. Functions
Electronic mail, data sharing, conferencing.
1. LAN
2. WAN
An internet is a network of networks
3. Internet
4. Intranet
a. Transmission media
Telecommunications systems covering large areas.
b. Bandwidth
Same as WAN. Depends on the link used. Modem dial-up up to
56 Kbps. ADSL up to 9 Mbps, dedicated line up to 45 Mbps.
c. Geographical spread
The Internet can cover any size of area. They use
telecommunications which covers most of the earth.
d. Functions
Electronic mail, information sharing using WWW, File sharing
using FTP.
1. LAN
2. WAN
3. Internet
An intranet is like the internet but confined to
4. Intranet
one organisation.
a. Transmission media
Telecommunications systems covering large areas.
b. Bandwidth
Slower than LAN. Depends on the link used. Modem dial-up up
to 56 Kbps. ADSL up to 9 Mbps, dedicated line up to 45 Mbps.
c. Geographical spread
Intranet can cover any size of area using telecommunications
links which cover most of the earth. West Dunbartonshire
Council has its own intranet.
d. Functions
Electronic mail, information sharing using WWW, File sharing
using FTP.
More Intranet
Usually owned and managed by a company, an
intranet enables a company to share its resources
with its employees without confidential information
being made available to everyone with Internet
access.
Company News (warnings about thieves!)
Suppler Addresses
News on advertising (TV, News Paper)
Email other stores
Network Manager
Person in charge of the network. He or she will be
responsible for all the computer systems attached
to the company network.
• Control software installation and upgrades
centrally.
• Control firewall protection
• Provide virus checking
• Do daily back-ups
• Provide technical support
• Implementing Network security measures
(usernames and passwords)
A very large network may have several network
managers.
Wide Area Network (WAN)
A computer network that spans a relatively large
geographical area. The Internet is the best-known
example of a wide area network.
Use a range of connection methods:
• Satellite
• Optical Fibre
Communication on a WAN
Email
Use email on Wide Area Networks. Users can
transfer files by attachments. (selling)
Newsgroups
Allows people with similar interests to discuss and
ask questions.
Electronic Forum
Similar to newsgroups, user needs to join before
they can read and send messages. (e.g scholar)
Access to information on a WAN
Information Service
• News
• Technical Information
• Other data (study)
Search Engines
A program that searches documents for specified
keywords and returns a list of the documents where
the keywords were found. Google, Ask Jeeves etc
Entertainment Services Available
Internet Radio
Live Video
Networked Games (allows user to participate in
tournaments and competitions)
Tele-working
Working from home instead of travelling
to work.
Users use communication technology to keep in touch
with their employer.
Advantages for Employee Disadvantages for
Employee
• Save on travel time and
• Feeling of isolation.
cost.
• Look after young family.
Save in child care.
• Work more hours.
• Need computer system a
home
Advantages for Employer
Disadvantages for
Employer
• Employers save money on
• Train works on
office space
communication software
• Tele-workers often harder
• Buy the computer system
at home
• Save money on wages by
employing people in other
parts of the world.
Video Conferencing
Allows people to communicate with each other using
sound, video and share data such as text and graphics
even though they are miles apart.
• Requires a high bandwidth connection (expensive).
However, can be cheaper than flying to the country.
• Specialised equipment (webcam)
Mainframes and Networks
Terminal
Mainframes
A large, powerful computer serving many connected
terminals and usually used by large, complex
organizations.
Terminal (“Dumb”)
Terminal
ATerminal
device that allows you to send commands to a
computer somewhere else. At a minimum, this usually
means a keyboard and a display screen an some
simple circuitry. No processing power.
Terminal
Thin Client Networks
Low specification systems running off a very high
specification server, small application tasks, eg
browsing the internet.
The topology of a network refers to the shape of the network,
how the computers are physically connected together.
A node is any device which is attached to the network.
e.g. a computer, printer, server, router.
node
A channel is the way in which data is transferred from
one node to another.
channel
This could a cable or some form of wireless technology.
Four topologies are covered in the Higher Course.
1. Bus
2. Star
3. Ring
4. Mesh
or
node
channel
Used in LANS.
All nodes are connected to a single channel.
A communication from one node is seen by all
the other nodes.
Each node will recognise and accept communications which
are addressed to it.
1. Bus
2. Star
3. Ring
4. Mesh
or
node
channel
Node Failure
There is typically a mechanism to bypass a failed node
so failure of one node will only affect that node. Rest
of network will still function.
Channel Failure
A channel failure will cause the whole network to fail.
1. Bus
2. Star
3. Ring
4. Mesh
node
channel
Used in LANS.
Each node has its own channel to the central node.
The whole network depends on the proper functioning of the
central node.
Cabling cost is high because each node has its own
channel but it is easy to extend the network.
1. Bus
2. Star
3. Ring
4. Mesh
node
channel
Node Failure
A failure of one node will only affect that node. Failure
of the central node will disable the entire network.
Channel Failure
A channel failure will only affect the outer node on
that channel.
1. Bus
2. Star
3. Ring
4. Mesh
node
channel
Used in LANS.
Channels and nodes form a ring.
Only one node can transmit at a time and data passes
between nodes until it reaches its destination.
The network has to be disrupted when a new node is added.
Designing and extending the network is more difficult than with
a star network.
1. Bus
2. Star
3. Ring
4. Mesh
node
channel
Node Failure
There is typically a mechanism to bypass a failed node
so a failure of one node will only affect that node.
Channel Failure
A channel failure will disable the entire network.
1. Bus
2. Star
3. Ring
4. Mesh
node
channel
Used in WANS. e.g. telephone grid.
There are alternative channels between nodes.
Several nodes can transmit at a time and data can be
redirected when some channels are busy.
The extra cabling makes this an expensive type of network
to set up but it is very robust.
1. Bus
2. Star
3. Ring
4. Mesh
node
channel
Node Failure
The failure of one node will only affect that node.
Channel Failure
A channel failure will have no effect as alternative
channels are available. It may, however, slow down
traffic on the network.
Network Operating Systems
10 – 20 Years ago networks and their operating systems
where:
• Very expensive
• Difficult to configure
Today’s NOS
• Modern OS have network capability built into them
• Very easy to configure and inexpensive
TCP/IP
A common software standard for connecting a network,
nowadays very easy and inexpensive.
Internet Protocol (IP)
A packet-based protocol for delivering data across networks.
Features of NOS
• Multi User Access
• Privacy and Security of network
• File and Print Services
• Data Sharing
Protocol
An agreed upon format for transmitting data between
two devices. Determines:
• error checking used
• data compression method
HTTP - Hyper Text Transfer Protocol
TCP-Transmission Control Protocol
• Ensure that packets travel safely on an internet.
• Keeps track of package
• Detects errors
Packet
Unit of data formatted for transmission on a network.
Data is broken up into packets for sending over a
packet switching network.
IP-Internet Protocol
• Responsible for moving packets of data.
• IP Address
There are two different types of network operating
systems
Client/Server
Peer-to-Peer
Client/Server
Allows the network to centralise functions and
applications in one or more dedicated file servers.
Server
Computer running software that enables it to serve
specific requests from other computers. The servers
are usually more powerful computers and are held in a
central location
Server will need server software such as Windows
NT® Server or Novell Netware®.
Client
A computer, usually a desktop. Which accesses
data/information from the server on the network. Will
have its own processor. Which it uses.
Client networks need client software which is installed
on the desktops.
Client/Server
Question? What services does a client/server network
provide?
Advantages
• Resources and data security are controlled through
the server. (Centralised)
• New technology can be easily integrated (adding
more cables and stations)
• Expensive peripherals can be shared
• Backup routines can be easily implemented
Disadvantages
When server goes down, operations will cease across
the network.
Cable failure can bring down a segment of a network
Large networks will require network managers to
ensure efficiency across the network
Large networks require initial investment
Peer-to-Peer & Client-Server
Allows users to share resources and files located on
their computers and to access shared resources found
on other computers.
(Peer=equal) All machines have equal status.
Works well in the home or a small office.
Advantages
Cheap and easy to implement, no need for dedicated
server
Easy to share files, access peripherals and have
several people using the internet.
Disadvantages
Does not provide the security available on a
client/server network
Organisation and management can become a problem
Backup can become difficult
Difficult to set up email. Only one email account.
Types of Network Servers
A network may have several types of servers.
• File servers
• Print servers
• Application servers
• Email Servers
• Web Servers
Network Topology
The physical topology of a network is the way in which
the cables and computers are connected to each
other.
The main types of physical topologies are:
• Bus
• Star
• Ring
• Mesh
Node
Processing locations on a network. A node can be any
device attached to a network, for example, a
workstation, a server, and a printer.
Every node has a unique network address.
Bus
Has a single communication cable, running the length
of the network.
Uses coaxial cable.
All nodes are connected to a single channel.
DIAGRAM
Advantages
Disadvantage
• Easy to install
• Cheap to install
• Fault along bus cable will
affect whole network
• Network can have a slow
• Loss of a single node does
response
not hinder the network
Star
Connects all computers to one central server.
A high speed computer will act as the central controller
which allows for very fast communication.
The cables used in star topologies are either shielded
or unshielded twisted pair wires (STP or UTP).
DIAGRAM
Advantages
Disadvantage
• If the link fails only the
node connected will fail
• Cabling is expensive (lots
needed)
• Provides high security
Ring
Messages are passed along a chain.
Data sent around the network can potentially be
accessed by any device hooked onto it.
Data travels in one direction.
DIAGRAM
Advantages
Disadvantage
• Supports high data transfer
• Expensive to install
• Easy to add other nodes
• Difficult to install
(Electronics)
• High bandwidth
Mesh
Multiple channels between nodes on the
network
Data can be sent through one of several routes through
the network.
DIAGRAM
Advantages
Disadvantage
• Failure of a node or
channel (cable) does not
affect the network
• Expensive to install
(cables)
Some nodes on a network are devices which are there to
manage the flow of data.
When data is sent it includes a destination address.
Each node on the network has its own address to uniquely
identify it.
Three common devices used for managing the flow of data are:
1. Hub
2. Switch
3. Router
1. Hub
2. Switch
3. Router
Nodes are connected to a hub via channels.
When data is received from a node it is broadcast to all the
other ports.
This is inefficient as the data is intended for only one of the
other nodes.
Stackable hubs with 8, 16 or 24 ports can be linked to form
large LANS.
It may also amplify the signal if long distances are involved.
Hub
A common connection point for devices in a network.
Hubs are commonly used to connect segments of a
LAN.
A hub contains multiple ports. When a packet arrives at
one port, it is copied to the other ports so that all
segments of the LAN can see all packets.
Advantage
Disadvantage
• No installation needed
• All devices on the
network share the same
bandwidth
• Cheap
1. Hub
2. Switch
3. Router
A switch is sometimes known as an intelligent hub.
When data is received from a node it is examined and then
sent directly to the destination known.
This is more efficient than a hub as the data goes directly
to the destination node.
It is also more secure as nodes only see the data which is
intended for them.
Switches are more complex than hubs and are therefore more
expensive.
Switch – ‘Smart Hub’
Will look at traffic it receives and based on the destination
address it will direct the traffic to the port.
EtherFast 4124 24-Port 10/100
Ethernet Switch will boost your
network performance
Advantage
Disadvantage
• Devices don’t share the
same bandwidth.
• Require additional set-up
• Packet is delivered to
address port.
• Expensive
1. Hub
2. Switch
3. Router
Routers connect different networks together.
They control and manage the flow of data over the different
networks.
They connect smaller networks into larger internetworks.
They connect LANS to telecommunications lines and
the Internet.
They cope with the differences in topologies and transmission
media.
Router
Much of the work to get a message from one computer
to another is done by routers, because they're the
crucial devices that let messages flow between
networks, rather than within networks.
A router links the two networks and connects both
networks to the Internet.
Wireless Communications
Wireless communication increases flexibility of use and
is becoming more popular for home, office and public
spaces.
•
No wiring required and ability to move around.
• Problems - Can be affected by electrical
interference.
• Problems - Easy to hack into unless firewall security is
enabled.
There are many technical reasons for the increasingly
widespread use of networks. These include:
• Advances in computer hardware.
e.g processor speed, main memory capacity, backing
storage, data transfer rates.
• Improvements in network related software.
including network browsers and network operating systems
The use of networks which can be local, national or even
international poses legal problems for governments.
Three Acts in particular are relevant for possible network
misuse.
Computer Misuse Act
This Act makes it illegal to breach network security for any
reason.
“Hackers” can be fined or imprisoned for gaining access and
looking at or altering data and also for introducing viruses.
Copyright, Designs & Patents Act
It is very easy on a network to transfer audio, video and
text at high speed. This has led to a huge increase in the
unauthorised pirating of music, films and books.
This Act makes it illegal to make unauthorised copies of
material.
Offenders can be fined or imprisoned for being involved in this
activity and FAST(The Federation Against Software Theft)
have had many companies and individuals prosecuted.
Data Protection Act(1998)
http://www.informationcommissioner.gov.uk/
The principles of this Act also apply to network use.
The Act gives individuals(Data Subjects) rights to:
• gain access to their data.
• seek compensation if inaccurate information causes damage.
• "opt-out" of having their data used for direct marketing.
• "opt-out" of fully automated decision-making about them.
Data Protection Act(1998)
Organisations processing personal data ("controllers") must
comply with the data protection principles. These require data
to be:
• Accurate.
• adequate, relevant and not excessive.
• processed for limited purposes.
• fairly and lawfully processed.
Data Protection Act(1998)
• processed in accordance with individuals' rights.
• kept secure.
• not kept longer than necessary.
• not transferred to non-EEA (European Economic
Area) countries without adequate protection.
Select suitable hardware, including peripherals, to
support the following tasks:
Producing a multimedia catalogue
Setting up a LAN in a school
Developing a school website
Describe how each piece of hardware will help with the task.
Network Interface Card (NIC)
Card inserted in a computer so that it can be
connected to a network.
Hardware Factors
• Continuing bandwidth explosion ( 1Mb – 10Mb)
• Use of intensive applications and need for more
bandwidth (streaming video & audio, Virtual private
networks)
• Falling costs of setting up networks
Need to consider:
Processor
Memory
Backing Storage
Processor
Performance – execute and process many application
at a high speed.
Flexibility – adapt to change in OS and applications.
Power – power consumption.
Software Support – Compilers, operating systems and
libraries are available.
Memory
• Shared , distributed or a combination of memory
• Size and type used
• Cache memory
Backing Storage
Network storage is about storing data so that can
accessed by network clients.
Hard Disk
Server
Clients
Software Factors
Browser
Program that enables a computer to look at and
interact with WWW. Internet explorer and Netscape.
Network Operating Systems
Is run on the server.
• Novell
• Windows NT
• Windows 2000 Server
Workstation Operating Systems
NT Workstation
Windows 98
Mac OS
Bandwidth
A measure of the capacity of a communications
channel. The higher a channel's bandwidth, the more
information it can carry.
LAN
Depend on the number of people sharing the network
Reducing Demand
Data Compression
Data is compressed before it is transmitted then it
requires less bandwidth.
Caching
Data is stored locally, then data only needs to travel
over short distance.
Wireless
A wireless network allows computers to share printers,
files or an internet connection without any wires
between them.
Disadvantage
Lower bandwidth. Slower than cabling
Advantage
No cables around office
No disruption during installation of network
Move around office with laptop
Bluetooth
A global initiative by Ericsson, IBM, Intel, Nokia and
Toshiba to set a standard for cable-free connectivity
between mobile phones, mobile PCs, handheld
computers and other peripherals.
Problems
Security
Encryption
A way of coding the information in a file or e-mail
message so that if it is intercepted by a third party as it
travels over a network it cannot be read.
Social Issues
Many people will become physically more isolcated
from each other.
Third world countries
Ethical Issues
Netiquette
A way of behaving when connected to the internet or
sending email messages.
• Not sending spam (unsolicited commercial emails)
• Not SHOUTING when sending emails
• Avoid sending large attachments
Reading pages
Questions
1.