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.
a. Transmission media
c. Geographical spread
d. Functions
b. Bandwidth
In looking at the four categories of networks we will compare them using the following four characteristics:
Refers to the type of cabling or wireless method used to transfer data.
Relates to the speed at which data can be transferred throughout the network.
Looks at the size of the area which the network covers.
Considers what tasks the network can carry out for the users.
1. LAN
2. WAN
3. Internet
4. Intranet
a. Transmission media
c. Geographical spread
d. Functions
b. Bandwidth
Fibre-optic cable, Unshielded twisted pair(UTP) cable, co-axial cable (as used in a tv aerial.)
This depends on the cabling and hardware used. UTP cable allows data transfer at 10 – 100 Mbps
Physical cabling is laid to connect the network. Usually one building, school, office, factory.
Peripheral sharing, electronic mail, data sharing.
http://fcit.usf.edu/network
1. LAN
2. WAN
3. Internet
4. Intranet
a. Transmission media
c. Geographical spread
d. Functions
b. Bandwidth
Telecommunications systems covering large areas.
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.
WANs can cover any size of area. They use telecommunications which covers most of the earth.
Electronic mail, data sharing, conferencing.
1. LAN
2. WAN
3. Internet
4. Intranet
a. Transmission media
c. Geographical spread
d. Functions
b. Bandwidth
Telecommunications systems covering large areas.
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.
The Internet can cover any size of area. They use telecommunications which covers most of the earth.
Electronic mail, information sharing using WWW, File sharing using FTP.
An internet is a network of networks
1. LAN
2. WAN
3. Internet
4. Intranet
a. Transmission media
c. Geographical spread
d. Functions
b. Bandwidth
Telecommunications systems covering large areas.
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.
Intranet can cover any size of area using telecommunications links which cover most of the earth. West Dunbartonshire Council has its own intranet.
An intranet is like the internet but confined to one organisation.
Electronic mail, information sharing using WWW, File sharing using FTP.
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 ManagerPerson 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
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
• Save on travel time and cost.
• Look after young family. Save in child care.
Disadvantages for Employee
• Feeling of isolation.
• Work more hours.
• Need computer system at home
Advantages for Employer
• Employers save money on office space
• Tele-workers often harder at home
• Save money on wages by employing people in other parts of the world.
Disadvantages for Employer
• Train works on communication software
• Buy the computer system
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
Terminal
Terminal
Terminal
Mainframes
A large, powerful computer serving many connected terminals and usually used by large, complex organizations.
Terminal (“Dumb”)
A 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.
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.
A channel is the way in which data is transferred from one node to another.
e.g. a computer, printer, server, router.
This could a cable or some form of wireless technology.
Four topologies are covered in the Higher Course.
node
channel
Investigate Topolgies
• What type of network uses this topology
• How many channels connect the nodes
• Is communication seen by only one node or all
• What will happen in a node failure
• What will happen in a channel failure
1. Bus
2. Star
3. Ring
4. Mesh
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.
or
nodechannel
1. Bus
2. Star
3. Ring
4. Mesh
Node Failure
Channel 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.
A channel failure will cause the whole network to fail.
ornodechannel
1. Bus
2. Star
3. Ring
4. Mesh
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.
nodechannel
1. Bus
2. Star
3. Ring
4. Mesh
Node Failure
Channel Failure
A failure of one node will only affect that node. Failure of the central node will disable the entire network.
A channel failure will only affect the outer node on that channel.
nodechannel
1. Bus
2. Star
3. Ring
4. Mesh
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.
nodechannel
1. Bus
2. Star
3. Ring
4. Mesh
Node Failure
Channel Failure
A channel failure will disable the entire network.
nodechannel
There is typically a mechanism to bypass a failed node so a failure of one node will only affect that node.
1. Bus
2. Star
3. Ring
4. Mesh
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.
nodechannel
1. Bus
2. Star
3. Ring
4. Mesh
Node Failure
Channel Failure
The failure of one node will only affect that node.
A channel failure will have no effect as alternative channels are available. It may, however, slow down traffic on the network.
nodechannel
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 TopologyThe 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
• Easy to install
• Cheap to install
• Loss of a single node does not hinder the network
Disadvantage
• Fault along bus cable will affect whole network
• Network can have a slow response
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
• If the link fails only the node connected will fail
• Provides high security
Disadvantage
• Cabling is expensive (lots needed)
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
• Supports high data transfer
• Easy to add other nodes
• High bandwidth
Disadvantage
• Expensive to install
• Difficult to install (Electronics)
Mesh
Multiple channels between nodes on the network
Data can be sent through one of several routes through the network.
DIAGRAM
Advantages
• Failure of a node or channel (cable) does not affect the network
Disadvantage
• 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.
1. Hub
2. Switch
3. Router
Three common devices used for managing the flow of data are:
Stackable hubs with 8, 16 or 24 ports can be linked to form large LANS.
Nodes are connected to a hub via channels.
When data is received from a node it is broadcast to all the other ports.
It may also amplify the signal if long distances are involved.
This is inefficient as the data is intended for only one of the other nodes.
1. Hub
2. Switch
3. Router
HubA 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
• No installation needed
• Cheap
Disadvantage
• All devices on the network share the same bandwidth
It is also more secure as nodes only see the data which is intended for them.
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.
Switches are more complex than hubs and are therefore more expensive.
This is more efficient than a hub as the data goes directly to the destination node.
1. Hub
2. Switch
3. Router
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
• Devices don’t share the same bandwidth.
• Packet is delivered to address port.
Disadvantage
• Require additional set-up
• Expensive
They connect LANS to telecommunications lines and the Internet.
Routers connect different networks together.
They control and manage the flow of data over the different networks.
They cope with the differences in topologies and transmission media.
They connect smaller networks into larger internetworks.
1. Hub
2. Switch
3. Router
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 ActThis 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
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.
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.
Data Protection Act(1998)
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.
The principles of this Act also apply to network use.
http://www.informationcommissioner.gov.uk/
Data Protection Act(1998)
Organisations processing personal data ("controllers") must comply with the data protection principles. These require data to be:
• fairly and lawfully processed.
• processed for limited purposes.
• adequate, relevant and not excessive.
• Accurate.
Data Protection Act(1998)
• not kept longer than necessary.
• processed in accordance with individuals' rights.
• kept secure.
• 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.
Clients
Server
Hard Disk
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.
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