Question What are the main components of networking?Write a detailed note on the advantages of networking
Answer ROBEL,
HERE IS SOME USEFUL MATERIAL.
REGARDS
LEO LINGHAM
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What are the main components of network? Write a detailed note on the advantages of
networks.
You will all have come across the term 'Computer Networks' many times. The chances are you know all about LANs and WANs, network topologies, Intranets and Internet.
In order for a computer to operate on a network, there are a range of different components that are required. As part of the OCR syllabus, you need to be able to describe various devices and explain their role within a network.
This mini website will give you a brief overview of the main components.
1.CLIENT / IMAGE SERVER.
2.SCANNER
3.CLIENT / GATEWAY
4.MODEM
5.PRINTER
6.CLIENT / PRINT SERVER
7.LASER PRINTER
8.CLIENT POINT
9.FILE SERVER
10.TAPE BACKUP.
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ROUTER
A Router is a device that transfers data from one network to another in an intelligent way. It has the task of forwarding data packets to their destination by the most efficient route.
In order to do this, the router has a micro computer inside it. This holds a table in memory that contains a list of all the networks it is connected to, along with the latest information on how busy each path in the network is, at that moment. This is called the 'routing table'.
When a data packet arrives, the router does the following:-
Looks up all the paths it has available to get to that address.
Sends the packet along the least congested (fastest) path.
Other tasks the Router can perform:
Filter traffic - useful for preventing hacker attacks for example
Routers operate at the network level of the OSI model.
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REPEATERS
All signals fade as they travel from one place to another.
Each type of network cable has a maximum useable length. If you go beyond that length, the signal will be too weak to be useful.
Of course, computers on a real network can easily be more than 200 metres apart. Therefore the network cable is split up into segments. Each segment is less than the maximum length allowed. Joining the segments together is a device known as a 'Repeater'.
A Repeater boosts the signal back to its correct level.
Here are some typical maximum cable lengths:
Thick Ethernet -500m
Star - uses a hub
Bus - does not use a hub
Star - uses a hub
Bus - does not use a hub
To allow the Star and Tree network topologies to work properly, each computer must be able to send data packets to any other computer on the network.
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HUB
The network 'Hub' allows computers to share data packets within a network.
Each computer will be connected to a single 'port' on the hub. So if you purchase an '8 port hub', you will be able to connect up to eight computers together.
You can also 'daisy chain' hubs to allow even more computers to join the network.
However there is a problem with doing this - see 'Switches' for more details.
Typical network making use of a hub:
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SWITCHES
A network cable can only have one data packet in it at any instant.
So if two or more computers want to place a data packet on to the network at exactly the same time, then a 'data collision' will take place.
The network protocol is set up to deal with this. Basically it declares the collided data as unusable and forces the two computers to re-send their data packets at a slightly different time.
This is fine for a lightly loaded network with only a few computers on-line. You will not notice the small delay caused by data collisions.
But imagine what happens when a hundred PCs are sharing the same network and they are all wanting to send their data packets. This will most likely result in thousands of data collisions per second - each one costing a small amount of time. You will certainly notice the network 'slowing down'.
The clip below shows how a network SWITCH can help with this problem.
A switch has a number of ports and it stores the addresses of all devices that are directly or indirectly connected to it on each port.
As a data packet comes into the switch, its destination address is examined and a direct connection is made between the two machines.
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PROTOCALS
A 'protocol' is a rather technical word. But it simply means an agreed method of doing something.
You can have a 'Medical Protocol' or even a 'Dance Protocol' where you both agree to dance in the same style. The dancers below have agreed to follow the 'Tango' protocol -in this case, if they do not agree, it will surely result in sore feet and bruised shins!
A 'NETWORK PROTOCOL' is the agreed method of communication to be used within the network.
Each device / computer will use this protocol.
Elements of a network protocol
The list below indicates some the things that need to be considered:-
Error checks of the data packets when they arrive- how is it done
Data packets received correctly - what method/signal will be used to tell the other machine that the data has arrived correctly
Data compression - does the protocol allow this to take place and if so, what method does it use?
There are many protocols in use across various networks. Have you heard of these? :-
Kermit - popular for use with modems
Files are simple to find
User computers can be switched off without any problem of a file becoming unavailable.
All data is available from anywhere in the network
Database is easily backed up.
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GATEWAYS
There are many different network protocols in use today. For example the large internet company called AOL has its own special email protocol.
If your computer does not use the AOL protocol (and the chances are it won't). Then how do you get email to your friend on the AOL network?
Answer: A gateway.
A gateway converts the data passing between dissimilar networks so that each side can communicate with each other. i.e converts data into the correct network protocol.
The gateway is a mixture of hardware components and software.
This is unlike a standard 'Bridge' which simply joins two networks together that share the same protocol
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FILTERS
In some small networks, every machine is equally likely to have a resource that another machine needs to use.
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Server.
But now imagine there are a dozen computers on the network and each one needs to print out a document every few minutes. The machine that is connected to the printer is going to be tied up most of the time.
In this case it makes sense to allocate a machine exclusively to service printer requests. This machine is called a 'printer server'
File server.
Consider a network of a dozen computers. There could be thousands of files scattered across each machine. Two problems arise:
a) how do you find the file you need?
b) how do you back up your data to keep it safe?
The solution is to keep all your files on one computer. This machine is called the 'file server'.
Advantages:
Files are easily sharedG
Data is easily backed up.
Database server.
Many companies rely on a central store of information to run their operations. Information such as sales and stock data is usually kept in a database.
Very often a machine will be dedicated to run a specific database. This machine is called a 'database server'
Advantages:
A specially designed computer can be selected to run the database e.g lots of memory.
Email server
Intranet server.
The email server will provide all the usual facilities such as address books, spam filtering and so on.
Quite often, staff want to use the same website over and over again. The Internet Proxy server will store a local copy of often-used web pages to speed up access and to reduce bandwidth consumption (which costs money).
Many companies run their own private internal web services. This is called an Intranet and is run from the Intranet server.
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MODEM
Some trivia: 'Modem' is a made-up word.
Originally engineers called it the 'MODulation - DEModulation' box. But it was such a mouthful that naturally they ended up calling it the MODEM.
A modem converts the digital data from the computer into a continuous analogue wave form that the telephone system is designed to deal with (MODulation). The reason for this is that the telephone system was originally designed for the human voice i.e. continuous signals. The modem also converts the analogue signal from the telephone network back into digital data that the computer can understand. (DEModulation).
Standard modems come in two forms. An external box that links to your computer either through a serial or USB port, or an internal modem that is plugged directly to the motherboard inside the computer.
Up to quite recent times, modems connected to the standard telephone line at speeds up to 56 kilobits per second. This was OK until broadband became available which offers ten times the speed. However many people still have to use a 56Kb modem to connect to the internet because their local exchange has not been converted to broadband as yet.
Wi-Fi modems
In addition to telephone modems, radio has now become very popular as a means of connecting to the internet. The device that allows you to do this is called the Wi-Fi modem
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NETWORK CARDS
Network cards are required in every machine connected to the network. They allow the signal from the network to be transmitted to the machine – this could be via a fixed cable, infra red or radio waves
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CABLES
How do you transfer data from one point to another on a network?
This has to be done by some physical effect.
There are three main methods of transferring data:
Radio or Microwave
Infrared
Electrical:
A multi-wired cable with a socket at each end is used to connect the various devices together e.g. computer to hub, hub to switch or switch to router etc
The Ethernet network cable shown above transfers data by means of electrical signals. A typical network cable called 'Cat 5' is used which is especially designed to carry the signal as efficiently as possible.
Radio or Microwave
Microwaves are just a small part of the radio spectrum, but because they are so widely used, they tend to be called by their own name.
Data is sent out through aerials mounted on tall towers. The 'cable' is effectively the microwave link between towers. Some large companies use microwave towers spread along hilltops to allow one office to communicate with others in the same country.
They do this because it is cheaper than renting telephone lines for carrying the same amount of data.
On a much smaller scale, laptops can communicate with the local area network with radio links:
Infra-Red
This is a very familiar method of transferring data if you are at all aware of your remote control ! The television remote control makes use of an infra-red link.
PDA and personal organisers often make use of an infra-red link to synchronise calendars and 'to-do' lists.
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ADVANTAGES OF NETWORKS
Files can be stored on a central computer (the file server) allowing data to be shared throughout an organisation.
Files can be backed up more easily when they are all on a central fileserver rather than when they are scattered across a number of independent workstations.
Networks also allow security to be established, ensuring that the network users may only have access to certain files and
applications.
Software and resources can be centrally managed.
Network versions of software often allow for their speedy installation on workstations from the file server.
Expensive devices such as laser printers or scanners can be shared.
Users can access their files from any workstation
Networks allow the orderly flow of information between connected nodes. Their main advantages include:
being easy to set up new users and equipment
allowing the sharing of resources
ease of administering users
ease of administering software licenses
allowing electronic mails to be sent between users
allowing simple electronic access to remote computers and sites
allowing the connection of different types of computers which can communicate with each other.
No matter what type of computer equipment you are using, installing a network will make your life as an educator run more smoothly. Current networking software provides many advantages for the educational environment.
Program Security
Store copies of programs in locked, read-only spaces on the server
Protect program files from unauthorized copying
Prevent tampering with programs
More Secure Personal Work Files
Save personal work in private spaces on hard disk
Password protected from inadvertent or malicious copying and/or deletion
No loss of information from damaged or lost floppy disks
Reduced Need for Floppy Disks
Floppy disks are needed only for archiving old files
Boot disks may be needed to start up workstations (Remote booting removes the need for boot disks.)
Shared Files
Share data and program files to all network users
Publicly accessible area to store assignments, tests, clipart, and other files
No copying of entire class sets of data disks
Shared Printers
Share the cost of printers among all users
Gain access to different types of printers
Current networking software has built-in print spooling capabilities
Shared Resources
Share peripheral devices
Access powerful information resources (CD-ROM drives)
Network modems to access outside resources
Library card catalogues
Databases from all over the world
Wire services (newspapers, radio stations, television stations)
Easy Maintenance
Well-planned network meets needs for several years
Single major task of maintenance of boot disks for workstations
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