WEEK 5

INTRODUCTION TO NETWORKING

      A network is a collection of connected intelligent computing devices. The connection is not necessarily a fancy one. A connection between two computers by direct cabling is qualified to be a network. By this definition, a workstation which is loaded with a computer, a scanner, and a printer, is not treated as a network.

 








COMPUTER NETWORKING

      A computer network is simply two or more computers connected together so

they can exchange information.  A small network can be as simple as two

computers linked together by a single cable.

 

TYPE OF NETWORK

 








A network is a medium that connects computers around the world. With the network, information or data can be sent quickly without the limitations of distance and time.

     
 Computer networks are divided into five types:

1)      Local Area Network (LAN) is a small-scale private network inside the building.LANs are often used for connecting personal computers and workstations in a corporate office or factories to use shared resources (eg printers) and exchange information.

2)      Metropolitan Area Network (MAN) basically a LAN version of the larger size and usually use the same technology to the LAN. MAN could include corporate offices are located adjacent or also a town and can be used for private purposes (private) or public. MAN is able to support data and voice, even may be associated with cable television network.

3)      Wide Area Network (WAN) its scope covers a wide geographical area, often covering a country or even continent. WAN consists of a collection of machines that aim to run the programs (applications) user.

4)      Internet, Actually there are many in this world networks, often using hardware and software that is different. People who connect to the network often wish to communicate with others who connect to other networks. These desires need relationships between networks that are often not kampatibel and different. Usually to do this required a machine called a gateway in order to have sex and perform the necessary translation, both hardware and software. A collection of interconnected networks is called the Internet.

5)      Wireless Networking is a solution to the communication can not be done by using a cable network. For example, people who want to get information or to communicate despite being on top of a car or plane, it is absolutely necessary because the cable network without a cable connection is not possible to be made in the car or plane.Currently, wireless networks have rapidly adopted the use of satellite services and can provide faster access speeds than the network cables.

NETWORK COMPONENT

      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

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'.

Function of router is:

1)      Reads the data packet's destination address

2)      Looks up all the paths it has available to get to that address.          

3)      Checks on how busy each path is at the moment     

4)      Sends the packet along the least congested (fastest) path

                                                                                                                                  BRIDGE                                                                                                                               

      A Bridge does just what you would expect it to do - it joins two networks together so as far as data packets are concerned it looks like one large network.

PROTOCOL

      A 'protocol' is a rather technical word. But it simply means an agreed method of doing something.

      A 'NETWORK PROTOCOL' is the agreed method of communication to be used within the network.

      Elements of a network protocol:

Ø  The list below indicates some the things that  need to  be considered:-

1)      Speed of the network - for example 10Mbit /s

2)      Error checks of the data packets when they arrive- how is it done

3)      Error correction of the data packets - method to be used

4)      Data packets received correctly - what method/signal will be used to tell the other machine that the data has arrived correctly

5)      How does the receiving machine know that the sending machine has finished sending all of the data? - what is the code to indicate this

6)      Data compression - does the protocol allow this to take place and if so, what method does it use?

Ø  There are many protocols in use across various networks:

1)      TCP - the protocol that the internet uses

2)      Kermit - popular for use with modems

3)      X.25 - a packet switched protocol

      Anyone can invent a protocol. Indeed some large companies develop their own often hoping the rest of the world will use it as well.

      Most widely used network protocols have been agreed and developed by international standards organisations such as the ITU (International Telecommunication Union).

GATEWAY

      A gateway converts the data passing between dissimilar networks so that each side can communicate with each other.

      The gateway is a mixture of hardware components and software.

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.

 

SWITCH

      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.

END NODES

      Within a vast computer network, the individual computers on the periphery of the network, those that do not also connect other networks, and those that often connect transiently to one or more clouds are called end nodes. Typically, within the cloud computing construct, the individual user / customer computer that connects into one well-managed cloud is called an end node. Since these computers are a part of the network yet unmanaged by the cloud's host, they present significant risks to the entire cloud. This is called the End Nodes problem. There are several means to remedy this problem but all require instilling trust in the end node computer.

BLUETOOTH

      Bluetooth is a proprietary open wireless technology standard for exchanging data over short distances (using short-wavelength radio transmissions in the ISM band from 2400–2480 MHz) from fixed and mobile devices, creating personal area network (PANs) with high levels of security. It can connect several devices, overcoming problems of synchronization. The devices can switch roles, by agreement, and the slave can become the master. At any given time, data can be transferred between the master and one other device.

 

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. Personal organisers often make use of an infra-red link to synchronise calendars and 'to-do' lists.