Presentation on Computer Networking PPT-Evolution-Types-TopologiesPresentation on Computer Networking PPT-Evolution-Types-Topologies for School & College Students.
Presentation on Computer Networking
1. ARPANET :This was the first network which was planted in 1969. It means Advanced Research Projects Agency NETwork. Its aim was to connect different computers of different universities and U.S. defense to exchange messages and data. This network was expanded very soon by the students , scientists , engineers etc. for their work. The users were able to share their interests.2. NSFnet :This was the network which was started in 1980 by National Science Foundation. It was a high capacity network than ARPANET which was more capable than ARPANET . It was used to do research work on the network and some kind of private business.3. INTERNET : It is a worldwide network of Computers network. It was developed in 1990 by different companies to allow the users to connect one network to the other to communicate. It is a super network. It uses a set of protocols called TCP/IP.
4. INTERSPACE :It refers to a vision of what the internet will become in future. It is a client/server software program that allows multiple users to communicate online with real time audio , video and text in dynamic 3D environment.Servers are of two types
It is a computer which can only be used as a server not as a node . It means its only job is to provide facilities of data , software , hardware resources etc. to the nodes. This type of server is generally used for very big and large networks. The networks using which use this type of server is called Master-Slave networks.
Non – Dedicated Servers
In a network a workstation which can double up as a server is called a non-dedicated Server . It means it can be used as a server and as a node. This type of server is generally used in small networks . The small networks using such a server are called Peer-to-Peer Networks.
Network Interface Unit
It is an interpreter which is attached to server and all the workstations to maintain the connection between them. It is also called Terminal Access Point (TAP).
Transmission Media or Communication Channels
They refer to the connecting cables that connect two or more workstations .
Types of Communication Channels
1. Guided media : The medium of communication which includes the cables.
The following are the important types of cables :
2. Unguided media : The medium of communication which includes the waves through air ( vacuum ) .
TYPES OF NETWORK
LOCAL AREA NETWORK (LAN )
METROPOLITAN AREA NETWORK (MAN)
WIDE AREA NETWORK (WAN )
LOCAL AREA NETWORK ( LAN )
It is a small computer network that are confined to a localized area like an office , a building etc. Only a definite number of computers can be connected in this network to share the resources . Its range can be up to a few Kilometers.Its main features are
Total diameter not more than 5 km
Data communication at the rate of 100 Mbps
Owned by single organization
Low Error Rates
Provides user access to several resources like
printers, Modem etc.
Metropolitan Area Network ( MAN )
This network is larger in size than LAN and it spreads over a city. It means a very large number of computers can be connected in this in a city or from one city to the other.
Example : The Cable TV networks which are spread over a city.
MODEM( MOdulation/DEModulation )
The device which is used to connect and communicate with computers with the help of telephonic lines . It converts digital data into analog form and vice versa.
Working :A modem is a computer peripheral that allows to connect and communicate with the other computers through telephone lines. In MoDem , Mo stands Modulation and Dem stands for Demodulation . Modulation means to convert digital signals to analog signals and Demodulation is reverse of that. The data is transferred form source to the destination through telephone wires and they can only understand analog signals so there is need to convert digital signals to analog . And computer can only understand digital signals . This conversion is done by MoDem.
Network Switching Techniques
( 1 ) Circuit Switching : In this technique first of all the complete physical connection between two computers is established and then data is transmitted from the source computer to the destination computer. Its important property is to set up an end-to-end connection between computer before any data can be sent.
( 2 ) Message Switching : In this technique the source computer sends data or the message to the switching office first which stores the data. It then looks for a free link to another switching office and then sends the data to this office. Hence it is also known as store and forward.
( 3 ) Packet Switching : In message switching there is no limit on block size but in Packet switching a fixed size of packet which can be transmitted across the network is specified. In this all the packets of fixed size are stored in the main memory. It improves the performance as the access time is reduced.
The way of interconnection of the nodes in a network is called the Topology.
The different factors on which selection of a topology depends are :
( a ) Cost : A Network of computers can reduce the cost to a large extent.
( b ) Reliability : It is more reliable to work in a Computer Network . Hence if a node fails to work the data can be achieved from some other nodes.
( c ) Flexibility : The topology should allow for easy reconfiguration of the network.
The different topologies are :
It is consisted of a central node to which all other nodes are connected by a single path. Its different advantages and disadvantages are :
( 1 ) One Device per connection : In this topology failure of a single connection typically involves disconnecting one node from an otherwise fully functional network.
( 2 ) Simple Access protocols : In this access protocols are very simple.
( 1 ) Long Cable Length : This topology uses a very long cable as each node id directly connected to the centre.
( 2 ) Central Dependency : If the central node fails , the entire network stops working.
Bus or Linear Topology
It is consisted of a single length of the transmission medium onto which the various nodes are attached . Its different advantages and disadvantages are :
( 1 ) Short Cable Length : There is a single common data path connecting all nodes , so this topology uses a very short cable .
( 2 ) Easy to Expand : In this topology additional nodes can be connected at any point along its length.
( 1 ) Fault detection : In this topology it is very difficult to detect a faulty node .
( 2 ) Nodes must be intelligent : All the nodes working in this topology must be intelligent.
Ring or Circular Topology
In this each node is connected to two and only two neighbouring nodes. Data is transmitted from one to another node and is transmitted onwards to another. In this topology the data travels only in one direction.
Its different advantages and disadvantages are :
( 1 ) Short Cable Length : There is very short cable which is used to develop a Computer Network
( 2 ) Suitable for optical fibers : In this topology for very fast speed transmission optical fibers can be used.
( 1 ) Node Failure causes network failure : In this topology if one node fails to pass the data through itself , the entire network fails.
( 2 ) Network reconfiguration is difficult : It is not possible to shut down a small section of the ring .
A variation of bus topology is the tree topology. The shape of the network is just like an inverted tree with the central root branching and sub-branching to the extremities of the network.
( 1 ) Easy to Expand : It is very easy expand this topology . It means nodes can be connected easily.
( 2 ) Fault isolation is easy : It is easy to find the faulty node in this topology.
( 1 ) Dependency on root computer : The total dependence is on the root computer . If it fails to work , the entire network will stop working.
( 2 ) Complex Access Protocols : The protocols designed for this topology are generally very complex.
The different Prevention methods are used while working in Network environment for security.
( 1 ) Authorization : It determines whether the ISP has granted the access to the web service or not. It is done by asking the user legal login-Id.
( 2 ) Authentication : It is a way to check the password protection of an authorised user.
( 3 ) Firewall : It is a system designed to prevent the unauthorised users to access to or from a private network. In this we can also encrypt the data.
( 4 ) Encrypted Smart cards : It is smart hand-held card that can generate a token that a computer can recognise. Every time a new token is generated.
( 5 ) Biometric System : It includes some unique aspect of a person’s body such as finger prints etc. To establish his identity
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