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What is Computer Network?

Computer Network is :


A collection of computers and other devices that are connected together by communication channels for sharing information and resources is called computer network.


Why do we need Computer Network?

We need Computer Network :


If you link 2 or more computers together you have a Network

Servers are computers that store and send data to other computers

For Example an E-mail Server

Clients are computers that receive and use data from servers

For Example your desktop PC receiving e-mail


Uses / Benefits of Computer Network

Uses / Benefits of Computer Network :


The main benefits or uses of computer network are:

  • 1.Communication
  • 2.Sharing Resources
  • 3.Sharing Software
  • 4.Data Sharing


Communication :


Using a network, different people can communicate with each other all over the world. People can communicate at very low cost via e-mail, chatting, telephone, video telephone, video conferencing, groupware, and SMS services etc.

Sharing Resources :


In a computer network, resources such as, printers, scanners, fax machines and modems can be shared among different users. Suppose several personals computers and a laser printer are connected to a network. Each users can access the printer.

Sharing Software :


In a computer network, usually application programs and other software are stored on the central computer. Users connected to a network can access these programs or software.

Data Sharing :


In a network environment, any authorized user can access data stored on other computers on the network. For example, on the Internet, a large number of Internet users can access same database



What is the Advantages(benefits) of Networking?

The Advantages(benefits) of Networking is :


Connectivity and Communication:


Networks connect computers and the users of those computers. Individuals within a building or work group can be connected into local area networks (LANs); LANs in distant locations can be interconnected into larger wide area networks (WANs).

Data Sharing:


One of the most important uses of networking is to allow the sharing of data. Before networking was common, an accounting employee who wanted to prepare a report for her manager would have to produce it on his PC.

Hardware Sharing:


Networks facilitate the sharing of hardware devices. For example, instead of giving each of 10 employees in a department an expensive color printer (or resorting to the “sneakernet” again), one printer can be placed on the network for everyone to share.

Internet Access:


The Internet is itself an enormous network, so whenever you access the Internet, you are using a network. The significance of the Internet on modern society is hard to exaggerate, especially for those of us in technical fields.

Internet Access Sharing:


Small computer networks allow multiple users to share a single Internet connection. Special hardware devices allow the bandwidth of the connection to be easily allocated to various individuals as they need it Data Security and Management: In a business environment, a network allows the administrators to much better manage the company's critical data.

Performance Enhancement and Balancing:


Under some circumstances, a network can be used to enhance the overall performance of some applications by distributing the computation tasks to various computers on the network.

Entertainment:


Networks facilitate many types of games and entertainment. The Internet itself offers many sources of entertainment, of course. In addition, many multi-player games exist that operate over a local area network. Many home networks are set up for this reason, and gaming across wide area networks (including the Internet) has also become quite popular.



Advantages and disadvantages of networks

Advantages and disadvantages of networks :



Advantages of networks :

Sharing devices such as printers saves money. Site (software) licences are likely to be cheaper than buying several standalone licences. Files can easily be shared between users. Network users can communicate by email and instant messenger. Security is good - users cannot see other users' files unlike on stand-alone machines. Data is easy to backup as all the data is stored on the file server.

Disadvantages of networks :

Purchasing the network cabling and file servers can be expensive. Managing a large network is complicated, requires training and a network manager usually needs to be employed. If the file server breaks down the files on the file server become inaccessible. Email might still work if it is on a separate server. The computers can still be used but are isolated. Viruses can spread to other computers throughout a computer network. There is a danger of hacking, particularly with wide area networks. Security procedures are needed to prevent such abuse, eg a firewall.


What is proxy arp? What function does it serve?

Proxy ARP And Function does it serve :


It allows host A to impersonate host B and respond to an arp request on behalf of host B. The original intention of this is to allow a router to respond to an arp request on one of its networks for a host on another of its networks. In this way, the router is able to make the different networks work in a more transparent way.


What is Protocol?

Protocol :


A protocol is a set of rules that governs data communications. A protocol defines what is communicated, how it is communicated and when it is communicated.


What is the function of network protocol?

The functions of network protocol are :


a) Encapsulation

b) Segmentation & resembling

c) Connection Control

d) Ordered delivery

e) Flow Control

f) Error control

g) Addressing

h) Multiplexing

i) Transmission service.
 


What is references model?

References model :
References model : Protocol standard is also know as a reference model.


Describe about References model

Describe about References model :



It has two types ,These

i) OSI & ii) TCP/IP

OSI : The full form of OSI is the open System interconnection. OSI deals with connect opebn systems that is systems that are open communication with other system. It has seven phases/layer for communicating data from source to destination, this is why it is called seven layer model.

1) Application
2) Presentation
3) Session
4) Transport
5) Network
6) Data Link
7) Physical

Fig : OSI Layer

1) Physical layer : The layer od OSI that co-ordinates the function required to transmit a bit over a physical medium called physical layer. It deals with the mechanical and electrical specification of devices.

Characteristics : 
i) Physical characteristics of interfaces & media 
ii) It represents the data
iii) Data rate
iv) Synchronization of bits
v) Physical topology
vi) Transmission mode
vii) Line configuration


2) Data Link layer : The layer of OSI that transforms the physical layer to a reliable link is called data link layer.

Characteristics : 
i) It deals with framing
ii) Physical addressing
iii) Flow control
iv) Error control
v) Access control
vi) Traffic regulation mechanism


3) Network Layer : The layer that responsible source to destination to delivery of packet
multiple network is called network layer.

Characteristics :
i) Logical addressing
ii) Routing
iii) Connecting different network.

4) Transport Layer :
The layer of OSI that is for process to process delivery of  the entire message is called transport layer.

Characteristics : 
i)  Service point addressing
ii) Segmentation and re-assembly
iii) Connection control
iv) Flow control
v) Error control
vi) Port control

5) Session Layer : The Layer of OSI that allows of different machine to establish session among them is called session layer.

Characteristics : 
i) Provides enhanced service to the u 
ii) It allows the user to log into a remain time sharing system.
iii) It means dialogue control among the devices
iv) It allows traffic to go in both direction at the same time
v) Provides token management facility
vi) Synchronization of the devices.

6) Presentation Layer : The layer which is concerned with the semantics of the information exchange between the two systems is called presentation layer.

Characteristics : 
i) Translation
ii) Encryption
iii) Compression
iv) Relation between the layers


7) Application Layer : The layer that provides human or user to access the network is called application layer.
Characteristics :
i) mail-Service
ii) File transfer/management
iii) Remote log in
iv) Directory service
v) Access of WWW. 


What is an Optical fiber?

An Optical fiber :


Optical Fiber : Optical fiber is a flexible, transparent fiber made of glass(Silica) or plastic, slightly thicker than a human hair.It can functions as a waveguide or light pipe to transmit light between the two and of the fibers

Fiber optical is an application. Optical fiber optical fibers are widely used in fiber-optic communications which permits transmission over longer-distances and higher bandwidths than other forms of communication.


Mention five categories of it application?

Mention five categories of it application :


 Application of Optical Fiber : 
The application of optical fiber are given below :

i) SONET : 
            It transfer multiple digital bit streams over optical fiber using lasers from light emiting diods(LEDs).

ii) Cable TV : 
              Some cable TV comanies use a combination of Optical fibe and coaxial cable, thus creating a hybrid network.

iii) Backbone structure : 
                          Optical fiber provides the backbone structure while coaxial cable provides the connection to the user premises.

iv) LAN : 
          Local are networks such as 100Base FX network Fast (Ethernet) and 1000base -X also use fiber-optic cable.

v) Long distance communication : 
                                  Fiber-optic communication which permits transmission over longer distances and at higher bandwidths than other forms of communication
 


What is Network Topology?

Network Topology :


The physical arrangement of modes in a network is called network topology. This defines the structure of a network. It means how the modes or computer are physically situated in the network.


Discuss different types of Network Topology

Discuss different types of Network Topology :


Types :

The types of Network topology are : 

1. Bus Topology

2. Ring Topology

3. Star Topology

4. Tree Topology

5. Mesh Topology

6. Hybrid Topology



1. Buys Topology : 
                     Bus networks use a single networking or connecting wire called backbone to which all the node or computers are peripheral devices are attached.

Advantages :

i) Easier to construct

ii) Cheaper than to other networks

iii) Less noise in data transmission.


Disadvantages : 

i) If one computer or backbone is demaged than whole system/network failed.

ii) More management cost.



2. Ring Topology : 
                     The ring topology connects the nodes of network in a circular chain with each node connected to the next. The final node in the chain is connected the ring.


Advantages : 

i) Connection structure is simple

ii) Less costly to other network.

iii) Less chance of collision. 

Disadvantages : 

i) It is unreliable.

ii) If the connection is broker than the network is collapse.


3. Star Topology : 
                  In this topology all computers arev connected to a central switch called HUB. A HUB is the central centrolling device.


Advantages : 

i) Intelligent HUB can monitor traffic and helps to privent collision.

ii) In star topology broker, connection cannot effect the whole network.


Disadvantages : 

i) If the HUB is demaged the whole network collapse.


4. Tree Topology :
                    Tree is used multipoint link. Nodes ia a tree are linked to a central HUB that controls the traffic to the network. Not every devices plug directly into the central HUB. Majority devices are connected to secondary HUB.


Advantages :

i) Les expensive than mesh topology.

ii) Easy to installation and reconfigureation.

iii) Include robustness.

iv) Easy to fault isolation and fault identification.


Disadvantages :

i) More cable is reguired than  ring and bus topology.



5. Mesh Topology : 
                    The types of topology where each nodes are directly connected with another nodes. 


Advantages :

i) Most reliable.

ii) Each computer is connected another without any disturbing.


Disadvantages :

i) Costly

ii) Difficult to construct.


6. Hybrid Topology : 
                      Here, a pure star or ring or completely connected network is rarely used. Instead, an organization will use some sort of hybrid network,which is a combination of two or more different network topologies.


Advantages :

i) It is reliable.

ii) Less cheaper of collision.

Disadvantages : 

i) More expensive

ii) Difficult to construct. 
 


What is Sattelite?

Sattelite :


 It term is no line of light between tree sending and tree receiving station tree tries type of transmission is called satellite transmission.

Physical Description :

* A communication satellite is a microwave relay station.

* It is used to lines two or more ground based microwave transmitter


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