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What is a Computer Network?

 A computer network is an interconnected collection of autonomous computers that communicate with one another using sets of rules known as protocols. Connected means that computers can exchange information via wired or wireless connections. Autonomous means that the computers must function independently, i.e. there is no master/slave relationship where one computer controls another.
         The group can be as small and simple as two computers and a printer set up in a house or as large and complex as thousands of computers and hundreds of printers and other devices.
         In order for the computers to communicate with each other, they must share three elements:
1       a network media and topology,
2       a protocol, and
3       a software client or service.
Importance of networking
E-Communication
E Exchange of information
E Sharing information
E Sharing hardware resources
E Sharing software resources
E Preserving information
E Protecting information
 
 
.
Network Architecture
Network Node Relation:- based on how the computer in a network are configured and how  they access information networks are classified into two types
Ø Peer-to-peer
Ø client-server
Peer-to-Peer
ü  Also known as a workgroup is a low-cost, easily implemented network solution generally used in small network environments that need to share a few files and maybe some hardware, such as printers.
ü  all systems are equal, or peers. Each system can share hardware or files and access the same things on other systems.
ü  is often referred to as decentralized networking because the network files, data, and administration are not handled from a central location.




Advantages of Peer-to-Peer Networks

v Cost - Because peer-to-peer networking does not require a dedicated server, such networks are very cost-effective.

v Ease of installation

o   Disadvantages of Peer-to-Peer Networks

v Security - security must be applied to each computer and resource individually.

v Data backup - each system must have its data backed up individually.

v Resource access - difficult to locate resources on the network.

v Limited numbers of computers - Peer-to-peer networking is effective only on small networks (fewer than 10 computers).

v Additional load on computers for resource sharing

v Lack of central organization, which can make data hard to find

v Users must administer their own computers

v Weak and intrusive security

Client/Server Networking Model

         Scalable, allowing additional computers or other networked devices to be added with little difficulty.

         Centralized management of all network services, security, and streamlined/updated backup procedures.

                

Two different types of computers are required: the client and the server





 

                         Servers

Ø  Workhorses of the network.

Ø  Require additional resources and computing power.

Ø  Servers also require a network operating system.

Ø  Network may have a single server that offers more than one network service or hundreds of servers, each performing a dedicated task.

 

§  Client Computers

Ø  Connect to the network and access the resources of the server.

Ø  Software is needed to allow the client to connect to the network, which is mostly now built into desktop operating systems.

o   Advantages of Client/Server Networking

Ø  Centralized management and security

Ø  Scalability

Ø  Simplified backups

Ø  Number of users: A server-based network can support thousands of users

Ø  Central file storage, which allows all users to work for the same set of data and provides easy backup of critical data, and keeps data from getting lost among computers

Ø  Ability of servers to pool available hardware and software, lowering overall costs

Ø  Optimized dedicated servers, which are faster than peers at sharing network

Ø  Freeing users from the task of managing the network

Ø  Easy manageability of a large number of users

Ø  Ability to share expensive equipment, such as laser printers

Ø  Less intrusive strong central security, since a single password need to access all shared resources on the network

o   Disadvantages of Client/Server Networking

Ø  High cost - additional hardware and software costs

Ø  Administration requirements - need technically skilled people to manage and maintain the network and the servers.

Ø  Single points of failure - If the server fails, the clients can't access the services that reside on the server. Great effort and expense are needed to ensure the high availability of network servers.

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