Saturday, 28 October 2017

Computer network introduction


What is a Network?




A network is simply defined as something that connects things together for

a specific purpose. The term network is used in a variety of contexts,

Including telephone, television, computer, or even people networks.

A computer network connects two or more devices/computers together to share a nearly limitless range of information and services, including:



·        Documents

·        Email and messaging

·        Websites

·        Databases

·        Music



In below diagram Ok and An connected through a network.







Now come to the Point Protocol:--



Protocols are rules that govern how devices communicate and share


information across a network. Examples of protocols include:



1. IP – Internet Protocol

2. HTTP - Hyper Text Transfer Protocol



Multiple protocols often work together to facilitate end-to-end network

Communication. Protocols are covered in great detail later .

















Basic Types of Network:--




Network types are often defined by function or size or no of connected workstations. The two most common categories of networks are:



·        LANs (Local Area Networks)

·        WANs (Wide Area Networks)





A LAN is generally a high-speed network that covers a small geographic

area, usually contained within a single building or campus. A LAN is

usually under the administrative control of a single organization. Ethernet is the most common LAN technology.





A WAN can be defined one of two ways. The book definition of a WAN is a

network that spans large geographical locations, usually to connect multiple

LANs.





A MAN (Metropolitan Area Network) is another category of network,

though the term is not prevalently used. A MAN is defined as a network that

connects LAN’s across a city-wide geographic area.





An internetwork is a general term describing multiple networks connected

together. The Internet is the largest and most well-known internetwork.











Network Architectures


A host refers to any workstation that is connected to a network. A host can also

 defined as any device assigned an IP address.

A host can use following functions:

• A host which request data, called as a client.

• A which provide data, called as a server.

• A host can both request and provide data, called as a peer.

Because of these functions, multiple network architectures have

been developed, including:



1.     Peer-to-Peer

2.     Client/Server

3.     Mainframe/Terminal



In a basic peer-to-peer architecture, all hosts on the network can both

request and provide data and services. For example, two Windows 10

workstations configured to share files would be considered a peer-to-peer

network.

Peer-to-peer networks are very simple to configure like static routes, yet this architecture presents several challenges. Data is difficult to manage and back-up, as it is spread across multiple workstation. Security is equally problematic, as user

accounts and permissions much be configured individually on each host.



Explanations No 1:--



In a client/server architecture, systems are assigned specific roles. Clients

request data and services stored on servers. An example of a client/server

network would be Windows 10 workstations accessing files off of a

Windows 2007 server.



Advantage of the client/server:--



There are several advantages to the client/server architecture. Data and

services are now centrally located on one or more servers, consolidating the

security and management of that data. As a result, client/server networks can

scale far larger than peer-to-peer networks.



disadvantage of the client/server:--

One key disadvantage of the client/server architecture is that  server can

present a single point of failure. This can be mitigated by adding redundancy at the server layer.