chapter-iii networking concepts

8/13/2019 Chapter-III Networking Concepts

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NetworkingIntroduction:-

When computers appeared in business, software programs were designed

for a singleuser. Various tasks were accomplished by processing them batch wise

fashion.Reasons behind the development of Networking Technology:-

1. As computers spread throughout business, developers began offering complex

software designed for multiple users.

2. The electronic transfer of information between computers became a major focus

of the computer industry (Data communications).3. The demand for larger and faster high-capacity networks has increased as

businesses have realized the value of networking their computer systems.


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Definition of NetworkA network is a set of technologies including hardware, software and media that can be

used to

1. Connect computers together2. Communicate and exchange information

3. Share resources in real time

Common Uses of a network:-

Networks allow many users to access shared data and programs almost instantly Network open up new ways to communicate, such as e-mail and instant messaging

By allowing users to share expensive hardware resources such as printers,

networks reduce the cost of running an organization.


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Illustration


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Types of NetworksBasically networks can be categorized as follows:

1. Local Area Network(LAN)

2. Metropolitan Area Network(MAN)

3. Wide Area Network(WAN)

Local Area Networks (LANs):

A local area network (LAN) is a data communication system consisting of

several devices such as components and printers. This type of network containscomputers that are relatively near each other and are physically connected using

cables, wireless media. A LAN can include either two or three PCs or even

hundreds of computers of different kinds. In general any network that exists within a

single building or even a group of adjacent buildings is considered as a LAN.

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Metropolitan Area Networks (MANs):-

The metropolitan area network (MAN) is a large-scale network that

connects multiple corporate LANs together. MANs are not usually owned by a

single organization and are maintained by a group or single network provider thatsells its services to customers. This type of networks usually take the role of high

speed networks that allow sharing of regional resources.

Wide Area Networks (WANs):-

A wide area network (WAN) is two or more LANs connected together,

generally across a wide geographical area. These remote LANs are connected

through a telecommunication network(usually a phone company) or via the internet

through an Internet service provider (ISP).


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Other Useful NetworksCampus Area Networks (CANs):-

A campus area network (CAN) follows the same principle as a local area

network but on a larger scale. With a CAN different campus offices and

organizations can be linked together. For example some university departments ororganizations might be linked to the CAN even though they already have their own

separate LANs.

Home Area Networks (HANs):-

A home area network (HAN) is a network contained within a users

home that connects a persons digital devices from multiple computers and their

peripheral devices such as a printer to telephones, VCRs, DVDs, televisions and

otherdigital devices that are wired into the network.


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Client/Server ArchitectureClient/Server Networks:

A popular type of server-based network is the client/server network, where

individual computers (nodes) share the processing and storage workload with a

central server. This architecture requires special software for the nodes and theserver. Client/server software can be used on LANs or WANs. A single client/server

program can be used on a LAN where all the other software is based on a simple file

server system.

The most common example of client/server computing involves a database that

can be accessed by many different computers on the network. The database is stored

on the network server and the users computer stores and runs the client portion ofthe database.

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A node is a processing location that can be a PC or some other device such as a

networked printer. Usually server-based networks include many nodes and one or

more servers, which control user access to the networksresources.

In Client/Server networks, the central computer is known as the file server/network

server/application server. Files and programs used by more than one user are oftenstored on the server.

In a file server network each node has access to the files and programs on the server

but not to the file on other nodes. When a node needs information from the server, it

request the file containing the information. The server then forwards the file

containing the information to the requested node(s).

Users must logonto the network to gain access to its resources.

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A simple LAN with a file server


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Network Topologies An important feature of a network is its topology. Topology represents the layout

of the cables and devices that connect the nodes of the network. Before actually

constructing a network, designers consider several factors in deciding which

topology to be used.

Data moves through the network in a structure called packets. Packets are pieces of

a message broken down into small units by sending PC and reassembled by the

receiving PC.

There are two important reasons in considering a topology for a network:-

1. A correctly designed network using the appropriate technology for the

organization's needs will move data packets efficiently.

2. A proper topology prevents collisions that normally happens when multiple nodes

try to transmit data at the same time

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Types of topologiesNetwork topologies can be categorized as follows:-

1. Star Topology:-

It is the most common topology. In a star network, all nodes are connectedto a device called a hub and communicate through it. Data packets travel through the hub

and are sent to the attached nodes eventually reaching their destinations. An advantage inusing the star topology is that a broken connection between a node and the hub does notaffect the rest of the network. However if the hub is lost, all nodes connected to that hubwill be unable to communicate.

2. Ring Topology:-

The ring topology connects the networks nodes in a circular chain with each

node connected to the next. The last node connects to the first, completing the ring. Thedata known as token is addressed to a node. On a mismatch, the token is passed to thenext node. Thus there is no danger of collisions because only one packet of data travelsthe ring at a time. However if the ring is broken, the entire network will be unable tocommunicate.

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3. Bus Topology:-

This type of topology uses a one cable. All the nodes and peripheral

devices are connected in a series to that cable. The main advantage of bus topology

is that it uses the least amount of cabling. However some extra circuitry is needed toavoid collisions of data packets. A broken connection can bring down all or part of

the network.

4. Mesh Topology:-

It is the least-used network topology and also the most expensive to

implement. In this type of network a cable runs from every computer to the other.

The advantage in mesh topology is that data is definitely transmitted to thedestination node. Thus if one connection goes down there are other ways to route the

data to its destination.


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Star Network


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Ring Network


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Bus Network


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Mesh Network


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Protocols A protocol is an agreed-upon format for transmitting data between two devices over LAN. To

effectively communicate a user must have the same protocol installed on the local PC and

remote PC to make a connection.

Protocols break data into small packets for transportation.

Linking devices pass data packets to the various pieces of equipment

Some of the commonly used protocols are:

1. TCP/IP:-

TCP/IP is the protocol of the internet and is required on any computer that must

communicate across the internet. Also TCP/IP is the default networking protocol of Windows

and many other operating systems.2. HTTP:

It stands for Hyper Text Transfer Protocol. It looks after the transmission of HTTP

requests and responses to and from client/server . A HTTP request submitted by the client is

received and processed by the server and a HTTP response is sent back to the client which in

general may be a web page being displayed after clicking link or on submission of a form

data.Contd...


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3. SMTP:-SMTP stands for Simple Mail Transfer Protocol. SMTP is an Internet standard for

electronic mail (e-mail) transmission across Internet protocol (IP) networks. Whileelectronic mail servers and other mail transfer agents use SMTP to send and receive mailmessages, user-level client mail applications typically only use SMTP for sending

messages to a mail server for relaying. For receiving messages, client applications usuallyuse either the Internet Message Access Protocol (IMAP) or a proprietary system (such asMicrosoft Exchange or Lotus Notes/Domino) to access their mail box accounts on a mailserver.

4. FTP:-

File Transfer Protocol(FTP) is a standard network protocol used to copy a

file from one host to another over a TCP/IP-based network, such as the Internet. FTPis built on a client-server architecture and utilizes separate control and dataconnections between the client and server applications, which solves the problem ofdifferent end host configurations (i.e., Operating System, file names). FTP is usedwith user-based password authentication or with anonymous user access.


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Internet FundamentalsIntroduction:-

Internet is a giant global network with large collection of networks and millions ofcomputers set up by the Defense Department of the Research Project

Network(ARPANET).

By 1990 the network came to be known as Internet

Internet has changed the way people communicated, the way companies didbusiness etc.

Business has taken note of the potential ability of the internet and is trying tointegrate this technology into its overall business strategy.

Internet connects thousands of networks and hundreds of millions of users aroundthe world

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Internet is made up of three kinds of networks:

1. High speed backbone networks such as supercomputers.

2. Mid level networks such as those at universities and

companies

3. Small networks connected to the Internet such as individual

LANs and computers in organization.


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History of the InternetIn 1969, the US Defense Department set up Advanced Research Projects Agency to

establish superiority in military technology.

The goal of the ARPANET was to research on distributed computer systems as the

US military wanted to develop a failure tolerant computer network forcommunication. The idea is to have a communication infrastructure with out a

central system so that even if a part of the system breaks down or is destroyed by

enemy action, rest of the communication system should not be disturbed.

Later TCP/IP protocols were developed in the mid 1970s by Vinton Cerf and Robert

Kahn.

Another reason for creating such a network is to allow people in remote locations to

share scarce computing resources. By being a part of the network, these users could

access far away systems such as governmental mainframes or university owned

supercomputers and conduct research or communicate with other users.


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Common uses of InternetInternet acts as a carrier for several different services. They include

The World Wide Web

Electronic mail(E-mail) News

File Transfer Protocol(FTP)

Chat

Instant Messaging

Online Services

Peer-to-peer services

Note:- To use these services, a user requires a computer connected to the Internet.

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