CLIENT SERVER AND MULTIMEDIA NOTES

8/7/2019 CLIENT SERVER AND MULTIMEDIA NOTES

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INTERNET AND MULTIMEDIA( By mr. Mochoge Cleo)

CLIENT SERVER PROGRAMMING

Introduction

Client/server describes the relationship between two computer programs in which one

program, the client, makes a service request from another program, the server, whichfulfills the request. Although the client/server idea can be used by programs within a

single computer, it is a more important idea in a network. In a network, the client/server

model provides a convenient way to interconnect programs that are distributed efficiently

across different locations. Computer transactions using the client/server model are verycommon. For example, to check your bank account from your computer, a client program

in your computer forwards your request to a server program at the bank. That programmay in turn forward the request to its own client program that sends a request to a

database server at another bank computer to retrieve your account balance. The balance

is returned back to the bank data client, which in turn serves it back to the client in yourpersonal computer, which displays the information for you.

The client/server model has become one of the central ideas of network computing. Mostbusiness applications being written today use the client/server model. So does the

Internet's main program, TCP/IP. In marketing, the term has been used to distinguishdistributed computing by smaller dispersed computers from the "monolithic" centralized

computing ofmainframe computers. But this distinction has largely disappeared asmainframes and their applications have also turned to the client/server model and become

part of network computing.

In the usual client/server model, one server, sometimes called a daemon, is activated andawaits client requests. Typically, multiple client programs share the services of a

common server program. Both client programs and server programs are often part of a

larger program or application. Relative to the Internet, your Web browser is a client

program that requests services (the sending of Web pages or files) from a Web server(which technically is called a Hypertext Transport Protocol or HTTP server) in another

computer somewhere on the Internet. Similarly, your computer with TCP/IP installed

allows you to make client requests for files from File Transfer Protocol (FTP) servers in

other computers on the Internet.

Other program relationship models included master/slave, with one program being in

charge of all other programs, and peer-to-peer, with either of two programs able toinitiate a transaction.

1) In information technology, a server is a computer program that provides services to

other computer programs (and their users) in the same or other computers.

2) The computer that a server program runs in is also frequently referred to as a server

(though it may be used for other purposes as well).

3) In the client/server programming model, a server is a program that awaits and fulfillsrequests from client programs in the same or other computers. A given application in a


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computer may function as a client with requests for services from other programs andalso as a serverof requests from other programs.

Specific to the Web, a Web server is the computer program (housed in a computer) that

serves requested HTML pages or files. A Web clientis the requesting program

associated with the user. The Web browser in your computer is a client that requests

HTML files from Web servers.

( By mr. Mochoge Cleo)

THE SURVIVAL PLAN

Client/server survival guideIt will help you survive, but it wont be easy. Nobody, unfortunately, has that

magic map with all the correct paths. I will share with you my insights, which whencombined with yours-may help you take the least treacherous path.

A survival guide is just more than a map. It contains instructions for how to find

food, build shelter, navigate in strange terrain, and protect yourself from snakes and

scorpions. There are five leading technologies for developing client/server applications: Database servers

TP monitors Groupware

Distributed objects The Web

What is Client/Server?As the name implies, client and server are separate logical entities that work

together over a network to accomplish a task.

Characteristics

All client/server systems have the following distinguishing characteristics:-

1. Service-Client/server is primarily a relationship between processes running onseparate machines

2. Shared resources-A server can service many clients at the same time and

regulate their access to shared resources.

3. Asymmetrical protocols-There is a many-to-one relationship between clients and

server. Clients always initiate the dialog by requesting a service. Servers are

passively waiting requests from the clients. Note that in some cases a client maypass a reference to a callback object when it invokes a service. This lets the server

call back the client. So the client becomes a server.4. Transparency of location-The server is a process that can reside on the same

machine as the client or on a different machine across the network. Client/server

software usually masks the location of the server from the clients by redirecting

the server calls when needed. A program can be a client, a server or both.

5. Mix-and-match-The ideal client/server software is independent of hardware oroperating system software platforms. You should be able to mix-and-match client

and server platforms.

6. Message-based exchange-Clients and servers are loosely coupled systems that

interact through a message-passing mechanism. The message is the delivery

mechanism for the service request and replies.


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7. Encapsulation of service-The server is a specialist. A message tells a serverwhat service is requested; it is then up to the server to determine how to get thejob done. Servers can be upgraded without affecting the clients as long as the

published message interface is not changed.

8. Scalability-Client/sever systems can be scaled horizontally or vertically.

Horizontal scaling means adding or removing client workstations with only a

slight performance impact. Vertical scaling means either migrating to a larger and

faster server machine or distributing the processing load across multiple servers.

9. Integrity-The server code and server data is centrally managed, which results in

cheaper maintenance and guarding of shared data integrity. At the same time, the

clients remain personal and independent.

The client/server characteristics described above allow intelligence to be easilydistributed across a network.

CLIENTS, SERVERS, AND OPERATING SYSTEMS:

What does a server need from an operating system?

In distributed computing environment, operating systems functions are either baseor extended services. The base services are part of the standard operating system, whilethe extended services are add-on modular software components that are layered on top of

the base services. Functionality equivalent extended services are usually provided bymore than one vendor.

Base servicesServer programs exhibit a high level of concurrency. Ideally, a separate task will be

assigned to each of the clients the server is designed to concurrently support. Taskmanagement is best done by multitasking operating system. Multitasking is the natural

way to simplify the coding of complex application that can be divided into a collection ofdiscrete and logically distinct, concurrent tasks.

Servers also require a high level of concurrency within a single program. Servercode will run more efficiently if tasks are allocated to parts of the same program rather

than to separate programs (these tasks are called co-routines or threads).

Server Operating System Requirements:-

1. Task preemption

An operating system with preemptive multitasking must allot fixed timeslots ofexecution to each task. Without preemptive multitasking, a task must voluntarily

agree to give up the processor before another task can run.

2. Task priority

An operating system must dispatch tasks based on their priority. This feature

allows servers to differentiate the level of service based on their clients priority.

3. SemaphoresAn operating system must provide simple synchronization mechanisms for

keeping concurrent tasks from bumping into one another when accessing shared

resources these mechanisms, known as semaphores, are used to synchronize theactions of independent server tasks and alert them when some significant event

occurs.

4. Interprocess communications (IPC)

An OS must provide the mechanisms that allow independent processes toexchange and share data.

5. Local/Remote Interprocess communication


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An OS must allow the transparent redirection of interprocess calls to a remoteprocess over a network without the application being aware of it. The extension ofthe interprocess co

mmunication across the machine boundaries is the key to the development of

application when resources and processes can be easily moved across machines.

6. Threads

These are units of concurrency provided within a program itself. Threads are used

to create event-driven server programs. Each waiting event can be assigned to athread that blocks until the event occurs. In the meantime, other threads can use

the CPUs cycles productively to perform useful work.

7. Intertask protection

The OS must protect tasks from interfering with each others resources. A singletask must not be able to bring down the entire system.

8. Multiuser High-performance File SystemThe file system must support multiple tasks and provide the locks that protect

integrity of the data. Server programs typically work on many files without too

much deterioration in performance.9. Efficient memory management

The memory system must be efficient to support very large programs and very large data

objects.

10. Dynamically Linked Run-Time ExtensionsThe OS services should be extendable. The mechanism must be provided to allow

services to grow at run time without recompiling the operating system.

11. Extended services

Extended services provide the advanced system software that exploit the

distributed potential of networks, provide flexible access to shared information,and make the system easier to manage and maintain.

Extended services include:-

a) Ubiquitous Communications

The Os extensions must provide a rich set of communications protocol

stacks that allow the server to communicate with the greatest number of clientplatforms.

b) Network Operating System ExtensionsThe operating system extensions must provide facilities for extending

the file and print services over the network.

c) Binary Large Objects

Images, video,graphics, intelligent documents, and databasessnapshots are about to test the capabilities of our operating systems, databases,

and networks.

d) Global Directories and Network Yellow PagesThe operating system extension must provide a way for clients to

locate servers and their services on the network using a global directoryservice. Network resources must be found by name.

e) Authentication and Authorization ServicesThe OS extensions must provide a way for clients to prove to the

server that they are who they claim to be. The authorization systemdetermines if the authenticated client has

the permission to obtain a remote service.


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f) System ManagementThe OS extension must provide an integrated network and system

management platform. The system should be managed as a single server

or as multiple servers assigned to domains.

g) Network Time

The OS extensions must provide a mechanism for clients and servers

to synchronize their

clocks. This time must be coordinated with some universal timeauthority.

h) Database and Transaction ServicesThe OS extensions must provide a robust multi-user Database

Management System(DBMS). The DBMS ideally support SQL for decision support and

server-stored procedures for transactions services.

i) Internet Services

The Internet is a huge growth opportunity for servers e.g. HTTP

daemons, secure sockets layer (SSL), firewalls, Domain Name Service,HTML-based file systems etc.

j) Object-oriented Services

This is an area where extended services will flourish for a longtime to come. Services are becoming more object-oriented. The OS will

provide object broker services that allow any object to interact with any otherobject across the network.

WILL THE REAL CLIENT SERVRER PLEASE STAND UP?

Many systems with very different architectures been called client/server systemvendors often use client/server as if the term can only be applied to their specific

packages. For example, file sever vendors swear they first invented the term, anddatabase server vendors are known in some circles solely as the client/server vendors.

The idea of splitting an application along client/server lines has been used over

the last twelve years to create various forms of networked software solutions. Typically

these solutions are built on top of off-the-shelf middleware software packages.

Middleware is a vague term that covers all the distributed software needed tosupport interactions between client/server systems.

Each of these solutions, however, is distinguished by the nature of the service it

provides to its clients, as shown below:-

File Servers

With a file server, the client typically a PC) passes requests for file records over anetwork to the file server. This is a very primitive form of data service that necessitates

many message exchanges over the network to find the requested data.File servers are useful for sharing files across a network. They are indispensable for

creating shared repositories of documents, images, engineering drawings, and other largedata objects.


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Database ServersWith a database server, the client passes SQL requests as messages to the database

server. The results of each SQL command are returned over the network. The code thatprocesses the SQL request and the data reside on the same machine. The server uses its

own processing power to find the requested data instead of passing all the records back toa client and then letting it to find its own data, as was the case for file server.

Transaction Servers

With a transaction server, the client invokes remote procedures (or services) thatreside on the server with SQL database engine. These remote procedures on the server

execute a group of SQL statements.The network exchange consists of a single request/reply message (as opposed to

single/reply message for each SQL statement in a transaction). The SQL statements eitherall succeed or fail as a unit. These grouped SQL statements are called transactions.

DBMS

server

ServerSQL Calls

Applicatio

n

Application

DBMS

server

ServerTransactions

Application

Application


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Groupware Servers

Groupware addresses the management of semi-structured information such as text,image, mail, bulletin boards, and the flow of work. These client/server systems place

people in direct contact with other people.Lotus Notes and Microsoft Exchange are leading examples of such systems,

although a number of other applications do exist.Most cases applications are created using a scripting language and a form based

interfaces provided by the vendor. Typically the communication middleware between theclient and the server is vendor-specific. However, many groupware products now use e-

mail as their standard messaging middleware.

Object Application ServersWith an object server, the client/server is written as a set of communicating objects.

Client objects communicate with server objects using an Object Request Broker (ORB).

The client invokes a method on a remote object. The ORB locates an instance of thatobject server class, invokes the requested method, and returns the results to the client

object.

Groupware messagesServer

Application

Application

Remote Method

invocation

ORBORB

Application

DBMS

server

ServerTransactions

Application

ApplicationTP Monitors


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objects

object

Web Application Server

The World Wide Web is the first truly intergalactic client/server application. This newmodel of client/server consists of thin, portable, universal clients that talk to super fast

servers.

CGI

Internet

HTML Documents

Web Browser

FAT SERVERS OR FAT CLIENTS?

Client/server applications can also be differentiated by how the distributed application

is split between the client and the server.The fat server model places more functions on the server. The fat client model does

the reverse.

Groupware, transaction, and Web servers are examples of fat servers; database and

file servers are examples of fat clients.

Fat client

Client

HTMLForms

Java

Server Application

HTTP

Over

TCP/IP

GUI Application Data


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2-TIER VERSUS 3-TIERHigh-brow client/server pundits prefer to use terms like 2-tier, 3-tier, and N-tier

client/server architectures instead of fat clients and fat servers. But its the same basic

idea.

Its all about how you split the client/server application into functional units that you

can assign either to the client or to one or more severs. The most typical functional unitsare:-

The use interface

The business logic

The shared dataThere are many variations of multi-tier architectures depending on how you split the

application and the middleware you use to communicate between tiers.In the 2-tier client/sever architecture, the application logic is buried either inside the

user interface on the client or within the database on the server (or both). Examples of 2-

tier systems are:- File servers and Database servers with stored procedures

Let's suppose I'm going to write a piece of software that students at a school can useto find out what their current grade is in all their classes. I structure the program so

that a database of grades resides on the server, and the application resides on theclient (the computer the student is physically interacting with).

When the student wants to know his grades, he manipulates my program (by clicking

buttons, menu options, etc). The program fires off a query to the database, and thedatabase responds with all the student's grades. Now my application uses all this data

to calculate the student's grade, and displays it for him.

This is an example of a 2-tier architecture. The two tiers are:

1. Data server: the database serves up data based on SQL queries submitted by the

application.

2. Client application: the application on the client computer consumes the data and

presents it in a readable format to the student.

Now, this architecture is fine, if you've got a school with 50 students. But suppose theschool has 10,000 students. Now we've got a problem. Why?

Because every time a student queries the client application, the data server has toserve up large queries for the client application to manipulate. This is an enormous

drain on network resources.

So what do we do? We create a 3-tier architecture by inserting another program at theserver level. We call this the server application. Now the client application no longer

directly queries the database; it queries the server application, which in turn queriesthe data server.


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What is the advantage to this? Well, now when the student wants to know his finalgrade, the following happens:

1. The student asks the client application.

2. The client application asks the server application.

3. The server application queries the data server.

4. The data server serves up a recordset with all the student's grades.

5. The server application does all the calculations to determine the grade.6. The server application serves up the final grade to the client application.

7. The client application displays the final grade for the student.

It's a much longer process on paper, but in reality it's much faster. Why? Notice step6. Instead of serving up an entire recordset of grades, which has to be passed over a

network, the server application is serving up a single number, which is a tiny amountof network traffic in comparison.

There are other advantages to the 3-tier architecture, but that at least gives you ageneral idea of how it works.Incidentally, this website is a 3-tier application. The client application is your web

browser. The server application is the ASP code which queries the database (the thirdtier) for the question-and-answer you requested.

GUI & Applications

DBMS,Legacy,

Resource Managers

Tier 1

In the 3-tier client/server systems, the application logic (process) lives in the middle

tier; it is separated from the data and user interface. Examples of 3-tier client/server

systems are:- TP monitors

Object Transaction monitors andWeb application servers.

Resource managerApplication

DBMS

SQL File

I/O HTTP

RPC,ORBC

MOM

HTTP

SQLDATA

ACCESS


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servicesLegacy

Browser/Beans/ActiveX

Tier 2

Tier 1

Tier 3

The benefits of the 3-tier model are as follows:

Scalability: The key 3-tier benefit is improved scalability since the application serverscan be deployed on many machines. Also, the database no longer requires a connection

from every client -- it only requires connections from a smaller number of applicationservers. In addition, TP monitors or ORBs can be used to balance loads and dynamically

manage the number of application server(s) available.Better Re-use: The same logic can be initiated from many clients or applications. If an

object standard like COM/DCOM or CORBA is employed (as discussed in tooldependence), then the specific language implementation of the middle tier can be made

transparent.Improved Data Integrity: since all updates go through the middle tier, the middle tier

can ensure that only valid data is allowed to be updated in the database and the risk of arogue client application corrupting data is removed.

Improved Security: Security is improved since it can be implemented at multiple levels

(not just the database). Security can be granted on a service-by-service basis. Since the

client does not have direct access to the database, it is more difficult for a client to obtain

unauthorized data. Business logic is generally more secure since it is placed on a moresecure central server.

Reduced Distribution: Changes to business logic only need to be updated on the

application servers and do not have to be distributed to all the clients.

Improved Availability: mission-critical applications can make use of redundant

application servers and redundant database servers. With redundant servers, it is possible

to architect an application so that it can recover from network or server failures.Hidden Database Structure: since the actual structure of the database is hidden from the

caller, it is possible that many database changes can be made transparently. Therefore, a

service in the middle tier that exchanges information/data with other applications couldretain its original interface while the underlying database structure was enhanced during a

new application release.

INTRODUCTION TO INTERNET

Introduction:


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The rest, as they say, is history in the making. The Internet has been improved through

the developments of such services as Gopher and the World Wide Web.Even though the Internet is predominantly thought of as a research oriented network, it

continues to grow as an informational, creative, and commercial resource every day and

all over the world.

Who Pays for the Internet?

There is no clear answer to this question because the Internet is not one "thing", it's many

things. No one central agency exists that charges individual Internet users. Rather,individuals and institutions who use the Internet pay a local or regional Internet service

provider for their share of services. And in turn, those smaller Internet service providersmight purchase services from an even larger network. So basically, everyone who uses

the Internet in some way pays for part of it.

2-what makes the internet work?

The unique thing about the Internet is that it allows many different computers to connect

and talk to each other. This is possible because of a set of standards, known as protocols,

that govern the transmission of data over the network: TCP/IP (Transmission Control

Protocol/Internet Protocol). Most people who use the Internet aren't so interested in

details related to these protocols. They do, however, want to know what they can do on

the Internet and how to do it effectively.

The Client/Server Model:

The most popular Internet tools operate as client/server systems. You're running a

program called a Web client. This piece of software displays documents for you andcarries out your requests. If it becomes necessary to connect to another type of service--

say, to set up a Telnet session, or to download a file--your Web client will take care of

this, too. Your Web client connects (or "talks") to a Web server to ask for information on

your behalf.

The Web server is a computer running another type of Web software which provides

data, or "serves up" an information resource to your Web client.

All of the basic Internet tools--including Telnet, FTP, Gopher, and the World Wide Web-

-are based upon the cooperation of a client and one or more servers. In each case, you

interact with the client program and it manages the details of how data is presented to youor the way in which you can look for resources. In turn, the client interacts with one ormore servers where the information resides. The server receives a request, processes it,

and sends a result, without having to know the details of your computer system, becausethe client software on your computer system is handling those details.

The advantage of the client/server model lies in distributing the work so that each toolcan focus or specialize on particular tasks: the server serves information to many users

while the client software for each user handles the individual user's interface and other

details of the requests and results.

The Use of Local Clients:


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Every computer should be equipped with basic client software packages that allow you toperform functions such as electronic mail, Telnet, Gopher, and FTP.

Internet and World Wide Web

Internet is the worlds largest computer network, the network of networks, scattered all

over the world.

A network of networks, or Internet, is a group of two or more networks that are: Interconnected physically

Capable of communicating and sharing data with each other

Able to act together as a single network

Machines on one network can communicate with machines on the other networks, andsend data, files, and other information back and forth.

For this work, the networks and machines that are part of the Internet have to agree eitherto speak the same language or use an interpreter. This language is software that

enables the different types of machines on separate networks to communicate and

exchange information.To be used by different types of machines and yet be understood by all of them, thesoftware must follow a set of rules or protocol. The Internet, with a capital I, is the

networks of networks, which either uses the TCP/IP protocol or interacts with TCP/IPnetworks via gateways (the interpreters). The Internet presents these networks as one

seamless network for its users.The Internet covers the globe and includes large, international networks as well as many

smaller, local-area networks (LANs).The Internet offers access to data, graphics, sound, software, text, and people through a

variety of services and tools for communication and data exchange:- Remote login (Telnet)

File transfer protocol (FTP) Electronic mail (e-mail

News (USENET or network news)

Hypertext (WWW)

WHATS SPECIAL ABOUT INTERNETThere are three obvious reasons. Internet is the cheapest and fastest means to:

Get information

Provide information

Compile information

Getting Information on the InternetThe amount of information available through the Internet is staggering. To make all of it

more easily available to users, programs such as the gopher were developed to help

present material in some logical fashion. The most recent and very successful attempt atpresenting information over the Internet is the World Wide Web (WWW). You could get


the information about people, products, organizations, research data, electronic versions

of printed media etc. from the Internet.Providing Information on the Internet

Most of what you want to provide could be considered as advertising. While that maysound somewhat commercial, it is the best and the most inexpensive way to let people


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You can also get a dedicated line called a T-1 or T-3. A T-1 (Tee-one) line can handle1280 kilobytes per second. A T-3 line can handle ten times that speed.

How Do I Connect to the Internet?

Computer

Connection

Phone Line, Cable, DSL, Wireless, ...

Modem Network Software - TCP/IP

Application Software - Web Browser, Email, ... Internet Service Provider (ISP)

Internet Basics

For most people who are new to the Internet, the first experience is quite overwhelming.

However as one gets the feel of the Internet, it becomes clear that Internet is similar toany medium of information and or/ communication.

Once you know how to send and receive electronic mail, subscribe to mailing lists, joinand participate in discussion groups and Internet chats, your power to communicate with

people anywhere in the world increases dramatically.

What Should I Do?Before you can decide how you want to use the Internet, you should get an idea about

what all you can do and what is there in the cyber space. For beginners, use one of thepowerful web browsers like Internet Explorer or Netscape Navigator.


Web browsers are mainly used to access pages of the World Wide Web.By clicking on the hypertext links on a page it is possible to jump from one Internet site

to another, regardless of its location. Hypertext links are usually highlighted or differentcolored text, images or icons.

Given below is a list of activities that you could do with a web browser:-


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Visit Web sites Send and receive electronic mail Read and post articles in newsgroups

Download files to your PC.

Chat with other users on-line

Play games with others on-line

Access on-line multimedia including radio and video broadcasts

Search the Internet for Information Subscribe to electronic newsletters, e-zines etc.

Do on-line shopping

Post your resumes on the Internet

Create your own web sites Create an e-mail ID and account for you

Find a persons details Send flowers or gifts to others

INTERNET PROTOCOLSv The most commonly used protocols are:-v Transmission Control Protocol/Internet Protocol (TCP/IP)

v File Transfer Protocol (FTP)v Hyper Text Transfer Protocol (HTTP)

v Telnetv Gopher

v Wide Area Information Service (WAIS)

Transmission Control Protocol/Internet ProtocolTCP/IP is actually a collection of protocols or rules, that govern the way data travels

from one machine to another across networks.

IP-The IP does the following:

Envelopes addresses the data

Enables the network to read the envelope and forward the data to its

destination.

Defines how much data can fit in a single envelope (a packet).

TCP- The TCP component does the following:

Breaks data up into packets that the network can handle efficiently.

Verifies whether all the packets have arrived at their destination.

Reassembles the data.

File Transfer Protocol (FTP)FTP stands for File Transfer Protocol, and is part of the TCP/IP protocol suit. It is the

protocol, or set of ruled, which enables the files to be transferred between computers.FTP works on the client/server principle. The basic steps to use FTP are:-


Connect to the FTP server Navigate the file structure to find the file you want

Transfer the file.


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The specifics of each step will vary depending on the client program being used and thetype of Internet connection. There are a wide variety of files that are publicly availablethrough anonymous FTP.

Shareware-software that you can use for free for a trial period but then pay a fee for

Freeware-completely free software, for example fonts, clipart and games.

Upgrades & Patches-upgrades to current software and fixes for software problems.

Documents-examples include research papers, articles and Internet documentation.

Hypertext Transfer Protocol (HTTP)HTTP is short for Hypertext Transfer Protocol. It is a set of rules, or protocol, that

governs the transfer of hypertext between two or more computers.

Hypetext is text that is specifically coded using a standard system called HypertextMarkup Language (HTML). The HTML codes are used to create links.

HTTP is based on the client/server principle. HTTP allows a computer A to establish aconnection with a computer B (the server) and make a request.

HYPERTEXTIn a hypertext document, certain words within the text are marked as links to other areasof the current document or to other documents

The user moves to a related area by moving his or her mouse pointer to the link andclicking once with the mouse button

Links are used to point to another part of the same document, in which case clicking thelink will cause the browser to move to a new part of the currently displayed document

Telnet

Telnet is a protocol, or set of rules that enables one computer to connect to anothercomputer. This process is also referred to s remote login

The users computer, which initiates the connection, is referred to as the local computer,and the machine being connected to, which accepts the connection, is referred to as the

remote, or host computer.

Telnet is the protocol used to establish a login session on a remote computer on the

network. While many computers on the Internet require users to have authorization,

others are open to the public and can be logged onto with telnet. Telnet is not a method to

transfer files from one machine to another, but rather is a way to remotely connect to

another system with privileges to run specific programs on that system. Some uses of the

Telnet protocol include:

connecting to a library catalog to search that library's collection connecting to a location

that allows public priveleges to search its campus information system connecting to alocation that gives you an up-to-the minute weather report


Basic Telnet Commands

open - establishes a connection to the specified host.


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close - closes an open connection and leaves you in the telnet software quit - closes anyopen telnet sessions and exits the telnet software. When using a telnet program likeNCSA Telnet, you invoke these commands by way of pull-down menus or command

keys.

Gopher

Gopher is a protocol that is designed to search, retrieve, and display documents fromremote sites on the Internet.

It is also possible to initiate on-line connections with other systems via Gopher.

Information accessible via Gopher is stored on many computers all over the Internet.

These computers are called Gopher servers.

Users interact with Gopher via a hierarchy of menus and can use full-text searchingcapabilities of Gopher to identify desired documents.

Gopher can work with the following internet tools or systems:- Search local WAIS idiocies; query remote WAIS servers and funnel the results to

Gopher clients.

Query remote FTP sites and funnel the results to Gopher clients Be queried by WWW clients either using native HTTP querying.

Gopher is a client/server system that allows you to access many Internet resources simply

by making selections from a sequence of menus. Each time you make a selection, Gopher

carries out your request to the computer that contains the information and "serves" it up.For example, if you select a menu item that represents a text file, Gopher will get that

file--wherever it happens to be--and display it for you. As you use Gopher, some menuitems lead to other menus. If you choose one of these, Gopher will retrieve the new menuand display it for you. Thus you can move from menu to menu, using only a few key

strokes or a mouse to navigate. The power of Gopher is that the resources listed in a

menu may be anywhere on the Internet. As Gopher connects to computers to comply withyour menu selection, you don't need to be preoccupied with the behind-the-scenes work

of connecting to and disconnecting from these various computers. Gopher does this for

you without your even needing to be aware of it. This automatic connecting makesGopher popular and useful.

Where did Gopher come from?

"Born" in April 1991, gopher began as a project at the Microcomputer, Workstation, and

Networks Center at the University of Minnesota to help people on campus get answers tocomputer-related questions. At the time, the computer center staff had accumulated

answers to thousands of questions regarding computers and software.

What was needed was an easy and efficient way to deliver this information to students,

faculty and staff. Thus, the creation of Gopher reaffirms the adage that necessity is themother of invention.

Why is it called Gopher?

The name "Gopher" is appropriate for three reasons:


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1. Just as a real gopher successfully navigates beneath the prairie, the InternetGopher tunnels

through the invisible paths of the Internet to help you find the information

you want.

2. The name refers to someone who fetches things or provides service for other

people.

3. The Golden Gopher is the mascot of the University of Minnesota.

INTERNET ADDRESSINGIn general, Internet addressing is a systematic way to identify people, computers and

Internet resources.

IP Address

If you want to connect to another computer, transfer files to or from another computer, or

send an e-mail message, you first need to know where the other computer is-you need thecomputers address.An IP (Internet Protocol) address is an identifier for a particular machine on a particular

network e.g 202.54.1.6The IP addresses have the following characteristics in common:-

IP addresses are unique

No two machines can have the same IP number.

IP addresses are also global and standardized

All machines connected to the Internet agree to use the same scheme forestablishing an address.

Domain Name

A domain name is a way to identify and locate computers connected to the internet. Notwo organizations can have the same domain name e.g Microsoft.com, ibm.com,nasa.gov etc.

The major categories for top-level domain names are:-

com-commercial entities

edu-educational institutions

net-organisations directly involved on Internet operations

org-miscellaneous organizatons that dont dont fit any other category, such as non-profitgroups

gov-united states Federal Government entities

mil-United states military

Introduction to the World Wide Web

The World Wide Web (also referred to as WWW or W3) is the fastest growing area ofthe Internet. While gopher was an important step in allowing users to "browse" through

the Internet's vast resources, the World Wide Web has raised excitement about the

Internet to new heights.What makes the World Wide Web appealing and innovative is its use of hypertext as a

way of linking documents to each other. A highlighted word or phrase in one documentacts as a pointer to another document that amplifies or relates to the first document. When

looking at a WWW document, the reader doesn't have to follow every pointer, or link(also called a hypertext link), only those that look interesting or useful. In this way, the


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user tailors the experience to suit his or her needs or interests. The other very appealingaspect of the World Wide Web is the use of graphics and sound capabilities. Documentson the WWW include text, but they may also include still images, video, and audio for a

very exciting presentation. People who create WWW documents often include a

photograph of themselves along with detailed professional information and personal

interests. (This is often called a person's home page.)

What makes the WWW work?WWW is another example of client/server computing. Each time a link is followed, the

client is requesting a document (or graphic or sound file) from a server (also called a Web

server) that's part of the World Wide Web that "serves" up the document. The server uses

a protocol called HTTP or HyperText Transport Protocol. The standard for creatinghypertext documents for the WWW is HyperText Markup Language or HTML. HTML

essentially codes plain text documents so they can be viewed on the Web.Uniform Resource Locator(URL)

A URL identifies a particular Internet resource; for example a Web Page, a Gopher

server, a library catalog, an image, or a text file. URLs represent a standardizedaddressing scheme for Internet resources, and help the users to locate these resources byindicating exactly where they are. Every resource via the World Wide Web has a unique

URL.

URLs consists of letters, numbers, and punctuation. The basic structure of a URL ishierarchical, and the hierarchy moves from left to right:

Protocol://server-name.domain-name.top-level-domain:port/directory/filename

A URL (Uniform Resource Locator) (pronounced "you-are-EL" or, in some quarters,

"earl") is the address of a file or other resource accessible on the Internet

URL structure

protocol://host.domain[:port]/path/file.extension [?optional stuff]

http://www.hellohelpme.com/index.html

http: protocol

//www. host

hellohelpme.com domain

/index.html the individual document

the extension html shows that it was coded with html (web documents frequently havethe extension html or htm)

Protocol might be - http, file, gopher, wais, news, telnet, https, ....

The CASE of URLs may be important! Use only lower case in URLs that youbuild!

"optional stuff" - after a ? - is usually search parameters or values for variables. Often

used to pass parameters

Example includes:

http://www.lnl.net/alexis/index.html


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gopher://gopher.state.edu

WEB BROWSERSA browser is a piece of software that acts as an interface between the user and the inner

workings of the Internet, specifically the World Wide Web. Browsers are also referred as

web clients, or Universal clients because in the client/server model, the browser functions

as the client program.

The browser acts on behalf of the user. The browser: Contacts a web server and sends a request for information.

Receives the information and then displays it on the users computer.

A browser can be graphical or text-based and can make the Internet easier to use and

more intuitive. A text-based shows the user only the textual matter. A graphical browserallows the user to see more of what the WWW has to offer such as graphics, photographs

and multimedia.A browser program enables your computer to extract information from remote computers

working on any platform through the WWW. The program on your computer is called

WWW client. The WWW program [usually] on another computer that the browser"talks" to is called the serverTechnically, a Web browser is a client program that uses the Hypertext Transport Control

Protocol (HTTP) to make requests of Web servers throughout the Internet on behalf ofthe browser user

Examples of the browsers

Microsoft Internet Explorer Netscape Navigator

WEB BROWSING

Internet browsing or net surfing, as it is often called, is the process of visiting differentweb sites on the Internet hosted by various companies, organizations, educational

institutions, magazines, individuals, etc. the Internet contains a wealth of information that

can help your business. Armed with a good Internet browser, you can easily get around to

a myriad of sites, gathering competitive information, conducting market research, reading

publications, and staying in touch with whats happening at your business associations.

Chatting:Internet Relay Chat (IRC), the other method for Internet conversation, is less common

than talk because someone must set up the Chat before others can join in. Chat sessions

allow many users to join in the same free-form conversation, usually centered around a

discussion topic. When users see a topic that interests them, they type a command tojoin and then type another command to choose a nickname. Nicknames allow people in

the session to find you on IRC Networks or Channels.

Search Engines

A web search engine is an interactive tool to help people locate information available viathe World Wide Web. Web search engines are actually databases that contain references

to thousands of resources. Users interact with database, submitting questions that ask thedatabases if it contains that match a specific criteria.

There are many web search engines available on the web. A web search engine providesan interface between the user and the underlying database. The interface presents the user


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with a place to type in a search string, which may be a word, a phrase a date or someother criterion and a way to submit the request.The web search engines runs the search string against a database, returns a list of

resources that match the criteria and displays the results to the user.

Some of the most popular search engines are:

AltaVista (http://www.altavista.digital.com)

Excite (http://www.excite.com)

Lycons (http://www.lycons.com)Yahoo! (http://www.yahoo.com)

A look at search engines:

The World Wide Web is "indexed" through the use of search engines, which are also

referred to as"spiders," "robots," "crawlers," or "worms". These search engines comb through the Web

documents, identifying text that is the basis for keyword searching. Each search engine

works in a different way. Some engines scan for information in the title or header of thedocument; others look at the bold "headings" on the page for their information. The factthat search engines gather information differently means that each will probably yield

different results. Therefore, it's wise to try more than one search engine when doing Websearching.

The list below lists several search engines and how each one gathers information, plus

resources that evaluate the search engines.

Selected Search Engines (listed alphabetically)

Alta Vista

Alta Vista, maintained by The Digital Equipment Corp., indexes the full text of over 16

million pages including newsgroups. Check out the Alta Vista Tips page.

Excite Netsearch

Excite includes approximately 1.5 million indexed pages, including newsgroups. Check

out the Excite NetSearch handbook.

InfoSeek Net Search

Indexes full text of web pages, including selected newsgroups and electronic journals.Just under one-half million pages indexed. Check out the InfoSeek Search Tips.

Inktomi

As of December 1995, the Inktomi search engine offers a database of approximately 2.8million indexed Web documents and promises very fast search retrievals. Results are

ranked in order of how many of your searched terms are used on the retrieved pages.

Lycos

Lycos indexes web pages (1.5 million +), web page titles, headings, subheadings, URLs,

and significant text.


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Search results are returned in a ranked order.

MagellanMagellan indexes over 80,000 web sites. Search results are ranked and annotated.

Open Text Index

Indexes full text of approximately 1.3 million pages. Check out the Open Text Help

pages for tips on using this search engine.

WebCrawlerMaintained by America Online, WebCrawler indexes over 200,000 pages on

approximately 75,000 web servers. URLs, titles, and document content are indexed.

WWWW -- World Wide Web Worm

Approximately 250,000 indexed pages; indexed content includes hypertext, URLs, and

document titles.

YahooA favorite directory and search engine, Yahoo has organized over 80,000 Web sites(including newsgroups) into 14 broad categories. Yahoo also maintains a comprehensive

list of links to Yahoo - Computers and Internet:Internet:World Wide Web: Searching the

Web other web search engines, indexes, and guides.

Finally the internet is a huge source of information in all fields of knowledge.Datum will take your hand through this incredible world of information to get what you

need in a fast, reliable and professional way.

Advantages and Disadvantages of the InternetInternet has been perhaps the most outstanding innovation in the field of communication

in the history of mankind. As with every single innovation, internet has its ownadvantages and disadvantages. But usually, greater magnitude of advantages outweighs

its disadvantages.

During his evolution journey from Neanderthals to Homo erectus and then to Homo

sapiens, man has come long way. Because of his continuous quest for more and more

amenities and facilities, the nineties have seen a major turn around with the invention ofcomputers. 10 years ago, the term internet was practically anonymous to most of the

people. And today internet has become the most ever powerful tool for man throughout

the world. The internet is a collection of various services and resources.

Although, many people still think e-mail and World Wide Web as the principle

constituents of internet, there is lot more in store than e-mail, chat rooms, celebrity websites and search engines. It also became the best business tool of modern scenario. Today

internet has brought a globe in a single room. Right from news across the corner of the

world, wealth of knowledge to shopping, purchasing the tickets of your favorite movie-

everything is at your finger tips. Internet has great potential and lot to offer however,


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like every single innovation in science and technology, internet has its own advantagesand disadvantages.

Advantages

Communication:

The foremost target of internet has always been the communication. And internet has

excelled beyond the expectations .Still; innovations are going on to make it faster, morereliable. By the advent of computers Internet, our earth has reduced and has attained the

form of a global village.

Now we can communicate in a fraction of second with a person who is sitting in the otherpart of the world. Today for better communication, we can avail the facilities of e-mail;

we can chat for hours with our loved ones. There are plenty messenger services inoffering. With help of such services, it has become very easy to establish a kind of global

friendship where you can share your thoughts, can explore other cultures of different

ethnicity.

Information

Information is probably the biggest advantage internet is offering. The Internet is a virtualtreasure trove of information. Any kind of information on any topic under the sun is

available on the Internet. The search engines like Google, yahoo is at your service on theInternet. You can almost find any type of data on almost any kind of subject that you are

looking for. There is a huge amount of information available on the internet for just aboutevery subject known to man, ranging from government law and services, trade fairs and

conferences, market information, new ideas and technical support, the list is end less.

Students and children are among the top users who surf the Internet for research. Today,it is almost required that students should use the Internet for research for the purpose of

gathering resources. Teachers have started giving assignments that require research on

the Internet. Almost every coming day, researches on medical issues become much easier

to locate. Numerous web sites available on the net are offering loads of information for

people to research diseases and talk to doctors online at sites such as, Americas Doctor.During 1998 over 20 million people reported going online to retrieve health information.

Entertainment

Entertainment is another popular raison d'tre why many people prefer to surf the

Internet. In fact, media of internet has become quite successful in trapping multifaceted

entertainment factor. Downloading games, visiting chat rooms or just surfing the Web aresome of the uses people have discovered. There are numerous games that may be

downloaded from the Internet for free. The industry of online gaming has tasted dramatic

and phenomenal attention by game lovers. Chat rooms are popular because users canmeet new and interesting people. In fact, the Internet has been successfully used by

people to find life long partners. When people surf the Web, there are numerous thingsthat can be found. Music, hobbies, news and more can be found and shared on the

Internet.

Services

Many services are now provided on the internet such as online banking, job seeking,


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purchasing tickets for your favorite movies, guidance services on array of topicsengulfing the every aspect of life, and hotel reservations. Often these services are notavailable off-line and can cost you more.

E-CommerceEcommerce is the concept used for any type of commercial maneuvering, or business

deals that involves the transfer of information across the globe via Internet. It has become

a phenomenon associated with any kind of shopping, almost anything. You name it and

Ecommerce with its giant tentacles engulfing every single product and service will makeyou available at your door steps. It has got a real amazing and wide range of products

from household needs, technology to entertainment.

Disadvantages

Theft of Personal informationIf you use the Internet, you may be facing grave danger as your personal information

such as name, address, credit card number etc. can be accessed by other culprits to make

Your problems worse.

Spamming:

Spamming refers to sending unwanted e-mails in bulk, which provide no purpose andneedlessly obstruct the entire system. Such illegal activities can be very frustrating for

you, and so instead of just ignoring it, you should make an effort to try and stop theseactivities so that using the Internet can become that much safer.

Virus threat

Virus is nothing but a program which disrupts the normal functioning of your computersystems. Computers attached to internet are more prone to virus attacks and they can end

up into crashing your whole hard disk, causing you considerable headache.

Pornography:

This is perhaps the biggest threat related to your childrens healthy mental life. A very

serious issue concerning the Internet. There are thousands of pornographic sites on the

Internet that can be easily found and can be a detrimental factor to letting children use theInternet.

Though, internet can also create havoc, destruction

Spamming

Sometimes having an e-mail account can be very frustrating. People will fill up yourmailbox with advertisement, forwarded messages, product details, business offers, and all

sorts of unwanted junk.

Separating the messages you really want from the hundreds of unwanted mails is adaunting task. This process is called spamming, makes people hate e-mail.

INTERNET SECURITY


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Internet security involves the protection of a computer's internet account and files from

intrusion of an unknown user. Basic security measures involve protection by well

selected passwords, change of file permissions and back up of computer's data.

Security concerns are in some ways peripheral to normal business working, but serve to

highlight just how important it is that business users feel confident when using IT

systems. Security will probably always be high on the IT agenda simply because cyber

criminals know that a successful attack is very profitable. This means they will always

strive to find new ways to circumvent IT security, and users will consequently need to be

continually vigilant. Whenever decisions need to be made about how to enhance a

system, security will need to be held uppermost among its requirements.

Internet security professionals should be fluent in the four major aspects:

Penetration testing

Intrusion Detection

Incidence Response

Legal / Audit Compliance

Some apparently useful programs also contain features with hidden malicious intent.

Such programs are known as Malware, Viruses, Trojans, Worms, Spyware and Bots.

Bots are programs that take over and use the resources of a computer system over

a network \without consent, and communicate those results to others who may control

the Bots.

The above concepts overlap and they can obviously be combined. The terminology is

evolving.

Antivirus programs and Internet security programs are useful in protecting a computer or

programmable device / system from malware.

Such programs are used to detect and usually eliminate viruses. Anti-virus software can

be purchased or downloaded via the internet. Care should be taken in selecting anti-virussoftware, as some programs are not as effective as others in finding and eliminating

viruses or malware. Also, when downloading anti-virus software from the Internet, one

should be cautious as some websites say they are providing protection from viruses with

their software, but are really trying to install malware on your computer by disguising it

as something else.

Malware is the most general name for any malicious software designed for

example to infiltrate, spy on or damage a computer or other programmable device or


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system of sufficient complexity, such as a home or office computer system, network,

mobile phone, PDA, automated device or robot.

Viruses are programs which are able to replicate their structure or effect by

integrating themselves or references to themselves, etc into existing files or structureson a penetrated computer. They usually also have a malicious or humorous payload

designed to threaten or modify the actions or data of the host device or system

without consent. For example by deleting, corrupting or otherwise hiding information

from its owner.

A computer virus is a small program written to alter the way a computer operates,

without the permission or knowledge of the user. A virus executes itself. It often

places its own code in the path of executable files with a copy of the virusinfected file.

Virus can infect desktop computers and network servers alike. Some viruses are

programmed to damage the computer by damaging programs, deleting files, orreformatting the hard disk.

Viruses can be transmitted as attachments to an e-mail note or in a downloadedfile, or be present on a diskette or CD. The immediate source of the e-mail note,

downloaded file, or diskette you've received is usually unaware that it contains avirus. Some viruses wreak their effect as soon as their code is executed; other

viruses lie dormant until circumstances cause their code to be executed by thecomputer. Some viruses are benign or playful in intent and effect ("Happy

Birthday, Ludwig!") and some can be quite harmful, erasing data or causing yourhard disk to require reformatting. A virus that replicates itself by resending itself

as an e-mail attachment or as part of a network message is known as a worm.

Trojans (Trojan Horses) are programs which may pretend to do one thing, but in

reality steal information, alter it or cause other problems on a such as a computer or

programmable device / system.

Spyware includes programs that surreptitiously monitor keystrokes, or other

activity on a computer system and report that information to others without consent.w

Worms are programs which are able to replicate themselves over a (possibly

extensive) computer network, and also perform malicious acts that may ultimately

affect a whole society / economy.

Worms are programs that replicate themselves from system to system without

the use of a host file. This is in contrast to the viruses which require the spreadingof an infected host file. In a computer, a worm is a self-replicating virus that does

not alter files but resides in active memory and duplicates itself. Worms use partsof an operating system that are automatic and usually invisible to the user. It is

common for worms to be noticed only when their uncontrolled replicationconsumes system resources, slowing or halting other tasks.


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In computing the system software, hardware and information is always under threat ofeither being altered, destroyed, accessed illegally and stolen. These threats can be caused

by errors and by accidents, natural hazards, and crimes against information technology

crime using information technology or worms and viruses. Due to these threats there is a

great need to protect the computer system and its resources.

Measures and controls that ensure confidentiality, integrity, and availability of theinformation processed and stored by a computer.

PRIVATE KEY CRYPTOGRAPHY

In private key cryptography the same key is used by both parties. The sender uses this

key and an encryption algorithm to encrypt data; the receiver uses the same key and thecorresponding encryption algorithm to decrypt the data.

In symmetric-key cryptography, the algorithm used for decryption is the inverse ofthe algorithm used for encryption. This means that if the encryption algorithm uses a

combination of additions and multiplication, the decryption algorithm uses a combinationof division and subtraction.

Symmetric-key algorithms are efficient; it takes less time to encrypt a message using a

symmetric-key algorithm than it takes to encrypt using a public- key algorithm. The

reason is that the key is usually smaller. For this reason symmetric-key algorithms are

used to encrypt and decrypt long messages.

Symmetric algorithms has two major disadvantages. Each pair of users must have aunique symmetric key. This means that if N people in the world want to use this method,

there needs to be N (N-1)/2 symmetric keys. For example, for 1 million people to

communicate, 500 billion symmetric keys are needed. The distribution of the keysbetween two parties can be difficult

PUBLIC-KEY CRYPTOGRAPHY

In public-key cryptography, there are two keys: a private key and a public key. Theprivate key is kept by the receiver. The public key is announced to the public.

In public-key encryption/decryption, the public key that is used for encryption is

different from the private key that is used for decryption. The public key is available tothe public; the private key is available only to an individual.

Public key encryption/decryption has two advantages. First it removes the restriction

of a shared symmetric key between two entities (eg persons ) who need to communicatewith each other. A shared symmetric key is shared by the two parties and cannot be usedwhen one of them wants to communicate with a third party. In public-key

encryption/decryption, each entity creates a pair of keys; the private one is kept, and thepublic one is distributed. Each entity is independent, and the pair of keys created can be

used to communicate with any other entity. The second advantage is that the number of

keys needed is reduced tremendously. In this system, for 1 million users to communicate,

only two million keys are needed, not 500 billion, as was the case in symmetric-key

cryptography.

Public-key cryptography also has two disadvantages. The big disadvantage is the

complexity of the algorithm. If we want the method to be effective, the algorithms needs


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large numbers. Calculating the cipher text from plain text using the long keys takes a lotof time. That is the main reason that public-key cryptography is not recommended forlarge amounts of text.

Security can be enforced through:

Access control

Before using the computer resources a user can be required to use his or her credit card,debit card or ATM card. These cards are used for identification purposes. The users can

also be given unique identification characters like pin, password or digital signatures.

Biometrics can also be used for identification purposes. This is where the characteristics

of an individual like fingerprints and voice are used.

Data encryptionThis is where data is altered before storage or sending via the internet. In this state it

cannot be used until it is changed in to a form that can be read and understood.

Use of firewallsThis is a system of both hardware and software that blocks unauthorized users and

outside the organization from entering the intranet. The firewall all internets and othernetwork activity, a firewall identifies unauthorized users, searches for viruses and

implements other security measures.Is a combination of hardware and software that enforces a boundary between two or more

networks for example between a corporate network and the internet to which it isconnected.

A firewall protects networks from unwanted traffic. The primary goal of a firewall is tolet good traffic pass though which bad traffic gets blocked. The most important part of a

firewalls its access control features that distinguish between goal and bad traffic. ItProvides a single point of entry and exist from the network to another.

PROXIY SERVER

A proxy server is a form of application server that works differently from firewall. Proxy

Service change the network addresses of the nodes on the other network.For example in the internet would not know that other node exits behind the proxy server

nor the addresses of those nodes.

Audit control

This is a program which keeps a record of what computers are used, and the files that

are opened and who uses them. This creates a record of how transaction was carried outfrom the input to the output stage. The record is also known as audit trail.

Recovery strategiesWhen the computer crashes or resources are lost suddenly special software can be used

to recover the lost resources.

BackupAll programs and data in the computer should also be backed up. This where copies of

others are also stored in a secondary device.


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HACKERIs a person who gains unauthorized access to computers or telecommunications

systems, for a reason only known to themselves. It is a threat to organizations information

is always punishable by law.

CRACKERS

Is a person who illegally breaks into computers for malicious purposes. It can be for

financial gain, to shutdown hardware, pirate software or to destroy or alter data. It is alsopunishable by law.

ELECTRONIC MAIL

Finding an E-mail AddressHow do you go about finding someones e-mail address? You can find a person only if he

has taken the pains to register his details.

Although there is no comprehensive directory of e-mail or Internet addresses, there areseveral search and reference tools you can consult. Some of them are:-Lookup! Directory services (http://www.lookup.com)

Netfind (http://www.nova.edu)netPages (www.aldea.com)

etc

Free E-mail AccountsYou can have your personal e-mail account free of cost. All you need to access your

mailbox is an Internet connection.There are many companies, which offer this service, absolutely free. All you have to do is

register, choose an e-mail ID and give a password.Some of these sites, which offer this service, are:-

Microsoft Hotmail (http//://www.hotmail.com)

MailCity (http://www.mailcity.com)

Yahoo! Mail (http://www.mail.yahoo.com)

MAILING LISTSElectronic mail is far more flexible and powerful than you might at first imagine.

E-mail can be used to run a program in a remote computer and have the results sent back

to you.

E-mail also offers a great way to stay in touch with special interest groups. A mailing list

is a way to share information via electronic mail with many people, usually on a specifictopic or for a special purpose.People choose to be part of mailing list by subscribing to the list. Once you have joined

the list (or subscribing to the list), you will receive regular information by e-mail aboutthe subject that particular list is concerned with.

Mailing lists provide a way of keeping up with the developments and happenings in aparticular field of interest with minimum effort and cost.

How Does Mailing List Work?

This is how a mailing list works;A message is sent to a single e-mail address, which is referred to as the mailing list

address.


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This same message is then redistributed or reflected to all of the people subscribed tothe list.

The single, central e-mail address for the list is also referred to as a mail reflector.

Mailing lists originated on a network called BITNET. BITNET was created to connect

universities in the united states.

NEWSGROUPSNewsgroups on the internet have little to do with news, but everything to do with

discussion and debate.

Newsgroups are essentially public e-mail discussion forums where participants post

their messages to be seen by all readers of the newsgroup.Anyone reading the message can chose to reply either publicly (to the newsgroup) or

privately (to the originator of the message).Newsgroups provide a forum for interested people to discuss topics of common interest.

Mailing Lists vs NewsgroupsBoth mailing lists and newsgroups offer a forum of discussion on the Internet, but theyoperate in different ways.

Mailing lists relay the messages to your e-mail address. So you need to subscribe to themto read the messages.

But messages posted on a newsgroup could be viewed by anyone as long as the serviceprovides supplies the newsgroup.

Newsgroups Classifications:news-Groups concerned with news network.

comp-Computer oriented groups dealing with topic like technical advice, game hints,software information etc.

alt-alternative group dealing with a wide range of subjectsmisic-newsgroups that are difficult to classify.

biz-business newsgroups dealing with business subjects like marketing & advertising.

sci-groups devoted to scientific debate and research and development

Businesses must do their research and find out what people want, or figure out how tomake people want a product they are producing.

This needs to capture and record information about what people want has led to many IT-

based databases and data warehouses of which businesses are now boasting.

Types of discussion lists:

Moderated vs. Unmoderated Lists

Mailing lists can be moderated or unmoderated. The distinction is whether messages are

automatically forwarded to all subscribers (unmoderated) or whether a moderator (ahuman being) first screens and perhaps combines similar messages before sending them

to subscribers (moderated).

Open vs. Closed Lists

Electronic discussions can also be "open" or "closed." Anyone can subscribe to an open

discussion, but a closed discussion is limited to a particular group of persons, forexample, those in a particular professional field.


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Introduction to network news:Network News (sometimes referred to as Usenet News) is a service comprised of severalthousand electronic discussions providing users an effective way to share information

with others on just about any topic.

If you're unclear about the concept of Network News, it's helpful to think about a bulletin

board that you might see on campus.

Here, one might find posted messages advertising a futon for sale, asking for students to

join a math study group. In the newsgroup environment, the same kind of process take

place:

User X may access a newsgroup on a particular topic and post a message, question, orrespond to a previously posted message, and anyone accessing that newsgroup would

then be able to see User X's message.

Network News newsgroups provide this same kind of forum online, where users have

access to the messages posted by all other users of that newsgroup.Network News has been described as an "international meeting place" where you're likelyto find a discussion going on just about anything.

How Does Network News work?Messages posted on Network News newsgroups are sent from host computer to host

computer all over the world, using the network news transfer protocol.Because Network News newsgroups are located on one server, Network News is a very

efficient way to share information that might otherwise be disseminated to severalindividual users.

This way, several people can read a given newsgroup message, but the host system storesonly one copy of it.

E-MAIL ETHICSe-mail messages are a lot like letters. Simplicity, directness, and brevity will make people

read your messages. Our e-mails says a lot about our values, our attention to detail, and

the reputation of the organization we represent. Like any form of communication there

are certain manners that you should follow when using the e-mail. Here are someguidelines, which will help you in getting the most out of your electronic mailing system.

Let your messages have a personal touch. Write it the way you would say it. Useeveryday language. Vary your sentence length.

Be friendly, use humor to break up the tension of what you have to say.

Be succinct and considerate of the recipients time and online charges, especiallywith services that charge by the hour or by the size of the messages. E-mail

messages work best if they are short and to the point.

Know your recipient. Different people have different ideas of what is acceptable.

Find out and respect each persons wishes.

Avoid sarcasm, unless youre sure it will work, and think carefully before using e-mail to express anger. With e-mail, once its sent, its gone.

.Be careful about your use of irony or even some forms of humor, which can bemisinterpreted. Unlike face-to-face meetings or phone conversations, there are no

visual or oral clues to provide a sense of what is going on.

Be brief. This not only saves bandwidth but also cuts down on eyestrain.

Make the subject line precise.


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Dont copy the full text of along message into your response. Copy only parts youneed to refer to.

Dont assume that everyone likes emoticons (emotional icons). Some people findthem annoying.

Look sharp. Good writing is 90% clarity, and half of clarity is appearance. No onelikes facing a long unbroken block of text characters. Put a blank line betweenparagraphs to help you organize your thinking.

Use your technology. A memory-resident spellchecker or thesaurus will help youavoid the embarrassment of a misspelled word or a word used incorrectly.

Compose your messages off-line. A regular word processor is much morepowerful than the text editors used on most e-mail systems.

Read the message before sending it, like your title and company name or other e-

mail addresses you have crept in.

Most e-mail programs these days let you insert whats called a signature at the

bottom of the message. This can be anything from a clever quote to some

additional information about you, like your title and company name or other e-mail addresses you have.

Configure your e-mail client to check all your accounts in one shot.

If security is not a concern, configure your e-mail client to remember passwords.

Get a free-mail account for personal e-mail or mailing lists.

If you are sending large files as attachments, use some compression utility likepkzip, WinRAR, before sending them.

Dont send copies of e-mail to people unless they need to be copied. In addition tocluttering up their mailboxes, it can place them in an awkward position, makingthem feel as if they have to do something with the information. It can also be

intimidating to the main recipient.

Stay on the topic if you are posting to a public bulletin board, forum or newsgroup. Most are focused on a specific topic, and messages that stray too far from

the topic can be annoying.

Briefly describe who you are if the recipient doesnt already know.

Be aware that e-mail can be archived and, under certain circumstances, may not

be secure. On-line services and public e-mail providers protect the confidentialityof their subscribers e-mail, but some companies consider employee e-mail sent

over the office network to be company property and subject to security.

Avid Urgent or Priority unless it really is.

Avoid using all capital letters. ITS THE EQUIVALENT OF SHOUTING! Also,it is harder to read.

You should check your mail regularly. Unlike a fax or normal mail, an e-mailmessage in the most cases is not automatically delivered to your desk. You have

to log on to check your mail.

INTERNET CODE OF CONDUCTThe Internet relies on the cooperation of its constituents- users with users, service

providers with other service providers, and users and service providers with one another.The following guidelines for conduct were developed from an Internet Society (ISOC)

document available at http://www.isoc.org.


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Mailing Lists, Newsgroups and Bulletin Boardsv Post within the forums scope/topic.

v Avoid redundant, empty, or stupid postings.

v Respect the opinions of other participants.

v Be careful about the lack of social cues and possible ambiguities in text

communications.

v Use common courtesy when posting critical, negative comments (avoid flaming).v Be sensitive to the forums standards in respect to obscenity.

v Do not use expressions that are considered sexually harassing, racial, or in some

way discriminatory.

Advertising

v Do not post to lists or boards or newsgroups whose purpose states no advertising.Use browsing services such as WAIS, Gopher and WWW to list products and services.

v Use e-mail enabled information services like mailing lists to which users can

subscribe or send email to obtain information.Privacy

v Do not invade the personal privacy of others.

v Do not forward e-mail without permission.v Do not deliberately break into computer systems.

Securityv Systems break-ins or aiding others to break into systems is illegal.

v Getting passwords or other access information fraudulently is unacceptableIntellectual Property

v Copying or making available copies of protected works without the authorspermission is illegal.

HOW WEB BROWSERS AFFECT YOUR WORKHypertext Markup Language (HTML) is an authoring language used to create documents

on the World Wide Web.

The Beginnings of HTMLThe World Wide Web (www) grew out of experiments that were carried out at the CERN

laboratories in Switzerland. Tim Berners Lee, along with a team of developers, took time

out to investigate and build a way of transmitting information in a way, in a format that

became known as Hypertext transport Protocol, or just HTTP.

Using a markup language designed for simplicity and with a flexible structure, HypertextMarkup Language (HTML), allowed text and graphics to be displayed in web browser or

other suitably enabled application. Certain parts of the document could become

hyperlinks, which when clicked caused a different page or a different section of the pageto be displayed.

A markup language is simply a series of elements, each delimited with special characters,that define how text or other items enclosed within the elements should be displayed e.g

this is some emphasized text.HTML is a markup language broadly based on the standard Generalized Markup

Language (SGML). SGML is a way of describing languages, and is not itself a languageused to create pages.


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From these simple beginnings, extra feature were added to build version 4.0 of HTMLthat we use today. These extra features provided for more flexible text styling (such asthe element), and more control over the final layout of the page (such as the use

of tables and frames).

As far as serving up these pages of information, text files and graphics can be delivered

to the user by a web server application, which simply reads them from the disk and

converts the output to the correct HTTP protocol for transmission across the network. At

the client user end, the browser takes the incoming stream and converts it into a page thatcan be displayed.

The great strength of HTML and HTTP, besides university, is that the document can

contain information about the meaning of the content, and the way that writer intended it

to be perceived. It can be read by applications that dont actually display visually: e.g,blind people can use special application that converts it into speech.

HYPERTEXT & HYPERMEDIA

The basic concept of the World Wide Web, and the most revolutionary idea envisioned

by Berner-Lee, is the use of hypertext to link information on related topics over theInternet.

Hypertext is a non-linear way of organizing information on related topics over theInternet. When using Hypertext system, you can jump from one related topic to another,

quickly find information that interests you, and return to your starting point or move ontoanother related topic of interest.

On the web clickable hyperlinks, which can be either text or images, can connect you toanother web page or allow you to download a file, such as a sound, image, movie or

executable file. Therefore hypermedia is the linking of different types of media on theWorld Wide Web.

HTML AS A MARKUP LANGUAGEA markup language is a structured language that lets you identify common sections of a

document such as headings, paragraphs, and lists. An HTML file includes text and

HTML markup elements that identity these sections.

Browser ChaosAs different browsers tried to attract market share, a set of proprietary HTML elements

evolved that centered around the use of each particular browser. E.g. and

elements, which specifically developed for Netscape browser.

Adding to this confusing compatibility issue are the elements that are strictly proprietary,

such as (Internet Explorer only) which creates scrolling text and for (Netscape Navigator), which makes text to blink on and off. These

elements work only within the browser for which they were designed and are ignored by

other browsers.

XML: AN OPEN STANDARD FOR STRUCTRING

XML is a subset of SGML. Unlike HTML, XML is a meta-language, not a languageitself, but a language that lets you describe other languages.

As a meta-language, XML allows you to create your own elements to meet yourinformation needs, which significantly distinguishes it from the predefined elements of


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HTML. XML provides a format of describing structured data that can be shared bymultiple applications across multiple platforms.

XML Describes DataThe power of data representation in XML comes from separating display and style from

the structure of data and structure only and not presentation. Where HTML contains

elements that describe a word as bold or italic, XML declares an element to be a book

t