Internet Fundamental notes

8/18/2019 Internet Fundamental notes

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World Institute Of Technology

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CSE-208 F Internet FundamentalsClass Work: 50

.NOTE: For setting up the question paper, question no 1 will be set up from all the four

sections which will be compulsory and of short answer type. Two questions will be set from

each of the four sections. The students have to attempt first common question, which is

compulsory, and one question from each of the four sections. Thus students will have to

attempt 5 questions out of 9 questions.

Section A: Electronic Mail and Internet:

Introduction, advantages and disadvantages, Userids, Pass words, e-mail addresses, messagecomponents, message composition, mailer features, E-mail inner workings, E-mail management,Mime types, Newsgroups, mailing lists, chat rooms. Introduction to networks and internet,

history, Working of Internet, Internet Congestion, internet culture, business culture on internet.Collaborative computing & the internet. Modes of Connecting to Internet, Internet ServiceProviders(ISPs), Internet address, standard address, domain name, DNS, IP.v6.Modems and timecontinuum, communications software; internet tools.

Section B: World Wide Web :Introduction, Miscellaneous Web Browser details, searching the www: Directories searchengines and meta search engines, search fundamentals, search strategies, working of the searchengines, Telnet and FTP. Introduction to Browser, Coast-to-coast surfing, hypertext markuplanguage, Web page installation, Web page setup, Basics of HTML & formatting and hyperlinkcreation. Using FrontPage Express, Plug-ins.

Section C: Languages:Basic and advanced HTML, java script language, Client and Server Side Programming in javascript. Forms and data in java script, XML basics. Introduction to Web Servers: PWS, IIS,Apache; Microsoft Personal Web Server. Accessing & using these servers.

Section D: Privacy and security topics:Introduction, Software Complexity, Encryption schemes, Secure Web document, DigitalSignatures, Firewalls.

Text Book:

Fundamentals of the Internet and the World Wide Web, Raymond Greenlaw and EllenHepp – 2001, TMH Internet & World Wide Programming, Deitel,Deitel & Nieto, 2000, Pearson Education


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Reference Books:

Complete idiots guide to java script,. Aron Weiss, QUE, 1997 Network firewalls, Kironjeet syan -New Rider Pub. www.secinf.com www.hackers.com Alfred Glkossbrenner-Internet 101 Computing MGH, 1996

Section A: Electronic Mail and Internet

Email

Electronic mail (also known as email or e-mail) is one of the most commonly used serviceson the Internet, allowing people to send messages to one or more recipients. Email was inventedby Ray Tomlinson in 1972.

It is a system used for creating, sending and storing textual data in digital form over anetwork. Earlier, the e-mail system was based on Simple Mail Transfer Protocol (SMTP)mechanism, a protocol used for sending e-mails from one server to another. Today's e-mailtechnology uses the store-and-forward model. In this model, the user sends and receivesinformation on their own computer terminal. However, the computer is used only for connectingto the e-mail architecture. The creation, transmission and storage of e-mail takes place, onlywhen the connection with this e-mail architecture is established.

E-mail is one of the many technological developments that have influenced our lives. It haschanged the medium of communication. So, it becomes necessary for us to have a look at thebenefits and harmful effects of this popular mailing tool.

General Description of Electronic Mail

Electronic mail, email, is a computer based method of sending messages from one computeruser to another. These messages usually consist of individual pieces of text which you can sendto another computer user even if the other user is not logged in (i.e. using the computer) at thetime you send your message. The message can then be read at a later time. This procedure isanalogous to sending and receiving a letter.

Originally, email messages were restricted to simple text, but now many systems canhandle more complicated formats, such as graphics and word processed documents.When mail is received on a computer system, it is usually stored in an electronic mailbox for therecipient to read later. Electronic mailboxes are usually special files on a computer which can beaccessed using various commands. Each user normally has their individual mailbox.


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It is straightforward to send electronic mail between users of different computer systems which are

connected to major networks. Most major academic and research institutions and companies

throughout the world can now be reached by electronic mail. In addition, a growing number of

individuals can be contacted in this way. In the UK, most academic and research institutions are linkedby a network called JANET (or SuperJANET). This is effectively part of the Internet, so emailcan be exchanged with most national and international networks.

Email Facilities All email systems have the ability to send, receive and discard mail. Most systems have

facilities for storing mail which is to be kept rather than discarded. It is important to discard mailwhich does not need to be kept, as it uses storage space on disks. Mailboxes can soon accumulatea large number of mail messages making it difficult to read and process new mail, in addition towasting disk space.

There is almost always a connection between the email system and the computer's standard

file system which allows mail to be read from files or written to files. This enables greaterflexibility in how the mail system is used. For example, a mail message may be prepared in anormal file using a familiar text editor and then sent by the email system. Sections of other filesmay be included in the mail message as well.

Most systems have a reply facility, although some of these do not always work as expected.Care should be taken when using this facility in electronic mail, as replies do not always go backto the sender.

Advantages of Email

The benefits of e-mail are huge in number.

Easy to use: E-mail frees us from the tedious task of managing data for daily use. It helps usmanage our contacts, send mails quickly, maintain our mail history, store the requiredinformation, etc.Speed: An e-mail is delivered instantly and anywhere across the globe. No other service matchesthe e-mail in terms of speed.Easy to prioritize: Because e-mails come with a subject line, it is easy to prioritize them andignore the unwanted ones.Reliable and secure: Constant efforts are being taken to improve the security in electronicmails. It makes e-mail one of the secured ways of communication.Informal and conversational: The language used in e-mails is generally simple and thus, makesthe process of communication informal. Sending and receiving e-mails takes less time, so it can

be used as a tool for interaction.Easier for reference: When a person needs to reply to a mail, he/she can use the provision ofattaching previous mails as references. It helps refresh the recipient's know-how on what he isreading.


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Automated e-mails: It is possible to send automated e-mails using special programslike autoresponders. The autoresponders reply only to those messages with generalized, pre-written text messages.Environment friendly: Postal mails use paper as a medium to send letters. Electronic mailtherefore, prevents a large number of trees from getting axed. It also saves the fuel needed fortransportation.Use of graphics: Colorful greeting cards and interesting pictures can be sent through e-mails.This adds value to the e-mail service. Advertising tool: Nowadays, many individuals and companies are using the e-mail service toadvertise their products, services, etc.Info at your fingertips: Storing data online means less large, space taking file cabinets, foldersand shelves. You can access information far quicker if you learn how to use email this way.Leverage: Send the same message to any number of people. Adaptations are simple, too. If youhave a product or service to sell, email is an effective medium to get your message out.

Send reminders to yourself. Do you use more than one account? Email yourself messages fromwork to home or vice versa.

Disadvantages of Email

The e-mail service, though beneficial in our day-to-day life, has got its own drawbacks that areoff late coming to the fore.

Viruses: These are computer programs which have the potential to harm a computer system.These programs copy themselves and further infect the computer. The recipient needs to scan themails since; viruses are transmitted through them and have the potential to harm computersystems.

Spam: E-mails when used to send unsolicited messages and unwanted advertisements createnuisance and are termed as Spam. Checking and deleting these unwanted mails can unnecessarilyconsume a lot of time. It has therefore, become necessary to block or filter unwanted e-mails bymeans of spam filters. Spamming is practiced by sending hoax e-mails. E-mail spoofing isanother common practice, used for spamming. The act of spoofing involves deceiving therecipient by altering e-mail headers or addresses from which the mail is sent.Hacking: The act of breaking into computer security is termed as hacking. In this form ofsecurity breach, e-mails are intercepted by hackers. An e-mail before being delivered to therecipient, "bounces" between servers located in different parts of the world; hence, it can behacked by a professional hacker.Misinterpretation: One has to be careful while posting content through an e-mail. If typed in a

hurry, the matter could be misinterpreted.Lengthy mails: If the mail is too long and not properly presented, the reader may lose interest inreading it.


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Not suitable for business: Since the content posted via e-mails is considered informal, there is achance of business documents going unnoticed. Thus, urgent transactions and especially thoserequiring signatures are not managed through e-mails.Crowded inbox: Over a period of time, the e-mail inbox may get crowded with mails. Itbecomes difficult for users to manage such a huge chunk of mails.Need to check the inbox regularly: In order to stay updated, one has to check his e-mailaccount regularly.Lacks the personal touch: Some things are best left untyped. Email will never beat a handwritten card or letter when it comes to relationships.

Every new technology enters the social world with its share of benefits and drawbacks.Different people interpret and utilize it in different ways. In order to make the most of theavailable technology, users should try to understand both, the positive and negative sides of thetool they use. No technology can be deemed totally perfect!

How email works (MTA, MDA, MUA)

Email, as simple as it is to use, relies on a more complicated set of operating proceduresthan that of the Web. For most users, its operation is transparent, which means that it is notnecessary to understand how email works in order to be able to use it.

However, the short introduction below has been provided to help users understand its basicprinciples, give them an idea of how to best configure their email clients and inform them aboutthe underlying mechanisms of spam.

Email is based around the use of electronic mailboxes. When an email is sent, the messageis routed from server to server, all the way to the recipient's email server. More precisely, themessage is sent to the mail server tasked with transporting emails (called the MTA, for Mail

Transport Agent ) to the recipient's MTA. On the Internet, MTAs communicate with one anotherusing the protocol SMTP, and so are logically called SMTP servers (or sometimes outgoingmail servers).

The recipient's MTA then delivers the email to the incoming mail server (called the MDA,for Mail Delivery Agent ), which stores the email as it waits for the user to accept it. There aretwo main protocols used for retrieving email on an MDA:

POP3 (Post Office Protocol), the older of the two, which is used for retrieving email and, incertain cases, leaving a copy of it on the server.

IMAP ( Internet Message Access Protocol), which is used for coordinating the status ofemails (read, deleted, moved) across multiple email clients. With IMAP, a copy of everymessage is saved on the server, so that this synchronization task can be completed.

For this reason, incoming mail servers are called POP servers or IMAP servers,depending on which protocol is used.


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To use a real-world analogy, MTAs act as the post office (the sorting area and mail carrier,which handle message transportation), while MDAs act as mailboxes, which store messages (asmuch as their volume will allow) until the recipients check the box. This means that it is notnecessary for recipients to be connected in order for them to be sent email.

To keep everyone from checking other users' emails, MDA is protected by a user namecalled a login and by a password.

Retrieving mail is done using a software program called an MUA ( Mail User Agent ). Whenthe MUA is a program installed on the user's system, it is called an email client (such as MozillaThunderbird, Microsoft Outlook, Eudora Mail, or Lotus Notes). When it is a web interface usedfor interacting with the incoming mail server, it is called webmail.

Using email

An email client, a software program for writing, checking and sending email, is generallymade up of a number of windows. The main windows of this software are:• Incoming, In, Inbox: This represents the main mailbox for receiving email,

• Sent, Outbox, Out: These are copies of messages that you have sent.• Deleted, Trash: The trash bin containing deleted emails. When emails are shown in thetrash, you can still retrieve them. To permanently delete them, you will need empty the trashbin.

• Folders: Most clients can be used to file emails in folders, much like folders on a hard drive.

Email fields

Here are the meanings of the fields to be filled in when you send an email:

• From: this is your email address; most of the time you will not have to fill in this field,because it is generally set by the email client according to your preferences.

• To: This field is used for the recipient's email address.• Subject: this is the title that your recipients will see when they want to read the email• Cc (carbon copy): this allows an email to be send to a large number of people by writing their

respective addresses separated by commas


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• Bcc (blind carbon copy): This is a Cc, except that the recipient does not see the list of peoplein the Bcc field

• Message: This is the body of your message

The Carbon Copy function sends a copy to people not directly involved with the messagebut whom you wish to keep up to date with the message contents or show that you sent the emailto the recipient(s).

The Blind Carbon Copy function makes it possible to forward messages without any of therecipients or even the hidden recipients seeing that the message is being forwarded to them. It isgenerally recommended when sending an email to many people to forward it using Blind copy soas to prevent one of the recipients from replying to everyone or assembling a list of addresses.

Other email functions are:• Attached Files, Attachments: A file can be attached to an email by specifying its location on

the hard drive.• Signature: If the email client allows it, you are often able to set a signature, meaning a few

lines of text which will be added to the end of the document.

Userid and PasswordA computer system uses userids and passwords together to grant access to the system. You

need the correct combination of userid and password, to access your account.

Userid

The userid identifies you to the computer. Userids are typically some form of your name. (Your

last name, for example). A userid must be unique throughout the computer system. This allowsthe computer to distinguish between you and some other person. One confusing issue is thatdifferent systems refer to a userid (the thing that identifies you to the computer) with differentnames. Some that you may run across are:Login IDUsernameUseridBut, they all refer to that special name that identifies you to that particular computer system.

Your userid is also used for communication with other people through electronic mail.Since the userid identifies you to the computer, it is natural for it to be used to identify you toother computer systems. For example: The person Joe B. User could have this userid, "jbu3470".

The userid is made up of the person's initials and the digits of some personal identificationnumber.

Password


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To prevent other people from using your account via your userid, you are required to havea password. A password allows you and only you to access the computer system through youruserid. It basically proves to the computer system that you are who you say you are. So it should

be obvious that you DO NOT GIVE YOUR PASSWORD TO ANYONE!!!

User ID and Password Rules

Please review the User ID and Password guidelines below before selecting a User ID or selectingor changing your Password.

User ID: User IDs must be 7-14 charactersUser IDs must contain at least one letter; numbers are allowed, but not requiredUser IDs cannot contain spacesUser IDs cannot contain your Social Security Number, Tax Identification Number, or Customer

Access NumberNo special characters are allowed, such as: ! @ # $ % ^ &Use of an underscore is allowed but not required: _Do not use your Password as your User ID

Password: Passwords must be 7-14 charactersPasswords must include at least one letter and one numberPasswords cannot contain spacesSemicolons cannot be part of a PasswordPasswords are case-sensitive

Do not use your User ID as your PasswordIf you forget your User ID or Password, you can retrieve them through the "User ID & PasswordHelp" link.

Note: You cannot change your User ID once it is established.

What to do with a message

There are many operations that can be performed on emails:• New, Compose, Write: Write a new message• Erase, Delete, Remove: Erase a message• Store, Save, Backup, Drafts: Copy a message into a safer place

• Print: Print a message• Reply: Send a reply message to the sender (sometimes including their own message in the

body of the document, with each line proceeded by the symbol ">" and "Re:" followed by


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their chosen subject as the title, to show that it is a reply. The Reply All button makes itpossible to send a reply to the sender as well as everyone else who had been put as a recipientor on copy.

• Forward: Forwards the message to someone else, letting them know that the message comesfrom you. The subject is generally preceded by Fwd: to indicate that it is a forwardedmessage.

• Redirect, Transmit: Forward a message to someone, letting them know where it originallycame from. The subject is generally preceded by Fwd: to indicate that it is a forwardedmessage.

Email addressesElectronic mail must be addressed properly, in much the same way as a normal letter needs

to be addressed, in order that it can reach its intended recipient. However, with electronic mailthe addressing has to be slightly different and must be more precise than a conventional mailaddress.

Most email uses is addressed using internet addresses. These are supported by what isknown as the Domain Name Server (DNS). This is an internationally distributed naming schemeand the components of each address are structured in a hierarchical manner. These start with themailname of the person, followed by various address components, ending with the "Top level"domain (often a country code). In this respect, the addressing is in the same order as that of aconventional letter.

Email addresses (both for senders and recipients) are two strings separated by the character"@" (the "at sign"): user@domain

The right-hand part describes the domain name involved, and the left-hand part refers to theuser who belongs to that domain. One or more mail servers correspond to each domain.An email address can be up to 255 characters long and can include the following characters:• Lowercase letters from a to z;• Digits• The characters ".","_" and "-" (full stop, underscore, and hyphen)In practice, an email address often looks something like this:[email protected]

For [email protected]

The mailname comes first, indicating who the email is for. The "@" sign separates themailname from the site. The next components indicate details of the system to which the email is

sent.bham = Birminghamac = academic


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uk = Great BritainThe final component ("top level" domain) is normally the ISO3166 standard two letter

country code. There are, however, two main types of exception. One is Great Britain (gb) which

uses "uk". The other exceptions are mainly some of American domains (eg edu, mil, gov). Theseare at the same "level" in the naming scheme as countries.

Addresses of this form are also known as rfc822 addresses, because that is the name of theInternet standard in which the addresses were originally described.

Partially qualified addresses Some systems will allow the address to be specified in an incomplete form. For example,

[email protected] be expressed asE.V.Nebor@bham

This is known as a partially qualified address. The use of these names is NOT

RECOMMENDED, as they are not universally recognized and are a cause of many errors andmuch confusion. The full address should always be used.

Message Components

Header

The header of an e-mail address is where all the important addressing information is kept,along with data about the message itself. The following table describes the elements that makeup the header of an e-mail.

To The TO Field is where the email address of the messages recipient is entered.

Subject The subject is essentially a title, or a very short summary, of an e-mail. Ideally itshould contain some sort of reference to the emails content

CC

BCC

To Carbon Copy (CC) a message to someone is to send them a copy of the e-mail,even though they are not the e-mail’s intended recipient. This is a common practice inbusiness communications, where many people in an organization often need to bemade aware of certain communications, even if they are not actively involved in theconversation.BCC stands for Blind Carbon Copy. Any people included in the BCC recipient listof an e-mail receive a copy of the message, but their name is not included in themessage headers, and no one else who received the message knows that they were senta copy.


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Body

The body of the message is, of course, the most important part. Everything you need to say

is entered here, and this is what the recipient will be reading.

Message CompositionSteps are:

• Launching your e-mail program is usually as simple as clicking on the e-mail icon onyour desktop. Once the program is open, write a message by clicking on the ComposeMail, New Message or similar button.

• In the new message window, type the e-mail addresses of the recipients in the To field,or use the Address book to select one or more of the addresses.

• In the CC field, enter the address of anyone you want to receive a copy of the message.Type the e-mail address or choose it from the address book.

• Type the subject of the message.• Now type your message.• Finally, click on the Send button.

Mailer FeaturesMost mailers provide common features which provide functionality for manipulating your

mail box contents, composing messages and saving messages to the disk. The features are:

Compose, File and Reply

A Compose button provides following features :


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• New – Compose a message from scratch.• Reply – Reply to the current message.• Forward – Pass the message on.• Vacation – You are going away and want automatic responses to be generated, and have

email saved.A File button has the following functionality:

• Save – Save the current message into a file on disk.• Insert – Include a file in the body of the message being composed.• Exit – Leave the mailer.• Open – Open a file from the disk.• Attach – Append a file to a message.

A Reply button consists of following items:• To sender.• To all• Forward• Include• Include bracketed.

E-mail Inner Working If we split the mailing of a letter into three phases:

• In phase one, the steps needed to perform are compose, address, package, stamp anddeposit the letter in a suitable place for pick up.

• In phase two, a mail person, on a fixed schedule, retrieves the letter from its place ofdeposit. Then the letter, if correctly addressed and with the proper postage, is routed to itsfinal destination mailbox.

• In phase three, the recipient check for mail, retrieves the letter from the mailbox, opensthe envelope, reads the mail, and perhaps files it away.

Similar phases need to be carried out in the electronic setting:• Mailer, Mail Server, and Mailbox – Three mail components are necessary for the email

system to work.• Mailers A mailer is also called a mail program, mail application, or mail client. A mailer

is the software that allows you to manage, read, and compose email.• Mail Servers The mail server is a computer whose function is to receive, store and deliver

email.• Mailboxes An electronic mailbox is a disk file specifically formatted to hold email

messages and information about them,.There are several different ways in which users typically obtain their emails.• Store and Forward Features


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• Central Mail Spool and IMAP• Bounce Feature

E-mail ManagementEmail is now the de facto standard for business communication across organizations at this

time. Recent research shows the extensive use of emails in business and its projected growth inthe future presents major information management challenges and risks for many organizations.Just as any type of business information and record, email must be included as part of, andadhered to the organizational standards addressing information and records:

• Capture• Classification• Storage• Preservation• Management• Destruction

The vast quantities of emails held in inboxes, sent folders, and deleted item folders put theorganization at risk and adversely impact the performance of email servers in the organizations.Email servers were never designed to act as repositories for such great quantities of emails andmove control of this information away from the organization. Without the management ofemails, it is difficult for organizations to meet their legal preservation requirements in the eventof litigation and government investigations, increasing the effort and cost in responding to e-discovery and disclosure.

Email management systems centrally capture emails created and received by employees.Using a classification scheme to manage this content, retention periods and access controls canbe applied to manage emails. Metadata associated with the emails can be captured to allow thisinformation to be managed and retrieved. Email active archiving is one of the most commonapplications for email management. At their most basic, these solutions either copy or removemessages from the messaging application and some it at another location. Some approaches copyall messages coming into and out of the messaging application in real time, while others willphysically remove the messages from the message store. In some of these solutions, themessages are not archived, but attachments are and are replaced with either a stub or an outrightlink within the message.

These email management systems, while attractive and effective, are merely part of anoverall solution. Organizations need to have records management programs, consisting oforganization-wide policies and procedures, staff and activities, in which these computerapplications can be successfully utilized.

Here are four simple email management rules to help you keep control of your inbox:• Let your email program manage your email as much as possible.


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Email management starts with setting up and using filters. If you're using an email programsuch as Outlook, you can configure email rules to send your spam directly to the trash -meaning that you don't waste your time reading and deleting it.

• Do not check your email on demand.

You don't need to see every piece of email the second it arrives. If you're using an emailprogram that announces the arrival of new email, turn off the program's announcementfeatures, such as making a sound or having a pop-up screen announce the arrival of email.Checking email on demand can seriously interfere with whatever other tasks you're trying toaccomplish because most people will read email when they check it.

• Don't read and answer your email all day long.

You may get anywhere from a handful to hundreds of emails each day that need to beanswered, but they don't need to be answered immediately, interrupting whatever else you'redoing. Instead, set aside a particular time each day to review and answer your email.Schedule the hour or whatever time it takes you to answer the volume of email you get, and

stick to that schedule as regularly as possible.• Don't answer your email at your most productive time of day.

For me, (and for many others, I suspect), my most productive work time is the morning. If Istart my work day by answering my email, I lose the time that I'm at my most creative. If I'mwriting a piece, for instance, it takes me twice as long to compose it in the afternoon orevening than it would in the morning, when I feel fresh and alert.

Answering email, on the other hand, isn't usually a task that calls for a great deal ofcreativity. So by ignoring my email until the late afternoon, and answering it then, I get the dualbenefit of saving my most productive time for other more demanding tasks, and not continuallyinterrupting whatever other tasks I'm trying to accomplish.

MIME (Multipurpose Internet Mail Extensions)MIME is a standard which was proposed by Bell Communications in 1991 in order to

expand upon the limited capabilities of email, and in particular to allow documents (such asimages, sound, and text) to be inserted in a message. It was originally defined by RFCs 1341 and1342 in June 1992.Using headers, MIME describes the type of message content and the encoding used.MIME adds the following features to email service:

• Be able to send multiple attachments with a single message;• Unlimited message length;• Use of character sets other than ASCII code;• Use of rich text (layouts, fonts, colours, etc)• Binary attachments (executables, images, audio or video files, etc.), which may be divided if

needed.


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MIME uses special header directives to describe the format used in a message body, so thatthe email client can interpret it correctly.

Common MIME Types are listed in the table below:Type Subtype Description of Content Type File Extensions

Application PostscriptTextroff

Printable postscript documentTEX documentPrintable troff document

.eps, .ps

.tex

.t, .tr, .roff

Audio AiffAuMidiRealaudiowav

Apple soundSun Microsystems soundMusical Instrument Digital InterfaceProgressive Networks soundMicrosoft sound

.aif, .aiff,.aifc

.au, .snd

.midi, .mid

.ra, .ram

.wav

Image GifJpegPngTiff

Graphics Interchange FormatJoint Photographic Experts GroupPortable Network GraphicsTagged Image File Format

.gif

.jpeg,.jpg,.jpe

.png

.tiff, .tif

Model Vrml Virtual Reality Modeling Language .wrl

Text HtmlPlainSgml

Hypertext Markup LanguageUnformatted textStandard Generalized MarkupLanguage

.html, .htm

.txt

.sgml

Video AviMpegQuicktimeSgi-movie

Microsoft Audio Video InterleavedMoving Picture Experts GroupApple QuickTime movieSilicon Graphics movie

.avi

.mpeg, .mpg

.qt, .mov

.movie

News GroupsA newsgroup is a continuous public discussion about a particular topic. You can join a

newsgroup at any time to become part of a huge conversation between hundreds or eventhousands of people

A newsgroup is a discussion about a particular subject consisting of notes written to acentral Internet site and redistributed through Usenet, a worldwide network of news discussiongroups. Usenet uses the Network News Transfer Protocol (NNTP).

Newsgroups are organized into subject hierarchies, with the first few letters of thenewsgroup name indicating the major subject category and sub-categories represented by asubtopic name. Many subjects have multiple levels of subtopics. Newsgroups are divided into


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categories. The categories help to determine what kind of group and what kind of postings youwill find there. Some major subject categories are:

• news,• rec (recreation),• soc (society),• sci (science),• comp (computers), and so forth (there are many more).• Alt• talk

Use of Newsgroups We can use newsgroups for various purposes, for example:• Newsgroups are an excellent way to find out web sites to visit in your particular area of

interest or just pick up detailed information about area of interest.• You can buy and sell stuff. People often advertise things for sale in some newsgroup.

Users can post to existing newsgroups, respond to previous posts, and create newnewsgroups.

Newcomers to newsgroups are requested to learn basic Usenet netiquette and to getfamiliar with a newsgroup before posting to it. A frequently-asked questions is provided. Therules can be found when you start to enter the Usenet through your browser or an online service.You can subscribe to the postings on a particular newsgroup.

Some newsgroups are moderated by a designated person who decides which postings toallow or to remove. Most newsgroups are unmoderated.

Mailing ListsA mailing list is a collection of names and addresses used by an individual or an

organization to send material to multiple recipients. The term is often extended to include thepeople subscribed to such a list, so the group of subscribers is referred to as "the mailing list", orsimply "the list".

Types of mailing lists

At least two types of mailing lists can be defined:An announcement list is closer to the original sense, where a "mailing list" of people was

used as a recipient for newsletters, periodicals or advertising. Traditionally this was done throughthe postal system.

With the rise of email, the electronic mailing list became popular. The second type allows

members to post their own items which are broadcast to all of the other mailing list members.This second category is usually known as a discussion list.


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More definitions

When similar or identical material is sent out to all subscribers on a mailing list, it is oftenreferred to as a mailshot or a blast. A list for such use can also be referred to as a distribution list.

In legitimate (non-spam) mailing lists, individuals can subscribe or unsubscribethemselves.

Mailing lists are often rented or sold. If rented, the renter agrees to use the mailing list foronly contractually agreed-upon times. The mailing list owner typically enforces this by "salting"(known as "seeding" in direct mail) the mailing list with fake addresses and creating new saltsfor each time the list is rented. Unscrupulous renters may attempt to bypass salts by rentingseveral lists and merging them to find the common, valid addresses.

Mailing list brokers exist to help organizations rent their lists. For some organizations, suchas specialized niche publications or charitable groups, their lists may be some of their mostvaluable assets, and mailing list brokers help them maximize the value of their lists.

A mailing list is simply a list of e-mail addresses of people that are interested in the same

subject, are members of the same work group, or who are taking class together. When a memberof the list sends a note to the group's special address, the e-mail is broadcast to all of themembers of the list. The key advantage of a mailing list over things such as web-baseddiscussion is that as new message becomes available they are immediately delivered to theparticipants’ mailboxes.

Chat RoomsA chat room is a Web site, part of a Web site, or part of an online service such as America

Online, that provides a venue for communities of users with a common interest to communicatein real time. Forums and discussion groups, in comparison, allow users to post messages butdon't have the capacity for interactive messaging. Most chat rooms don't require users to haveany special software; those that do, such as Internet Relay Chat (IRC) allow users to download itfrom the Internet.

Chat room users register for the chat room of their choice, choose a user name andpassword, and log into a particular room (most sites have multiple chat rooms). Inside the chatroom, generally there is a list of the people currently online, who also are alerted that anotherperson has entered the chat room. To chat, users type a message into a text box. The message isalmost immediately visible in the larger communal message area and other users respond. Userscan enter chat rooms and read messages without sending any, a practice known as lurking.

Because chat room messages are spontaneous and instantly visible, there is a potential forabuse, which may or may not be intentional. Site hosts typically post a frequently askedquestions (FAQ) list to guide users to appropriate chat room behavior, such as introducing

yourself when you enter a room, making it clear when you are directing a question or response toa specific user, and reporting disruptive users, for example. Disruptive users may verbally abuse


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other chatters, monopolize the conversation, or even just disable it by repeatedly typing the sameword or phrase into the conversation, a practice (much frowned upon) known as scrolling.

Chat rooms can be found that focus on virtually any aspect of human endeavor or interest:

there are current communities based on classic movies, Irish ancestry, baton twirling, andpsychic readings, for example. Various sites, such as Yahoo, provide a directory of chat sites.Others, such as MSN Web Communities, guide users through the steps required to create theirown chat room.

Introduction to Networks and InternetWhen we communicate, we are sharing information. This sharing can be local or remote.

Between individuals, local communication usually occurs face to face, while remotecommunication takes place over distance. The term “tele-communication”, which includestelephony, telegraphy, and television, means communication at a distance. Data communicationsare exchange of data between two devices via some transmission medium such as a copper wire.

A data communication system has five components:• Message: The message is the information to be communicated. A popular form of

information includes text, numbers, pictures, audio and video.• Sender: The sender is the device that sends the data message. It can be a computer,

workstation, telephone handset, video camera, and so on.• Receiver: The receiver is the device that receives the message. It can be a computer,

workstation, telephone handset, television, and so on.• Transmission Medium: The transmission medium is the physical path by which a

message travels from sender to receiver. Some examples of transmission media includetwisted-pair wire, coaxial cable, fibre-optic cable, and radio waves.

• Protocol: A protocol is a set of rules that governs data communications. It represents anagreement between the communication devices. Without a protocol, two devices may beconnected but not communicating.

A computer network is a group of two or more computers connected to each electronically.This means that the computers can "talk" to each other and that every computer in the networkcan send information to the others. The computers in a network are autonomous in nature, thatmeans computers are independent or self governing. Usually, this means that the speed of theconnection is fast - faster than a normal connection to the Internet. A computer network allowssharing of resources and information among interconnected devices.

Types of Computer NetworksComputer network design can range from simple to very complex. Networking can be as

simple as connecting two computers, or a computer and a printer, while more complex networks


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can involve the connection of millions of computers and devices. Below is a brief outline ofdifferent computer network types.

Local area network

A local area network (LAN) is a network that connects computers and devices in a limitedgeographical area such as home, school, computer laboratory, office building, or closelypositioned group of buildings. Each computer or device on the network is a node. Current wiredLANs are most likely to be based on Ethernet technology, although new standards like ITU-T also provide a way to create a wired LAN using existing home wires (coaxial cables, phonelines and power lines).

The defining characteristics of LANs, in contrast to WANs (Wide Area Networks), includetheir higher data transfer rates, smaller geographic range, and no need for leasedtelecommunication lines. Current Ethernet or other IEEE 802.3 LAN technologies operate atspeeds up to 10 Gbit/s.

Personal area network

A personal area network (PAN) is a computer network used for communication amongcomputer and different information technological devices close to one person. Some examples ofdevices that are used in a PAN are personal computers, printers, fax machines, telephones,PDAs, scanners, and even video game consoles. A PAN may include wired and wireless devices.The reach of a PAN typically extends to 10 meters. A wired PAN is usually constructed withUSB and Firewire connections while technologies such as Bluetooth and infraredcommunication typically form a wireless PAN.

Home area network

A home area network (HAN) is a residential LAN which is used for communicationbetween digital devices typically deployed in the home, usually a small number of personalcomputers and accessories, such as printers and mobile computing devices. An importantfunction is the sharing of Internet access, often a broadband service through a CATV or DigitalSubscriber Line (DSL) provider. It can also be referred to as an office area network (OAN).

Wide area network

A wide area network (WAN) is a computer network that covers a large geographic areasuch as a city, country, or spans even intercontinental distances, using a communications channelthat combines many types of media such as telephone lines, cables, and air waves. A WAN oftenuses transmission facilities provided by common carriers, such as telephone companies. WAN

technologies generally function at the lower three layers of the OSI reference model: the physicallayer, the data link layer, and the network layer.


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Campus networkA campus network is a computer network made up of an interconnection of local area

networks (LAN's) within a limited geographical area. The networking equipments (switches,routers) and transmission media (optical fiber, copper plant, etc.) are almost entirely owned (bythe campus tenant / owner: an enterprise, university, government etc.).

In the case of a university campus-based campus network, the network is likely to link avariety of campus buildings including; academic departments, the university library and studentresidence halls.

Metropolitan area network

A Metropolitan area network is a large computer network that usually spans a city or alarge campus.

Enterprise private network

An enterprise private network is a network build by an enterprise to interconnect variouscompany sites, e.g., production sites, head offices, remote offices, shops, in order to sharecomputer resources.

Virtual private network

A virtual private network (VPN) is a computer network in which some of the links betweennodes are carried by open connections or virtual circuits in some larger network (e.g., theInternet) instead of by physical wires. The data link layer protocols of the virtual network aresaid to be tunneled through the larger network when this is the case. One common application issecure communications through the public Internet, but a VPN need not have explicit securityfeatures, such as authentication or content encryption. VPNs, for example, can be used toseparate the traffic of different user communities over an underlying network with strongsecurity features.

VPN may have best-effort performance, or may have a defined service level agreement(SLA) between the VPN customer and the VPN service provider. Generally, a VPN has atopology more complex than point-to-point.

Internetwork

An internetwork is the connection of two or more private computer networks via a commonrouting technology (OSI Layer 3) using routers. The Internet is an aggregation of manyinternetworks; hence its name was shortened to Internet.


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Backbone network

A Backbone network (BBN) or network backbone is part of a computer networkinfrastructure that interconnects various pieces of network, providing a path for the exchange of

information between different LANs or sub networks. A backbone can tie together diversenetworks in the same building, in different buildings in a campus environment, or over wideareas. Normally, the backbone's capacity is greater than the networks connected to it.

Global area network

A global area network (GAN) is a network used for supporting mobile communicationsacross an arbitrary number of wireless LANs, satellite coverage areas, etc. The key challenge inmobile communications is handing off the user communications from one local coverage area tothe next.

Intranets and Extranets

An intranet is a set of networks, using the Internet Protocol and IP-based tools such as webbrowsers and file transfer applications that are under the control of a single administrative entity.Most commonly, an intranet is the internal network of an organization.

An extranet is a network that is limited in scope to a single organization or entity and alsohas limited connections to the networks of one or more other trusted organizations or entities.Technically, an extranet may also be categorized as a CAN, MAN, WAN, or other type ofnetwork, although an extranet cannot consist of a single LAN; it must have at least oneconnection with an external network.

InternetThe Internet is a global system of interconnected governmental, academic, corporate,

public, and private computer networks. It is based on the networking technologies of the InternetProtocol Suite.

The Internet is a worldwide collection of computer networks, cooperating with each otherto exchange data using a common software standard. Through telephone wires and satellite links,Internet users can share information in a variety of forms. The size, scope and design of theInternet allow users to:

• connect easily through ordinary personal computers and local phone numbers;• exchange electronic mail (E-mail) with friends and colleagues with accounts on the

Internet;• post information for others to access, and update it frequently;• access multimedia information that includes sound, photographic images and even video;

and• Access diverse perspectives from around the world.


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An additional attribute of the Internet is that it lacks a central authority—in other words,there is no "Internet, Inc." that controls the Internet. Beyond the various governing boards thatwork to establish policies and standards, the Internet is bound by few rules and answers to no

single organization.Many people think that the Internet is a recent innovation, when in fact the essence of it has

been around for over a quarter century. The Internet began as ARPAnet, a U.S. Department ofDefense project to create a nationwide computer network that would continue to function even ifa large portion of it were destroyed in a nuclear war or natural disaster.

During the next two decades, the network that evolved was used primarily by academicinstitutions, scientists and the government for research and communications. The appeal of theInternet to these bodies was obvious, as it allowed disparate institutions to connect to eachothers' computing systems and databases, as well as share data via E-mail.

The nature of the Internet changed abruptly in 1992, when the U.S. government beganpulling out of network management, and commercial entities offered Internet access to the

general public for the first time. This change in focus marked the beginning of the Internet'sastonishing expansion. The Internet is also the communications backbone underlying the WorldWide Web (WWW).

Working of the Internet• Where to Begin? Internet Addresses

Because the Internet is a global network of computers each computer connected to theInternet must have a unique address. Internet addresses are in the form nnn.nnn.nnn.nnn wherennn must be a number from 0 - 255. This address is known as an IP address. (IP stands forInternet Protocol)

The picture below illustrates two computers connected to the Internet; your computer withIP address 1.2.3.4 and another computer with IP address 5.6.7.8.

If you connect to the Internet through an Internet Service Provider (ISP), you are usuallyassigned a temporary IP address for the duration of your dial-in session. If you connect to the

Internet from a local area network (LAN) your computer might have a permanent IP address or itmight obtain a temporary one from a DHCP (Dynamic Host Configuration Protocol) server. Inany case, if you are connected to the Internet, your computer has a unique IP address.


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• Protocol Stacks and Packets So your computer is connected to the Internet and has a unique address. How does it 'talk'

to other computers connected to the Internet? An example should serve here: Let's say your IP

address is 1.2.3.4 and you want to send a message to the computer 5.6.7.8. The message youwant to send is "Hello computer 5.6.7.8!". Obviously, the message must be transmitted overwhatever kind of wire connects your computer to the Internet. Let's say you've dialed into yourISP from home and the message must be transmitted over the phone line. Therefore the messagemust be translated from alphabetic text into electronic signals, transmitted over the Internet, andthen translated back into alphabetic text. How is this accomplished? Through the use ofa protocol stack. Every computer needs one to communicate on the Internet and it is usuallybuilt into the computer's operating system (i.e. Windows, UNIX, etc.). The protocol stack usedon the Internet is referred to as the TCP/IP protocol stack because of the two majorcommunication protocols used. The TCP/IP stack looks like this:

Protocol Layer Comments

Application Protocols LayerProtocols specific to applications such as WWW, e-mail, FTP,etc.

Transmission Control ProtocolLayer

TCP directs packets to a specific application on a computerusing a port number.

Internet Protocol Layer IP directs packets to a specific computer using an IP address.

Hardware Layer Converts binary packet data to network signals and back.(E.g. ethernet network card, modem for phone lines, etc.)

If we were to follow the path that the message "Hello computer 5.6.7.8!" took from ourcomputer to the computer with IP address 5.6.7.8, it would happen something like this:


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• The message would start at the top of the protocol stack on your computer and work it'sway downward.

• If the message to be sent is long, each stack layer that the message passes through maybreak the message up into smaller chunks of data. This is because data sent over the

Internet (and most computer networks) are sent in manageable chunks. On the Internet,these chunks of data are known as packets.

• The packets would go through the Application Layer and continue to the TCP layer. Eachpacket is assigned a port number. We need to know which program on the destinationcomputer needs to receive the message because it will be listening on a specific port.

• After going through the TCP layer, the packets proceed to the IP layer. This is whereeach packet receives its destination address, 5.6.7.8.

• Now that our message packets have a port number and an IP address, they are ready to besent over the Internet. The hardware layer takes care of turning our packets containing thealphabetic text of our message into electronic signals and transmitting them over thephone line.

• On the other end of the phone line your ISP has a direct connection to the Internet. The

ISPs router examines the destination address in each packet and determines where to sendit. Often, the packet's next stop is another router.

• Eventually, the packets reach computer 5.6.7.8. Here, the packets start at the bottom ofthe destination computer's TCP/IP stack and work upwards.

• As the packets go upwards through the stack, all routing data that the sending computer'sstack added (such as IP address and port number) is stripped from the packets.

• When the data reaches the top of the stack, the packets have been re-assembled into theiroriginal form, "Hello computer 5.6.7.8!"

Internet Congestion

Internet congestion occurs when a large volume of data is being routed on low bandwidthlines or across networks that have high latency and cannot handle large volumes. The result isslowing down of packet movement, packet loss and drop in service quality.


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Congestion Collapse is the situation in which the congestion becomes so great thatthroughput drops to a low level and thus little useful communication occurs.

Various techniques have been developed in attempt to minimize congestion collapse in

communication networks. In addition to increasing capacity and data compression, they includeprotocols for informing transmitting devices about the current levels of network congestion andhaving them reroute or delay their transmissions according to congestion levels.

Congestion Control The processes that are used to reduce congestion in a network. Thisincludes making decisions such as: deciding when to accept new Traffic, when to delete packetsand when to adjust the routing policies used in the network.

Internet CultureThe Internet offers the hope of a more democratic society. By promoting a decentralized

form of social mobilization, it is said, the Internet can help us to renovate our institutions andliberate ourselves from our authoritarian legacies. The Internet does indeed hold thesepossibilities, but they are hardly inevitable. In order for the Internet to become a tool for socialprogress, not a tool of oppression or another centralized broadcast medium or simply a waste ofmoney, concerned citizens must understand the different ways in which the Internet can becomeembedded in larger social processes.

In thinking about culturally appropriate ways of using technologies like the Internet, thebest starting-point is with people -- coherent communities of people and the ways they thinktogether.

Let us consider an example. A photocopier company asked an anthropologist named JulianOrr to study its repair technicians and recommend the best ways to use technology in supportingtheir work. Orr took a broad view of the technicians' lives, learning some of their skills andfollowing them around. Each morning the technicians would come to work, pick up theircompany vehicles, and drive to customers' premises where photocopiers needed fixing; eachevening they would return to the company, go to a bar together, and drink beer. Although thecompany had provided the technicians with formal training, Orr discovered that they actuallyacquired much of their expertise informally while drinking beer together. Having spent the daycontending with difficult repair problems, they would entertain one another with "war stories",and these stories often helped them with future repairs. He suggested, therefore, that thetechnicians be given radio equipment so that they could remain in contact all day, telling storiesand helping each other with their repair tasks.

As Orr's story suggests, people think together best when they have something important incommon. Networking technologies can often be used to create a space for "communities ofpractice", like the photocopier technicians, to think together in their own ways. This is perhaps

the most common use of the Internet: discussion groups organized by people who wish to pooltheir information and ideas about a topic of shared interest. At the same time, we should notconsider the Internet in isolation. Regardless of whether they are located in the same geographic


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region or distributed around the world, a community's members will typically think togetherusing several media, such as the telephone, electronic mail, printed publications, and face-to-facemeetings, and the Internet is best conceived as simply one component of this larger ecology of

media.Social networks also influence the adoption of new technologies: if the members of a

community already have social connections to one another than they are more likely to benefitfrom technological connections. Every culture has its own distinctive practices for creating andmaintaining social networks, and a society will be healthier in political and economic termswhen these practices are functioning well.

Authoritarian societies will attempt to suppress the cultural practices of networking, anddemocratic societies will promote them. Broad implementation of the Internet is one way topromote social networking, and the existing practices of networking can offer clues to the mosteffective ways of implementing the Internet.

Business Culture on Internet Today’s business environment is influenced greatly by market, economical, societal and

technological factors creating a lot of competition. Also these factors are unpredictable that theymay change unexpectedly at any time. Such changes in the business world have been defined asbusiness pressure.

The various environmental business pressures on companies today can be grouped intothree categories:

• Market • Societal • Technological

Strength of Internet business over traditional business can be made more clear by thecomparison of both. Online purchasing and selling through e-business offers opportunities andadvantages to the companies of all sizes engaged in different portfolios. Some of theseadvantages are:

• Sampling of products such as books, recorded lectures, and music cassettes is possible onWeb for business promotion.

• Business houses selling their goods through catalogues can reach additional globalcustomers at lower cost.

• For items subjected to frequent changes e.g. shares and bonds etc. . the changes inrates/quotations can be known instantly.

• Customer’s knowledge can be enhanced on topics such as news about local event, marketresearch, industrial report, software etc., which can be distributed easily over the Internet.

• A closer relationship can be developed amongst business sellers whose customer base ison the Internet.


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• For wholesalers, distributors, retailers etc., it is convenient and efficient to buy from websites.

• High quality, specialized products can be easily sold on Internet by the retailers. • Organizations can conduct interviews through Internet to select suitable candidates for

their requirements. • Group discussions can be conducted for corporate offices, industrial houses, business

firms, universities, etc. Disadvantages of Internet Business

1. Security2. Staying connected3. Availability4. Access5. Misunderstandings

Collaborative Computing and the Internet Collaborative computing is a term describing a variety of activities where people interact

with one another using desktops, laptops, palmtops, and sophisticated digital cellular phones. Ascomputers are best at handling data and representing information, person-to-personcommunication is enriched by an ability to share, modify, or collaboratively create data andinformation.

We believe collaborative computing is the future of the Internet. The Internet will evolvefrom its current role as a channel for information dissemination to a person-to-personcommunication medium.Some examples are listed below:

• Videoconferencing applications allow users to collaborate over local networks, privateWANs, or over the Internet.

• Internet collaboration tools provide virtual meetings, group discussions, chat rooms,whiteboards, document exchange, workflow routing and many other features.

• Multicasting is an enabling technology for groupware and collaborative work on theInternet that reduces bandwidth requirements.

• Instant messaging is like e-mail that happens in real time.• Workflow management is about coordinating the flow of documents (invoices, reports,

legal documents etc.) within an organization from one person to another.A good example of collaborative applications designed for Internet use are Microsoft’s

NetShow and NetMeeting.

Modes of Connecting to Internet


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There are four ways of connecting a client computer to the Internet: a dial-up connectionusing a telephone line or an Integrated Services Digital Network (ISDN), a Digital SubscriberLine (DSL), a cable TV connection and a satellite connection.

Dial-up Connection/Telephone Line Internet Connectivity

A dial-up connection uses the analog telephone line for establishing a temporarycommunication. Computer's digital signals must be converted to analog signals before they aretransmitted over standard telephone lines. This conversion is performed by a modem, a devicethat modulates (changes into an analog signal) and demodulates (converts an analog signal into adigital signal). Both the sending and receiving ends of a communication channel must have amodem for data transmission to occur. Using a dial-up line to transmit data is similar to using thetelephone to make a call. The client computer modem dials the preprogrammed phone numberfor a user's Internet Service Provider (ISP) and connects to one of the ISP's modems. After theISP has verified the user's account, a connection is established and data can be transmitted. When

either modem hangs up, the communication ends. The advantage of a dial-up line is that it costsno more than a local telephone call. Computers at any two locations can establish a connectionusing modems and a telephone network, to include wireless modems and cellular telephoneconnections. The limitation of a connection using the ordinary telephone line is a low speed, 28kbps. There are dedicated telephone lines that can transmit data at 56 kbps. Most 56 kbpsmodems connect at a speed less than 46 kbps because of the limitations of analog phone linesand telephone-company switches.

ISDN

ISDNs are special digital telephone lines that can be used to dial into the Internet at speedsranging from 64 to 128 kbps. These types of connections are not available everywhere telephone

companies have to install special ISDN digital switching equipment. ISDNs require use of aspecial "digital modem" that sends and receives digital signals over ISDN lines. With an ISDN,the telephone line is divided into three channels (BRI - Basic Rate Interface), two-64 kbps B(bearer) channels that send data and one 16 kbps D (data) channel that sends routing information.This type of access is commonly referred to as 2B+D. To use the ISDN access to the Internet, anISP has to offer the ISDN access. ISDN lines cost more than normal phone lines, so thetelephone rates are usually higher.

Cable TV Connection

Currently most households with cable TV have the option for cable modem Internet access.The cable modem offers a high-speed link at low cost for unlimited, "always connected" access.

The connection speeds range from 128 kbps up to 10 mbps (megabits per second). A cablemodem is a device that connects to the existing TV cable feed and to an Ethernet network card inthe user's PC (also called an NIC - Network Interface Card). The cable network is designed to


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support the highest speeds in the "downstream" direction, which is from the Internet to the clientcomputer. This downstream speed affects the performance of downloading Web pages andsoftware. The "upstream" bandwidth for data sent from a user's computer to the Internet is

typically less, in the range of 200 kbps to 2 mbps. The benefit of the cable modem for Internetaccess is that, unlike DSL, its performance doesn't depend on distance from the central cableoffice. However, with the cable TV network, the computer is put on a Local Area Network(LAN) with other users in the neighborhood and like with any LAN, the performance degradesas usage increases. A more disturbing issue is that of network security. One of the main purposesof a LAN is to allow file sharing among the computers on the LAN. This LAN feature doesn'twork well with cable Internet access, as most users do not want neighbors accessing their files.Turning the sharing option off can prevent file sharing. Also, installing the firewall hardware orsoftware may protect from hackers.

DSL (Digital Subscriber Line)

DSL service is a high-speed data service that works over POTS (Plain Old TelephoneService) copper telephone lines and is typically offered by telephone companies without costlyinstallation of a higher-grade cable. DSL uses a different part of the frequency spectrum thananalog voice signals, so it can work in conjunction with a standard analog telephone service,providing separate voice and data "channels" on the same line. ADSL (Asymmetric DSL) is thetype of DSL that provides different bandwidths in the upstream and downstream directions,giving the user a much bigger "pipe" in the downstream direction. ADSL can supportdownstream bandwidths of up to 8 mbps and upstream bandwidths of 1.5 mbps. For comparison,a T-1 connection also provides 1.5 mbps. This scheme works well for the typical Internet user;upstream communication is usually small (link requests) compared to downstreamcommunication (Web pages with graphics).

SDSL (Symmetric DSL) offers the same bandwidth capability in both directions. Besideshigher bandwidth, some of the advantages of ADSL access from telephone companies are thatthere are no per-minute charges and the user gets an "always-on" connection for a monthly fee.Most modern computers can be easily equipped to connect to a DSL service. This isaccomplished by connecting an ADSL modem to an Ethernet network card in the PC. Thedownside of DSL includes strict distance limitation that DSL circuits can operate within. As theconnection's length increases, the signal quality decreases and the connection speed goes down.DSL services that provide greater that 1.5 mbps require shorter distances to the central officecompared to a cable modem that can be located far away from the service provider.

The limit for ADSL service is 18,000 feet (5,460 meters), though for speed and quality ofservice reasons many ADSL providers place a lower limit on the distances for the service. At the

extremes of the distance limits, ADSL customers may see speeds far below the promisedmaximums, while customers near the central office have the potential for very high speeds.Unlike cable modem technology, DSL provides a point-to-point connection to ISP. DSL


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proponents claim this technology is both more secure and less prone to local traffic fluctuationsthan its cable rival. By not sharing a LAN segment with other users, the systems are not as opento intrusion or susceptible to performance degradations related to local traffic.

Satellite Connection

Getting the Internet feed from a satellite is really not all that different from getting TVsignals from one. In both cases data is being sent from the satellite to a user's equipment and thentranslated and decoded. One major limitation of satellite technology is that it can only send datafrom the satellite to a user's receiver—not the other way. To get around this problem, a separateISP connection is needed to send data to the Internet, typically over an analog modem. Thisconnection works in conjunction with the satellite feed. As information is requested via themodem line, data are sent back via the satellite. Since most Internet users need high bandwidthfrom the Web, downstream (typically Web pages and file downloads), and less bandwidth goingto the Web, upstream (typically link requests), this scenario of sending upstream data over a

standard modem line and downstream data over the high-bandwidth satellite feed has beeneffective. The newest satellite technology allows for two-way communications and higherupstream bandwidths. A satellite return channel can be added for traffic bound for the Internet.The upload speeds through this satellite return channel may peak at 128 kbps. Download speedswith this system are up to 400 kbps. Satellite technology has one strong advantage over cablemodems and DSL: accessibility. For many it is today's only high-speed option. It can reachareas that are otherwise difficult to establish contact with. The infrastructure exists to provide400 kbps downstream bandwidth to almost anyone with a 21" satellite dish. It is eight timesfaster than fastest analog telephone modems and three times faster than ISDN. However, it is notas fast as cable modems or DSL services, which both can provide more than megabits ofbandwidth. Also, cable and DSL access methods are cheaper. Equipment required for satellite

connection includes installation of a mini-dish satellite receiver and a satellite modem. Likecable modem systems, satellite provides a "shared bandwidth" pipe. This means that downloadperformance may vary depending upon other users of the satellite transponder. Another potentialproblem can be associated with severe weather. In severe snowstorms and heavy rain, users mayexperience signal fade.

The general rule about the Internet connection is the faster, the better. The bandwidth andtransfer rate determine how quickly pictures, sounds, animation and video clips will bedownloaded. Since multimedia and interactivity make the Internet such an exciting tool forinformation sharing, the speed is the key. Dial-up access provides an easy and inexpensive wayfor users to connect to the Internet, however, it is a slow-speed technology and most users are nolonger satisfied with dial-up or ISDN connections. Fortunately, the broadband access, we once

dreamed of, is now possible with TV cable, DSL and satellite links.

Internet Service Provider (ISPs)


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An ISP, or Internet Service Provider, is a company that offers internet access to individualsand businesses for a monthly or yearly fees. In addition to internet connection, ISPs may alsoprovide related services like web site hosting and development, email hosting, domain name

registration etc.Different ISPs, and sometimes even the same one, offer different types of internet

connections - dialup, cable and DSL broadband. Hardware such as dialup modem or a wirelessmodem and router are usually provided by the company. When you register with an ISP for itsservices, an account is created and you are provided with the login details –username andpassword. You connect to the internet via your account and this way the company keeps a watchon your online activities. ISPs can be both regional, confined to a geographic area, or national,servicing the entire country and they are connected with each other through Network AccessPoints (NAPs). ISPs are also referred to as Internet Access Providers.

Types of internet access

Most ISPs offer several types of internet access which essentially differ in connectionspeeds – the time taken for download and upload. Many also offer different plans or “packages”that vary in the download limit, number of email accounts on offer etc.Dialup internet access is probably the slowest connection and requires you to connect to theinternet via your phone line by dialing a number specified by the ISP. This means, dialupconnections are not “always on”, unless you want to raise a huge phone bill, you would sever theconnection when you finish work online.Cable internet access can be obtained from the local cable TV operator. However, ask them fora demo first or check with your neighbourers on the quality of service.Internet access via DSL broadband is indeed very fast and ISPs can offer different downloadspeeds – quicker the speed, higher will be the price. A wireless internet connection gives you

freedom and flexibility – you need not be confined to one place (the work table, for instance) andcan access the internet from any spot (even the bathroom) as long as your computer can catch thewireless signal. However, ensure that the provider secures the wireless connection with apassword.

In many countries, especially those in which internet is still a kind of luxury, the ISPs mayput a limit on the amount of data exchanged over a connection. For example, one may beallowed only a few GB (gigabytes) of download and upload each month. This is usuallysufficient for routine users but if you plan to download movies and music or other large files, youhave to keep a check on the amount of the data transfer.

How to choose an ISP?

• Monthly or yearly charge: Yes, we all need to keep a close watch on our wallets but thisdoes not mean you pick a lousy ISP just because it’s cheap. The price would also varyacross different plans – ensure you get the best deal.


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• Type of internet access: A dialup connection would be more than enough if you plan toaccess the internet for only a few hours each week. Want to download movies, musicetc.? Get a broadband connection.

• Regional or national ISP: Are you a frequent traveller? If so, talk to a national ISP andsee if they have a plan that lets you use the same connection (via a USB modem) fromdifferent places.

• Extra services from the ISP.

IP address (Internet Protocol address) Number that uniquely identifies each computer on the Internet. A computer's IP address

may be permanently assigned or supplied each time that it connects to the Internet by an Internetservice provider. In order to accommodate the extraordinary growth in the number of devicesconnected to the Internet, a 32-bit protocol standard, known as IPv4, began to be replaced by a128-bit protocol, IPv6, in 2000.

Another Definition of IP address

(Internet Protocol address) The address of a device attached to an IP network (TCP/IPnetwork). Every client, server and network device is assigned an IP address, and every IP packettraversing an IP network contains a source IP address and a destination IP address.

Every IP address that is exposed to the public Internet is unique. In contrast, IP addresseswithin a local network use the same private addresses; thus, a user's computer in company A canhave the same address as a user in company B and thousands of other companies. However,private IP addresses are not reachable from the outside world.

Logical Vs. Physical

An IP address is a logical address that is assigned by software residing in a server or router.In order to locate a device in the network, the logical IP address is converted to a physicaladdress by a function within the TCP/IP protocol software. The physical address is actually builtinto the hardware.

Static and Dynamic IP

Network infrastructure devices such as servers, routers and firewalls are typically assignedpermanent "static" IP addresses. The client machines can also be assigned static IPs by a networkadministrator, but most often are automatically assigned temporary "dynamic" IP addresses viasoftware that uses the "dynamic host configuration protocol" (DHCP). Cable and DSL modemstypically use dynamic IP with a new IP address assigned to the modem each time it is rebooted.

The Dotted Decimal Address: x.x.x.x


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IP addresses are written in "dotted decimal" notation, which is four sets of numbersseparated by decimal points; for example, 204.171.64.2. Instead of the domain name of a Website, the actual IP address can be entered into the browser. However, the Domain Name System

(DNS) exists so users can enter computerlanguage.com instead of an IP address, and the domain(the URL) computerlanguage.com is converted to the numeric IP address.

Although the next version of the IP protocol offers essentially an unlimited number ofunique IP addresses (IPv6), the traditional IP addressing system (IPv4) uses a smaller 32-bitnumber that is split between the network and host (client, server, etc.). The host part can befurther divided into sub-networks.

Class A, B and C

Based on the split of the 32 bits, an IP address is either Class A, B or C, the most commonof which is Class C. More than two million Class C addresses are assigned, quite often in largeblocks to network access providers for use by their customers. The fewest are Class A networks,

which are reserved for government agencies and huge companies.

Domain Name System (DNS)The World Wide Web that we know today would have not existed, if it was not for the

Domain Name System. Every day when you go online and open a website, the Domain NameSystem is the backend, which helps you see the website you want.

What does actually stand behind that almighty 3-letter abbreviation - DNS? DNS refers toDomain Name System and represents a powerful Internet technology for converting domainnames to IP addresses. Its special mission is to be a mediator between the IP addresses, thesystem-side names of the websites and their respective domains, and their user-side alpha-numeric titles. Another important function of the DNS is to control the delivery of emailmessages

Behind every site, there is an IP address. But, while it's easy to remember the name of awebsite, it's quite hard to remember the exact IP address. For example, everybody knows aboutGoogle.com, but if you had to remember "74.125.45.100", things would have been much harder.

How does DNS work?

A DNS program works like this - every time a domain name is typed in a browser it isautomatically passed on to a DNS server, which translates the name into its corresponding IPaddress (e.g. the domain name NTC Hosting.com is translated to 66.40.65.49). Thanks to theDNS, we do not need to bother to remember complicated numeric combinations to reach acertain website - we can use its meaningful and much easier to remember domain name instead.

Hierarchy of domain names


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IPv6 (Internet Protocol Version 6)Internet Protocol Version 6 (IPv6) is a network layer protocol that enables data

communications over a packet switched network. Packet switching involves the sending andreceiving of data in packets between two nodes in a network. The working standard for the IPv6protocol was published by the Internet Engineering Task Force (IETF) in 1998. The IETFspecification for IPv6 is RFC 2460. IPv6 was intended to replace the widely used InternetProtocol Version 4 (IPv4) that is considered the backbone of the modern Internet. IPv6 is oftenreferred to as the "next generation Internet" because of it's expanded

Internet Fundamental notes

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