the internet and its applications

Most services on the Internet use the Client Server Model.. Ch.9 - The Internet and its applicationsThere are many services on the Internet but the four most popular and most widely used

Ch.9 - The Internet and its applications

1 What is the Internet?

2 The benefits of the Internet

9 Finding information on the Internet

10 Relevant Documents and False Drops

11 Full search

12 Constrained search

13 Internet file formats

14 Compression and Archiving

The Internet is the largest network of computers These computers can be different

platforms, like Windows, Mac, UNIX, Next, Amiga and so on, but they can still

communicate with each other using TCP/IP, the "common language of the Internet"

In 1999 there were about 130 million people connected to the Internet In the year 2004there may be as many as 1 billion users Why are so many people getting connected? Whatare the benefits of the Internet, from the user’s point of view?

Ch.9 - The Internet and its applications

The most important benefit of the Internet is the ability to get in touch with and

communicate with other people E-mail for instance, reduces the threshold for making

contact with other people One example is when I was going to attend a conference in FloridaTech in 1996 I wrote an e-mail to the person who was administrating the conference andasked her if there were any people in Florida Tech who were interested in Multimedia andDistance Learning She sent me the names of four people and their e-mail addresses One ofthem was the Dean of Florida Tech I wrote e-mail messages to all four of them and theyreplied that they were willing to see me when I arrived

Another example was when we tried to find a teacher for the "Mobile Datacom" part of thiscourse There were people at Ericsson in Stockholm who knew this subject well, but no onehad time to teach, since they were involved in other activities

So I made some searches on the Internet and found an Ericsson owned company in

Gothenburg who worked with "Mobile Datacom" I read their home pages but they

contained only superficial information I then looked at their employment opportunitiespages, and I found very detailed information about what different departments were workingwith I found a department who were working with the parts which we wanted to cover inour course I made contact with the manager of that department and engaged him as a teacher.Another benefit is information that you will find on the Internet There are millions of webpages, news articles and so on The information on the Internet differs from information thatyou will find in libraries and book stores In libraries you only find broad information, that isinformation that interest a large number of people There is an economic reason for this Nopublisher will publish something which interests only a few people But on the Internet itcosts very little to publish, and you will often find this kind of narrow information, forinstance a home page describing a single person or a small company

The information on the Internet is growing very rapidly The number of web pages forinstance is doubling every 53 days

Ch.9 - The Internet and its applications

In October 1957 the former Soviet Union sent up Sputnik and took USA by surprise Tomany Americans, Sputnik was proof of Russia's ability to launch intercontinental missiles,and pessimists predicted the destruction of democracy As an answer to that threat,

president Eisenhower formed ARPA, Advanced Research Project Agency, in January 1958.ARPA's mission was to make sure that the USA took the lead in research, especially

research for military use

One of ARPA's project was ARPANET; a communication network that was built uponcomputers, and a communication technique that was invented in 1962 called packet

switching ARPANET had been built to protect the USA's communication structure in theface of a nuclear attack If one communication path was destroyed, the information packetsjust took another path through the network ARPANET consisted of four computers in

1969, and that was the seed from which the Internet grew

In those days computers were very expensive The people who built the ARPANET

thought that the main use was to use processor power from computers at a distance, through

a service called Telnet But it soon turned out that scientists were more interested in theircolleagues’ brain power than in computers’ processor power

The users invented a service called e-mail and it soon turned out that e-mail traffic amounted

to 75% of all the traffic This trend has continued through the evolution of the Internet Theprimary interest of people is to communicate with other people

In 1983 TCP/IP has been adopted as a standard and ARPANET became the Internet Thesame year the TCP/IP was included in the operating system UNIX, which made it easy forsystem managers to connect to the Internet

In 1988 the IRC which stands for Internet Relay Chat was written This was the first

Internet service for real time communication Up to the 1990’s the Internet was mostly a

playground for students, scientists and the military But in the 1990’s it all changed Onereason was that commercial companies and the general public were allowed to connect to theInternet Another reason was that WWW and Mosaic were invented and the use of theInternet became much friendlier

In 1994 there was a break through for presence of commercial companies on the Internet

In 1996 there were 54 million users connected to the Internet and by 1999 that number hadincreased to 130 millions

As we look into the future we see that the Internet is continuing to grow and that new

services are appearing all the time

Ch.9 - The Internet and its applications

This picture shows how different computer technologies fit together The vertical axis istime, which flows from top to bottom The core technology of the Internet is computernetwork technology As you can see, some interesting key events are marked ARPANETrepresents the beginning of the Internet and it is followed by the invention of the Internetservices like Telnet, E-mail, Usenet and so on

There is another technology called Hypertext which was invented by Vannevar Bush,

president Roosevelt’s science advisor In 1945 he wrote an article called "As we may think",where he described a device called "Memex" which used this hypertext or linking technology.Two people read Bush's article and were profoundly influenced by it One of them wasDouglas Engelbart, the inventor of the mouse, groupware and many other things In thesixties he built the first computer based machine called NLS which used this linking

technology The other person was Theodore Nelson and it was he who coined the termhypertext Theodore Nelson also had the idea to use this technology through the telephonenetwork to link all the literature in the world, and make it accessible to people

HyperCard, which appeared in 1987, was the first program on ordinary personal computerswhich used hypertext technology

Hypertext technology merged with the Internet when World Wide Web was invented WorldWide Web uses network technology together with the linking mechanism of hypertext.There is another technology called Graphical User Interface which was first invented byXerox when they developed their Star machine This technology was later adopted by Apple

on the Macintosh and still later by Microsoft with Windows All these technologies mergedwith the Internet when Marc Andreesen, a 23 year old student, wrote a program calledMosaic and later its successor called Netscape

Multimedia is another technology that was started by Philips when they invented the LaserDiscs Other storage devices, like CD-ROM and DVD (Digital Video Disc) appeared later

Multimedia means using several media, like text, graphics, sound, animation, video and so on,

in combination with each other to present information Even if there are multimedia elements

on the Internet today, the multimedia technology has not yet merged with the Internet Inorder to do so, you need to be able to transfer full screen, full motion video through theInternet, and that requires a bandwidth of approximately 500 kbps But that will happen inthe next few years

Expert system technology will also merge into the Internet Expert systems are intelligentprograms that can use rules to reason and act intelligently Fuzzy Logic is one powerfultechnique used in expert systems One of the first applications of expert system technology

on the Internet will be something called intelligent agents An agent is a program that keepstrack of you and your interests It will go out on the Internet and seek information that mightinterest you

In summary, what this picture is saying is that many powerful computer technologies aremerging into the Internet, which will be extremely powerful in the future, and people willprobably associate the information age with the Internet rather than with computers

Ch.9 - The Internet and its applications

This is a table from the Popular Science magazine that predicts what will happen to

bandwidth in the next couple of years Today most people have ordinary modems with 28.8kbps Some have modems with 56 kbps, Those who have access to ISDN use from 64 up to

128 kbps

You can also have access to the Internet through television cable network In 1998 somepeople had 500 kbps through that network, and that speed will increase to 1 Mbps in year2000

But you can also use the ordinary telephone network for higher speeds A promising

technology is ADSL (Asynchronous Digital Subscriber Loop) which can give a bandwidth of

up to 8 Mbps

Most services on the Internet use the Client Server Model A Client Server Model is adistributed system in which software is split between server tasks and client tasks A clientsends requests to a server, according to some protocol, asking for information or action, andthe server responds A server typically serves many clients A client can request servicesfrom different servers This model allows clients and servers to be placed independently onnodes in a network, on different hardware and operating systems

Ch.9 - The Internet and its applications

There are many services on the Internet but the four most popular and most widely used areWorld Wide Web, E-mail, Usenet News and FTP If you want to request information from aserver, you need to know how it organizes its information

A WWW server organizes its information in units called web pages A web page is a

document with text, pictures and links A web page can also contain other media elementslike sound, animation, video clips and so on Web pages are grouped into web sites A website is a number of pages that describe a particular subject Web pages within a web site havelinks between them but they can also have links to other web sites

The protocol used to transfer web pages is called HTTP, HyperText Transfer Protocol

An e-mail server organizes its information in units called mail messages Messages are stored

in mail boxes When mail messages are transferred between e-mail servers, a protocol calledSMTP, Simple Mail Transfer Protocol, is used When you retrieve messages from the e-mailserver to your computer a protocol called POP3, Post Office Protocol version 3, is used

A news server organizes its information in units called news articles News articles

discussing a particular subject are grouped in newsgroups In 1999 there were about 40 000different newsgroups discussing all kind of topics Newsgroups are grouped in news

categories and news categories are themselves grouped in news categories on a higher level.For instance, the news group "rec.travel.europe" belongs to a category "rec.travel", whichbelongs to the category "rec"

News articles are transferred from news server to news server with a copying mechanism.Every time a news server gets in touch with another news server it checks if the other newsserver has some new articles and copies them News articles migrate in this way through theInternet

Since every news server has an almost complete collection of news articles it means a lot ofredundancy Since news servers have limited amount of disk space, the news articles that areolder than one or two weeks are deleted The protocol used to transfer news articles is calledNNTP, Network News Transfer Protocol

An FTP server organizes its information just like your own computer, that is by usingdirectories which can contain files, or sub directories You can copy a file from an FTPserver to your computer (that is called downloading) or copy a file from your computer tothe FTP server (that is called uploading) The protocol used to transfer files is called FTP,File Transfer Protocol

Ch.9 - The Internet and its applications

Telnet is the oldest service on the Internet The user interface is typically old-fashioned withtext only In the bottom of the screen you have a command line where you can enter yourcommands Many institutions like libraries still use telnet, but they are slowly changing it toWWW The protocol used to communicate with a telnet server is also called telnet

Mail list servers keep track of two lists One is the subscriber list, which contains a list of mail addresses to subscribers The other one is a list of all the messages When somebodysends a message to the mail list server that message is stored on the list of messages and thenthe message is sent to all subscribers

e-There are thousands of different mail lists that you can subscribe to In order to subscribe to

a mail list, you need to send an e-mail message to the mail list server Then you will

automatically get all e-mail messages that people send to the mail list and you can also sendmessages yourself for other subscribers to read

A chat server organizes its information into channels (sometimes called rooms) In everychannel a real time discussion is going on You type text on your keyboard and that textappears on a shared screen area for other people to see You can see what other people arewriting You can also have private discussions with others if you want to

A gopher server works just like an FTP server The only difference is that a particular file ordirectory that the gopher server shows may not reside on that gopher server but on anotherone The gopher service is dying out and is being replaced with WWW

There are two ways to find information on the Internet The first is by using catalogues andthe second one is by using search engines This is not just typical for World Wide Web butalso for other services like E-mail, News, FTP and so on

The most well-known catalogue for WWW is Yahoo and the most well-known search engine

is Alta Vista There are many others

If you want to find an e-mail address you can use an e-mail catalogue You enter the name of

a person and you get that person’s e-mail address One good search engine for finding e-mailaddresses is the Yahoo People Search

As you know most news servers just keep track of the news articles from the last one ortwo weeks The older articles are deleted But what if you want to find some older articles?Deja News keeps track of older news articles Another benefit is that you can search withkeywords in Deja News, which greatly facilitates finding the relevant articles

There are a lot of FTP servers in the world and you can connect to most of them In mostcases it's enough to connect to a handful of good FTP sites to find the software you arelooking for

If you are looking for a particular software like Disinfectant, how do you find it? Well if youknow a name or a part of the name you can use Archie If you do not know the name but arelooking for some type of software, say video editing, you can search with VSL, VirtualSoftware Library