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The Internet - UCD School of Computer Science and Informatics

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The Internet - UCD School of Computer Science and Informatics Powered By Docstoc
					The Internet
Internet is based on 2 technologies: Communications and Computers

Communications Technology

• Telephone Network

       Invented in last century

       Revolution in communications

       In excess of 400 million phones

       Users identified by Phone Number e.g. International number:

                        353 1 716 2469

       Each number has a special format

Postal Network
Based on Post Offices

Users identified by their address which has a
special format:
        e.g.
               Name
                 Street
                  Town
                   County
                    Country

Letters go from place to place before reaching final destination i.e. a Point-to-point Network. The
Internet operates in a similar fashion to the postal system in the way that it handles its messages.

The Internet (Net)
The Internet is a global network of computers.

Accessing the Internet: Requirements

       • Computer + modem + phone line

       • Account with an Internet Service Provider
             (e.g. Ireland Online, Eircom etc.)

       • Some Internet Software
             (e.g. MS Explorer, Netscape)

Comp 1001: The Internet                                                                   1
Computer Account
A computer account allows you access and use a computer. It involves obtaining a Username and
a Password. (e.g. Username Carthy and Password sillyword123) The username identifies you to
the computer, while the password allows you verify that it is indeed you who is accessing the
computer. For security reasons, the password will not be displayed on the screen when you enter
it. Care should be taken to keep your password secret and not to use one which can be guessed.
The following make very poor passwords: any English word, name, phone number or car
registration. Having obtained an account, you login to the Internet provider’s computer using
appropriate software via your home computer and modem. You then run your Internet software
such as Electronic mail software or Browsing software (explained later).


Computers have addresses such as

               ollamh.ucd.ie

This is called a domain address. (This can also be given in numeric form: 137.43.20.1).

Computer users have addresses such as:

               carthy@ccvax.ucd.ie


An important address for any computer system is:

               postmaster@domain.top_domain

e.g.
               postmaster@ucd.ie

(The postmaster can help you find an e-mail address or allow you complain about a user’s
behaviour.)




             carthy@ccvax.ucd.ie

  Username
                                     Domain        Top-level Domain
                      Computer


Top-level Domains
com            Company
edu            Educational Establishment
gov            Government
mil            Military
org            Organisation (usually non-profit)



Comp 1001: The Internet                                                                   2
Countries
ie                Ireland
uk                United Kingdom
jp                Japan
au                Australia
etc.


Servers
Computers storing information or forwarding mail are sometimes called servers. A file server
is a computer which stores files on a network. These files might contain the software that users
require or the their data. A mail server is a computer that processes electronic mail (see below).
The term site may also refer to a computer or server that is on the Internet.

Electronic Mail (E-Mail)
Allows you send messages via computer networks to other computer users. The message may
include a file (containing a report, a book, pictures etc.). You need to know the e-mail address of
the recipient, just as you need to know a phone number to use a phone.

Features

  •    •   Fast delivery of message
  •    •   Recipients can read mail at their convenience
  •    •   Forward message to others
  •    •   Reply easily
  •    •   Store message permanently
  •    •   Send a single message to many users
  •    •   Scan your e-mail quickly
  •    •   Send files (attachments)
  •    •   Subscribe to mailing lists


Down Side

  •    •   Junk mail – called spam.
  •    •   Abusive (dangerous?) mail
  •    •   Privacy
  •    •   Costs (Infrastructure)

E-Mail Etiquette (Netiquette)
  • • Be careful because of immediacy! Very easy to reply in haste and regret at your leisure!
  • • Messages you send can become public!
  • • Message may arrive at any time and some users receive hundreds of messages. Need to
       supply context for your reply.
  • • Be careful with dry wit !




Comp 1001: The Internet                                                                  3
E-Mail Software
There are a number of E-Mail packages available such as Eudora, Pegasus Mail, Outlook, Outlook
Express and so on. Basically they usually allow many of the same facilities:

 • • Use of Nicknames or Aliases

 •   e.g. define Joe as an alias for carthy@ccvax.ucd.ie
 •   This allows you use Joe as the address instead of the longer form.
 •   • Use of Address Books to store lists of addresses you use
 •   • Use of folders to organise your messages
 •   • Ability to send files with messages and to receive them
 •   • Ability to check on a regular basis if new mail has arrived
 •   • Ability to send CCs (Courtesy Copies (carbon copies)

Mailing Lists
The idea is that a group of people interested in some topic e.g. neural network computers can set
up a mailing list. Individuals can send messages to this list. These messages will be collected and
will be sent to all users who belong to the mailing list at regular intervals. There are 1000’s of such
mailing lists available. This is a very popular way of keeping up to date in some area.

To join one, you simply send a message to the list administrator who will add your name to the
list. You can leave the list in a similar fashion.

Mail Filters
Software developed in an effort to avoid junk mail. Messages are automatically scanned and may
be discarded according to criteria you set e.g. trash messages from username Carthy!


Surfing The Net !
As we have seen the Net is a global network of computers located at various sites around the
world. Using a browser (browsing software) we can look at the information stored at the various
sites on the Net on our own machines. Once we have accessed the information we can download it
to our machine for perusal, printing or storage i.e. we can take our own permanent copy of much
of the information on the network (free of charge). The only proviso is that you have sufficient
space for the information. The capacity of even the most modern high specification PC is minimal
compared to the vast quantities of material available on the Net.

We use the term resources to refer to what’s available on the Net such as Software, reports, news,
maps, sports results, book reviews, film reviews, images (from fine art, scenic locations, super
models to the most degrading and obscene pornography that you probably cannot even imagine)
and so on.

The World Wide Web (The Web)
The World Wide Web (WWW or W3) can be viewed as being synonymous with the Internet (not
strictly true!). Basically, it involves a user friendly mechanism for accessing Internet resources.



Comp 1001: The Internet                                                                      4
Information is organised as a collection of interconnected pages. Each page may have one or many
pointers (links) to other pages, which in turn have pointers to other pages and so on as shown in
the diagram below.

This type of organisation is called hypertext. It is used in other applications as well, such as
in computer aided learning software. Many software packages provide online manuals in
hypertext form. [The term online means information is stored in a computer file and is accessible
via computer software].




                Hypertext Document
                                                                            sss


                                                                            kkk



          abc                                   ggg
                                                                                  rrr
          abc                                   hhh

          abc                                   xyz                               mmm




                    kkk
                                                      ggg
                    ppp
                                                      hhh

                                                      xyz




An interesting feature of Web documents is that the pointers may access (and often do) pages on
different computers in different countries! Thus when you are accessing a Web document, the
pages may have to travel from different continents to your machine.

To access a page of a Web document, you simply click the mouse on the pointer to that page. The
point usually takes the form of a highlighted piece of text or a picture or a button. By clicking the
mouse on the pointer, the system automatically fetches the page being pointed at. This then
displays the page from perhaps another Website (computer on the Web). This page will also have
pointers to other pages and so you can move from one computer to another. Hence the term
navigation is sometimes used for the way that information is accessed on the Web.
Comp 1001: The Internet                                                                    5
The first page of a Web document is called the Home Page. Each Website will typically have a
home page describing the site and what’s available at the site. In addition, users at that site may
have their own home pages describing their area of interest or activities. For example, UCD has a
home page on the UCD site. This in turn will allow you access information about UCD (e.g. phone
directory) or other Irish sites etc.

Each resource on the Web has an address similar to those described for E-mail. This is called the
resources URL (Universal Resource Locator).

For example the UCD home pageURL is http://www.ucd.ie

Internet Browsers
The two most popular browser are Netscape or MS Explorer while Apple offer the Safari
browser. A browser allows you access various Internet resources in a user friendly fashion.
Resources on the World Wide Web, have addresses that begin with http://. (http stands for
hypertext transport protocol) and the computers providing access to such Web resources are called
Web servers. [There are also News servers and ftp servers; see below].

Other Internet Utilities

• Network News and Newsgroups
Network news usually involves an network called USENET which strictly speaking is not part of
the Internet, but is accessible from the Internet. Essentially it involves electronic bulletin boards
which are similar to the bulletin board in a supermarket. Since they are computer based, they are
useful for discussions on specific topics as opposed to just selling services. There are thousands of
such bulletin boards on the Internet where they are referred to as newsgroups. A particular
newsgroup may be dedicated to such topics as a discussion on the philosophy of life on Mars;
Windows 95 performance; where to buy a good pizza; what constitutes a good pizza; the war in
Bosnia; the music of the Beatles etc. etc.

Millions of people are estimated to read network news on some topic each day. Anyone can send
their comments or questions to any of the Newsgroups. Very heated arguments can take place
where insults and sharp comments can start flying - these are called flames and the heated
argument is called a flame war.

An individual entry in a newsgroup is called a posting or an article. These articles are organised
into topics. A given newsgroup might be about buying a PC, topics in that newsgroup might
concern different CD-ROM drives; different tape backup mechanisms; RAM considerations and
so on. Users may have queries on a particular topic e.g. CD-ROM drives. These queries would
lead to replies and perhaps more queries. The collections of queries and replies is called a message
thread within a specific topic. The software you use to access the newsgroups displays these
threads in an organised fashion to make it easy for you to follow the thread of the topic. The
original article will be displayed first, followed by the queries and replies in chronological order.
Your browser can be used to access Network News. The news groups are organised into different
categories such as the following:

comp           Computer discussions                  news About Network News
rec            Recreation and Art                    sci        Science discussions
soc            Social issues                         talk       Fiery discussions
biz            Business                              bionet     Biology
misc           Miscellaneous                         alt.       Alternative !

Comp 1001: The Internet                                                                    6
Network newsgroups have names such as:

comp.risk                                    Risks of using computers
comp.society.privacy                  Privacy issues
news.announce.newgroups               Information about new newsgroups
news.announce.newusers                Information for new users
rec.mag                               Discussions about magazines
soc.right.human                       Human rights issues

Frequently Asked Questions (FAQs)
As you may imagine certain questions get asked very frequently especially questions from new
users. To facilitate handling such queries, lists of FAQs and their answers are available in most
news groups and are also associated with many of the activities associated with the Internet. So,
before posting a question to a newsgroup, check the FAQs list first. If not you risk getting
inundated with irritated responses questioning your mental statistics. A flood of such messages is
referred to as spamming. This treatment is reserved for those who infringe the rules of Netiquette!
One such infringement is to post a message selling some item in a newsgroup dealing with any
other topics other than selling such items. FAQs are available about Netscape, FTP, Network
News, E-mail mailing lists and so on.

• FTP (File Transfer Protocol)
The term ftp may be used as a noun or verb. When used as a verb it refers to the action of
transferring files from one computer to another i.e. ftp software allows you download resources
from the internet to your machine. One frequently sees phrases such as “... XYZ software may be
ftped from the University of Michigan archive”. There are many archives on the internet which
are simply collections of software and other resources that can be accessed via ftp (and other
Internet tools). Ftp software has been available long before browsers like Netscape which also
allow you download resources. The newer products such as Netscape are often easier to use than
ftp, but may not be as fast as ftp. Ftp sites may be accessed using Netscape by specifying their
addresses preceded by ftp:// e.g.. ftp://ftp.hea.ie allows you access an Irish ftp server which acts
as the Irish national archive. You may obtains copies of various software packages here. In
addition, it is worth noting that many famous ftp archives have mirror sites. A mirror site is simply
a site which duplicates the resources of another site. By accessing a mirror site in Ireland you can
save a lot of time rather than accessing the original site in the U.S. for example. The Fetch utility
(for the Macintosh) is one ftp package and is excellent ftp utility.

Anonymous FTP
Many of the resources available on the Internet are accessible via anonymous ftp. This means that
anyone with Internet access can obtain those resources without having to have an account on the
machine where the resources are held. It means that the site where the resources are stored
provides an anonymous FTP server which lets you login to the account called anonymous and use
any password you wish i.e. the password is simply ignored for that account.

By convention, users are expected to use their e-mail address as their password. This allows the
archive managers keep track of who is accessing their resources. Thus, I would use
“carthy@ccvax.ucd.ie” as my password when accessing an anonymous ftp server. Your ftp
software can be set up to automatically login to anonymous ftp sites.

• Chat (Internet Chat Relay (IRC))
Chat software allows you “chat” to others about some subject in an interactive session. This means
that you type an entry which can be read by people connected to the channel that you are
accessing. A channel is essentially a subject area that has been set up by a group of people who

Comp 1001: The Internet                                                                    7
want to char with each other. Channels may range from such serious topics as Windows 95 to fun
channels. Your chat software will allow you see the available channels and access the one(s) you
wish. You may simply look at what’s going on or contribute what you wish.

A potentially interesting way to while the time away! Beware of cybermonsters - they do exist!

• Telnet
Telnet software allows you login from your own computer and use a remote computer over the
Internet. For example, if I travelled abroad and had use of machine with Internet access, I could
use telnet to login to my computer account in UCD. From UCD, I can use telnet to login to other
computers on the UCD network, provided I have an account on those machines. On the Internet,
many machines provide an account called guest which users can login to without a password, to
access the resources of that machine. The difference between using ftp and telnet is that ftp only
allows you transfer files from one computer to another, whereas telnet gives you general access to
the resources on the machine you login to.

Telnet was one of the early methods of accessing resources on the Internet and browsers such as
Netscape usually allow you achieve the same objectives. An address such as telnet://machine-
name.ucd.ie allows you use Netscape to access a computer called machine-name.ucd.ie using
telnet.

Software on the Internet
• Viruses
As pointed out earlier, there is a wealth of software (including games) available on the Internet.
The onus is on the user to ensure that the software you obtain from the Internet is “safe” e.g. virus
free. A virus is simply a program which is designed not to do useful work and very often to do
something malicious such as deleting all the files on your hard disk. Anti-virus software is
available on the Internet and is also commercially available. If you intend obtaining software from
the Internet or any other source such as friends etc., then it is a highly recommended to obtain a
good anti-virus system to check anything you copy to your machine.

You should note that viruses may infect your machine by simply using your browser on the
Web. It is very important to install anti-virus software and keep it up to date with the latest
virus updates.

• Software Copyrights
Software comes from a variety of sources with different copyright rules applying.

Commercial software is licensed and users are required to pay for it. In addition, they are not
allowed pass copies to other users (either free of charge or for payment). Software companies
spend millions each year developing new software and it is reasonable that they should be able to
protect their investment.

Public Domain software carries no copyright and is released by its owner or author for public use,
free of charge. Users are free to do what they wish with it.

Shareware refers to software that you may use for a trial without obligation to buy it. The author
retains copyright. At the end of the trial, you are asked to either pay for the software or destroy
your copy. You are encouraged to pass copies to your friends (without charge) giving them details
of the authors copyright. Shareware is usually very cheap. Enforcing payment is practically


Comp 1001: The Internet                                                                    8
impossible and depends largely on goodwill. One way of encouraging payment is that you get a
copy of the manuals when you pay for the software.

Freeware refers to software which is free of charge, but the author retains copyright. You may
pass copies on without charge.

Some software may be free to private users but commercial users are charged on a shareware
basis.


• Compression
Files occupy storage, measured in bytes. Many files are quite large (several hundred kilobytes or
even a few megabytes) and it takes quite a while to transfer them from one computer to another. In
addition, obviously, they occupy significant amounts of disk storage. (It should be especially noted
that digital images and audio material require large amounts of storage)

To alleviate this problem, various data compression techniques may be used. Data compression
software can reduce storage requirements dramatically, with savings ranging from 10% to 90%
depending of the type of data being compressed. Some PCs use this type of software to effectively
double their hard disk storage capacity, i.e. all data stored on the hard disk is compressed, so that
an 80Mb disk appears as if it has 160Mb capacity. Data compression is also used by software
vendors who typically compress their software when distributing it on floppy disks, since it
reduces the number of floppy disks required.

Data compression is also very important for Internet users, since by compressing data, it can be
transmitted in less time. This is important because users are charged for either transmission time or
for the amount of data transmitted, or both. Compression techniques reduce both costs.

Popular data compression software includes products such as Stuffit Deluxe, PKZip, Compress
and Diskdoubler.

When a file has been compressed by such a program, it is usually given an extension such as

       picture.zip                           PKZip used
       pixture.sit                           Stuffit “
       picture.sea                           Stuffit “
       picture.z                             Compress (Unix)
       picture.dd                            DiskDoubler (Macintosh)


• Encoding Files
In addition to compression, files may be encoded for transmission. For example to send software
or images via e-mail, the file containing the software must be encoded. Two popular encoding
mechanisms are BinHex and UUencode. Your e-mail software will typically allow you use these
mechanisms to send and to receive such files. Files encoded with BinHex usually have the
extension hqx e.g. picture.hqx.

• Encryption
This is important in the protection of information and has been used for thousands of years. It is
the use of methods of scrambling or coding information (enciphering, scrambling, coding) to make
the information incomprehensible to all except the intended users. When a file is encrypted by a


Comp 1001: The Internet                                                                    9
user, the user specifies a key (password) for that particular file. The file can only be decrypted if
the correct key is used. Encryption software is available on the Internet.

Encryption is a major issue for Internet users for reasons of privacy and also to prevent fraud. For
example, it is possible to purchase goods and services via the Internet. One method (which should
be used with extreme caution) is to send your credit card number to the supplier. If you can
encrypt this, it reduces the chances of others obtaining and using your number. It does not prevent
the supposed supplier from ripping you off!! Such cases arise with telephone orders and have been
reported with the Internet as well. Caveat Emptor!

It should be noted that encryption and compression are important for computer users who never
access the Internet. Users may selectively encrypt sensitive files. In addition, they may compress
large files to reduce their storage requirements.

Internet Service Providers (ISPs)
Internet access is via an Internet Service Provider such as Eircom.


Controlling the Internet
•Some say its impossibl because of the sheer volume and dispersion of information.

• Censorship: This is an emotive topic fiercely resisted by many in the Internet community but
should there not be a balancing rights with responsibilities. Controls do apply to TV, Radio, Film
and Newspapers, so why not the Internet ?

Watch vested interests fight to protect copyrights:
                      Music industry
                      Computer Software industry
                      Film industry
                      Publishing industry




Comp 1001: The Internet                                                                    10

				
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