 |
The Internet: World wide collection of interconnected networks that use
TCP/IP.
 |
Network: Collection of 2 or more computers connected together via
communications devices and media. |
|
Uses: information resource, communications, financial, commerce,
passive entertainment, active entertainment, education, document
processing. |
|
|
History:
A Brief History of the Internet http://www.isoc.org/internet-history/brief.html,
Barry M. Leiner, Vinton G. Cerf, David D. Clark, Robert E. Kahn, Leonard Kleinrock, Daniel C. Lynch,
Jon Postel, Larry G. Roberts, Stephen Wolff
|
Computer
networks have been around for a long time. More important that
its past, the future will bring tremendous
capability, with both great opportunity and perhaps chaos. We
are still laying foundations for its use, management, and
funding. Legislators are still considering its taxation and
permitted use. This is the point in history that knowledgeable
voters need to be thinking about how this resource can serve the
public, and communicating those thoughts to government officials. |
|
AUTODIN (mid 1960s to 15 SEP 2000) |
|
ARPA Net (1969) to Internet: telnet/ FTP. Goal: reliable, robust
digital communications network |
|
BitNet: "Because It's Time Network", was created in 1981 and
is operated by the Corporation for Research and Educational Networking (CREN).
[Encarta Encyclopedia online] {BitNet was well established and in use between University of North Florida (Jacksonville) and
University of Florida (Gainesville) by 1981.} |
|
NSF Net (1985 - 1995): gopher. Network with 5 supercomputers. |
|
Internet: 1986 |
|
Internet 2
(I2), (academic). Goal: Develop and test advanced
technologies before being placed into general use.
 |
National
Science Foundation |
|
190
universities |
|
>60
companies |
|
US
Government |
|
|
Next Generation Internet (US Government)
|
Department
of Defense |
|
|
Other Networks: Global Multiprotocol Open Internet, Bitnet (predates
Internet), Internet,
Earn, NetNorth, GulfNet, UUCP, FidoNet, OSI, CompuServe (predates
Internet), Prodigy. |
|
|
Packet-Switching Concept
|
Goals of packet switching:
|
speed: Transmit packets in parallel. |
|
reliability: Reroute around disabled links. |
|
security: Randomize path selection to
decrease vulnerability in transit. |
|
|
Transmission Control Protocol / Internet Protocol (TCP/IP) ,
a packet-switching protocol. |
|
Protocol: A set of rules and procedures.
Protocols are followed in medical procedures, politics, and
communications systems. Example: telephone conversation. |
|
Packet switching network. View
this presentation online if you did not see it in class, or if you
missed class! |
|
|
Streaming Concept
|
Send, receive, buffer, play, discard (bitbucket) -> streaming. |
|
Packets are made available to the user upon packet arrival rather than
waiting for complete file transmission. |
|
No beginning or end of message is necessary. Can transmit continuous
broadcast, such as a radio station, over the Internet. Example, WTOP
(Washington, DC news station) http://www.wtop.com/listenlive.shtm |
|
|
Navigating the Web http://www.usna.edu/Library/Navweb.htm |
|
Network terminology
|
node: A terminal or connecting point in a
network. |
|
backbone: Long distance links between local
networks. |
|
host: A network device that is assigned an IP
address. |
|
traffic: Flow of messages on a network.
Think of traffic on the Interstate highways. |
|
|
Connecting to the Internet
|
Rapidly changing market. Shop around. Avoid long term contracts.
Beware of buying a computer at a discounted price that requires an
agreement to use a particular ISP for several years. Your overall
cost of computer plus service will be higher that just paying for the
computer and separately shopping for service. |
|
Connect via LAN
or via modem (dial=up access by telephone or cable) to a
Point of Presence (POP) of an Internet Service Provider
(ISP). Advanced Internet Technologies (AIT). |
|
An Online Service Provider is an ISP that charges more money to
include additional services, presumably of additional value. America
Online (AOL), Microsoft Network (MSN). |
|
A Wireless Service provider (WSP) is an ISP that permits wireless
connection to a POP. |
|
ISDN
(Integrated Services Digital Net0owrk), DSL (Digital Subscriber
Line, Sprint), CATV, T1, T3, modems, etc. |
|
Road
Runner: Time Warner Cable |
|
|
How Internet works
|
Client / Server
|
Client software, such as a web
browser or email client, issues task
requests to a server. |
|
Server software, such as a web
server, print server, file server, or email server, provides
services to clients. Services may include access to
hardware (expensive printer, computer, external storage),
software, data, or communications. |
|
|
(Components: wires and cables, hub,
concentrators, bridges, switches, routers, signal processing issues.) |
|
Open System Interconnection (OSI) Model: OSI_Model.pdf
[People going into networking should download this table.] |
|
|
Internet
Protocal (IP) addresses
|
Logical address |
|
Internet Protocol (IP) address uniquely
identifies a computer on the Internet. |
|
IPv4 (dotted decimal form: 255.255.255.255)
Each number is 8 bits, called an octet, and can have a value from 0 to
255 decimal. The 32 bit address size limits the number of
addresses available, which is why the system is being modified.
This is similar to the problem of running out of area codes in the world
of telephone communications. |
|
IPv6
Internet Protocol (IP) address (form: A0 B1 C2 D3 E4 F5 06 17) is a
128-bit address. This system will solve the address
assignment problem for the next decade. IPv4 is a subset of IPv6. |
|
IPv6 is already in use in some locations. USA is slow to
adopt. Changing systems is a capital investment and training
issue. |
|
Internet
Corporation for Assigned Names and Numbers (ICANN) assigns and
manages IP addresses. |
|
Hosts permanently connected to the Internet have "permanent"
(static) IP addresses. |
|
Dial-up users are assigned an IP address out of its allocated IP
address pool for temporary use while connected. This strategy is called
a dynamic IP address. If you disconnect and later reconnect, you
will probably have a different IP address from that pool. |
|
Local Area Networks might manage its own internal addressing scheme in
a way that does not require terminals to have an IP address that is
unique over the Internet. |
|
To find your current IP address while online:
|
WIN 2000 and WIN XP: type cmd to display the MS-DOS window. Type
ipconfig and press Enter. |
|
WIN 98: Select "Run" from the Start menu. Type winipcfg
and press Enter. |
|
|
|
Media Access Control (MAC) Address
|
Physical address or hardware address.
48 bit code, 12 hexadecimal digits. These address codes are necessary,
and are burned into network devices by the manufacturer. Network
cards have MAC addresses, for example. |
|
IEEE assigns the first 6 hex digits to identify the
manufacturer. This is called the Organizational Unique Identifier. |
|
The manufacturer assigns the last 6 hex digits. |
|
|
Domain
Name System
|
Domain Name Server: table look-up
by domain name to produce an IP address |
|
Top level domain: .com, .gov, .edu, .mil, .net, .org; transition: physical
--> logical --> arbitrary |
|
New
(2001) top-level domain names:
|
.shop .mp3 .inc
.kids .sport .family .chat
.video .club .hola |
|
.soc .med .law .travel
.game .free .ltd .gmbh
.tech |
|
.museum
.biz .info .name .pro
.aero .coop |
|
another one devoted to pornography
( .smut, .crud? ) |
|
|
|
Ports and Port Numbers: A port number is a way to identify a specific process to which an Internet or other network message is to be forwarded
when it arrives at a server. http://whatis.techtarget.com/WhatIs_Definition_Page/0,4152,212811,00.html |
|
System Port Numbers: ftp://ftp.isi.edu/in-notes/iana/assignments/port-numbers
. Ports are used in TCP [RFC793] to name the ends of logical connections which carry long term conversations. For the purpose of
providing services to unknown callers, a service contact port is defined.
|
The contact port is sometimes called the "well-known port". The Well Known Ports are assigned by the IANA and on most systems can
only be used by system (or root) processes or by programs executed by privileged users.
The range for assigned ports managed by the Internet Corporation for Assigned Names and Numbers
(ICANN)
is 0-1023. |
|
The Registered Ports are listed by ICANN and on most systems can be used by ordinary user processes or programs executed by ordinary
users. Registered Ports are in the range 1024-49151. |
|
The Dynamic and/or Private Ports are those from 49152 through 65535. |
|
Protocol Number: ftp://ftp.isi.edu/in-notes/iana/assignments/protocol-numbers
|
4 IP: Internet Protocol |
|
5 ST: Stream |
|
6 TCP: Transmission Control |
|
17 UDP: User Datagram |
|
21 FTP: File Transfer Protocol |
|
45 IDRP: Inter-Domain Routing Protocol |
|
46 RSVP: Reservation Protocol |
|
47 GRE: General Routing Encapsulation |
|
80 HTTP: Hypertext Transfer Protocol |
|
103 PIM: Protocol Independent Multicast |
|
110 POP3: Post Office Protocol Version 3 |
|
|
|
WWW
|
The World Wide Web is a collection of Web servers that use the
Internet for communication. |
|
The World Wide Web is NOT the Internet. WWW is a user of the
Internet. |
|
W3C is the authority for the World Wide Web (WWW = W3
=> W3) |
|
Web, internet, hypermedia informal glossary of terms: http://www.w3.org/Glossary |
|
Web architecture terms: http://www.w3.org/Architecture/Terms |
|
Uniform Resource Identifier (URI):
|
|
The following examples illustrate URI that are in common use.
ftp://ftp.is.co.za/rfc/rfc1808.txt
-- ftp scheme for File Transfer Protocol services
gopher://spinaltap.micro.umn.edu/00/Weather/California/Los%20Angeles
-- gopher scheme for Gopher and Gopher+ Protocol services. Gopher is
deprecated. Very few Gopher servers are still supported.
http://www.math.uio.no/faq/compression-faq/part1.html or
http://131.122.220.30/Library
for the US Naval Academy Library (great site!)
-- http scheme for Hypertext Transfer Protocol services
mailto:mduerst@ifi.unizh.ch
-- mailto scheme for electronic mail addresses
news:comp.infosystems.www.servers.unix
-- news scheme for USENET news groups and articles
telnet://melvyl.ucop.edu/
-- telnet scheme for interactive services via the TELNET Protocol.
This is the usual method for connecting to a supercomputer.
|
|
Uniform (or Universal) Resource Locator (URL): access method, hostname, port number,
directory name.
|
URL is an informal term (no longer used in technical specifications) associated with popular URI
(Uniform Resource Identifier) schemes: http, ftp, mailto, etc.
http://www.w3.org/Addressing/Overview.html#URL94 |
|
Universal was the original definition of choice but was deemed by most to be too ambitious, and the more frequently used
Uniform was instated by the now-defunct URI Working Group. http://malaysia.cnet.com/Briefs/Glossary/Terms/url.html |
|
A Uniform Resource Locator (URL) is a compact string
representation of the location for a resource that is available via
the Internet. [Masinter, Alvestrand, Zigmond, Petke,
"Guidelines for new URL Schemes", Network Working Group,
The Internet Society (1999). http://www.ietf.org/rfc/rfc2718.txt
] |
|
File URI, for files on an ftp server: "file://ftp.ABC.com/directory_path/myfile.txt" |
|
Gopher URI, for files on a gopher server (now considered
obsolete): "gopher://gopher.myschool.edu:9876/"
where "9876" is an example port number. 70 is the
default Gopher port number. |
|
USENET newsgroup: news:alt.computing |
|
HTTP, used for web pages: "http://www.myhost.com:9876/directory_path/mypage.html",
where "9876" is an example port number. 80 is the
default HTTP port number. |
|
|
Uniform Resource Name (URN): persistent, location-independent
resource identifiers |
|
|
HyperText Transfer Protocol (http:// ) |
|
Web server, webmaster, web administrator
|
A web server resides on a host computer and is assigned a
URI.
This server is software that that responds
to http protocol requests from Web clients. These
requests include requests to transmit files and perform related
tasks, and provides error messages when requested files are not
available. It is not
unusual for a host machine to host several servers, such as Web, ftp,
mail, news, chat, simultaneously. |
|
A web page is an electronic document that is written in Hypertext
Markup Language (HTML). A web page may include files of other
types by reference, such as graphics or sound. A web page may also
provide access to other files by hyperlinks. |
|
A web site is a directory accessible to a web server that has assigned
to it the name of a file as a default web page called a home page.
A web site usually contains one or more web pages that are linked together and
related data files. Even if such a file is not an HTML file,
it is transmitted to the client making the request. In addition to
files that may be referenced (directly or indirectly) by a home page, a
web site may contain other files. Sometimes non-referenced files
are placed on a web site for document sharing between people who know
what file names to ask for without having to use hyperlinks.
Non-referenced files may also be used for related tasks, such as
capturing and recording product order information, or grading on-line
quizzes. Designing the directory structure and access controls for
these files is a task requiring knowledge of the server, host operating
system, and attention to detail. |
|
A home page is a file on a web site with a specific file name
specified by the web server administrator. Often, the name is
"default" or "index". The default file
name is appended to a received URI if the incoming request does not
specify a file name. A home page usually acts as an index to other
documents on a web site. While a usual and nice feature of most
web sites, a home page is not a necessary component of a site
accessible via the World Wide Web. |
|
WWW server software: http://www.w3.org/Servers.html
|
A popular free good server is Apache which runs under UNIX. |
|
|
|
Web Browser
|
A Web browser is the client software in the World Wide Web
client-server system. This is the software used by people to issue
requests to retrieve files from Web sites, view Web pages, and do
related tasks. The activity of issuing requests is called surfing
the Web. The client browser determines if, and how, a received
file is handled locally. |
|
Mosaic. Written by National Center for Supercomputer Applications
(NCSA). Progenitor of Netscape. |
|
Internet Explorer |
|
Netscape Navigator |
|
Opera http://www.opera.com
(Smaller, loads faster than Netscape or Internet Explorer) |
|
Who is using what browsers and operating systems
|
|
|
Browsing the Internet
|
FTP: the earliest method, and still the fastest method for retrieving
a file if you know where it is. |
|
Gopher. Text based. Very few Gopher sites are still actively
maintained. |
|
Connecting to the Internet and starting a browser. |
|
Uniform Resource Identifier (URI): HTTP, domain name: IP address,
path, file name. |
|
Hyperlink:
|
A reference that can request a file on a web
site, if the
hyperlink is activated. |
|
Sometimes can locate a position within a file. |
|
|
Navigating Web pages using hyperlinks. |
|
Searching for information on the Web. |
|
|
Kinds of Search Engines
|
Catalogs
|
|
Search Engines
|
A search engine is a computer program with an associated database
of key words and web addresses. |
|
A response from a search query is a list prepared by a search
engine from its own database and transmitted to you. |
|
Search Engines update their database to increase its usefulness or
profitability. |
|
Commercial: Alta Vista, Infoseek, Yahoo, Excite, Lycos
|
Search results are heavily influenced by advertising. For a
fee, you can get your site listed closer to the top of a search
result. |
|
For information searches,
particularly for academic use, you must view many pages of
responses before you start viewing ones that are not given
preferential position in the listing based upon that site's fee
paid to the search engine owner. |
|
Lycos ftp search http://ftpsearch.lycos.com/?form=normal |
|
20 Feb 2002, 0708 hrs, NPR News: AltaVista announced
it is dropping its free email account service and focus on
profits from its search engine business. |
|
|
Academic ftp search: http://sunsite.cnlab-switch.ch:8000/ |
|
Veronica: Text based. Predates the WWW. Used to search Gopher
sites. |
|
Archie is shut down, and therefore unsupported and obsolete. |
|
|
Metasearch Engines
|
Often search smaller, less well known search engines and specialized sites. |
|
DogPile, Metacrawler |
|
|
Terminology
|
search text, key words |
|
spider, crawler, bot [buzz... ] |
|
hit, directory |
|
|
|
Types of Web Pages (You could come up with your own classification system.
The list is not exhaustive.)
|
Advocacy, business and marketing, information, news, portal, personal |
|
|
Multipurpose Internet Mail Extensions (MIME) Types, Multimedia:
|
graphics: JPEG, GIF, PNG |
|
animation: animated GIF
|
An animation is originated in the mind of its creator. It is a
sequence of static images displayed quickly, much in the same manner
as a movie on film. It is not a continuous image reproduced automatically from a
continuous recording process. |
|
A motion picture is a sequence of still pictures displayed rapidly, such as seen at a movie theater. |
|
A video is a continuous recording of the scan of an image, such as a video tape. |
|
|
audio: WAV, AU, MP3 (MPEG Layer 3) |
|
video: MOV, AVI, MPEG |
|
|
File compression [computer majors should know this]
|
Text:
|
exact reconstruction |
|
remove white space, compress duplication, encode |
|
index words, make dictionary of duplicate words, replace
duplicated words with code or links. |
|
|
Static Images:
|
exact reconstruction: bitmap, compress duplication |
|
parameterization: extract and encode geometric shapes |
|
approximation: transforms (Fourier). Any approximation
method removed information which cannot be restored. A goal is
to have an approximation that retains information you are interested
in, and omits information (such as noise) that you are not
interested in. |
|
|
Moving images, sound: not an easy problem. Can compress and send
packets. Still want to have smooth reception. Cannot hold all data.
|
approximation: Wavelet
transformation for compression. |
|
transmit just changes in image after initial image is sent. |
|
|
|
Smart Download
|
Packets stored. Local record kept of which packets are received. |
|
Interrupted download can be restarted, fetching next packet in
sequence. |
|
Very good for downloading very large files. |
|
|
Coding: HTML, XML, Java, ActiveX control
|
|
Interaction
|
Who bears the computational burden? client versus server. |
|
HTML: HyperText Markup Language.
|
See bottom of this lesson plan for a simple example. Most
kids graduating from public high schools now have programmed in
HTML. |
|
Static, no interaction other than hyperlinks |
|
HTML transactions are memoryless. |
|
Apparent "memory" is imbedded in hidden statements
retransmitted back to you. |
|
|
XML: Extensible Markup Language is the universal format for structured documents and data on the Web.
http://www.w3.org/XML/ |
|
CGI: executed on the host server
|
NCSA CGI Primer http://hoohoo.ncsa.uiuc.edu/cgi/ |
|
Executable, security problems, fast: C++,
Fortran, Cobol, assembly language |
|
Interpreted, more secure, slower: Perl, TCL, Unix shell, MS
Visual Basic, Applescript |
|
Collecting data centrally, interaction with other software,
particularly e-commerce. Multiplayer games. |
|
|
Java:
an interpreter, executed on the client computer
|
Demonstrations, animation, educational software for
exercises |
|
Java will significantly slow the responsiveness on a slow
computer. Its use should be carefully planned so that it adds
real value to the interaction when it is used. |
|
|
|
Teleconferencing, Internet telephone service
|
Data is compressed. |
|
Data is partitioned into packets. |
|
Packets are transmitted over internet. |
|
Packets are received, reassembled, and displayed. |
|
|
Virtual reality, VRML
|
Medical world: extend expert knowledge to field hospitals globally |
|
Star Trek holodeck |
|
|
"Push" technology
|
Preposition files on servers closer to users to make them more quickly
available when demanded. This is similar to the grocery store ordering
and stocking food on shelves close to your home. The gasoline distributors
attempt to do this. |
|
"Push" technology: Viewable online and later off-line. |
|
Good for stock brokers and traders |
|
News junkies |
|
Military command and control force status information |
|
|
Webcasting
|
Webcasting is the use of Internet for broadcasting by using the
streaming protocol. |
|
Webcasting, combined with "Push" technology, is used to
distribute syndicated programs for radio broadcast. This ensures
programs are available ahead of time and not as much at risk for delay
due to communication systems disruptions. |
|
audio and video programs: CNN, Focus
on the Family |
|
|
Security, privacy
|
authentication, firewalls |
|
https: use of http over secure sockets layer |
|
|
Electronic commerce
|
EDI: Electronic Data Interchange |
|
electronic money
|
CA: Certificate Authority |
|
digital certificate |
|
|
|
Web publishing
|
Five major steps to Web publishing:
|
Plan the web site: Purpose, characteristics of people you want to
visit the site, how to differentiate your site from similar ones. |
|
Analyze and design the web site:
|
Layout: text, graphics, audio, video, virtual reality. |
|
Do you have the resources to meet your design requirements?
Equipment, software, training |
|
|
Create the web site
|
Fast coding with inefficient and slow loading HTML can be done
with HTML editors.
|
Adobe GoLive, Macromedia Dreamweaver, Macromedia Flash |
|
MS Front Page, Lotus FastSite. These can do most of what you would want
as a beginner. |
|
HTML editors: Arachnophilia (free), Hot Dog |
|
Many productivity applications now can generate HTML. MS
Office 2000 components can generate web pages that are
functional and convenient, at the expense of large file
sizes and inefficient code. |
|
|
Cut out unnecessary HTML code manually with text editor. Can
generate some things easier manually. |
|
|
Deploy the web site
|
Issues: Passive versus Active sites (my terminology). Do
you need to capture responses, maintain an automated database,
do computations, and interact with customers? Do you need
to manage financial transactions? These require more
sophisticated permissions and protections than passive websites
that display static content. You may need to get advice
and services from a company such as Verisign, http://www.versign.com |
|
Web hosting at
|
|
|
Maintain the web site
|
Webmaster, Web Administrator, Server Administrator |
|
|
|
|
Email: Exchange of text messages and attachments
|
Mail server: POP3 server, holds email |
|
Email program, address book, mailbox |
|
Email address: UserName@DomainName |
|
SMTP: protocol for message format and addressing. |
|
POP3: Post Office Protocol 3, for retrieving email from a mail server. |
|
Free email at http://www.hotmail.com,
http://www.yahoo.com. |
|
Instant Messaging: notifies you when people are on line and allows you
to exchange messages or files. |
|
|
FTP: http://hoohoo.ncsa.uiuc.edu/ftp/faq.html
|
File Transfer Protocol |
|
Fast and efficient download of files from an FTP site. |
|
Anonymous ftp. Usually use your email address as the password to
log on. |
|
|
telnet (remote terminal emulation):
|
Connect as a terminal to a remote
computer |
|
This is the usual way to use a supercomputer |
|
|
Bulletin Boards and Discussions
|
USENET: newsgroups, news server, news reader |
|
mailing lists, list servers. "Majordomo" is a popular
list server. |
|
postings, thread |
|
Forum: moderated, unmoderated; discussion threads |
|
chat rooms, instant messaging, chat client and chat server |
|
|
Portal |
|
Netiquette = Network Etiquette:
|
Conserve bandwidth. Be polite. Avoid generating flame wars or
spam. |
|
Do not assume material is accurate or up to date. Be forgiving
of others who innocently pass on false material when it was not intended
to cause harm. |
|
If you must be critical, check your facts first. |
|
Assume anything you say on the Internet is public, and can and will be
used against you, perhaps even in a court of law. This is not a
forum for truly private conversations. Use a password protected
forum to increase the privacy. Use encrypted communications to
greatly increase privacy. |
|
|
Cookies:
|
Small static files placed on your computer by a web server. |
|
Contrary to urban legends, cookies cannot transmit a computer virus. |
|
|
Issues
|
Porn and stealth URIs: Whitehouse.gov versus Whitehouse.com (a similar site with a
different top level domain name), scsite.com versus scite.com (a similar
site with one letter dropped). |
|
<html>
<head>
<title>Here is a title for the Title Bar</title>
</head>
<body>
<p>Here is a simple web page.</p>
<p><Center>Here is centered text.</Center></p>
<p><B>Here is
bold text.</B><br>
<I>Here is italic text.</I><br>
Normal size. <big>Bigger
size. <big>Even
gibber.
<big>Neve bigreb.</big></big></big></p>
<H1> Heading 1 Text </H1>
<H2> Heading 2 Text </H2>
<H3> Heading 3 Text </H3>
<H4> Heading 4 Text </H4>
<H5> Heading 5 Text </H5>
<H6> Heading 6 Text </H6>
<Normal> Normal Size Text </Normal>
<p>Here is an
enumeration.
<ol>
<li>List Item one.</li>
<li>List Item two.</li>
<li>List Item three.</li>
</ol>
<p>Bullets
<ul>
<li>Bang 1</li>
<li>Ouch 2</li>
<li>Bandaid 3</li>
</ul>
<p>Now, a table with
3 rows and 4 columns.</p>
<table border="1"
width="100%">
<tr>
<td colspan="4">Row
1, spanning all 4 columns</td>
</tr>
<tr>
<td>Row 2, Column 1</td>
<td>Row 2, Column 2</td>
<td>Row 2, Column 3</td>
<td>Row 2, Column 4</td>
</tr>
<tr>
<td>Row 3, Column 1</td>
<td>Row 3, Column 2</td>
<td>Row 3, Column 3</td>
<td>Row 3, Column 4</td>
</tr>
</table>
<p>Here is <a
href="here_is_a_page_to_reference.htm">A
page</a> that is
referenced.</p>
<p>A picture.</p>
<p><img src="Gridlock.gif"
width="500"
height="300"
alt="Gridlock.gif (11281 bytes)"></p>
</body>
</html>