Transcript PowerPoint Presentation - Local to Global

Quick Overview
 Models
of computer communication
 Networks
 Networking terminology
 Internet history in a nutshell
 World Wide Web design basics
 HTML, browsers, protocols make it work
 Coding in HTML for the Internet
 Extensions to HTML and future trends
General Hardware Diagram for Networks
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Data transfer requires specific medium: copper wire,
fiber optic cable, radio signals (wireless)
Each computer must have an appropriate network
interface device or card (NIC): serial, Ethernet, wireless,
etc
General Software Diagram for Networking
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Data exchange requires protocols (agreed upon
rules of communication) between programs that
control hardware.
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Protocols involve signaling, response, data
content, timing, etc.
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Layers are used to handle the
complexity/changes inherent in hardware.
Recall using subroutines to handle hardware
access in BOE-BOT.
Network Topologies (Shapes)
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Various connection styles were explored:
backbone, Token ring, star topology, etc
 This creates a Local Area Network (LAN)
ARPANET in early 1970’s
ARPANET in mid-1980’s
The Internet Recently
Networking Protocols
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LANs and Wide Area Networks (WANs) require
some addressing method to route messages to
specific computers
Transmission Control Protocol/Internetworking
Protocol (TCP/IP) has been the most successful
Addresses are given in a dot notation:
172.21.7.11 is a typical IP address
Some arithmetic: Addresses range from 0.0.0.0
to 255.255.255.255 giving us 32 bits of address
This means about 232 or about 4 billion
addresses are possible. These are filled! IPv6
now in effect.
Routers use lookup tables to send packets of
data across network boundaries for delivery.
The Internet: LAN Point of View
Names Instead of Numbers
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It is hard to remember and type IP addresses
like 172.21.7.11 instead of natural names.
 Enter Domain Name Service or DNS. This
allows computer addresses to be arranged in
clusters, or domains, and addressed using
names instead of IP numbers.
 Example: math.hws.edu indicates some
computer found in the domain hws.edu. This
domain name is attached to routing tables so
routers know to send packets of data to our
campus firewall which forwards it to the server in
our campus LAN named math.
 Looks promising but there are still problems!
Documents Have Structure
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By the 1980s, many vendors offered competing
document formats, file systems, operating systems, etc.
 You needed to have technical skills and persistence in
locating, downloading or uploading a file, and
determining which application could view or print it!
 Also, hypertext authors were experimenting with links to
allow readers to move between documents using
graphical links. Example: Apple Computer’s Hypercard.
 No single system was in place to tie all this together and
allow non-specialists to post and/or have access to the
hundreds of Internet documents beginning to appear.
 Consequently, Internet commerce and novice user
participation was minimal due to these constraints.
The World Wide Web (WWW) Arrives
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Tim Berners-Lee, computer scientist at CERN, made a
number of important contributions which address these
problems.
 HTTP: Hypertext Transfer Protocol: How to name,
request, and transfer documents over the Internet.
 HTTPD: HTTP Daemon. Non-proprietary, client-server
oriented open source software to actually carry out the
HTTP protocol on many different operating systems.
 HTML: Hypertext Markup Language. A common
formatting language to allow consistent document
display on all computers. HTML documents also may
contain hypertext links to allow users to easily move from
one HTML file to another or browse the Web.
 HTML documents are typically named with extensions
.htm or .html and contain plain ASCII text. Coding!!!!
HTTP and Browser Basics
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An address or Uniform Resource Locator (URL) such as
http://math.hws.edu/vaughn/index.html indicates we are
referencing a document using the HTTP protocol from
the server math in domain hws.edu. The document itself
is found inside directory vaughn with its individual file
name index.html.
To send this request, we use a Web browser, a local
application which interacts with the Internet, and can
form HTTP requests, display HTML documents, etc.
Common browsers: Internet Explorer, FireFox, Opera,
Chrome, etc.
Other protocols and documents work with WWW.
ftp://math.hws.edu/vaughn/myFile.doc or (File Transfer
Protocol)
https://math.hws.edu/vaughn/secrets.pdf (Secure HTTP
uses encryption)
HTML Basics
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HTML documents are plain ASCII text created by users,
like you, using a simple ASCII text editor.
HTML documents are rendered by Web browsers to
appear with colors, fonts, images, formatting, tables, etc.
Control over the document display is done with HTML
tags such as <b>This text is bold</b>.
In order to have Web site content, most beginners learn
how to code in basic HTML then move on to using a
WYSIWYG HTML editor such as Dreamweaver, GoLive,
Aptana Studio, etc. You documents must be made
available on a Web Server which handles retrieval
requests.
Just like spreadsheets, HTML documents can be
enhanced with active, executing programs (VBScript,
Javascript, Flash, etc) to create DHTML or XHTML
pages.
Our First HTML Document
<html>
<head>
<title>My First Page </title>
</head>
<body>
This is my first web page!
<hr>
</body>
</html>
Rendering the HTML
via a Web browser
Where We are Going
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Learn the basic HTML tags to compose Web
pages.
Learn how to post pages on a campus server so
anyone on the Internet can access and see your
pages.
Learn more complex page design, composition
techniques, and the corresponding HTML tags.
Add Javascript code to HTML web pages to
make them active, not just static.
Introduction to an industrial-quality HTML editor.