Transcript Session2-InternetworkingAndWWW

1
Electronic Commerce
Session 2: Internetworking and the WWW
Session Objectives

After completing this session you will be
able to:




Describe the Internet and discuss its history
Describe the World Wide Web (WWW) and
write a simple HTML document
Describe different types of computer
networks
Discuss different methods of connecting to
the Internet
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The Internet



What is the Internet?
The history of the
Internet
The growth of the
Internet
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What is the Internet


The Internet is a large system of interconnected networks that span the globe
Internet-ready computers and personal
digital assistants (palm and pocket PCs)
can access this network2
5
What is the Internet Cont’d

The Federal Networking Council (FNC)
defines the Internet more formally as the
global information system that3:

is logically linked together by a globally
unique address space based on the Internet
Protocol (IP) or its subsequent
extensions/follow-ons
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What is the Internet Cont’d


is able to support communications using the
Transmission Control Protocol/Internet
Protocol (TCP/IP) suite or its subsequent
extensions/follow-ons, and/or other IPcompatible protocols; and
provides, uses or makes accessible, either
publicly or privately, high level services
layered on the communications and related
infrastructure described herein
7
What is the Internet Cont’d

The Internet allows:


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
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communication by e-mail
the reading of on-line newspapers, academic journals
and books
the joining of discussion groups,
participation in simulations and games
downloading of software, electronic books and music
businesses to market and sell products and services
(e-commerce)
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The History of the Internet


In the early 1960s the US department of defense
began investigating ways of creating networks of
computers that coordinate and control nuclear
weapons
This network was to withstand attack, so that
even if part of it was down it will continue to
function


This network was to have no central control
These new networks required multiple channels
to send information (leased lines inadequate)
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The History of the Internet Cont’d

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In 1969 the advanced research agency
(ARPA) used this network model to
connect four computers
This network was called ARPANET
During the 1970s and 1980s the academic
community contributed to this network
In the late 1980s this network became the
Internet
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Internet Growth

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In 1969 ARPANET (the Internet)
connected 4 computers
In 1990 the Internet connected 300,000
In 1995 the intranet was privatised


The structure was based on four network
access points (NAPs) operated by different
telecom companies in the US
As the Intranet grew, more NAPs were added
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Internet Growth Cont’d

The NAPs began selling Internet access rights to
large customers

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Internet service provides (ISPs) sold on the service to
small businesses and individuals
Growth in Internet hosts rose from under 10
million in 1995 to over 180 million in 2004
Millions of people now use the Internet
Billions of dollars are exchanged from the sales
of products and services
Estimated number of Web sites is 40 million and
billions of web pages
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The World Wide Web

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www.ransen.com/Repligator/Spider.htm
What is the World
Wide Web?
What is hypertext?
Hypertext markup
language (HTML)
example
What types of Web
sites exist?
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What is the World Wide Web

The World Wide Web (WWW) was an
Internet-based hypertext project that
allowed global information sharing2

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It is software that runs on machines
connected to the WWW
The WWW is based on two concepts1:


Hypertext and
a graphical user interface (a Web browser)
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What is Hypertext


In 1945, Vannevar Bush wrote an article in
the Atlantic Monthly describing a system,
called Memex, that would store all a
person’s books, records, letters and
research results on microfilm
Microfilm and indexes would then be used
to quickly access this information
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What is Hypertext Cont’d

In the 1960s, Ted Nelson described a
similar system:
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He incorporated a page linking system called
hypertext
Tim Berners-Lee wrote a hypertext server
in 1989 which
stored files written in hypertext markup language
(HTML)
 allowed other computers to read these files

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What is Hypertext Cont’d

Tim Berners-Lee hypertext server was
called httpd and his client browser
“WorldWideWeb”
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HyperText Markup Language
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HTML is a language that includes a set of
tags attached to text
These tags describe the relationship
between text elements
A hypertext link (or hyperlink) points to
another location in the same or another
HTML document (that might be stored on
the same or another computer)
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HTML Example
<html>
<!-- An HTML document typically contains a head and a body -->
<head>
<title>Hypertext Markup Language (HTML) Example</title>
</head>
<!-- This is the body part of the document -->
<body bgcolor="#0000AA">
<font color="#FFFFFF">
<h1><u>Hypertext Markup Language</u></h1>
Hypertext Markup Language (HTML) allows users to:
<ol>
<li>format and display text
<li>display images
<li>and so much more …
</ol>
<img src="HTMLexample.jpg">
<a href="#top">Go to top of page</a>
</font>
</body>
</html>
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Graphical Interface for Hypertext
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A Web browser is a graphical user interface used
to read and navigate through files written in
HTML
In 1993 the first graphical web browser was
developed; called Mosiac
Popular web browsers include:
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Internet Explorer
Netscape
Firefox
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Hypertext Servers (Web Servers)
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There are several Web servers available
today, however the most popular are (April
2004 survey)4:
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Apache HTTP Server (69.01%)
Microsoft Internet Information Server (IIS)
(23.26%)
Sun Java System Web Server (JSWS) (former
names are Sun One, iPlanet Enterprise Server
and Netscape Enterprise Server) (0.86%)
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Apache (“A Patchy” Server)
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Developed in 1994 by Rob McCool
The original core system has many patches
applied to it, and thus its name
Apache has dominated the Web since 1996
Available free
Runs on operating systems including
FreeBSD-UNIX, HP-UX, Linux, Microsoft
Windows, SCO-UNIX and Solaris
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Microsoft Internet Information
Server (IIS)
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Comes bundled with Microsoft Windows Server
operating system
IIS used on many corporate intranets (Microsoft
standard product)
Originally written to run on Windows NT and
Windows 2000; runs on Windows 2003 Server
and Windows XP
Supports ASP, ActiveX Data objects and SQL
queries
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Sun Java System Web Server
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This is a descendant of the original NCSA
server
Cost US$1500-per-CPU licensing fee
Runs on HP-UX, Solaris and Windows
Is ODBC compatible (i.e. full access to
ODBC databases)
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Web Site Types

There are numerous different types of Web sites
including:

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Development sites: are used by companies to
evaluate web site designs. The initial investment in
these sites are small since they use existing hardware
(i.e. no special hardware is purchased)
Intranets: these are corporate networks that hold
documents such as internal memos, corporate
handbooks, expense account worksheets, budgets and
newsletters
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Web Site Types Cont’d
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Extranets: which allow external entities, e.g.
suppliers and strategic partners to access a
subset of the information on the Intranet
Transaction-processing: These sites operate
24 hours a day, seven days a week and
require fast, reliable hardware and ecommerce software

Web sites hosting B2B and B2C activities must
have spare capacity to support an increase in
customer volume.
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Web Site Types Cont’d
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Content-delivery: sites must be available
seven days a week, 24 hours a day and
require fast and precise search engines to help
visitors locate information quickly

These sites deliver content such as news, histories
and other digital information.
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Networking
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What is a computer
network?
What are some of the
types of networks?
Characteristics of
networks

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http://www-structure.llnl.gov/Xray/comp/network.gif
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Network topology
Network protocols
Network architecture
Routers
Domain Names
Intranets, Extranets and
VPNs
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What is a Network

A network is a group of two or more
computer systems linked together
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Types of Networks
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There are several types of computer
networks:
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Local-area network (LANs)
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Computers that are geographically close to each
other (in the same building)
Wide-area network (WANs)
Computers are farther apart than LANs; typically
connected by telephone lines or radio waves
 Provides a single path between caller and receiver
(circuit switching)
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Types of Networks Cont’d
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Campus-area network (CANs)
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Metropolitan-area network (MANs)
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These computers are within a limited geographic
area, e.g. a campus
These networks are designed for towns and cities
Home-area network (HANs)

A network created in a person’s home
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Types of Networks Cont’d
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Both LANs and WANs are examples of packetswitched networks
In packet-switched networks:
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Messages are broken down into small pieces called
packets and are labeled electronically with their
origin, sequence and destination addresses
Each packet may take a different path
The destination computer puts the packets back
together in the correct order
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Characteristics of Networks

A network is characterised by its:

Topology
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Architecture
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The geometric arrangement of the computer system
This refers to the two major type of networks, peer-to-peer
or client/server
Protocol

The set of rules and signals used to communicate (e.g.
Ethernet or IBM’s Token Ring)
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Network Topologies
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Common network
topologies include:
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Star topology
Ring topology
Bus topology
Other topologies
include the:

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Mesh topology
Tree topology
http://www.webopedia.com/TERM/s/star_network.html
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Network Topologies Cont’d

Network topologies are considered either
logical or physical
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The physical lay out of the network is its
physical topology
The way signals are routed through a network
is the logical topology
Just because a network has a particular
physical topology does not mean that its
logical topology must be the same
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Network Topologies Cont’d
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For example:
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Twisted-pair Ethernet has a logical bus
topology on a physical star topology layout
IBM’s token ring has a logical ring topology
on a physical star topology
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Star Topology
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In a Star network all nodes are connected
through a central hub
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A node is a computer or device, e.g. a printer;
each node has a unique address called the
Data Link Control (DLC) address or the
Media Access Control (MAC) address
The main advantage of the star network is
that a malfunctioning node does not affect
the rest of the network
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Star Topology Cont’d
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The main disadvantage of the star network
is that:
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It requires more cabling than other topologies
(e.g. the ring network), and
If the hub goes down, the network no longer
functions
Standard twisted-pair Ethernet uses the star
topology
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Ring Topology
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Each node in a ring network is connected to two
other nodes to form a closed loop
Messages pass around the ring and each node
reads the message addressed to it
One advantage of a ring network is that it can
span larger distances than other networks (e.g.
bus) because each node regenerates the signal
One disadvantage is that malfunctioning nodes
can make other nodes inaccessible
IBM’s token ring uses a logical ring topology
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Bus Topology
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The nodes in a bus topology are connected to a
central cable call a bus or backbone
The bus has two end points
One advantage of the bus network is that if one
node goes down the network still functions
One disadvantage of the bus network is it can not
travel as long a distance as say a ring network due
to the diminishing signal strength
Ethernet 10Base-2 and 10Base-5 uses the bus
topology
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Mesh Topology
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In the mesh topology
many redundant
connections exist
between nodes; in a
true mesh, each node
is connected to every
other node
http://www.webopedia.com/quick_ref/topologies.asp
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Tree Topology
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The tree topology is a
hybrid where groups
of star-configured
networks are
connected to a linear
bus backbone
http://www.webopedia.com/quick_ref/topologies.asp
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Architecture
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The two main types
of architecture are
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Peer-to-Peer
Client/Server
http://www.rebri.org.nz/images/builder-big.jpg
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Peer-To-Peer (P2P) Networks
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In a P2P network each node has equivalent
capabilities and responsibilities
These networks are simpler than
Client/Server but do not offer the same
performance under heavy loads
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Client/Server Networks
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A network architecture where each node is either
a client or server
Client computers run applications, but rely on
servers for resources such as files and printing
capabilities
Servers are powerful computers that manage
files, printers or network traffic
This architecture is sometimes called the two-tier
architecture
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Protocols
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Protocols are agreed
formats for transmitting
data between devices6
The protocol determines:
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The error checking
required
Data compression
method used
The way the end of a
message is signaled T
The way the device
indicates that it has
received the message
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Protocols Cont’d

A protocol is a collection of rules for:

Formatting, ordering and error checking data
that is sent across a network
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e.g. The protocol might indicate when a sending
device has completed sending data
The ARPANET network used the network
control protocol (NCP)

It was based on an open architecture which
later became the Internet
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Protocols Cont’d
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Four key rules used by ARPANET were:
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Independent networks (e.g. A LAN or WAN) should
not require internal changes in order to be connected
to the network
Packets that do not arrive at their destination must be
resent from their source network
Router computers act only as receiving and
forwarding devices; They do not retain information
about the packets they handle
No global control of the network exist
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Internet Protocols
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There are many protocols used by the
Internet and the WWW, including

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TCP/IP
HTTP
FTP
Electronic mail protocols
IMAP
 POP
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TCP/IP
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The Internet uses two main protocols (developed
by Vicent Cerf and Robert Kahn)
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Transmission control protocol (TCP)
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Controls disassembly of message into packets at the origin
Reassembles at the destination
Internet protocol (IP)
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Specifies the addressing details for each packet

Each packet is labeled with its origin and destination
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Internet Protocol version 4 (IPv4)

Uses a 32 bit number to identify each
computer

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Called the IP address (4 billion addresses)
IP addresses uses the dotted decimal notation,
e.g. 0.0.0.0 or 255.255.255.255
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Internet Protocol version 6 (IPv6)
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Set to replace version 4
Changes the format of the packets
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Removes unused fields
Uses 128 bit number (2^128 addresses)
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Eight groups of 16 bits
e.g.
CD18:0000:0000:AF23:0000:FF9E:61B2:884D
 To simplify zeroes may be removed
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CD18:::AF23::FF9E:61B2:884D
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IP Addresses
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IP addresses are assigned by:
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American Registry for Internet Numbers (ARIN)
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Reséaux IP Européens (RIPE)
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North America, South America, the Caribbean and subSaharan Africa
Europe, Middle East and the rest of Africa
Asia-Pacific Network Information Centre (APNIC)
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Asia-Pacific area
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Hypertext Transfer Protocol (HTTP)
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The hypertext transfer protocol (HTTP) was
developed by Tim Berners-Lee in 1991
HTTP was designed to transfer pages between
machines
The client (or Web browser) makes a request for a
given page and the Server is responsible for
finding it and returning it to the client
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Hypertext Transfer Protocol (HTTP)


The browser connects and requests a page from the server
The server reads the page from the file system, sends it to
the client and terminated the connection
Request sent to Web server
Web Server
Client
Response sent with files (one for each
Web page, image, sound clip etc.)
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File Transfer Protocol (FTP)

FTP is a protocol that allows a user to:

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list files at a remote site
Transfer files between local and remote computers
Using FTP you can not run applications on a
remote site
Also you can only look at the names of the files
on the remote computer; rather than being able to
read them
FTP is still used today; e.g. to transfer large files
between computers, or to upload Web sites
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Electronic Mail Protocols


Electronic mail uses the client/server model
The organisation has an email server
devoted to handling email


Stores and forwards email messages
Individuals uses email client software to
read and send email (e.g. Microsoft
Outlook, or Netscape Messenger)
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Electronic Mail Protocols Cont’d

Simple Mail Transfer Protocol (SMTP)


Specifies format of mail messages
Post Office Protocol (POP)

tells the email server to:
Send mail to the user’s computer and delete it
from the server
 Send mail to the user’s computer and do not delete
it from the server
 Ask whether new mail has arrived

58
Electronic Mail Protocols Cont’d

Interactive Mail Access Protocol (IMAP)

Newer than POP, provides similar functions
with additional features
e.g. can send specific messages to the client rather
than all the messages
 A user can view email message headers and the
sender’s name before downloading the entire
message


Allows users to delete and search mailboxes
held on the email server
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Electronic Mail Protocols Cont’d

The disadvantages of POP


You can only access messages from one PC
The disadvantage of IMAP

Since email is stored on the email server,
there is a need for more and more expensive
(high speed) storage space
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Terminal Emulation
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Telnet is a terminal emulation program for
TCP/IP networks
The telnet program runs on a local machine and
allows connection to a remote machine
Commands entered through the telnet program
will be executed on the Server; this gives the user
the ability to control the Server
To log into the Server a valid username and
password is required
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Routers
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Computers that decide how best to forward on a
packet to its destination is called a routing
computer
The Internet uses routers to isolate each LAN or
WAN
Each WAN or LAN can use their own protocol
for packet traffic within the LAN or WAN
The actual programs which contains the routing
rules are called routing algorithms
62
Routers Cont’d

These programs apply their routing
algorithms to information they have stored
in routing tables



This information includes lists of connections
that lead to particular groups of other routers
Which connections to use first
Rules for handling instances of heavy packet
traffic and network congestion
63
Routers Cont’d


When a company connects to the Internet it must
connect at least one router to routers owned by
other companies that make up the Internet
The Internet backbone are a set of routers that
handle packet traffic along the Internet’s main
connecting points


These are very large computers that can handle more
than 50 million packets per second
A router connected to the Internet always has more
than one path to direct packets
64
Domain Names


To make Internet addresses easier to remember an
alternative, domain names, was provided which
used words
Domain names

May have two or more groups separated by a period,
e.g. www.cavehill.uwi.edu




Edu – an education institution
Cavehill and uwi – the computer’s name
www – part of the world wide web
Not all computers follow this convention, e.g
games.yahoo.com
65
Domain Names Cont’d

The rightmost part of the domain name is called
the top-level domain (or TLD), e.g. .edu, or .com


also Country domains e.g. .bb
In 2000 seven new general TLDs were added:






.aero – air transport industry
.biz – businesses
.coop – cooperatives
.museum – museums
.name – individuals
.pro - professionals
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Uniform Resource Locator

The combination of the domain name and
the protocol name is called the uniform
resource locator (URL)

E.g. http://www.yahoo.com
http is the protocol
 www.yahoo.com is the domain name

67
Intranets and Extranets


An Intranet is an interconnected network
(internet) that does not extend beyond the
organisation that created it
An extranet is an intranet that has extended
to include specific entities outside of the
organisation, e.g. business partners,
customers or suppliers

Extranets can replace faxes, telephones, email
and overnight carriers, at a lower cost
68
Intranets





Low cost distribution of internal corporate
information
Based on client server model
Intranets use Web browsers, internet-based
protocols including TCP/IP, FTP, Telnet, HTML
and HTTP
Distributing paper is often more expensive
Intranets can also be used to provide software
updates and patches, which update users
computers automatically – using scripts
69
Extranet



Networks that connect companies with
suppliers, business partners and authorised
users
Each user has access to the databases, files
and other information stored on computers
connected to the extranet
Fedex changed from an Intranet to Extranet
for package tracking on their Web site
70
Public and Private Networks


A public network is any network available to the
public, e.g. Internet
A private network is a private (e.g leased) line
between two computers




Leased line is a permanent connection between two
points
line is always active (unlike telephone connection)
The advantage is security (only the two parties can
connect to the network)
The disadvantage is the cost due to the scaling
problem: to connect 5 pairs, 5 lines are required
71
Virtual Private Networks


A VPN is an extranet that uses public
networks and their protocols to send
sensitive information using IP tunneling
IP tunneling creates a private passageway
through the public Internet that provides
secure transmissions
72
Virtual Private Networks Cont’d





VPN software encrypts the package content and
places it into another packet (encapsulation)
The outer packet is called an IP wrapper
The receiving computer decrypts it using the
(VPN software)
The connection is ‘virtual’ since it is only
temporary, it is created when information needs
to be transmitted
A VPN is an extranet, but not every extranet is a
VPN
73
Connecting to the Internet

What are some of the
ways of connecting to
the Internet?
http://www.co.delaware.ny.us/links.htm
74
Internet Connection Options

Internet service providers (ISPs) provide several
ways to connect to the Internet, including:





Voice grade telephone lines
Broadband connections
Leased lines
Wireless
The major distinguishing factor is bandwidth (the
amount of data that can be transferred per unit of
time)
75
Bandwidth and Connections


Symmetric connection: provides the same
bandwidth in both directions
Asymmetric connections: provide different
bandwidths for either direction


Upstream bandwidth (upload bandwidth): the amount
of information that can travel from the user to the
Internet in a given amount of time
Downstream bandwidth (download or downlink
bandwidth): the amount of information that can be
transferred from the Internet to the user in an amount
of time
76
Voice-grade Telephone Connections

Most common way to connect to ISP


Modem (analog) connected to telephone lines
POTS (plain old telephone service)


28 to 56Kbps
Digital subscriber line (DSL) protocol


Does not use a modem
Uses a piece of network equipment similar to a
network switch

Integrated services digital network (ISDN) first used DSL
protocol suite in 1984

More expensive, but offers bandwidth of 128Kbps – 256Kbps
77
Broadband Connections Cont’d


Connections that operate at speeds higher than
200Kbps are considered broadband
One of the latest is asymmetric digital subscriber
line (ADSL)


Bandwidths from 100-640Kbps upstream and from
1.5 to 9 Mbps downstream
For businesses a high-speed DSL (HDSL) is
available

768Kbps of symmetric bandwidth
78
Broadband Connections Cont’d

Cable modems (connected to the same
broadband coaxial cable that serves a
television)

Upstream bandwidth of 300Kbps to 1 Mbps
and downstream bandwidth of 10Mbps
79
DSL v Cable



DSL is a private line with no competing traffic
Cable connections bandwidth change with the
user load (number of subscribers using the
service)
Problems

Web users in rural areas often do not have cable
access and have limited telephone access (low cost
voice-grade lines, rather than data-grade lines) thus
bandwidth is limited (<14Kbps)
80
Leased-Line Connections


Large firms with a large amounts of Internet
traffic can lease lines from telecommunication
carriers
Various technologies are used; classified by the
amount of telephone lines they include:




DS0 (digital signal zero) carries one digital signal
(64Kbps)
T1 (or DS1) carries 24 DS0 lines (1.544Mbps)
Fractional T1 (128Kbps and upwards)
T3 (or DS3) carries 30 T1 lines (44.736Mbps)

Connections more expensive than POTS, ISDN and DSL
81
Wireless Connections





Satellite
Bluetooth
Wireless Ethernet (Wi-Fi)
Fixed-Point Wireless
Cellular Telephone Networks
82
Satellite

Satellite microwave
transmissions




Customer placed
receiving dish in yard
Download bandwidth
of around 500 kbps
Maximum upload
bandwidth of 150kbps
Self installation
makes cost lower
http://www.ccpo.odu.edu/~arnoldo/ocean405/satellite.gif
83
Bluetooth




One of the first wireless
protocols
Operates reliably over 35
feet and can be part of up
to 10 networks of eight
devices each (personal
area networks, or PANs)
Bandwidth of 722kbps
Good for wireless
printing
http://www.bakercountyhealth.org/services/dental/blue-tooth.jpg
84
Bluetooth Advantages


Bluetooth technology consumes very little
power
Bluetooth devices can discover each other
and exchange information automatically
(e.g. a user can print to a printer on a
network without logging on)
85
Wireless Ethernet (Wi-Fi) (802.11b)



Most common
wireless on LANs
Bandwidth 11Mbps at
300 feet
A computer with a
Wi-Fi network can
communicate with a
wireless access point
(WAP) to become a
part of the network
http://www.homenethelp.com/web/diagram/images/shareing-soft-wireless.gif
86
Wireless Ethernet Advantages


Wi-Fi devices can roam, i.e. shift from one
WAP to another without user intervention
Increasingly WAPs are becoming available
in public places, e.g. airports
87
Wireless Ethernet Developments

In 2002 an improved version of Wi-Fi, called
802.11a was introduced




The 802.11a protocol is capable of transmitting at
speeds up to 54Mbps
802.11a is not compatible with 802.11b
Later in 2002, the 802.11g protocol was
introduced which is compatible with 802.11b
devices and has speeds of 54Mbps
In 2004-2005, 802.11n expected (320Mbps)
88
Fixed Point Wireless


Uses a system of
repeaters (transmitterreceiver devices) to
forward a radio signal
from the ISP to
customers
Users’ antennas are
connected to a device that
converts radio signals to
Wi-Fi packets which are
sent to their computers
http://www.erinc.com/apps_wireless/images/fixed_wireless2.gif
89
Cellular Telephone Networks



In 2003, about 500
million mobile (cell)
phones worldwide
Originally slow data
communication (10
kbps – 384kbps)
Third generation cell
phones

Up to 2 Mbps
http://www.mtco.com/graphics/cellularpic.jpg
90
Cellular Telephone Networks Cont’d



Cell phones send and receive messages using the
short message service (SMS) protocol
Some cell phones include Web browser which
provide web access, email, short message service
Companies also sell Internet access through their
cellular networks


Fixed fee plus charge for amount of data transferred
Business potential of mobile commerce

Companies are identifying the kinds of resources
individuals might want to access (and pay for) using
wireless devices
91
References
[1] Schneider, Gary, P., “Electronic Commerce: The second wave”, Thomson Course
Technology, Fifth Annual Edition, 2004
[2] Zhao, Jensen J., “Web design and development for e-business”, Prentice Hall, 2003
[3] Federal Networking Council, “FNC Resolution: Definition of the Internet”, 1995. Online
document available at http://www.itrd.gov/fnc/Internet_res.html
[4] NetCraft, “April 2004 Web Server Survey”, 2004. Online document available at
http://news.netcraft.com/archives/2004/04/01/april_2004_web_server_survey.html
[5] Furdyk, Michael, “Ultimate Guide to Networking: Part One”, 1999. Online document
available at http://www.hardwarecentral.com/hardwarecentral/print/158/
[6] Webopedia, “Network”, 2004. Online document available at
http://networking.webopedia.com/TERM/N/network.html
[7] Berlin, Dan, et al., “CGI Programming Unleased”, Sams.net Publishing, 1996, pp. 101-102
92