Wdf222 cep ii

Subject Name
Web Design and Fundamentals

Code

Credit Hours

WDF222

By
D.Balaganesh

D.Balaganesh Lincoln University College

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Code

Credit Hours

Network
• Network
one computer connected to more then one
computer is called Network


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Advantages of networking
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Connectivity and Communication
Data Sharing
Hardware Sharing
Internet Access
Internet Access Sharing
Data Security and Management
Performance Enhancement and Balancing
Entertainment

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Network

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• Network: A set of devices (nodes) connected by communication links
• Node: Computer, printer, or any device capable of sending and/or
receiving data
• To be considered effective and efficient, a network must meet a
number of criteria


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Type of Connection


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Type of Connection
• Point-to-point
– Dedicated link between two devices
– The entire capacity of the channel is reserved
– Ex) Microwave link, TV remote control

• Multipoint
– More than two devices share a single link
– Capacity of the channel is either

• Spatially shared: Devices can use the link simultaneously
• Timeshare: Users take turns


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Physical Topology


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Mesh Topology
• Dedicated point-to-point link to
every other nodes
• A mesh network with n nodes
has n(n-1)/2 links. A node has
n-1 I/O ports (links)
• Advantages: No traffic
problems, robust, security, easy
fault identification & isolation
• Disadvantages: Difficult
installation/reconfiguration,
space, cost


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Star Topology
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Dedicated point-to-point link only to a central controller, called a hub
Hub acts as an exchange: No direct traffic between devices
Advantages: Less expensive, robust
Disadvantages: dependency of the whole on one single point, the hub


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Bus Topology
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One long cable that links all nodes
tap, drop line, cable end
limit on the # of devices, distance between nodes
Advantages: Easy installation, cheap
Disadvantages: Difficult reconfiguration, no fault isolation, a fault or
break in the bus stops all transmission


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Ring Topology
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Dedicated point-to-point link only with the two nodes on each sides
One direction, repeater
Advantages: Easy reconfiguration, fault isolation
Disadvantage: Unidirectional traffic, a break in the ring cab disable the
entire network


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Hybrid Topology
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Example: Main star topology with each branch connecting several stations
in a bus topology
To share the advantages from various topologies


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Categories of Networks


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LAN
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Usually privately owned
A network for a single office, building, or campus a few Km
Common LAN topologies: bus, ring, star
An isolated LAN connecting 12 computers to a hub in a closet


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MAN
• Designed to extend to an entire city
• Cable TV network, a company’s connected LANs
• Owned by a private or a public company


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WAN
• Long distance transmission, e.g., a country, a continent, the world
• Enterprise network: A WAN that is owned and used by one company


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Network Vs Internet
Internet
Network of network is called Internet


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Internet programming language
Internet
E-mail
SMS(short message service)
Social networking sites
Websites
Blog
- Share your life's stories, videos and photos
VOIP
- Voice over Internet Protocol
Podcast - type of digital media consisting of an episodic series of
audio,

video, PDF

• Rss(Really simple Syndication) -

TechNet provides RSS
feeds for its security bulletins, advisories, magazine features, and other
security-related alerts for IT professionals.

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The Internet
• Internet is a network of interconnected
computers that is now global
• Internet born in 1969 - called ARPANET
• 1969 ARPANET was connection of computers
at UCLA, Stanford, UCSB, Univ. of Utah


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The Advanced Research Projects Agency
Network
• In 1969, the U.S. Defence Department funded
a project to develop a network, which can
withstand the bombing. Basically the idea was
to develop a very secure network which can
work even after a nuclear attack. This project
was known as ARPANET.


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Internet Connections
Various technologies available to connect a home computer to
the Internet
Phone modem converts computer data into an analog audio signal
for transfer over a telephone line, and then a modem at the
destination converts it back again into data
Digital subscriber line (DSL) uses regular copper phone lines to
transfer digital data to and from the phone company’s central office
Cable modem uses the same line that your cable TV signals come in
on to transfer the data back and forth

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Internet Connections
Broadband
A connection in which transfer speeds are faster than
768 kilobits per second
– DSL connections and cable modems are
broadband connections
– The speed for downloads (getting data from the
Internet to your home computer) may not be the
same as uploads (sending data from your home
computer to the Internet)

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Data
• Analog data
– Voice
– Images
• Digital data
– Text
– Digitized voice or images


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Modem


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Analog Signaling
amplitude (volts)

1 cycle
• represented by sine waves

phase
difference

time
(sec)

frequency (hertz)
= cycles per second

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Code

Three Components of Data
Communication

• Data
– Analog: Continuous value data (sound, light, temperature)
– Digital: Discrete value (text, integers, symbols)

• Signal
– Analog: Continuously varying electromagnetic wave
– Digital: Series of voltage pulses (square wave)

• Transmission
– Analog: Works the same for analog or digital signals
– Digital: Used only with digital signals

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Modem
• Anlog
• Digital
• Modulation
– Digital to analog conversion
• Demodulation
– Analog to Digital Conversion
Modulation and D.Balaganesh Lincoln University College called Modem
demodulation is

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Modem Internet Connections
• Dial-up connection via modem (56K)
• Cable modems

– Network card and cable modem required
– Always-on and 25 times faster than dial-up


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Faster Internet Connections
ISDN (Integrated Services Digital
Network)
– 64K or 128K
– Always-on and expensive

• DSL (Digital Subscriber Line)
– Up to 125 times faster than dialup

• DSS (Digital Satellite Service)
– 500K
Need proximity to a telephone switching station

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ISP (Internet Service Provider)
If you want to connect to the Internet, you need
to subscribe via an Internet Service Provider.
The ISP gives you a connection to the Internet
either via your telephone line or via a special
digital high speed line. An example of a
popular ISP is AOL (America On-Line).


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Internet Service Provider (ISP)
• Provides internet access to businesses,
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organizations and individuals
Provides telecommunications equipment
User ID and password required
Connects you to backbone
E-mail account monthly fee
Should have local access telephone
numbers

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SERVICES OF INTERNET
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WWW
FTP
Telnet
E-mail


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What is the difference between the World Wide Web (WWW) and
the Internet?
WWW is the acronym for the World Wide Web. It is also commonly
known as ‘The Web’. The WWW is hypertext based information retrieval
tool

• The World Wide Web (WWW) is just a small
part of the Internet as a whole.
• The Internet, relates to all the hardware and
software involved, and as well as including the
WWW, also includes FTP (File Transfer
Protocol – more about this later), email and
newsgroups.

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World Wide Web Basics

Files interconnected via hypertext
Web pages make up a web site
Home Page
Links or hyperlinks
Web servers


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FTP (File Transfer Protocol)
File Transfer Protocol, is an Internet utility software used to upload
and download files. It gives access to directories or folders on remote
computers and allows software, data and text files to be transferred
between different kinds of computers.

• FTP is just a way of transferring data from one place to another
over the Internet. If is often used for downloading large files
from a web site. You do not really need to know anything
about how it works, in most cases you willclick on a link within
a web page, and your web browser (such as Microsoft
Internet Explorer) will take care of the FTP transfer for you, all
you have to decide is where to store the file which you wish to
download.

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The basic objectives of FTP are
• to give flexibility and promote sharing of computer
programs, files and data
• to transfer data reliably and more efficiently over
network
• to encourage implicit or indirect use of remote
computers using Internet
• to shield a user from variations in file storage
systems among hosts

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Telnet (Remote Computing)
• Telnet (Remote Computing)
Telnet or remote computing is telecommunication utility software,
which uses available telecommunication facility and allows you to
become a user on a remote computer. Once you gain access to the
remote computer, you can use it for the intended purpose. The
TELNET works in a very step by step procedure. The commands
typed on the client computer are sent to the local Internet Service
Provider (ISP), and then from the ISP to the remote computer that
you have gained access. Most of the ISP provides facility to TELENET
into your own account from another city and check your e-mail
while you are traveling or away on business College
D.Balaganesh Lincoln University

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E-Mail (Electronic Mail)
E-mail or Electronic mail is a paperless method of sending messages,
notes or letters from one person to another or even many
people at the same time via Internet. E-mail is very fast compared to
the normal post. E-mail messages usually take only few seconds to
arrive at their destination

Features of E-mail:
• One-to-one or one-to-many communications
• Instant communications
• Physical presence of recipient is not required
• Most inexpensive mail services, 24-hours a day and seven days a week
• Encourages informal communications

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Voice Messaging
Voice Messaging
It is a new communication approach which is similar to electronic mail except
that it is audio message rather than text messages that are processed. A
sender
speaks into a telephone rather than typing, giving the name of the recipient
and
the message. That sender's voice signal is then digitalised and stored. The
system
can then either deliver the message at a specified time in future or it can be
retrieved from a database by the recipient.

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E-Commerce
Electronic commerce or e-commerce as it is popularly known refers to the
paperless exchange of business information using Electronic Data
Interchange,
Electronic mail, Electronic Bulletin Boards, Electronic Fund Transfer and other
network based technologies. Electronic Commerce (EC) not only automates
manual process and paper transactions, but it also helps organisations to
move
into a fully electronic environment and change the way they usually operate.


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Internet Important Terms
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HTTP
URL
Hyperlink
Browser
Cookies
Internet cache
SECURITY

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HTTP (Hypertext Transfer Protocol)
• HTTP stands for Hypertext Transfer Protocol.
This is the language your web browser uses to
request pages & graphics from the web server.
You can see that your web browser is using
the HTTP protocol when it is shown at the
start of a web address such as
http://www.yahoo.com

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Code

Credit Hours

URL (Uniform Resource Locator)
• The URL (Uniform Resource Locator) is just
another name for a web address.
• The URL consists of the name of the protocol
(usually HTTP or FTP) followed by the address
of the computer you want to connect to, e.g. a
URL of “ftp://ftp.cdrom.com” would instruct
your web browser to use the FTP protocol to
connect to the computer called
ftp.cdrom.com.

Subject Name

• URLWorld

Code

Credit Hours

Wide Web Basics

– No spaces and Case sensitive
– HTTP (Hypertext Transfer Protocol)

• HTML (Hypertext Markup Language)
– .htm or .html file extension

http://www.cnn.com/showbiz/movies.htm
Web
protocol
standard

Web
Folder
server
D.Balaganesh Lincoln Universityname
College
name

Document name
and filename
extension

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Code

Credit Hours

Network Addresses
Hostname
A name made up of words separated by dots that
uniquely identifies a computer on the Internet
IP address
An address made up of four one-byte numeric values
separated by dots that uniquely identifies a computer
on the Internet
Is there a correspondence between the parts
of a hostname and an IP address?

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Code

Credit Hours

Host number
Domain Name System
The part of the IP address that specifies a particular
host (machine) on the network Yes, but what is it?
Domain name
The part of a hostname that specifies a specific
organization or group
Top-level domain (TLD)
The last section of a domain name that specifies the
type of organization or its country of origin


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Code

Domain Name System
matisse.csc.villanova.edu
Computer
name
Domain name

TLD


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Domain Name System

Figure 15.10 Top-level domains, including some relatively new ones

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Domain Namethan the United States
System
Organizations based in countries other
use a top-level domain that corresponds to their two-letter
country codes
Do you
email
someone
in another
country?

Figure 15.11
Some of the top-level domain names
based on country codes

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Code

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Domain Name System
Domain name system (DNS)
A distributed system for managing hostname resolution
Domain name server
A computer that attempts to translate a hostname into
an IP address
Should the tables containing hostname/IP
mappings be sorted or unsorted? Why?

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Code

Credit Hours

Domain Name Addressing

• Domain names can include any number of parts separated by
periods, however most domain names currently in use have
only three or four parts.
• Domain names follow hierarchical model that you can follow
from top to bottom if you read the name from the right to the
left.
• For example, the domain name gsb.uchicago.edu is the
computer connected to the Internet at the Graduate School of
Business (gsb), which is an academic unit of the University of
Chicago (uchicago), which is an educational institution (edu).
• No other computer on the Internet has the same domain name.


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Uniform Resource Locators

Credit Hours

• The IP address and the domain name each identify a particular
computer on the Internet.
• However, they do not indicate where a Web page’s HTML
document resides on that computer.
• To identify a Web pages exact location, Web browsers rely on
Uniform Resource Locator (URL).
• URL is a four-part addressing scheme that tells the Web
browser:
 What transfer protocol to use for transporting the file
 The domain name of the computer on which the file resides
 The pathname of the folder or directory on the computer on
which the file resides
 The name of the file

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Structure of a Uniform Resource Locators
pathname

protocol

http://www.chicagosymphony.org/civicconcerts/index.htm
Domain name

http => Hypertext Transfer Protocol

filename

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Hyperlink
A hyperlink is a piece of text (or a graphic) on a
Web page, which when clicked on will
automatically:
- Take you to a different part of the same page
- Take you to a different page within the Web
site

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What is a web browser?
Web browsing applications include ‘Internet
Explorer’ (from Microsoft) and ‘Netscape
Navigator/Communicator’. In both cases there
are many different versions, and you will find
that the later versions offer much more
versatility as well as a better range of built-in
features. The web browser allows you to view
web pages

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• What are cookies?
• Some web sites can store hidden information about you on your hard disk
using cookies. This information is stored in small text file. Cookies can be
useful, for instance, a site may store your preferences about a web site, so
that when you re-visit the site your preferences can be accessed
automatically. Cookies are used by some web sites to identify you; this saves
you having to “log in” to the web site each time you visit.


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What is an Internet cache?
Each time you display a web site within your web browser, a copy of the
information (both text and pictures) is saved on your hard disk. The reason
for this is that the next time you want to re-visit the site, the information is
quickly loaded from the copy on your hard disk, rather than slowly from the
actual Internet site.
• As pictures are stored in the cache, if you are visiting a site which has many
separate web pages, with say a company logo on each page, then all
subsequent pages from that site will load a little faster as the logo graphics
will load from the cache, not via the Internet


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SECURITY CONSIDERATIONS
• What is a digital certificate?
• A digital certificate is used to encrypt information for secure transmission
across the Internet. A digital certificate can be used to create a digital
signature for an email, the signature guarantees the identity of sender, and it
also ensures that the message cannot be tampered with in transit. A digital
certificate can be purchased from a certificate authority such as
www.verisign.com who will verify your identity. Digital certificates are used
by Internet based shopping web sites to encrypt your credit card details so
they cannot be intercepted as they travel the Internet. You can view the
digital certificate for a secure web site by double clicking on the padlock in
the web browser status bar, e.g. https://www.paypal.com

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• What is encryption?
• Encryption is a means of 'scrambling' an email message. It is used to make
a
message more secure, so that only the intended recipient of the message will
be able to read the message. There are many means of enabling this
encryption, both via hardware and software. A famous encryption program is
called PGP(Pretty Good Privacy)


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• What is a firewall?
• A fire wall consists of software and hardware protection against invasion
via
the Internet. In most larger companies any connection to the Internet
automatically goes through a firewall which would have been installed and
customised by the companies technical IT team. In most cases you will be
unaware of the firewall existence.


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Code

Network Layer


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Layered Model: Sending a Letter


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Code

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OSI Model(Open Systems Interconnection)

ISO is the organization. OSI is the model


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Interaction between layers in the OSI model
Layer and interface


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Physical Layer
• The physical layer is responsible for movements of individual bits from
one hop (node) to the next
• Mechanical and electrical specification, the procedures and functions


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Code

Physical Layer: Duties
• Physical characteristics of interfaces and
media
• Representation of bits
• Data rate
• Synchronization of bits
• Line configuration
• Physical topology
• Transmission mode

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Data Link Layer
• The data link layer is responsible for moving frames from
one hop (node) to the next
• Transform the physical layer to a reliable (error-free) link


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Code

Data Link Layer: Duties
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Framing
Physical addressing
Flow control
Error control
Access control


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Network Layer
• The network layer is responsible for the delivery of
packets from the source host to the destination host


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Code

Network Layer: Duties
Logical addressing and routing


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Code

Transport Layer
• The transport layer is responsible for delivery of a
message from one process to another


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Transport Layer: Duties
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Service-point (port) addressing
Segmentation and reassembly
Connection control
Flow control
Error control


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Reliable Process-to-Process Delivery of a Message


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Session Layer
• Session layer is responsible for dialog control and
synchronization


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Presentation Layer
• Presentation layer is responsible for translation,
compression, and encryption


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Application Layer
• Application layer is responsible for providing services to
the user


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Code

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Application Layer: Services
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Network virtual terminal
Mail services
File transfer, access, and management
Directory services


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Summary of Layers


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Code
OSI layer vs TCP/IP Layer

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TCP/IP PROTOCOL SUITE

To divide the services required to perform a task, the
Internet has created a set of rules called protocols. These
allow different local and wide area networks, using
different technologies, to be connected together and
carry a message from one point to another. The set, or
suite, of protocols that controls the Internet today is
referred to as the TCP/IP protocol suite. The
abbreviations (TCP and IP) will become clear as we
explain different protocols.


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The original TCP/IP

Code

Credit Hours

protocol suite was defined as having
four layers: host-to-network (or link), internet (network),
transport and application.

The TCP/IP protocol suite

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Code

TCP/IP and OSI Model


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Code

Credit Hours

TCP/IP Protocol Suite

• Host-to-network : Physical and data link layer
– No specific protocol

• Network layer
– IP(Internet Protocl), ARP(Address Resolution Protocol),
RARP(Reverse ARP), ICMP(Internet Control Message Protocol),
IGMO(Internet Group Message Protocol)

• Transport layer
– TCP(Transmission Control Protocol), UDP(User Datagram Protocl),
SCTP(Stream Control Transmission Protocol),

• Application Layer
– Combined session, presentation, and application layers


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