Comp 107 unit 7 and 8 (networking, internet and intranet)

Subject Name Code Credit Hours
Copyright @ 2016 Lincoln University College
Unit 7 and 8
Introduction to Networking, Internet
and Intranet
By
Liang

Data Transfer
• Data transmission, digital transmission, or
digital communications is the physical transfer
of data (a digital bit stream) over a point-to-
point or point-to-multipoint communication
channel.

Examples
• Examples of such channels are copper wires,
optical fibres, wireless communication
channels, storage media and computer buses.
• The data are represented as an
electromagnetic signal, such as an electrical
voltage, radiowave, microwave, or infrared
signal.

Network
• Network
one computer connected to more then one
computer is called Network
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Advantages of networking
• 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
• 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
– Eg. 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. Each 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
• 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
• 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
• 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
• 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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Local Area Network (LAN)
• 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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Metropolitan Area Network (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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Wide Area Network(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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Internetwork
• Internetwork (internet) : two or more networks are
connected by internetworking devices
• Internetworking devices: router, gateway, etc.
• The Internet: a specific worldwide network
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Internetwork Example• A heterogeneous network : four WANs and two LANs
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Network Vs Internet
Internet
Network of network is called Internet
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Internet
• Internet programming language
• E-mail
• SMS(short message service)
• Social networking sites
• Websites
• Browser
• Blog - Share your life's stories, videos and photos
• VOIP - Voice over Internet Protocol(Call from computer,
telemarketer)
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Internet(con’t)
• Rss(Really simple Syndication) - TechNet
provides RSS feeds for its security bulletins,
advisories, magazine features, and other
security-related alerts for IT professionals. Eg,
short cut other
pages.
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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
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
• represented by sine waves
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time
(sec)
amplitude(volts)
1 cycle
frequency (hertz)
= cycles per second
phase
difference

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)
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Modem
Process
• Modulation
– Digital to analog conversion
• Demodulation
– Analog to Digital Conversion

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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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,
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
• 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.
• The WWW is basically the text and pictures which you can
view using your web browser, such as Microsoft Internet
Explorer, or Netscape Navigator.
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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 will click 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.

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
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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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Internet Important Terms
• 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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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.
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World Wide Web Basics
• URL
– No spaces and Case sensitive
– HTTP (Hypertext Transfer Protocol)
• HTML (Hypertext Markup Language)
– .htm or .html file extension
Document name
and filename
extension
Folder
name
Web
server
name
Web
protocol
standard
http://www.cnn.com/showbiz/movies.htm

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
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Domain Name System
Host number
The part of the IP address that specifies a particular
host (machine) on the network
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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Domain Name System(cont’)
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Domain Name System (cont’)
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Figure 15.10 Top-level domains, including some relatively new ones

Domain Name System(cont’)
Organizations based in countries other than the United States
use a top-level domain that corresponds to their two-letter
country codes
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Figure 15.11
Some of the top-level domain names
based on country codes
Do you
email
someone
in another
country?

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
• 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
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http://www.chicagosymphony.org/civicconcerts/index.htm
protocol
Domain name
pathname
filename
http => Hypertext Transfer Protocol

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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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 Eg. temp folder
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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

SECURITY CONSIDERATIONS(Cont’)
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.
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SECURITY CONSIDERATIONS(Cont’)
• 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
customized by the companies technical IT team. In most cases you will be
unaware of the firewall existence.
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Internet vs intranet
• Intranet is an internal private computer network or connection of
one or more computer networks, whose use and access is restricted
to an organization and its employees or members.. Such an
intranet, mostly operates through a website, run by a local server,
acting as a resource sharing medium. You could call it a scaled-
down private Internet.
• Internet is a network of more than billion computers spread
worldwide! It uses an ever improving set of Internet protocols
(HTTP, FTP, SMTP, etc.) to transfer data. Unlike the intranet, the
Internet and the information sharing service called the 'World Wide
Web',
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Comp 107 unit 7 and 8 (networking, internet and intranet)

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