Transcript The Internet - WordPress.com

MAKERERE UNIVERSITY
College of Computing and Information Sciences
School of Computing and Informatics Technology
BIT 1102: COMMUNICATIONS TECHNOLOGY
AND THE INTERNET
8. The Internet Protocol Suite and the Internet
Internet protocol Suite:
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 In this lecture, we discuss another model known
as the TCP/IP Model, also known as the
Internet Protocol suite.
 This is a simplified and more widely
implemented set of protocols than the OSI (Open
Systems Interconnection) model.
 The main difference between the OSI and the
TCP/IP is the number of layers illustrated.
BIT 1102: Communications Technology & the
Internet
TCP IP
3
 Generally consists of 4 Layers.
Layer 4:
Application
Layer 3:
Transport
Layer 2:
Network
Layer 1:
Data Link Layer
BIT 1102: Communications Technology & the
Internet
TCP / IP SUITE SUMMARY
4. Application
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A layer that communicates with
the application. Protocols include:
DNS, HTTP, FTP, DHCP,SMTP etc.
3. Transport
Reliable end to end data delivery.
TCP is connection oriented while UDP
is connection less
2.Network (also Implementation of IP Addresses
known as the
to enable best effort transmission of
Internet work)
packets through routing (Internet
Protocol resides here)
1.Link (also
Defines physical features / type of
known as the
network .Protocols include Ethernet,
Network Access) ATM, FDDI etc
BIT 1102: Communications Technology & the
Internet
Qn:
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 Differentiate between the OSI and the TCP/IP
reference models for communication and critique
both models.
BIT 1102: Communications Technology & the
Internet
DNS: An Introduction:
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• Located at the application layer, the Domain Name
System (DNS) is an important aspect of the Internet.
• DNS translates IP addresses into Human readable
names known as domain names (and Vice versa) so
that the user does not need to remember the
thousands of numeric (IP) addresses on the Internet.
• For
example, www.makerere.ac.ug could be
196.43.133.84.
• Imagine having to know each IP address of
the website you’re going to visit!!!.
BIT 1102: Communications Technology & the
Internet
DNS
7
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Quick exercise:
Find out the IP address of the following Domain
names.
www.google.com
www.msn.com
www.trueafrican.com
HINT:
Use the ping command in DOS and then type the
website name. Note the set of numbers that are
sent back to your screen. Eg at DOS prompt, type
PING Google.COM
BIT 1102: Communications Technology & the
Internet
Internetworking - The Internet and the
world wide web
8
 Internetworking refers to the connecting of two or
more distinct networks together.
 One of the most prominent networks is the Internet.
 TCP/IP is the architecture on which the Internet is based.
This architectural model provides a common frame of
reference for discussing Internet communications.
BIT 1102: Communications Technology & the
Internet
The Internet
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• The Internet is described by many as a “Network
of networks”
• The Internet is made up of millions of computers
connected together across the globe.
• As we discussed before, data across the Internet is
transmitted via packed switching using the
Internet protocol (IP).
• Current versions of IP include IPV4 and a newer
version-IPV6.
BIT 1102: Communications Technology & the
Internet
Brief History of the Internet
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• 1958: Advanced Research Project Agency (ARPA)
later known as DARPA is created in the United
states.
• 1969: Development of Packet switching and the
first packets are transmitted over a network named
ARPANET.
• 1982/1983: Introduction of the TCP/IP protocol
suite that enable communication between
different networks.
•
BIT 1102: COMMUNICATION TECHNOLOGY
AND THE INTERNET
Internet History continued
11
 1983: First TCP wide Area Network known as the
NFSNET was created by the National Foundation
of Science (NFS) as a University backbone.
 1989/1990: Due to the popularity of the TCP/IP,
several other networks implemented it. Tim
Bernes Lee at CERN creates first few www pages
and develops the HTTP. The term Internet is
introduced with over 100,000 internet hosts
worldwide.
BIT 1102: COMMUNICATION TECHNOLOGY
AND THE INTERNET
WORLD INTERNET USAGE AND POPULATION
STATISTICS
March 31, 2011
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WORLD REGIONS
Population
2011 estimate
Internet Users
Dec. 31, 2000
Internet
Users
Latest Data
AFRICA
1,037,524,058
4,514,400
118,609,620
ASIA
3,879,740,877
114,304,000
922,329,554
EUROPE
816,426,346
105,096,093
476,213,935
MIDDLE EAST
216,258,843
3,284,800
68,553,666
NORTH AMERICA
347,394,870
108,096,800
272,066,000
LATIN AMERICA/
CARIB
597,283,165
18,068,919
215,939,400
OCEANEA/AUSTRALIA
35,426,995
7,620,480
21,293,830
WORLD TOTAL
6,930,055,154
360,985,492
2,095,006,0
05
Source: http://www.internetworldstats.com/stats.htm
The World Wide Web:
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 The World wide web can be described as the huge amount
of Information stored on the internet that can be accessed
by users Worldwide.
 It is referred to as the “web” because users move from one
resource to another using the “hyper links”.
 Tim Bernes Lee is the founder of the World Wide Web ,
HTTP, and HTML- Language that is a standard used to
develop websites)
 The World Wide Web consortium (w3.org) helps develop
the web standards.
BIT 1102: Communications Technology & the
Internet
Discussion:
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 How has the Internet and the worldwide Web
affected us in the following aspects:
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Education:
Health:
Economic Development:
Socially / personally:
Politically
ETC
BIT 1102: COMMUNICATION TECHNOLOGY
AND THE INTERNET
Intranet
15
• An Intranet can be defined as the private network
that uses internet protocols like HTTP and FTP to
securely share information in the internal
environment such as an Organisation.
• To access the intranet, a user generally has to be
authenticated / authorized through mechanisms
such as login passwords.
• An example of an Intranet is the Students Results
Management System at CoCIS which only allows
CoCIS students to access their results from within
the Institution.
BIT 1102: Communications Technology & the
Internet
Intranet cont’d
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 Intranet can be described as the “mini internet”
within an organisation that suites the internal
needs of that organisation.
 An extranet can be viewed as part of the
intranet that is accessible to selected and
authorised outsiders such as suppliers, Vendors
etc. External Examiners of MUK can access needed
information
BIT 1102: Communications Technology & the
Internet
Why Intranets
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 They enable knowledge sharing and interactive
Discussions.
 Easy and speedy communication within an
organisation
 Enables distribution of confidential company
sensitive information such as personnel records,
operation manuals, work policies, strategies etc.
(read more about Intranets)
BIT 1102: Communications Technology & the Internet
The Internet: How do we get access?
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 We have defined what the Internet is and the vast
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information stored the WWW,
Next we attempt to answer these questions.
How does one get access to the internet?
What access methods are available?
What are the considerations to be made?
BIT 1102: COMMUNICATION TECHNOLOGY
AND THE INTERNET
Internet Service Providers
19
• An ISP is an organisation that provides an
individual or company with internet access and
services usually at a monthly / annual fee.
• In Uganda, we have several ISPs such as
–
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MTN
Uganda telecom
Bush net
Afsat
Infocom
Orange
Airtel
ETC
BIT 1102: COMMUNICATION TECHNOLOGY
AND THE INTERNET
Some consideration
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 What service is being provided eg Broadband,
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Dail up Modem?
Speed: (Bandwidth is the amount of information
that can be transferred across a network in a given
time. Measured Bit/kiloBits /mega Bits per
second).
Cost: (can the individual / organisation afford?)
Availability: eg some areas may not have a
particular service perhaps due lack of
infrastructure.
Internet services are discussed next
Dial-up Internet Access
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 Dial-up internet access involves the user
connecting to the internet using a Modem over
telephone lines.
 Dial up modems have a theoretical speed of 56
KBPS but dial up internet transfer speeds will
generally average between 33-45 KBPS due to data
transmission and conversion delays (overhead).
 After many years of usage, Dial-Up Internet is
slowly being replaced by newer technologies such
as the ISDN and Broadband
ISDN
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 ISDN (Integrated Services Digital Network ) is a network
technology that supports digital transfer of simultaneous
voice and data traffic. Similar to DSL in this respect, an
ISDN Internet service works over ordinary telephone lines.
 Supports data rates of 128 Kbps.
 ISDN emerged as an alternative to
traditional dialup networking during the 1990s. The much
higher network speeds supported by newer broadband
technologies like DSL have drawn many consumers away
from ISDN service.
BIT 1102: COMMUNICATION TECHNOLOGY
AND THE INTERNET
Broadband Internet
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 The most common type of Internet service is called
broadband internet which is generally referred to
as “High speed internet”.
 Broadband generally refers to as an Internet
connection with a speed of at least 200kb/s though
this is not industry standard.
 Broadband Technologies include :
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DSL (Digital Subscriber line ). This includes
ADSL and SDSL.
Cable Internet
Satellite internet
i) Digital subscriber Line x DSL
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 Using a DSL modem, DSL is a digital
communications Technology that offers high speed
internet services over plain old Telephone Service
lines.
How DSL works:
 It works by utilising unused frequencies on the
normal telephone line that was developed to cater
for the human voice.
 The modem converts digital signals into voltage of
suitable frequency range
Synchronous Digital Subscriber Line
(ADSL)
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 ADSL is one of the most popular DSL technologies
in home and small office Internet connections.
ADSL transmission rates generally vary from 512
KBPS to 8MBPS for upload and download speeds
respectively.
 The User needs to be located roughly 3 miles from
the phone exchange company. (phone line restricts
distance because of the high frequency
transmissions).
Synchronous Digital Subscriber Line
(ADSL) cont’d
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 “Asynchronous” as opposed to “Synchronous” DSL
(SDSL) means that ADSL has lower upload than
download speeds while SDSL has equal speeds.
 SDSL requires more specialised equipment.
 Other variations of DSL include HDSL, VDSL etc
BIT 1102: COMMUNICATION TECHNOLOGY
AND THE INTERNET
Cable internet
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 Another popular Broadband Access method (about
22m users in US) that has high speeds.
 This technology uses cable modem to provide
internet services over the cable TV Infrastructure
by utilizing the free bandwidth.
BIT 1102: COMMUNICATION TECHNOLOGY
AND THE INTERNET
Other services
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 Other Internet access methods include Satellite
Internet that provides internet Access via global
satellite. This provides access where Land-based
Infrastructure such as phone lines may not be
available such as in war zones or other remote areas.
 Broadband wireless internet technologies such as
Wimax are being developed to provide the “last
mile” connection between wired Broadband services
such as DSL to wireless networks. Wimax is
sometimes referred to as Wireless Metropolitan
Network (wMAN)- read more
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 Read about the internet – its history
and use and how organizations
connect to it.
BIT 1102: Communications Technology & the
Internet