Introduction to Internet

Technologies(CCS 110)

BY: HARUN KAMAU

 Outline
2

 WWW and Internet

 Internet services
 Internet protocols
 Web standards
 Internet Governance
 Domain name system

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Internet
3

 It is a world-wide global system of interconnected computer

networks, linked by wires, cables, and wireless connections
 Internet uses the standard Internet Protocol TCP / IP.
 Every computer in internet is identified by a unique IP address.
 IP Address is a unique set of numbers such as 41.89.192.2 which
identifies a computer location.
 A special computer DNS Domain Name Server is used to give name
to the IP Address so that user can locate a computer by a name.
 For example, a DNS server will resolve a name http://www.maseno.
ac.ke to a particular IP address to uniquely identify the computer
on which this website is hosted.
 Internet is accessible to every user all over the world

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 World wide web (www)
4

 It is a collection of interconnected documents and other

resources.
 The WWW is accessed via Internet
 The WWW was proposed in 1991 by Tim Berners-Lee at
CERN.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Internet vs WWW
5

 The Internet is a collection of computers or

networking devices connected together.
 They have communication between each other.
 Decentralized design that there is no centralized body
controls how the Internet functions.
 The Web is a collection of documents that are
interconnected by hyper-links.
 These documents are accessed by web browsers and
provided by web servers

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Intranets & Extranets
6

 The first serious use of Web technology within business was

for the implementation of Intranets
 Internet, Intranets, and Extranets are all networks that
transmit data.
 The difference is geographical location and security
 An Intranet is a secure network contained within an
organization. It uses a firewall for maintaining security.
Intranets are used only by company employees
 An Extranet is a secure network that allows outsiders to use
an Intranet with permission. It is used to connect company
suppliers, contractors and partners with employees

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Demystifying the internet
7

 It is a group of a network consisting of public, private, government,

universities, school, and other academic as well as business networks
connected by various technologies such as wireless, optical, and electronic.
 It is provided as a service by Internet Service Provider(ISP).
 The ISP operates as a link between the Internet and the user. To have an
internet connection, the user must have access to an Internet service
provider, which offers internet through Digital Subscriber line, satellite,
cable, Wireless, Dial up or fiber optic cable
 How does the Internet Work?
• Through communication protocols
• A communication protocol is a specification of how communication between
two computers will be carried out

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Pros and cons
8

 Connectivity, communication, and sharing

 Sharing of files
 Online Education
 Online business
 Entertainment
 Social media
 Online jobs
 Work from home, collaboration, and access to a global workforce
 Cloud storage

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 cons
9

 Addiction
 Cyber crime
 Socially
 unfit content for children
 Identity theft, hacking, viruses, and cheating
 Health issues and obesity
 Plagiarism
 Access Issues

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Terminologies
10

 Client
A client is the requesting program in a client/server relationship, e.g, the
user of a Web browser is effectively making client requests for pages
from servers all over the Web.
 Server
In general, a server is a computer program that provides services to other
computer programs in the same or other computers.
 Web Page:
A mixture of text, graphics, sound and animation in the HTML format, to make
information accessible in a easy to understand format using the Internet.
 Web Development
 The process of creating, modifying web pages.

By: Harun kamau-maseno university

CCS 110 ‒ Internet Technologies
 Terminologies
11

Hypertext: A format of information which allows one to

move from one part of a document to another or from
one document to another through hyperlinks
URL: Uniform Resource Locator. Is a unique identifier
used to locate a particular resource on the network
Markup language: Defines the structure and content of
hypertext documents
Web Site:A collection of web pages connected (linked)
by Hypertext -clickable links.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Terminologies
12

Web Site Storage/Hosting:

After a web site is designed it must be stored on a computer
that can be accessed through the Internet and the World-
Wide Web
World-Wide Web:
The World-Wide Web (WWW) is a pair of software applications,
which allow both distribution of and access to information on
the Internet. The web is not the Internet but a means of
distributing and accessing the information that is on it.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Terminologies
13

 ISP (Internet Service Provider):

An ISP is a company that provides individuals and other
companies access to the Internet and other related
services such as Web site development and hosting (web
site storage).
Individual assignment:
Identify ISPs in Kenya

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Communication between nodes
14

 Communication happens using either:

 Circuit switching
 Packet switching

Circuit switching
 Assuming two computers A and B are communicating, a communication path
will have to be established. This path would be dedicated to A and B for the
duration of their message exchange. Establishing a connection between
two points using a specific path on a network for the duration of a message
exchange is called circuit switching. This is exactly how the public switched
telephone network (PSTN) works.
 The problem with circuit switching is that the line is tied up regardless of
how much information is exchanged. E.g railway, one way highway
 Circuit switching is a big problem for computers because their information
exchange is typically “bursty” rather than even and constant

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Packet switching
15

 Two computers might want to exchange a file, but after that file is
exchanged the computers may not engage in communication again for
quite some time. Thus, we call the need to exchange data between
computers “discrete,” not continuous. An alternative to circuit
switching is packet switching.
 It is a mechanism which describes how data can be sent across a
network in small pieces called packets.
 The packets are numbered so they can be reassembled in the correct sequence
at the destination.
 Each packet contains destination and return addresses.
 The packets are transmitted over the network as capacity becomes available.
 The packets are forwarded across the network separately and do not
necessarily follow the same route; if a particular link of a given path is busy,
some packets might take an alternate route.
 The IP packet datagram has both header information and data.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Packet switching cont’d
16

The header information includes such things as:

 Total length of the packet
 Destination IP address
 Source IP address
 Time to live (TTL) .The time to live is decremented by routers as
the packet passes through them; when it hits zero, the packet is
discarded; this prevents packets from getting into an “infinite loop”
and tying up the network
 Error checking information

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Internet Protocol Suite
17

 The Internet Protocol Suite includes a number of standard

protocols. The two most common are:
‒ Transmission Control Protocol (TCP)
‒ Internet Protocol (IP)
 A computer communication protocol is a description of the
rules computers must follow to communicate with each other.
 TCP/IP defines how electronic devices (like computers)should
be connected to the Internet, and how data should be
transmitted between them.
 The TCP/IP protocol is embedded in TCP/IP software that is
part of the operating system (OS)

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 TCP/IP
18

 TCP handles communication between applications

‒ TCP uses a fixed connection.
‒ If one application wants to communicate with another via TCP, it sends
a communication request. This request must be sent to an exact address.
After a ‘handshake’ between the applications a communication line opens.
 IP handles communication between computers
 IP is a connection-less protocol. With IP, messages are broken down
into small independent ‘packets’ and are sent between computers via
the Internet. IP is responsible for ‘routing’ each packet to its correct
destination.
 Communicating via IP is like sending a long letter as a large number of
small postcards, each finding its own (often different) way to the
receiver.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 TCP/IP cont’d
19

 TCP/IP is TCP and IP working together.

 TCP takes care of the communication between your
application software (your browser) and your network
software - the handshake
 IP takes care of the communication with other computers -
the postal system which lets you address the package and put
it into the post
 TCP is responsible for breaking data down into IP packets
before they are sent, and for assembling the packets when
they arrive.
 IP is responsible for sending the packets to the correct
destination. Every computer has a IP address

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Evolution of internet
20

 The concept of Internet was originated in 1969 and has undergone several
technological & Infrastructural changes as discussed below:
 The origin of Internet devised from the concept of Advanced Research Project
Agency(ARPANET)
 ARPANET was developed by United States Department of Defense.
 Basic purpose of ARPANET was to provide communication among the various
bodies of government.
 Initially, there were only four nodes, formally called Hosts.
 In 1970, data networking was provided by early packet switching networks such
as ARPAnet, NPL network, CYCLADES, and Merit Network.
 In 1972, the ARPANET spread over the globe with 23 nodes located at different
countries and thus became known as Internet.
 In 1973 Internet Protocol suite was developed, through research published by
ARPA, Bob Kahn, and Vint Cerf, at Standford University.
 By the time, with invention of new technologies such as TCP/IP protocols, DNS,
WWW, browsers, scripting languages etc. Internet provided a medium to
publish and access information over the web.
By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies
 cons
21

 Addiction
 Cyber crime
 Socially
 unfit content for children
 Identity theft, hacking, viruses, and cheating
 Health issues and obesity
 Plagiarism
 Access Issues

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Group Activity
22

 Internet is old. Give a chronological order of its

evolution to the current status.
 Discuss how the Internet and Web are currently used
 Are there challenges in their use?
 How can these challenges be overcome?
 In a group of 5 people give a detailed report on the
issues highlighted

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Web browser(Web client)
23

 It is a program that retrieves information from the

Web.
 Microsoft Internet Explorer
 Netscape, Mosaic
 Opera
 Mozilla firefox
 Chrome
 Torch
 Lynx

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Web server
24

 It is a program that waits for requests from the web

browser.
 It provides four major functions
 Serving web pages
 Running gateway programs (CGI) and returning output

 Controlling access to the server

 Monitoring and logging all access

 E.g. Apache, IIS, Netscape Web server, …

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Searching the web
25

 Search for information in web is trivial with www. Here are search
techniques for precise information retrieval. Done through search engine
 “” :Return pages containing the words in the “”
 + Inserting a plus sign before a keyword indicates that the keyword must
be on a page that is returned.
 AND The word AND entered between keywords will find pages that have all
of those keywords in a page.
 OR The word OR entered between keywords will find pages that have at
least one of the keywords in it, but not necessarily all keywords on a page.
 NEAR The word NEAR entered between keywords will find pages with the
keywords in close proximity to one another in the page.
 NOT The word NOT entered before a keyword will find pages that do not
contain the keyword.
 ()Parentheses used around keywords can create a much more
sophisticated search. If you enter “Web master” AND (consultant OR
software)

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Internet Reference Models
26

OSI Reference Model

 OSI is acronym of Open System Interconnect. This model is
developed by the International organization of
Standardization ISO in the year 1984 and therefore also
referred as ISO-OSI Model.
 The OSI model consists of seven layers as shown in the
following diagram. Each layer has a specific function,
however each layer provide services to the layer above.
 The OSI model doesn't perform any functions in the
networking process. It is a conceptual framework so we
can better understand the complex interactions that are
going on.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 OSI Model
27

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Physical Layer(1)
28

 The Physical layer is responsible for the following

activities:
 Activating, maintaining and deactivating the physical
connection.
 Defining voltages and data rates needed for
transmission.
 Converting digital bits into electrical signal.
 Deciding whether the connection is simplex, half duplex
or full duplex.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Data Link Layer(2)
29

 The data link layer performs the following functions:

 Performs synchronization and error control for the
information which is to be transmitted over the physical
link.
 Enables error detection, and adds error detection bits
to the data which are to be transmitted.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Network Layer(3)
30

Following are the functions of Network Layer:

 To route the signals through various channels to the
other end.
 To act as the network controller by deciding which
route data should take.
 To divide the outgoing messages into packets and to
assemble incoming packets into messages for higher
levels.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Transport Layer(4)
31

The Transport layer performs the following functions:

 It decides if the data transmission should take place on
parallel paths or single path.
 It performs multiplexing, splitting on the data.
 It breaks the data groups into smaller units so that they
are handled more efficiently by the network layer.
 The Transport Layer guarantees transmission of data
from one end to other end.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Session Layer(5)
32

 The Session layer performs the following functions:

 Manages the messages and synchronizes conversations
between two different applications.
 It controls logging on and off, user identification, billing
and session management.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Presentation Layer(6)
33

The Presentation layer performs the following functions:

 This layer makes it sure that the information is
delivered in such a form that the receiving system will
understand and use it.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Application Layer(7)
34

The Application layer performs the following functions:

 It provides different services such as manipulation of
information in several ways, retransferring the files of
information, distributing the results etc.
 The functions such as LOGIN or password checking are
also performed by the application layer.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 TCP/IP Model
35

TCP/IP model is practical model and is used in the Internet.

TCP/IP is acronym of Transmission Control Protocol and
Internet Protocol.
 The TCP/IP model combines the two layers Physical and
Data link layer into one layer i.e. Host-to- Network
layer. The following diagram shows the various layers of
TCP/IP model:

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 TCP/IP protocol stack
36

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 TCP/IP protocol stack
37

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Application Layer(4)
38

 This layer is same as that of the OSI model and performs

the following functions:
 It provides different services such as manipulation of
information in several ways, retransferring the files of
information, distributing the results etc.
 The functions such as LOGIN or password checking are also
performed by the application layer.
 Protocols used: TELNET, FTP, SMTP, DN, HTTP, NNTP are
the protocols employed in this layer.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Transport Layer(3)
39

 It does the same functions as that of transport layer in OSI

model. Here are the key points regarding transport layer:
 It uses TCP and UDP protocol for end to end transmission.
 TCP is reliable and connection oriented protocol.
 TCP also handles flow control.
 The UDP is not reliable and a connection less protocol also
does not perform flow control.
 Protocols used: TCP/IP and UDP protocols are employed in
this layer.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Internet Layer(2)
40

 The function of this layer is to allow the host to insert

packets into network and then make them travel
independently to the destination. However, the order of
receiving the packet can be different from the
sequence they were sent
 Protocols used: Internet Protocol IP is employed in
Internet layer.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Host-to-Network Layer(1)
41

 This is the lowest layer in TCP/IP model. The host has to

connect to network using some protocol, so that it can
send IP packets over it. This protocol varies from host
to host and network to network.
 Protocols used: ARPANET, SATNET, ETHERNET, packet
radio are the protocols which are used in this layer.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Transmission Control Protocol (TCP)
42

 Transmission Control Protocol TCP corresponds to the Transport Layer of

OSI Model.
 TCP is a reliable and connection oriented protocol.
 TCP offers:
 Stream Data Transfer.
 Reliability.
 Efficient Flow Control
 Full-duplex operation.
 Multiplexing.
 TCP offers connection oriented end-to-end packet delivery.
 TCP ensures reliability by sequencing bytes with a forwarding
acknowledgement number that indicates to the destination the next byte
the source expect to receive.
 It retransmits the bytes not acknowledged with in specified time period.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Internet Protocol (IP)
43

 Internet Protocol is connectionless and unreliable

protocol. It ensures no guarantee of successfully
transmission of data.
 In order to make it reliable, it must be paired with
reliable protocol such as TCP at the transport layer.
 Internet protocol transmits the data in form of a
datagram as shown in the following diagram:

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 User Datagram Protocol (UDP)
44

 Like IP, UDP is connectionless and unreliable protocol. It

doesn’t require making a connection with the host to
exchange data. Since UDP is unreliable protocol, there is
no mechanism for ensuring that data sent is received.
 UDP transmits the data in form of a datagram. The
UDP datagram consists of five parts as shown in the
following diagram:

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 File Transfer Protocol (FTP)
45

 FTP is used to copy files from one host to another. FTP offers
the mechanism for the same in following manner:
 FTP creates two processes such as Control Process and Data
Transfer Process at both ends i.e. at client as well as at server.
 FTP establishes two different connections: one is for data
transfer and other is for control information.
 Control connection is made between control processes while
Data Connection is made between
 FTP uses port 21 for the control connection and Port 20 for the
data connection.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Trivial File Transfer Protocol (TFTP)
46

 Trivial File Transfer Protocol is also used to transfer the files but it
transfers the files without authentication. Unlike FTP, TFTP does not
separate control and data information. Since there is no
authentication exists, TFTP lacks in security features therefore it is
not recommended to use TFTP.
Key points
 TFTP makes use of UDP for data transport. Each TFTP message is
carried in separate UDP datagram.
 The first two bytes of a TFTP message specify the type of message
 The TFTP session is initiated when a TFTP client sends a request to
upload or download a file.
 The request is sent from an ephemeral UDP port to the UDP port 69
of an TFTP server.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Telnet
47

 Telnet is a protocol used to log in to remote computer

on the internet. There are a number of Telnet clients
having user friendly user interface. The following
diagram shows a person is logged in to computer A, and
from there, he remote logged into computer B.

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies

 Port Numbers
48

 A port number is used to distinguish between the individual networking

applications that are running simultaneously above the TCP/IP protocol
stack
 port numbers for standard TCP/IP services may be referred to as well-
known port numbers
 ‒ 80 HTTP (Hypertext Transfer Protocol) - WWW
 ‒ 194 IRC (Internet Relay Chat) - Conferencing
 ‒ 21 FTP (File Transfer Protocol)
 ‒ 25 SMTP (Simple Mail Transfer Protocol) - E-mail
 ‒ 23 Telnet
 Server processes are associated with a fixed port and the client must
know the port in order to connect with the network service
 A Web server will normally be listening for connections on port 80. A web
browser will use this port number by default when attempting to connect
to the remote computer

By: Harun kamau-maseno university CCS 110 ‒ Internet Technologies