The Internet is the largest computer
network in the world, connecting millions of
computers. A network is a group of two or
more computer systems linked together.
• In 1969, the US Department of Defense started
a project to allow researchers and military
personnel to communicate with each other in
• The project was called DARPAnet (Defence
Advanced Research Projects Agency) and it is
the foundation of the Internet.
• Later its also called ARPAnet (Advanced
Research Projects Agency)
• Throughout the 1970's, what would later
become the Internet was developed. While
mostly military personnel and scientists used it
in its early days, the advent of the World Wide
Web in the early 1990's changed all that.
• Current amount over 1.9 billion users around
• The overall responsibility for managing Internet Protocol address
or domain names at upper levels is vested in the Internet
Assigned Numbers Authority (IANA), which delegates the actual
administration of most functions to other bodies.
• At global regional levels, the principal bodies providing allocation
and registration services that support the operation of the
Internet globally are:
• RIPE NCC (Réseaux IP Européens Network Coordination Centre)
• ARIN (American Registry for Internet Numbers)
• APNIC (Asia Pacific Network Information Centre)
• LACNIC (Latin American and Caribbean IP address Regional
• AfriNIC (African Regional Registry for Internet Number Resources)
• Dial-up-connections : speed 56kbps
• ISDN : speed 128 Kbps
▫ ADSL(Asymmetrical Digital Subscriber Line)
▫ Cable : speed 42 Mbps
• Lease lines : up to 12mbps
• FTTH- Fiber to the Home
As you now know, the Internet is the
monitor, modem, cables, phone lines, etc).
• Tim Berners-Lee, a software engineer, invented the
World Wide Web in 1991.
• The Web is a system of Internet servers that
support specially-formatted documents.
• These specially formatted documents are text
documents created in HTML, a formatting
language. In conjunction with the World Wide
Web, your web browser interprets these text
documents so they become web pages.
• Web pages contain formatted text, graphics,
sound, animation, and video, allowing point and
• “An address that points to a particular
document or other resource on the Internet,
used most frequently on the World Wide Web
• A computer user can visit an Internet document
by typing its URL into a Web browser or similar
application used to access the Internet.
• An internet web site address.
• Domain names are used in URLs to identify
particular Web pages.
• The first-level set of domain names are the toplevel domains (TLDs), including the generic
top-level domains (gTLDs), such as the
prominent domains com, net and org, and the
country code top-level domains (ccTLDs).
• "Interconnection, collection of computers for
the purpose of sharing resources &
Communication that we can take as a
• Resources we can divide in to three categories,
Information such as files & folders, Hardware
such as printers and software such as MS
Is a method for communication
Sharing of printers and other resources
Can centralize administration and support
Can reduce the cost involved in communication
& information gathering
Different types of computer network
designs is by their scope or scale.
• LAN (Local Area Network)
• WAN (Wide Area Network)
• MAN (Metropolitan Area Network)
• WLAN (Wireless Local Area Network)
• PAN(Personal Area Network)
• CAN(Campus Area Network)
• LAN (Local Area Network):
“A computer network that connect two or
more electrical or electronic devices or
equipments in a single network”
• WAN (Wide Area Network):
• MAN (Metropolitan Area Network):
“A data network designed for a town
or city”. In terms of geographic breath, MANs
are larger than local-area networks (LANs), but
smaller than wide-area networks (WANs). MANs
are usually characterized by very high-speed
connections using fiber optical cable or other
• Wireless Local Area Network
“A LAN based on (Wi-Fi) wireless
• A type of network in which each workstation
has equivalent capabilities and responsibilities.
This differs from client/server architectures, in
which some computers are dedicated to serving
the others. Peer-to-peer networks are generally
simpler, but they usually do not offer the same
performance under heavy loads.
• A network architecture in which each computer
or process on the network is either a client or a
server. Servers are powerful computers or
processes dedicated to managing disk drives
(file servers), printers (print servers), or
network traffic (network servers).Clients are
PCs or workstations on which users run
applications. Clients rely on servers for
resources, such as files, devices, and even
• Intranet: A network based on TCP/IP protocols
(an internet) belonging to an organization,
usually a corporation, accessible only by the
organization's members, employees, or others
with authorization. An intranet's Web sites look
and act just like any other Web sites, but the
firewall surrounding an intranet fends off
• Extranet: A buzzword that refers to an intranet
that is partially accessible to authorized
outsiders. Whereas an intranet resides behind a
firewall and is accessible only to people who
are members of the same company or
organization, an extranet provides various
levels of accessibility to outsiders. You can
access an extranet only if you have a valid
username and password, and your identity
determines which parts of the extranet you can
• Data Communication is the process of moving
data & information from one place to another
through a transmission system.
• The communication media is the matter or
substance that carries voice or data.
• Different types of transmission media are
currently in use. All these types can be group
two categories as Guided and Unguided media.
• The Guided media are follows through physical
media and unguided media are those in which
is the data is broadcast through air.
• Transmission media
• Cable is the medium through which information
usually moves from one network device to
• There are several types of cable which are
commonly used with LANs. In some cases, a
network will utilize only one type of cable,
other networks will use a variety of cable
Is the common medium
Is mainly used in star topology networks
Cheap and easy to work with
There are several categories available in Twisted
▫ CAT1, CAT2, CAT5, CAT5E
Categories of Unshielded Twisted
Voice Only (Telephone Wire)
Data to 4 Mbps (Local Talk)
Data to 10 Mbps (Ethernet)
Data to 20 Mbps (16 Mbps Token Ring)
Data to 100 Mbps (Fast Ethernet)
No hub needed
• Radio Waves
▫ Omni directional
▫ Suffers from interferences
▫ Use to TV, Radio, Cell phone
Microwaves travel nearly in a straight line
Tall building is a barrier
100 meter high towers, repeaters for every 80km
Is widely used for mobile phone, television etc.
Used for long distance telephone
Private business network
Mostly used with Microwave
Using in long distance communications
Used for weather forecasting, television
broadcast, amateur radio communications,
Internet communications, and the Global
▫ Is limited for a small area (eg: for a room)
▫ Walls/barriers will block the signals
▫ Mainly used for TV remote control, IRD port.
▫ Founding members are Ericsson, IBM, Intel, Nokia
▫ Short range wireless communication technology.
▫ Used to data synchronization between 2 devices
▫ Is limited for a small area
▫ Mainly used in Mobile phones, digital cameras,
headsets, scanners, keyboards, mouse and other
devices to connect to a computer.
• Topology refers to the shape of a network, or
the network's layout. How different nodes in a
network are connected to each other and how
they communicate is determined by the
network's topology. Topologies are either
physical or logical.
• BUS, RING, STAR, MESH etc.
Considerations When Choosing a
Length of cable needed
• “A Protocol is a set of rules(standards) that
governs the communications between
computers on a network.”
• Most common network protocol is TCP/IP
• Eg: http, ftp, smtp, telnet, ssh, https, etc.
Properties of Protocol
• Detection of the underlying physical connection
(wired or wireless),
• How to start and end a message
• How to format a message
• What to do with corrupted or improperly
formatted messages (error correction)
• How to detect unexpected loss of the
connection, and what to do next
• Termination of the session and or connection.
• When networks fist come in to being,
computers could typically communicate with
computers from the same manufacturer. In the
Interconnection(OSI) reference model was
created by the International Organization for
Standardization(ISO) to break this barrier.
• It is describes how data and network
information are communicated.
• A reference model is a conceptual blue print of
how communications should takes place.
• These processes divide into logical groups
2. Data Link
Provides the user interface to
communicate to the computer. Eg HTTP
----------------------------------------------------Presents data to the 7th layer and data
translation like encryption, conversion
----------------------------------------------------Manage presentation layers entities. (keep
different application data separately)
----------------------------------------------------Performs error correction before
----------------------------------------------------Manages the device addressing.(IP
addressing) , Routes data. [Packets]
----------------------------------------------------Combines packets in to bytes and error
----------------------------------------------------Moves bits between devices(physical
connection/cabling, electronic singnals)
A network server
• A network server is a computer designed to
process requests and deliver data to other (client)
computers over a local network or the Internet.
Network servers typically are configured with
additional processing, memory and storage capacity
to handle the load of servicing clients. Common
types of network servers include:
online game servers
• Short for modulator-demodulator. A modem is
a device or program that enables a computer to
transmit data over, for example, telephone or
cable lines. Computer information is stored
digitally, whereas information transmitted over
telephone lines is transmitted in the form of
analog waves. A modem converts between
these two forms.
• A MAC address, or Media Access Control address, is
a 48- or 64-bit address associated with a network
• While IP addresses are associated with software,
MAC addresses are linked to the hardware of
• For this reason, the MAC address is sometimes
called the hardware address, the burned-in address
(BIA), or the physical address. MAC addresses are
expressed in hexadecimal notation in the following
format: 01-23-45-67-89-AB, in the case of a 48-bit
• “An identifier for a computer or device on a
TCP/IP network”. Networks using the TCP/IP
protocol route messages based on the IP
address of the destination.
• The format of an IP address is a 32-bit numeric
address written as four numbers separated by
periods. Each number can be zero to 255.
• For example 126.96.36.199 could be an IP
What is an IP address
A way to identify machines on a network
A unique identifier
Used to connect to another computer
Allows transfers of files and e-mail
IP addresses consist of four sections
Each section is 8 bits long
Each section can range from 0 to 255
Written, for example, 188.8.131.52
These four sections represent the machine itself
and the network it is on
The network portion is assigned.
The host section is determined by the network
5 Classes of IP address A B C D and E
Class A reserved for governments
Class B reserved for medium companies
Class C reserved for small companies
Class D are reserved for multicasting
Class E are reserved for future use
Class A begins 1 to 126
Class B begins 128 to
Class C begins 192 to
Addresses beginning 127 are reserved for
loopback and internal testing
xxx.0.0.0 reserved for network address
xxx.255.255.255 reserved for broadcast
IP addresses are:
Global and Standardised
• Class A :
184.108.40.206 – 220.127.116.11
• Class B :
18.104.22.168 – 22.214.171.124
• Class C :
126.96.36.199 – 188.8.131.52
• Class D :
224.x.x.x (multicasting &
• Class E :
240.x.x.x (for future use)
Current Private IP addresses as
• Class A
10.0.0.0 through 10.255.255.255
• Class B
172.16.0.0 through 172.31.255.255
• Class C
192.168.0.0 through 192.168.255.255
• IPv4 addresses have 32 bits in them and so allow
a maximum of four billion addresses
• IPv6 stands for Internet Protocol version 6. It is
the second version of the Internet Protocol to be
used generally across the virtual world.
• IPv6 addresses have 128 bits.
• IPv6 is the future of Internet addressing, mainly
because industry experts believe that they are
close to running out of available addresses
• 128 bits - written as eight 16-bit hex numbers.
How to Determine your IP Address?
• Go to the start menu and select Run.... Then
type cmd in the box and click OK.
• At the C:> prompt type ipconfig. Then press
Enter. Your IP address, subnet mask and
default gateway will be printed on the window.
• If you want more detailed information about
your network connection, type ipconfig /all at
the prompt. Here you can get additional
information about your IP configuration.
• For Domain Name System (or Service or
Server), an Internet service that translates
domain names into IP addresses.
• Every time you use a domain name, therefore,
a DNS service must translate the name into the
corresponding IP address.
DNS has a table of Domain names and IP
addresses. It’s map the domain name with the IP
address and its route to the particular server.
• Short for Dynamic Host Configuration
Protocol, a protocol for assigning dynamic IP
addresses to devices on a network.
• With dynamic addressing, a device can have a
different IP address every time it connects to