ICT 101 LECTURE 2 - BASICS OF COMPUTER NETWORKS.pptx

Lecture 2 : Introduction to Computer Networks
Assistant Lecturer:
Tony Chaula Msc.
Faculty of Science and Education (FASE)
Science Block, Second Floor, Office No. 11
UNIVERSITY OF IRINGA
ICT 101: INFORMATION TECHNOLOGY

Introduction to Computer Networks
Basics of Computer Networks
What is a Computer Network?
Is a collection of two or more computers or
communication devices which are connected
together via transmission media guided by a set
of rules to allow user to communicate with each
other and share data and other network
resources.

• A typical computer Network

Essentials/Basic requirements of a computer network
• At least two computers, Server or Client workstation.
• Networking Interface Cards (NIC)
• A connection medium, usually a wire or cable,
although wireless communication between
networked computers and peripherals is also
possible.
• Network Operating system software, such as
Microsoft Windows NT or 2000, Novell NetWare, Unix
and Linux.

• A Network Interface Card (NIC)

Why computer networks?

Why computer networks?
• To facilitate communication and sharing of
information
• Sharing resources such as databases, files.
• Sharing peripherals such as modems, printers, tape
backup drives, or CD-ROM drives.
• To meet more real time demands such as instant
messaging and vidoconferencing
• Centralized administration and support

Types of Networks
• LAN (Local Area Network)
• MAN (Metropolitan area Network)
• WAN (Wide Area Network)
• PAN (Personal Area Network)
• Internet
• Intranet
• VPN (Virtual Private Network)

LAN (Local Area Network)
• LANs are networks usually confined to a
geographic area, such as a single building or a
college campus.
• LANs can be small, linking as few as three
computers, but often link hundreds of
computers.

Types of Networks
MAN (Metropolitan area Network)
• The refers to a network linking the
networks located at two or more sites
within a city.

Metropolitan area
Network

WAN (Wide Area Network)
• Wide area networking combines multiple
LANs that are geographically separate.
• Different LANs connected using services
such as dedicated leased phone lines,
satellite links, etc …
• Can be as simple as connecting a few
campuses or can be as complex as hundreds
of branch offices globally.

WAN (Wide Area Network)

PAN (Personal Area Network)
• PANs cover areas generally associated with individual
workspaces (e.g., a home office or an office cubicle).
• Within these spaces, individual networks connecting
two or more devices may be enabled using wireless
technologies.

Types of Networks
Personal Area
Network (PAN)

Internet
• The Internet is a system of linked
networks that are worldwide in scope.
• It facilitates data communication services
such as remote login, file transfer,
electronic mail, the World Wide Web.

Internet
• The Internet was initially restricted to
military and academic institutions.
• Internet websites now provide personal,
educational, political and economic
resources to every corner of the planet.

Internet
• It is the largest computer network in the
world.
• The Internet and the World Wide
Web(www).
• They are often are often used
interchangeably but they are not the same.
• So what is the difference between the
Internet and the World wide Web(www)?

Internet
• The internet is physical network connecting
all computers in the world.
• The World Wide Web is a virtual network
of web sites connected by hyperlinks (or
"links").
• Web sites are stored on servers on the
internet, so the World Wide Web is a part
of the internet.

Intranet
• An intranet is a private network utilizing
Internet-type tools, but available only
within that organization.
• For large organizations, an intranet provides
an easy access mode to corporate
information for employees.

VPN (Virtual Private Networks)
• VPN uses a technique known as tunneling to
transfer data securely on the Internet to a
remote access server on your workplace
network
• Save money by using the public Internet instead
of making long–distance phone calls to connect
securely with your private network.

Categories of Network
Network can be divided in to two main
categories:-
• Peer-to-peer.
• Server – based or Client/Server

• Peer-to-peer.

Peer-to-peer
• In peer-to-peer networking there are no
dedicated servers or hierarchy among the
computers.
• All of the computers are equal and therefore
known as peers

Peer-to-peer
• Normally each computer serves as Client/Server.
• There is no one assigned to be an administrator
responsible for the entire network.
• Suitable for small organizations.

• Server – based.

Server – based
The term Client/server refers to the concept of
sharing the work involved in processing data
between the client computer and the most
powerful server computer.

Server – based
- A Client is a less powerful computer that is
connected to the server. It requests
information and services from the server.

Server – based
- A Server is a computer or system that provides
resources, data, services, or programs to other
computers, known as clients, over a network
Note:
A device could be both a server and a client at the same
time.

Server – based
- The client/server network is the most efficient
way to provide:
• Databases and management of applications such
as Spreadsheets, Accounting, Communications
and Document management.
• Network management.
• Centralized file storage.

Types of Messaging
• Most network messaging can be described as
one-to-one communications.
• Sending device addresses an outgoing
message for delivery to a single receiver.
• But in some cases we need to send messages
to more than one receiver.

Types of Messaging
Most network devices are capable of issuing three
types of messages:
• Unicast
• Broadcast
• Multicast

Types of Messaging
Unicast Messaging
• In unicast messaging, or unicasting, each
Frame/message is addressed to one recipient.
• If a device needs to send the same message to
multiple destinations, it must perform a
replicated unicast.

Types of Messaging
Unicast Messaging
• The same transmission is repeated for each
destination.
• With unicasting there is no risk of sending a
message to an unintended recipient.

Unicast Messaging

Unicast Messaging/Replicated Unicast

Types of Messaging
Broadcast Messaging
• In broadcast messaging, or broadcasting,
each frame/message contains a special
address to indicate that the destination is all
devices (referred to as the broadcast
domain).

Types of Messaging
Broadcast Messaging
• Such transfers are also referred to as point-
to-multipoint.
• Sending device transmits a broadcast frame
once and the network directs the frame to
all other devices.

Broadcast Messaging
• This method is most efficient in cases when all
network devices require the same message
being broadcast.
• If this is not the case, a destination device not
requiring the message wastes processing
resources.
• It must read and subsequently discard the
incoming frame.

Broadcast Messaging

Types of Messaging
Multicast Messaging
• Also a point-to-multipoint communication.
• In multicast messaging, or multicasting, the network
delivers a transmitted message to a select number of
devices.
• Not to all devices as in the case of a broadcast.
• Multicasting can be described as selective or directed
broadcasting.

Types of Messaging
Multicast Messaging
• Multicast content is selectively forwarded from
the server to the two branch offices where
multicast group members are located.
• Network switches and routers must be enabled
to process multicast messages, otherwise they
will be broadcast.

Multicast Messaging

Types of Addressing
• A typical organizational network consisting
of multiple interconnected LANs.
• There are two types of addresses which are
used to transfer messages between all
devices in such a network.

Types of Addressing
Since there are multiple LANs connected to each
other through an internetwork.
• Each Local Area Network (LAN) must have a
unique address for successful message delivery
over the internetwork.
• Every device on a LAN must have a unique
address for successful message delivery over the
LAN’s broadcast domain.

Types of Addressing
There two (2) of Addressing.
• Local Area Network (LAN) Addressing
• Internetwork Addressing

What is an Internetwork?
Is a collection of two or more Local Area Networks
(LANs) which are connected together via
transmission media guided by a set of rules to
allow network user to communicate with each
other and share data and other network
resources.

Types of Addressing
• A comparison can be made with the addresses
used to identify a building in a city.
• For example, 8610 UoI is the equivalent of a
unique device address on a network.
• While 8610 UoI, Iringa Campus is the equivalent
of the combined device and network address on
an internetwork.

Multicast Messaging
8610 UoI, Iringa Campus
8610 UoI, Mwaza Campus
8610 UoI, Dodoma Campus
8610 UoI, Arusha Campus
Dodoma Arusha
Iringa Mwanza

Local Area Network (LAN) Addressing
• LANs are used to interconnect PCs
and other network devices in a
geographically limited area
• Typically not exceeding a single
building.

• The role of the LAN is to enable
users to access resources (e.g.,
devices, software programs, data
files) that are not directly connected
to or stored on their work stations.

• The size and complexity of an
organizational network determines the
number of times a message is
processed by network access devices
(e.g., switches, wireless access points
(WAPs) before reaching its
destination.

• The endpoint of a message is a
specific device, which can be
uniquely identified by an address
assigned to its network interface
card (NIC).

Types of Addressing

Types of Addressing
• The term medium access control (MAC)
address is often used to describe the
unique address of a device.
• It is common to express MAC addresses
using hexadecimal (hex) notation.

Types of Addressing
• An example of a MAC address is 00-10-2F-C3-16-12
• Alternate terms (names) used to describe MAC
addresses include:
 Layer 2 address.
 Data Link layer address.
 NIC address.
 Hardware address.
 Device address.

Internetwork Addressing
• The role of an internetwork is to enable
communication between devices
connected to two or more separate
networks.
• An internetwork can span a small or large
geographic area, connecting LANs that
belong to the same or different
organizations.

Types of Addressing
• A small internetwork can connect LANs
on different floors of a building. The
largest internetwork in existence is the
Internet

Example of an internetwork

Types of Addressing
• An internetwork like the Internet links all types
of similar or dissimilar networks (e.g., Ethernet
LANs, mobile telephone networks).
• To Uniquely identify each device on any network
connected to the Internet
• We use an address called the Internet protocol
(IP) address

There are two types of IP addresses
1. Private IP Addresses
2. Public IP Addresses
• Non-unique private IP addresses are
assigned to devices for internal use.
• Such addresses cannot be used to send
messages over the Internet.

Types of Addressing
Internetworking Addressing
• The term IP address is often used to
describe the internetwork address of a
device, since IP is used globally to link to
the Internet.

Types of Addressing
Internetworking Addressing
• Alternate terms (names) used to describe IP
addresses include:
• Internet address.
• Layer 3 address.
• Network layer address.
• Subnet address.
• Internetwork address.
• Routing address

Types of Addressing
• An IP address is divided into four parts separated by
dots
• Each part has a number ranging from 1 to 255
• Example of an IP Address :- 1.1.1.1 ,192.168.0.1,
255.255.255.255
An IP address has two parts.
1. network identification (netid)
2. host identification (hostid)

Types of Addressing
Classes of IP addresses
1. Class A 10.0.0.0 through 10.255.255.255
2. Class B 172.16.0.0 through 172.31.255.255
3. Class C 192.168.0.0 through
192.168.255.255
4. Class D
5. Class E

Types of Addressing
There are Five (5) classes of IP addresses

Types of Addressing
•MAC addresses are used to identify the source
and destination of each message on LANs.
•When multiple LANs are connected to an
internetwork using routers, both MAC and IP
addresses are used as follows:-

Types of Addressing
•All routers on an internetwork keep tables of
the IP addresses of networks connected to the
internetwork.
•A router connected to a network keeps a table
of both the MAC address and the IP address of
each device on that network.

Types of Addressing
•When a router receives a message intended for a
device on a network connected to itself, it uses
the information in its table to forward the message
to the appropriate device, using the MAC address.
•When a router receives a message intended for a
device on a network connected to another router,
it uses the IP address to place the message on a
path to that router.

Networking Devices
The four Basic Networking devices
are:-
• Hubs
• Bridges
• Switches
• Routers

Networking Devices
Hubs/Repeaters
• Used to connect together two or more Computers
or Ethernet segments of any media type.
• In larger network designs, signal quality begins to
deteriorate as segments exceed their maximum
length.
• Hubs provide the signal amplification required to
allow a segment to be extended a greater distance.

Networking Devices
Hubs/Repeaters

Networking Devices
Hubs/Repeaters
All devices connected
to a hub are
Considered to be in
the same network
Segment

Networking Devices
Hubs/Repeaters
• Although hey allow LANs to extend beyond normal distance
limitations still limit the number of nodes that can be
supported.
• A hub takes any incoming signal and repeats it out all ports.
• In a segment connected using a hub only one device can send
a signal at a time forcing all other devices to listen to it.

Networking Devices
Hubs/Repeaters
• When two devices send a signal at a tim collision
occurs.
• To use a hub you must have a collision detection
or collision avoidance mechanism.

Networking Devices
Bridges
• The function of a bridge is to connect separate
networks together.
• Bridges connect different networks types (such as
Ethernet and Fast Ethernet) or networks of the same
type.
• Bridges map the addresses of the nodes residing on
each network segment and allow only necessary
traffic to pass through the bridge.

Networking Devices
Bridges
• When a packet is received by the bridge, the bridge
determines the destination and source segments.
• Then the packet is "forwarded" to the correct
segment.
• Also called "store-and-forward" devices because they
look at the whole Ethernet packet before making
forwarding decisions.
• This allows for greater distances than hubs.

Networking Devices
Bridges
Each port on a bridge
is Considered to be
one network
Bridges have fewer
Ports that switches

Networking Devices
Bridged Network

Networking Devices
Switches
• Ethernet switches are an expansion of the
concept in bridging.
• Switches can link more networks together than a
bridge
1. Cut-through Switches
2. Store-and-forward Switches

Networking Devices
Switches
• In the past, cut-through switches were
faster because they examined the packet
destination address only before forwarding
it on to it destination segment

Networking Devices
Switches
• Each port on a switch is considered to be a
separate network/segment.
• Switches are sometimes referred to as multiport
bridges.
• Offer more capability and processing power than
bridges.
• Forward messages using MAC addresses.
• Each each Port on a switch can be used to connect a
device.

Networking Devices
Switches

Networking Devices
Router
• Routers filter out messages by specific protocol
IP (Internet Protocol)rather than by packet address.
• Routers also divide networks logically (using IP addresses)
instead of physically(two networks with different IP address )
• An IP router can divide a network into various networks so
that only traffic destined for particular IP addresses can pass
between segments.

Networking Devices
Router
• Network speed often decreases due to this type of
intelligent forwarding.
• Such filtering takes more time than that exercised in a switch
or bridge, which only looks at the Ethernet address.
• However, in more complex networks, overall efficiency is
improved by using routers.

Networking Devices
How does a Router Work?
• A router has a special networking software with various
networking protocols that allow it to logically link different
networks.
• It processes and filters network traffic/messages and send
them to specific networks and devices.
• It accomplishes this task by keeping a record of addresses of
all the Networks directly connected to it in a table called
The Routing Table

Networking Devices
Router

Networking Devices
Wireless Router

Networking Devices
Wireless Router
With simcard slot

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ICT 101 LECTURE 2 - BASICS OF COMPUTER NETWORKS.pptx