4. LAN, MAN & WAN
Introduction to Computer Networks
Network in small geographical Area (Room, Building
or a Campus) is called LAN (Local Area Network)
speed (10 to 100 mbps)
Network in a City is call MAN (Metropolitan Area
Network)
Network spread geographically (Country or across
Globe) is called WAN (Wide Area Network)
8. Applications of Networks
Introduction to Computer Networks
Resource Sharing
Hardware (computing resources, disks, printers)
Software (application software)
Information Sharing
Easy accessibility from anywhere (files, databases)
Search Capability (WWW)
Communication
Email
Message broadcast
Remote computing
Distributed processing (GRID Computing)
9. Network Topology
The network topology
defines the way in
which computers,
printers, and other
devices are connected.
A network topology
describes the layout of
the wire and devices as
well as the paths used
by data transmissions.
Introduction to Computer Networks
10. Bus Topology
Commonly referred to
as a linear bus, all the
devices on a bus
topology are connected
by one single cable.
Key characteristics
Flexible
Expandable
Moderate Reliability
Moderate performance
Introduction to Computer Networks
11. BUS TOPOLOGY
• Advantages
– Easy to install
– Requires less
cabling than
mesh,star,tree,ring.
• Disadvantages
– Difficult to add device
– Limitation on
maximum number of
devices linked.
– Fault identification and
isolation is the
problem
– Any fault in cable can
stop the entire
transmission
12. Star & Tree Topology
Introduction to Computer Networks
The star topology is the most
commonly used architecture in
Ethernet LANs.
When installed, the star
topology resembles spokes in
a bicycle wheel.
Larger networks use the
extended star topology also
called tree topology. When
used with network devices that
filter frames or packets, like
bridges, switches, and routers,
this topology significantly
reduces the traffic on the wires
by sending packets only to the
wires of the destination host.
13. STAR & TREE TOPOLOGY
ADVANTAGES
• Less expensive
• It is easy to install and
configure
• Addition and deletion
involves only one
connection between hub
and device
• It require less cabling
• Fault identification and
removal is easy
DISADVANTAGES
• If hub fails whole network
goes down
• There is no alternate
routing
• It require most cable than
tree.
14. Ring Topology
Introduction to Computer Networks
A frame travels around the ring,
stopping at each node. If a node
wants to transmit data, it adds the
data as well as the destination
address to the frame.
The frame then continues around
the ring until it finds the
destination node, which takes the
data out of the frame.
Single ring – All the devices on
the network share a single cable
Dual ring – The dual ring topology
allows data to be sent in both
directions.
15. RING TOPOLOGY
ADVANTAGES
• It is easy to install and
reconfigure
• Addition and deletion
require only to connection
• Alarm is issued if signal
problem issue
• Fault identification and
removal is easy
DISADVANTAGES
• A break the ring disables
the entire network. This
can be removed by using
dual ring or switch that
closes the break.
16. Mesh Topology
The mesh topology
connects all devices
(nodes) to each other
for redundancy and
fault tolerance.
It is used in WANs to
interconnect LANs and
for mission critical
networks like those
used by banks and
financial institutions.
Implementing the mesh
topology is expensive
and difficult.
Introduction to Computer Networks
17. MESH TOPOLOGY
ADVANTAGES
• There is no traffic problem due
to dedicated point to point link.
• The network is robust as if one
link becomes unusable then
also the network can work.
• The Network is very secure as
only intended receiver will get
the data.
• Fault identification and
removal is very easy.
DISADVANTAGES
• Installation is difficult as
every device is connected
to every other devices.
• Cost is very high due to
more cabling and more
ports for each device.
• Addition and deletion is
difficult as it will remove
all connection.
19. Networking Media
Networking media can
be defined simply as
the means by which
signals (data) are sent
from one computer to
another (either by cable
or wireless means).
Introduction to Computer Networks
20. Networking Devices
Introduction to Computer Networks
HUB, Switches, Routers,
Wireless Access Points,
Modems etc. are required
to link them together.
These are called
internetworking devices.
22. REPEATERS
• It is an electronic device that operate on only the physical layer.
• Its job is to regenerate the signal over the same network before the signal
becomes too weak or corrupted so as to extend the length to which the
signal can be transmitted over the same network.
• An important point to be noted about repeaters is that they do not amplify
the signal.
• When the signal becomes weak, they copy the signal bit by bit and
regenerate it at the original strength.
• It is a 2 port device.
23. BRIDGES
• A bridge operates at data link layer. A bridge is a repeater.
• It is also used for interconnecting two LANs working on the same protocol. It has a
single input and single output port, thus making it a 2 port device.
Types of Bridges
• Simple Bridge: links two segments and contains a table the list address of all the
station included in each of them.
• Multi Bridge: connect more than two LAN
• Transport Bridge: builds table of station addresses on its own as it performs its bridge
function.
25. Routers
• A router is a device like a switch
that routes data packets based
on their IP addresses.
• Router is mainly a Network
Layer device.
• Routers normally connect LANs
and WANs together and have a
dynamically updating routing
table based on which they make
decisions on routing the data
packets.
• Router divide broadcast
domains of hosts connected
through it.
26. Switches
• A switch is a multiport bridge with a buffer and a design that can boost its efficiency(a large
number of ports imply less traffic) and performance.
• A switch is a data link layer device.
• The switch can perform error checking before forwarding data, that makes it very efficient
as it does not forward packets that have errors and forward good packets selectively to
correct port only.
27. HUB
• A hub is basically a multiport repeater.
• A hub connects multiple wires coming from different branches, for
example, the connector in star topology which connects different
stations.
• Hubs cannot filter data, so data packets are sent to all connected
devices.
• Also, they do not have intelligence to find out best path for data
packets which leads to inefficiencies and wastage.
28. BANDWIDTH
• Bandwidth describes the maximum data
transfer rate of a network or Internet
connection.
• It measures how much data can be sent over a
specific connection in a given amount of time.
• For example, a gigabit Ethernet connection
has a bandwidth of 1,000 Mbps (125
megabytes per second)
30. Types of Hub
• Active Hub:-
– These are the hubs which have their own power supply and can
clean, boost and relay the signal along with the network.
– It serves both as a repeater as well as wiring centre.
• These are used to extend the maximum distance between
nodes.
• Passive Hub :-
– These are the hubs which collect wiring from nodes and power
supply from active hub.
– These hubs relay signals onto the network without cleaning and
boosting them and can’t be used to extend the distance between
nodes.
31. Computers: Clients and Servers
In a client/server
network arrangement,
network services are
located in a dedicated
computer whose only
function is to respond
to the requests of
clients.
The server contains the
file, print, application,
security, and other
services in a central
computer that is
continuously available
to respond to client
requests.
Introduction to Computer Networks
32. TCP/IP
• TCP/IP, or the Transmission Control
Protocol/Internet Protocol, is a suite of
communication protocols used to
interconnect network devices on the
internet.
• TCP/IP can also be used as a
communications protocol in a private
network (an intranet or an extranet).
33. How TCP/IP works
• TCP/IP uses the client/server model of communication in which a
user or machine (a client) is provided a service (like sending a
webpage) by another computer (a server) in the network.
• Collectively, the TCP/IP suite of protocols is classified as stateless,
which means each client request is considered new because it is
unrelated to previous requests. Being stateless frees up network
paths so they can be used continuously.
• The transport layer itself, however, is stateful. It transmits a single
message, and its connection remains in place until all the packets in
a message have been received and reassembled at the destination.
35. Applications
E-mail
Searchable Data (Web Sites)
E-Commerce
News Groups
Internet Telephony (VoIP)
Video Conferencing
Chat Groups
Instant Messengers
Internet Radio
Introduction to Computer Networks
