Computer Networks
Reynolds Duddu
Objectives
1.
2.
3.
4.
5.
Basic model of data communication, OSI Model, TCP/IP suite and
various concepts of networking.
Data Link Layer and various flow control and error control
protocol.
Different LAN protocols like Ethernet, Token ring and Token Bus
and FDDI.
Connecting devices, Network and transport layer protocols.
Application layer functions, protocols, switching and switched
networks like ATM.
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Objectives
UNIT 1: Introduction to Data Communication
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Books
1.
2.
Data Communication and Computer Networking by B. A.
Forouzan, 3rd Ed., Tata Mc Graw Hill.
Data and Computer Communications by William Stalling, 7th
Edition, Pearson Education.
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Course Structure
1.
Theoretical Subject – need for reinforcement
– Quizzes MCQs
– Assignments (5) MCQs
– Projects (2) – CISCO Packet Tracer/ Graphical Network
Simulator-3 (GNS 3)
2. Network Engineer
– CCNA Certification
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Quiz 0
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Contents
•
•
•
•
•
•
•
•
•
•
Communication System Model
Data Communication Networks
Protocol: Need of Protocol, TCP/IP Protocol Suite
OSI Model
Transmission Modes
Categories of Network
Topologies of Network.
Signal Encoding Techniques: Digital to Digital Conversion- Unipolar, Polar:
NRZ, RZ, Biphase, Bipolar
Transmission of Digital Data: DTE, DCE Interface, EIA-232D, Null Modem,
Modems: Traditional Modem, 56K Modem.
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Computer Network
• A computer network is a set of nodes connected
by communication links
• Node – a device which can send/receive data
• Ex: ?
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Computer Network
• A computer network is a set of nodes connected
by communication links
• Node – a device which can send/receive data
• Ex: PC/Mobile/Printer/Router etc.
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Computer Network
• A computer network is a set of nodes connected
by communication links
• A communication link caries data
• Ex:?
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Computer Network
• A computer network is a set of nodes connected
by communication links
• A communication link caries data
• Ex: Wired/Wireless
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Computer Network
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Devices
• End devices are either the source or destination
of data transmitted over the network.
• Intermediary devices interconnect end devices.
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Data Communication System
Data communication: Exchange of data between two devices via a medium
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Data Communication System - Components
1. Sender
2. Medium
3. Receiver
4. Message
5. Protocol
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Network Criteria
•
•
•
Performance: Delay and Throughput
Reliability: Frequency of failure and time taken to recover
Security: Protecting data
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Data flow/Transmission Modes
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Simplex
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Half- Duplex
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Full Duplex
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Connection Types
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Point-to-Point Line Configuration
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Point-to-Point Line Configuration
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Multipoint Line Configuration
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Network Components
• Nodes
• Communication Link (Media)
• Service/Message
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Network Components
• Nodes
– Intermediary
– End Nodes
• Communication Link (Media)
– Wired: Ethernet (Straight, Crossover), Optical fibre, Coaxial, USB
– Wireless: Infrared (Remote), Radio (Bluetooth, WiFi), Microwaves
(Mobile), Satellite (GPS)
• Service/Message
– VoIP, Storage, E-mail, online games, WWW, Messaging, Video
Calls
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Network Components
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Network Categories
1. Local Area Network (LAN)
2. Metropolitan Area Network (MAN)
3. Wide Area Network (WAN)
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Network Categories
1. Local Area Network (LAN)
–
Connects the computers by covering the local area
within 10m to 1.5 km usually offices, colleges,
groups of buildings
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Network Categories
2. Metropolitan Area Network (MAN)
–
–
Superior version of LAN often connects cities or locations
covering a range of 5-60 KM
Govt. Buildings /police stations
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Network Categories
3. Wide Area Network (WAN)
–
WAN extends over large geographical area.
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LAN, MAN & WAN
Comparison
LAN
MAN
Metropolitan Area Network
WAN
1. Full form
Local Area Network
Wide Area Network
2. Speed
Higher bandwidth, Data transfer speed ranges
Moderate bandwidth, speed of data
from 4 Mbps to 16 Mbps and can maximize up to transfer normally reaches up to 100
100 Mbps.
Mbps.
3. Installation and
Maintenance
The installation and maintenance process of the The installation and maintenance
The installation process and
LAN is easy.
process of the MAN is a little difficult. maintenance of WAN is very difficult.
4. Coverage
The range of LAN is between 10 and 1500
meters.
5. Ownership
The LAN is often owned by by a single person or MAN is owned by both Public and
organization.
private parties.
6. Networking Devices
Wi-Fi, Ethernet Cables, Token Ring and Fiber
Distributed Data Interface (FDDI), TCP/IP, etc.
7. Uses
8. Examples
Slower bandwidth, normally speed of
transfer have 10 Mbps.
The range of MAN is between 5 to 60 The range of the Wide Area Network
km.
is up to 100000 km.
WAN can be owned publicly or
privately.
Modem and Wire Cables like optical
cable and twisted pair cables.
Optical wires, routers, switches,
bridges, firewall modems and
Satellite.
It used in places like colleges, offices, or
hospitals.
It used in Small towns and in a
particular city.
It used by a large number of people
across the city, country and even
Continent.
Intranet
Cable TV network.
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Network Topology
• Topology refers to how various nodes, devices,
and connections on your network are physically
or logically arranged in relation to each other.
• Physical –Placement of nodes
• Logical – Flow of Data in the network.
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Network Topology Types
1.
2.
3.
4.
5.
6.
Bus
Ring
Star
Tree
Mesh
Hybrid
1.
2.
3.
4.
5.
6.
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Network Topology Types
1.
2.
3.
4.
5.
6.
Bus
Ring
Star
Tree
Mesh
Hybrid
1. Bus
2. Ring
4. Tree
5. Mesh
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6. Hybrid
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Bus Topology
• Orients all the devices on a
network along a single cable
(backbone)
• All the computers connected
in the network will receive
all the network traffic.
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Bus Topology
Advantages
Disadvantages
• It is very simple to design & easy
to implement for small networks
• Require less cabling compared to
other topologies.
• It is easy to expand by simply
joining two cables together
(scalable).
• Very cost-effective.
• The network stands on a single
cable. So, if any damage caused
to this cable the whole network
falls.
• As the traffic is shared by all the
nodes in the network, the
performance of the network
decreases as the traffic increases.
• Vulnerable
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Ring Topology
• Nodes are arranged in a
circle (or ring)
• The data can travel through
the ring network one
direction, with each device
having
exactly
two
neighbors.
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Ring Topology
Advantages
• Performance better
than Bus topology
• All nodes have equal
access
Disadvantages
• Unidirectional. Single
point of failure will
affect
the
whole
network
• Vulnerable (Security)
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Star topology
• Every node in the network
is directly connected to one
central hub/switch
• Most common topology
• Central node manages data
transmission
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Star Topology
Advantages
Disadvantages
• Easy to design implement
• Scalable
• Centralized
administration
• Single point of failure
affects the whole network
• Bottlenecks
due
to
overloaded switch/hub
• Increased cost due to
extra hub/switch
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Tree topology
• Central node act as a trunk
with nodes extending like a
branch
• Parent-child hierarchy to
how
the
nodes
are
connected.
• A combination of star and
bus topology
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Tree Topology
Advantages
• Easily scalable
• Troubleshooting errors
is easy
Disadvantages
• The entire network
depends on the health
of the root node
• Expensive
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Mesh topology
• Each node is connected to
every other nodes in the
network
• Fault tolerant and reliable
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Bus Topology
Advantages
• Fault tolerant
• Reliable
Disadvantages
• Issues with broadcasting
messages.
• Expensive and impractical
for large networks.
• Time consuming to set up
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Hybrid topology
• Hybrid topologies combine
two or more different
topology structures
• Ex. Tree topology
• Found in large companies
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Bus Topology
Advantages
• Flexible
Disadvantages
• Cost
• Network complexity
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Parameter\
Topology
Delay
Complexity
Bus
Star
Ring
Slow response time
because of one
computer transmit at
a time
Rank: 3
Good response
time, depends on
delay of hub
Rank 9
When the token
become empty, the
computer can send,
this helps to reduces
chances of collision
then reduce delay.
Rank:6
Easy to connect or
remove nodes in a
network without
affecting any other
node
Rank: 9
average
complexity each
device connects
to central device
with only one
link only
Rank: 7
all devices connected
with each other’s
Rank: 3
Tree
Mesh
Slowly because of
more traffic.
Rank 3
Manages high
amounts of traffic,
because multiple
devices can
transmit data
simultaneously.
Rank 9
More complex
because of tree is
combination a star
network topology
and a bus topology
Rank: 7
Installation is very
complex in mesh
topology, as each
node is connected
to every others node
Rank: 3
Note: Rank 9= Excellent, 8 = Very Good, 7 = Good and soon
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Parameter\
Topology
Bus
Star
Ring
Security
Any computer that is
connected to bus
topology network will
be able to see all the
data transmissions on
all the other
computers
Rank: 2
Security depends
on central device
security
Rank: 7
Compared Bus
topology it gives
far much better
performance,
signals don’t
necessarily get
transmitted to all
the workstations.
Rank: 6
Congestion
Control
Signal send source
from broadcast and
travels to all work
stations connected to
bus cable. Although
the message broadcasted
but only one computer
at a time can transmit a
packet on a bus
topology
Tree
Mesh
data travels from one
device to the next
until they reach their
destination
Rank: 4
The data pass over
more than one node
Rank: 4
It provides high
privacy and
security, due to
point-to-point
links
Rank: 9
Specially-formatted
frame, called a token,
travels around the
ring, stopping at each
host. The destination
host takes the data out
of the frame. No data
collisions.
Rank: 7
It is ideal when the
workstations are located in
groups, with each group
occupying a relatively small
physical region. An example
is a university campus in
which each building has its
own star network, and all the
central computers are linked
in a campus wide system.
Rank: 8
Data can be
transmitted from
different devices
simultaneously.
This topology can
withstand high
traffic
Rank: 9
Rank: 4
Note: Rank 9= Excellent, 8 = Very Good, 7 = Good and soon
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Parameter\
Topology
Bus
Star
Routing
Methodology
when device sends
broadcast message onto
the cable that all other
devices see the message
only the intended
recipient accepts the
message
Rank: 2
Reliability
Cost
Ring
Tree
Mesh
communicate
across the
network by
passing data send
through the hub.
Rank: 6
Very organized
Rank:7
All the computer is
connected to the central hub,
in the computer networking,
tree topology is known
as combination of a star
network topology and a bus
topology
Rank: 5
It has multiple
links, so if one
route is blocked
then other can be
accessed for data
communication
Rank:6
If the common cable
fails, then the whole
system will crash
down
Rank: 2
If hub fails, then the
whole system will crash
down.
Rank: 6
If the cable fails or any
computer shuts down,
then the whole system
will crash down.
Rank:3
In case of any node failure,
other hierarchical networks
are not affected.
Rank:5
A failure of one
device does not
cause a break in the
network or
transmission of
data.
Rank: 9
Cost of the cable is
less as compared to
another topology
Rank: 9
Star topology requires
more wires & hub,
compared to the ring
and bus topology
Rank: 5
High cost because of
costly connection
device
Rank: 3
Large cabling is
required as
compared to star
and bus topology.
Rank: 5
The length of cable
used very long,
The cost to
implement is
higher than other
network topologies
Rank: 3
Note: Rank 9= Excellent, 8 = Very Good, 7 = Good and soon
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Paramete
r\
Topology
Bus
Advant
ages
• It works well when
you have a small
network.
• It's the easiest
network topology
for connecting
computers or
peripherals in a
linear fashion.
• It requires less
cable length than a
star topology.
Star
• Centralized
management of the
network, through
the use of the
central computer,
hub, or switch.
• Easy to add
another computer
to the network.
• If one computer on
the network fails,
the rest of the
network continues
to function
normally.
Ring
Tree
Mesh
 No collisions.
 No
terminators
required.
 Data packets
travel
at great speed.
 Easer to fault
find.
• It is a combination of bus
and star topology
• It provides high
scalability, as leaf nodes can
add more
nodes in the hierarchical
chain.
• Other nodes in a network
are not affected, if one of
their nodes get damaged
• It provides easy
maintenance and fault
identification.
• Supported by several
hardware and software
vendors.
• Point-to-point wiring for
individual segments.
• A fault is one
terminal on the
network will not
affect the rest, as
the data has multiple
redundancy paths,
depending on the
size of the network,
that are
open to it.
• Data transmitted
via different
cables reducing
network clogging
keeping data
transfer rates at an
acceptable level.
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Paramete
r\
Topology
Disadv
antage
s
Bus
Star
• It can be difficult to
identify the problems if the
whole network goes
down.
• It can be hard to
troubleshoot individual
device issues.
• Bus topology is not
great for large networks.
• Terminators are
required for both ends of
the main cable.
• Additional devices
slow the network down.
• If a main cable is
damaged, the network fails
or splits into two.
• May have a higher
cost to implement,
especially when
using a switch or
router as the central
network device.
• The central
network device
determines the
performance and
number of nodes the
network can handle.
• If the central
computer, hub, or
switch fails, the
entire network goes
down and all
computers are
disconnected from
the network
Ring
Tree
Mesh
• Requires more
cable than the bus.
• Not common as
the bus.
• A break in the
ring will bring it
down.
• Less device
available.
• Large cabling is
required as compared
to star
and bus topology.
• On the failure of a
hub, the entire
network fails.
• Tree network is very
difficult to
build Architecture
than other network
topologies
• A large amount of
cabling is required.
• Complicated
implementation
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