1. Data Communication
and
Computer Networks
Computer Networks
*Note: Some content is copied from internet source. I thank the creators of the copied content.
Data Communication
and
Computer Networks
Computer Networks
Course Instructor:
Dr. C. Sreedhar
*Note: Some content is copied from internet source. I thank the creators of the copied content.

3. Unit 1
Introduction:
 Data Communication, Components,
Data Representations, Dataflow,
Network Topologies, categories of networks,
Internet, protocols and standards.
Internet, protocols and standards.
Network Models:
Layered tasks, OSI Reference model, layers in OSI model,
TCP/IP Protocol suit,
Addressing – Physical address, Logical address, port addresses.
Unit 1
Data Communication, Components,
Data Representations, Dataflow,
Network Topologies, categories of networks,
Internet, protocols and standards.
Internet, protocols and standards.
Layered tasks, OSI Reference model, layers in OSI model,
Physical address, Logical address, port addresses.

4. Unit 2
Physical layer and Transmission Media:
Analog and digital signals,
Digital signals –Bit rate, Bit length,
Transmission of digital signals,
Transmission Impairments – Attenuation, Distortion and Noise,
Transmission Impairments – Attenuation, Distortion and Noise,
Performance – Bandwidth, Throughput, Latency, Jitter.
Data Link Layer:
Error detection – Introduction, Block coding
detection, error correction,
hamming distance and minimum hamming distance, CRC
codes, Checksum.
Unit 2
Physical layer and Transmission Media:
and digital signals,
Bit rate, Bit length,
Transmission of digital signals,
Attenuation, Distortion and Noise,
Attenuation, Distortion and Noise,
Bandwidth, Throughput, Latency, Jitter.
Introduction, Block coding – error
detection, error correction,
hamming distance and minimum hamming distance, CRC

5. Unit 3
Network layer:
Design Issues - store-and-
Services to transport layer
Connection oriented services
Routing Algorithms:
Routing Algorithms:
The optimality principle, shortest path routing,
Flooding,
Distance vector and Link state,
Multicast Routings.
Unit 3
-forward,
Services to transport layer - Connection less and
Connection oriented services
The optimality principle, shortest path routing,
Distance vector and Link state,

6. Unit 4
Congestion Control:
Principles, congestion prevention policies,
congestion control in virtual circuits and
datagram subnets, load shedding, jitter control.
Internetworking:
Internetworking:
Tunneling, Internet work routing, Fragmentation.
The IP protocol, IP address,
Gateway routing protocols: OSPF, BGP.
Unit 4
Principles, congestion prevention policies,
congestion control in virtual circuits and
datagram subnets, load shedding, jitter control.
Tunneling, Internet work routing, Fragmentation.
The IP protocol, IP address,
Gateway routing protocols: OSPF, BGP.

7. Unit 5
Transport Layer:
UDP, TCP- service model, protocol, segment header,
connection management, Transmission Policy.
Application Layer:
The DNS Name Space,
The DNS Name Space,
Resource Records, Name Servers.
Unit 5
service model, protocol, segment header,
connection management, Transmission Policy.
Resource Records, Name Servers.

9. DCCN Lab: List of Experiments
Basic network command and Network configuration commands.
Create a network models using packet tracer.
Perform an Initial Switch Configuration using packet tracer
Investigate the TCP-IP and OSI Models using packet tracer
Implement Cyclic Redundancy Code
Implement Dijkstra’s algorithm to find the best path
Implement the Distance vector routing algorithm.
Implement congestion control using leaky bucket algorithm
Implement Domain name server
Implement client server model
DCCN Lab: List of Experiments
Basic network command and Network configuration commands.
Create a network models using packet tracer.
Perform an Initial Switch Configuration using packet tracer
IP and OSI Models using packet tracer
Implement Cyclic Redundancy Code
algorithm to find the best path
Implement the Distance vector routing algorithm.
Implement congestion control using leaky bucket algorithm

10. Unit 1
• Data Communications
• Definition
• Components of DC
• Data representation
• Data flow
• Data flow
• Networks
• Network criteria
• Types of connections
• Categories of topology
• Network Models
Unit 1
• Protocols and Standards
• Definition
• Standards

11. ata Communication: Definition
Data communications
are the exchange of
data between two
devices via some form
of transmission
devices via some form
of transmission
medium such as a wire
cable.
ata Communication: Definition

12. Data Communication
The effectiveness of a data communications system
depends on four fundamental characteristics:
• Delivery: deliver data to the correct destination
• Accuracy: system must deliver the data accurately
• Accuracy: system must deliver the data accurately
• Timeliness: system must deliver data in a timely
manner
• Jitter: refers to the variation in the packet arrival tim
The effectiveness of a data communications system
depends on four fundamental characteristics:
: deliver data to the correct destination
: system must deliver the data accurately
: system must deliver the data accurately
: system must deliver data in a timely
: refers to the variation in the packet arrival tim

13. ata Communication: Components
ve components
Sender
Message
Transmission medium
Transmission medium
Protocol
Receiver
otocol is defined as a set of
s that governs data
munications.
ata Communication: Components

14. ements of a Protocol
• Syntax
• Structure or format of the data
• Indicates how to read the bits -
• Semantics
• Interprets the meaning of the bits
Elements of Protocol
1.14
• Interprets the meaning of the bits
• Knows which fields define what action
• Timing
• When data should be sent and what
• Speed at which data should be sent or speed at which it is being
received.
Structure or format of the data
field delineation
Interprets the meaning of the bits
Elements of Protocol
Interprets the meaning of the bits
Knows which fields define what action
When data should be sent and what
Speed at which data should be sent or speed at which it is being

15. Data Representation
• Text:
• Text is represented as a bit pattern.
• Unicode uses 32 bits to represent a symbol or character
• Numbers
• Numbers are also represented by bit patterns.
• number is directly converted to a binary number
• number is directly converted to a binary number
• Images
• Images are also represented by bit patterns.
• image is composed of a matrix of pixels
• each pixel is assigned a bit pattern.
• Audio and Video:
Text is represented as a bit pattern.
Unicode uses 32 bits to represent a symbol or character
Numbers are also represented by bit patterns.
number is directly converted to a binary number
number is directly converted to a binary number
Images are also represented by bit patterns.
image is composed of a matrix of pixels

16. Data Flow
mmunication between two devices can be simplex or half
l-duplex
mmunication between two devices can be simplex or half-duplex, or

17. Review
•Data Communications
• Definition
• Characteristics that affect DC
• Components of DC
• Data representation
• Data representation
• Data flow
Characteristics that affect DC

18. Data
Data
Data
Data
Data
Data

19. NETWORKS
NETWORKS
network
network is
is a
a set
set of
of devices
devices (nodes
(nodes
nks
nks.
.
node
node can
can be
be a
a computer,
computer, printer,
printer,
ending
ending and/or
and/or receiving
receiving data
data generated
generated
ending
ending and/or
and/or receiving
receiving data
data generated
generated
etwork
etwork.
.
link
link can
can be
be a
a cable,
cable, air,
air, optical
optical
ansport
ansport a
a signal
signal carrying
carrying information
information
NETWORKS
NETWORKS
(nodes
(nodes)
) connected
connected by
by communicatio
communicatio
printer,
printer, or
or any
any other
other device
device capable
capable
generated
generated by
by other
other nodes
nodes on
on th
th
generated
generated by
by other
other nodes
nodes on
on th
th
optical
optical fiber,
fiber, or
or any
any medium
medium which
which ca
ca
information
information.
.

20. Network Criteria
• Performance:
• Measured: transit time and response time
• Transit time: time required for a message to travel from A
• Response time: elapsed time between inquiry and response
• Evaluated using two metrics:
• Evaluated using two metrics:
• throughput and delay (more throughput and less delay).
• Reliability:
• measured by the frequency of failure
• Security
• Network security issues include protecting data from unauthorized access
Measured: transit time and response time
Transit time: time required for a message to travel from AB
Response time: elapsed time between inquiry and response
throughput and delay (more throughput and less delay).
measured by the frequency of failure
Network security issues include protecting data from unauthorized access

21. • Point to Point - single transmitter and
Ex: Television remote control
• Multipoint - multiple recipients of single transmission
• Ex: Telephone Line
Types of Connections
single transmitter and receiver
multiple recipients of single transmission
Types of Connections

22. Physical topology
ology refers to the way in which a network is laid out physically
Physical topology
ology refers to the way in which a network is laid out physically

23. Mesh topology
every device has a dedicated point
every other device.
Total no. of connections???
Manages high amounts of traffic
Manages high amounts of traffic
Withstands failure of link.
Adding nodes easily added
Can avoid problems, malicious users
amount of cabling
number of I/O ports
installation and reconnection are difficult
ctical example: connection of
ephone regional offices
topology
every device has a dedicated point-to-point link
every other device.
Total no. of connections??? n(n-1)/2
Advantages
Manages high amounts of traffic
Manages high amounts of traffic
Withstands failure of link.
Adding nodes easily added
Can avoid problems, malicious users
Disadvantages
amount of cabling
number of I/O ports
installation and reconnection are difficult

24. A star topology
If the hub goes down, the whole system goes
down.
e star topology is used in local-area
tworks (LANs)
each device needs only one link and on
I/O port to connect it to any number of
others
Advantages
less expensive than a mesh topology.
robust: If one link fails, only that link is
robust: If one link fails, only that link is
affected
Disadvantages
If the hub goes down, the whole system goes
down.

25. bus topology
des are connected to the bus cable by drop lines and taps
rop line is a connection running between device and main cable.
ap is a connector
ap is a connector
e long cable acts as a backbone to link all the devices in a network
Advantages
s uses less cabling than mesh or star topologies
Disadvantages
ficult reconnection and fault isolation
gnal reflection at the taps can cause degradation
ault or break in the bus cable stops all transmission
topology
des are connected to the bus cable by drop lines and taps
rop line is a connection running between device and main cable.
e long cable acts as a backbone to link all the devices in a network
Advantages
s uses less cabling than mesh or star topologies
Disadvantages
gnal reflection at the taps can cause degradation
ault or break in the bus cable stops all transmission

26. Ring topology
Ring topology

27. Ring Topology
Each device has a dedicated point to point connection with only two devices on e
e of it.
Signal is passed along the ring in one direction till it reaches destination
Each device has a repeater
When a device receives signal to be passed, its repeater regenerates bits and
sses along.
Advantages
asy to install and reconfigure
ault isolation is simple
Disadvantages
directional traffic
ak in the ring disables entire network; solved by dual ring
Ring Topology
Each device has a dedicated point to point connection with only two devices on e
Signal is passed along the ring in one direction till it reaches destination
When a device receives signal to be passed, its repeater regenerates bits and
Advantages
Disadvantages
ak in the ring disables entire network; solved by dual ring

28. A hybrid topology: a star backbone with three bus networks
Main Star topology with each branch connecting several stations in a
bus topology
hybrid topology: a star backbone with three bus networks
Main Star topology with each branch connecting several stations in a

29. • Local Area Networks (LANs)
• Short distances
• Designed to provide local interconnectivity
• Wide Area Networks (WANs)
• Long distances
• Provide connectivity over large areas
Categories
• Provide connectivity over large areas
• Metropolitan Area Networks (MANs)
• Provide connectivity over areas such as a city, a campus
Categories of Networks
Provide connectivity over areas such as a city, a campus

30. AN
N
vately owned and links devices in a single office,building,campus
N size is limited to few kms
Ns allow resources to be shared between devices.
N uses oonly one type of transmission medium
mmon LAN topologies: Bus, Star, Ring
ta rate in LANs 100 or 1000 Mbps
office,building,campus.
Ns allow resources to be shared between devices.
one type of transmission medium

31. WANs: a switched WAN and a point
: a switched WAN and a point-to-point WAN

32. A heterogeneous network made of four WANs and two LANs
heterogeneous network made of four WANs and two LANs

33. LAN MAN
ocal Area Network Metropolitan Area Network
onnects group of computers in
small geographic area
Covers large region such as
cities, towns
etup cost is low Setup cost is higher than LAN
andwidth is low Bandwidth is higher than LAN
wisted pair, fiber optic cables Twisted pair, fiber optic cables
overage: ~ 2 miles Coverage: 100 miles
MAN WAN
Metropolitan Area Network Wide Area Network
Covers large region such as Spans large locality and connects
countries together
Setup cost is higher than LAN Most expensive network setup
Bandwidth is higher than LAN Highest bandwidth among all
types of networks
Twisted pair, fiber optic cables High speed communications:
fiber optic, wireless, satellite
Coverage: 100 miles Coverage: 1000 Km

34. Elements of Protocol
Elements of a protocol:
• Syntax
• Semantics
• Timing
yntax: structure or format of data
yntax: structure or format of data

35. Elements of protocol
• Semantics: meaning of each section of bits
Timing: when data should be sent and how fast they can be sent
meaning of each section of bits
when data should be sent and how fast they can be sent

36. Standards
o categories
De facto: not approved by an organized body but adopted
De jure: Legislated by an officially recognized body
ndards Creation Committees
International Standards Organization (ISO)
International Standards Organization (ISO)
International Telecommunications Union (ITU)
American National Standards Institute (ANSI)
Institute of Electrical and Electronics Engineers (IEEE)
Electronic Industries Association (EIA)
Internet Engineering Task Force (IETF
: not approved by an organized body but adopted
: Legislated by an officially recognized body
International Standards Organization (ISO)
International Standards Organization (ISO)
International Telecommunications Union (ITU)
American National Standards Institute (ANSI)
Institute of Electrical and Electronics Engineers (IEEE)
Electronic Industries Association (EIA)
Internet Engineering Task Force (IETF)

38. Need for Layered Architecture
• E.g., A can only speak Chinese, B can only speak Spanish, how can
A communicate with B?
• A finds a translator C, who can speak Chinese and English
• B finds a translator D, who can speak Spanish and English
• Two layers:
• Two layers:
• Higher layer: A and B
• Lower layer: C and D
Need for Layered Architecture
E.g., A can only speak Chinese, B can only speak Spanish, how can
a translator C, who can speak Chinese and English
a translator D, who can speak Spanish and English
38

39. A Two-layer example
messages in
How to communicate?
A
r
messages in
Chinese
messages in English
C
Lower layer provides services to the next higher layer.
messages in
How to communicate?
B
39
messages in English
messages in
Spanish
D
Lower layer provides services to the next higher layer.

40. ISO OSI Model

41. Origin for ISO OSI Model
Origin for ISO OSI Model

42. HE
HE OSI MODEL
OSI MODEL
ablished
ablished in
in 1947
1947,
, the
the International
International
multinational
multinational body
body dedicated
dedicated to
to worldwide
worldwide
ndards
ndards.
.
ISO
ISO standard
standard that
that covers
covers all
all aspects
aspects
ISO
ISO standard
standard that
that covers
covers all
all aspects
aspects
Open
Open Systems
Systems Interconnection
Interconnection (OSI)
(OSI)
he
he late
late 1970
1970s
s.
.
International
International Standards
Standards Organization
Organization (ISO)
(ISO) is
is
worldwide
worldwide agreement
agreement on
on international
international
aspects
aspects of
of network
network communications
communications is
is
aspects
aspects of
of network
network communications
communications is
is
(OSI)
(OSI) model
model.
. It
It was
was first
first introduced
introduced

43. Seven layers of the OSI model
layers of the OSI model

44. The interaction between layers in the OSI model
interaction between layers in the OSI model

45. exchange using the OSI model
using the OSI model

46. Layer 1: Physical Layer
Responsible of:
• Transmitting individual bits from one to the next.
• Physical characteristics of interface and media.
• Representation of bits: a stream of bit(0s,1s),
• Data rate.
• Data rate.
• Synchronize of bits
• Line configuration
• Physical topology
• Transmission mode
Layer 1: Physical Layer
Transmitting individual bits from one to the next.
Physical characteristics of interface and media.
Representation of bits: a stream of bit(0s,1s),

47. Physical Layer cont.

48. Layer 2: Data Link layer
Responsible of:
• Moving frames from one hop (node) to the next.
• Framing: divided the stream of bits received from the network layer
manageable data units called frames.
• Physical address (MAC address).
• Physical address (MAC address).
• Flow control.
• Error control: added trailer to the end of frame.
• Access control.
• Hop to hop delivery
Layer 2: Data Link layer
Moving frames from one hop (node) to the next.
Framing: divided the stream of bits received from the network layer
Error control: added trailer to the end of frame.

49. Data Link layer cont.
10110110101 01100010011
01100010011 10110000001

50. Hop-to-Hop delivery

51. Data Link Layer Example
Data Link Layer Example