CONNECT WITH US
CONNECT WITH US
WEBSITE: www.eduengineering.net
TELEGRAM: @eduengineering
-
INSTAGRAM: @eduengineering
Regular Updates for all Semesters
All Department Notes AVAILABLE
Handwritten Notes AVAILABLE
Past Year Question Papers AVAILABLE
Subject wise Question Banks AVAILABLE
Important Questions for Semesters AVAILABLE
Various Author Books AVAILABLE
,UNIT I INTRODUCTION AND APPLICATION LAYER
Data Communication - Networks – Network Types – Protocol Layering – TCP/IP Protocol
suite –OSI Model – Introduction to Sockets - Application Layer protocols: HTTP – FTP –
Email protocols(SMTP - POP3 - IMAP - MIME) – DNS – SNMP
1.1 Data Communication
When we communicate, we are sharing information. This sharing can be local or
remote.
The term telecommunication, which includes telephony, telegraphy, and television,
means communication at a distance (tele is Greek for "far").
The word data refers to information presented in whatever form is agreed upon by
the parties creating and using the data.
“Data communications are the exchange of data between two devices via some
form of transmission medium such as a wire cable”.
For data communications to occur, the communicating devices must be part of a
communication system made up of a combination of hardware (physical equipment) and
software (programs).
The effectiveness of a data communications system depends on four fundamental
characteristics:
I. Delivery: The system must deliver data to the correct destination. Data must be received by
the intended device or user .
2. Accuracy: The system must deliver the data accurately. Data that have been altered in
transmission and left uncorrected are unusable.
3. Timeliness: The system must deliver data in a timely manner. Data delivered late are useless.
4. Jitter: Jitter refers to the variation in the packet arrival time. It is the uneven delay in
the delivery of audio or video packets.
1.1.1 Components
A data communications system has five components
1.Message: The message is the information (data) to be communicated. Popular forms of
information include text, numbers, pictures, audio, and video.
Downloaded from www.eduengineering.net
,2.Sender: The sender is the device that sends the data message. It can be a computer,
workstation, telephone handset, video camera, and so on.
3. Receiver: The receiver is the device that receives the message. It can be a computer,
workstation, telephone handset, television, and so on.
4. Transmission medium: The transmission medium is the physical path by which a message
travels from sender to receiver. Some examples of transmission media include twisted-pair
wire, coaxial cable, fiber optic cable, and radio waves.
5. Protocol: A protocol is a set of rules that govern data communications. It represents an
agreement between the communicating devices. Without a protocol, two devices may be
connected but not communicating.
1.1.2 Data Representation
Information today comes in different forms such as text, numbers, images, audio, and
video.
Text
In data communications, text is represented as a bit pattern, a sequence of bits (O s or 1 s).
Different sets of bit patterns have been designed to represent text symbols. Each set is called a
code, and the process of representing symbols is called coding.
Unicode, which uses 32 bits to represent a symbol or character used in any language in the
world. The American Standard Code for Information Interchange (ASCII), now constitutes the
first 127 characters in Unicode and is also referred to as Basic Latin.
Numbers
Numbers are also represented by bit patterns. However, a code such as ASCII is not used
to represent numbers; the number is directly converted to a binary number to simplify
mathematical operations.
Images
Images are also represented by bit patterns. In its simplest form, an image is composed
of a matrix of pixels (picture elements), where each pixel is a small dot. The size of the
pixel depends on the resolution. The size and the value of the pattern depend on the image.
For an image made of only black-and-white dots (e.g., a chessboard), a I-bit pattern is enough
to represent a pixel. If an image is not made of pure white and pure black pixels, you can
increase the size of the bit pattern to include gray scale
There are several methods to represent color images. One method is called RGB, so called
because each color is made of a combination of three primary colors: red, green, and blue.
The intensity of each color is measured, and a bit pattern is assigned to it. Another method is
called YCM, in which a color is made of a combination of three other primary colors: yellow,
cyan, and magenta.
Audio
Audio refers to the recording or broadcasting of sound or music. Audio is by nature different
from text, numbers, or images.
Downloaded from www.eduengineering.net
, Video
Video refers to the recording or broadcasting of a picture or movie. Video can either be
produced as a continuous entity (e.g., by a TV camera), or it can be a combination of
images, each a discrete entity, arranged to convey the idea of motion.
1.1.3 Data Flow / transmission mode
Communication between two devices can be simplex, half-duplex, or full-duplex as
shown in Figure 1.2.
Simplex
In simplex mode, the communication is unidirectional, as on a one-way street. Only one
of the two devices on a link can transmit; the other can only receive (see Figure 1.2a).
Keyboards and traditional monitors are examples of simplex devices.
Advantage of Simplex mode:
o In simplex mode, the station can utilize the entire bandwidth of the communication
channel, so that more data can be transmitted at a time.
Disadvantage of Simplex mode:
o Communication is unidirectional, so it has no inter-communication between
devices.
Half-Duplex
In half-duplex mode, each station can both transmit and receive, but not at the same time.
When one device is sending, the other can only receive, and vice versa (see Figure 1.2b)
Downloaded from www.eduengineering.net
CONNECT WITH US
WEBSITE: www.eduengineering.net
TELEGRAM: @eduengineering
-
INSTAGRAM: @eduengineering
Regular Updates for all Semesters
All Department Notes AVAILABLE
Handwritten Notes AVAILABLE
Past Year Question Papers AVAILABLE
Subject wise Question Banks AVAILABLE
Important Questions for Semesters AVAILABLE
Various Author Books AVAILABLE
,UNIT I INTRODUCTION AND APPLICATION LAYER
Data Communication - Networks – Network Types – Protocol Layering – TCP/IP Protocol
suite –OSI Model – Introduction to Sockets - Application Layer protocols: HTTP – FTP –
Email protocols(SMTP - POP3 - IMAP - MIME) – DNS – SNMP
1.1 Data Communication
When we communicate, we are sharing information. This sharing can be local or
remote.
The term telecommunication, which includes telephony, telegraphy, and television,
means communication at a distance (tele is Greek for "far").
The word data refers to information presented in whatever form is agreed upon by
the parties creating and using the data.
“Data communications are the exchange of data between two devices via some
form of transmission medium such as a wire cable”.
For data communications to occur, the communicating devices must be part of a
communication system made up of a combination of hardware (physical equipment) and
software (programs).
The effectiveness of a data communications system depends on four fundamental
characteristics:
I. Delivery: The system must deliver data to the correct destination. Data must be received by
the intended device or user .
2. Accuracy: The system must deliver the data accurately. Data that have been altered in
transmission and left uncorrected are unusable.
3. Timeliness: The system must deliver data in a timely manner. Data delivered late are useless.
4. Jitter: Jitter refers to the variation in the packet arrival time. It is the uneven delay in
the delivery of audio or video packets.
1.1.1 Components
A data communications system has five components
1.Message: The message is the information (data) to be communicated. Popular forms of
information include text, numbers, pictures, audio, and video.
Downloaded from www.eduengineering.net
,2.Sender: The sender is the device that sends the data message. It can be a computer,
workstation, telephone handset, video camera, and so on.
3. Receiver: The receiver is the device that receives the message. It can be a computer,
workstation, telephone handset, television, and so on.
4. Transmission medium: The transmission medium is the physical path by which a message
travels from sender to receiver. Some examples of transmission media include twisted-pair
wire, coaxial cable, fiber optic cable, and radio waves.
5. Protocol: A protocol is a set of rules that govern data communications. It represents an
agreement between the communicating devices. Without a protocol, two devices may be
connected but not communicating.
1.1.2 Data Representation
Information today comes in different forms such as text, numbers, images, audio, and
video.
Text
In data communications, text is represented as a bit pattern, a sequence of bits (O s or 1 s).
Different sets of bit patterns have been designed to represent text symbols. Each set is called a
code, and the process of representing symbols is called coding.
Unicode, which uses 32 bits to represent a symbol or character used in any language in the
world. The American Standard Code for Information Interchange (ASCII), now constitutes the
first 127 characters in Unicode and is also referred to as Basic Latin.
Numbers
Numbers are also represented by bit patterns. However, a code such as ASCII is not used
to represent numbers; the number is directly converted to a binary number to simplify
mathematical operations.
Images
Images are also represented by bit patterns. In its simplest form, an image is composed
of a matrix of pixels (picture elements), where each pixel is a small dot. The size of the
pixel depends on the resolution. The size and the value of the pattern depend on the image.
For an image made of only black-and-white dots (e.g., a chessboard), a I-bit pattern is enough
to represent a pixel. If an image is not made of pure white and pure black pixels, you can
increase the size of the bit pattern to include gray scale
There are several methods to represent color images. One method is called RGB, so called
because each color is made of a combination of three primary colors: red, green, and blue.
The intensity of each color is measured, and a bit pattern is assigned to it. Another method is
called YCM, in which a color is made of a combination of three other primary colors: yellow,
cyan, and magenta.
Audio
Audio refers to the recording or broadcasting of sound or music. Audio is by nature different
from text, numbers, or images.
Downloaded from www.eduengineering.net
, Video
Video refers to the recording or broadcasting of a picture or movie. Video can either be
produced as a continuous entity (e.g., by a TV camera), or it can be a combination of
images, each a discrete entity, arranged to convey the idea of motion.
1.1.3 Data Flow / transmission mode
Communication between two devices can be simplex, half-duplex, or full-duplex as
shown in Figure 1.2.
Simplex
In simplex mode, the communication is unidirectional, as on a one-way street. Only one
of the two devices on a link can transmit; the other can only receive (see Figure 1.2a).
Keyboards and traditional monitors are examples of simplex devices.
Advantage of Simplex mode:
o In simplex mode, the station can utilize the entire bandwidth of the communication
channel, so that more data can be transmitted at a time.
Disadvantage of Simplex mode:
o Communication is unidirectional, so it has no inter-communication between
devices.
Half-Duplex
In half-duplex mode, each station can both transmit and receive, but not at the same time.
When one device is sending, the other can only receive, and vice versa (see Figure 1.2b)
Downloaded from www.eduengineering.net
