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Data Communication and
Computer Network
UNIT-1
• Basics of Computer Networks: Computer Network, Definition, Goals, Applications, Components, Topology
and its types, Types of Networks, (LAN, MAN, WAN, Internet), Broadcast & Point-To-Point Networks,
Modes of transmission (Serial, Parallel, Synchronous, Asynchronous and Isochronous).
• Modes of Communication: Simplex, Half Duplex, Full Duplex, Protocols and Standards.
• Network Models: Design issues of the layer, Protocol Hierarchy,
• ISO-OSI Reference Model: Internet Model, TCP/IP Protocol Suite, Ports, and Comparison of ISO-OSI and
Internet Model. Multiplexing (FDM, WDM and TDM), and switching (Circuit switching, Packet Switching and
Comparison of both)
• Computer Network is a group of computers connected with each
other through wires, optical fibres or optical links so that various
devices can interact with each other through a network.
• The aim of the computer network is the sharing of resources among
various devices.
Features Of Computer network
• 1) Communication speed
• Network provides us to communicate over the network in a fast and
efficient manner. For example, we can do video conferencing, email
messaging, etc. over the internet.
• 2) File sharing
• File sharing is one of the major advantage of the computer network.
Computer network provides us to share the files with each other
•
• 3) Backup
• Since the files are stored in the main server which is centrally located.
Therefore, it is easy to take the back up from the main server.
• 4) Software and Hardware sharing
• We can install the applications on the main server, therefore, the user
can access the applications centrally. So, we do not need to install the
software on every machine. Similarly, hardware can also be shared.
• 5) Security
• Network allows the security by ensuring that the user has the right to
access the certain files and applications.
• 6) Scalability
• Scalability means that we can add the new components on the network.
Network must be scalable so that we can extend the network by adding
new devices. But, it decreases the speed of the connection
• 7) Reliability
• Computer network can use the alternative source for the data
communication in case of any hardware failure.
Network Architecture

• two types of network architectures are used:

• Peer-To-Peer network- It is a network in which all the computers are
linked together with equal privilege and responsibilities for processing
the data.
• Peer-To-Peer network is useful for small environments, usually up to
10 computers.
• Peer-To-Peer network has no dedicated server.
• Special permissions are assigned to each computer for sharing the
resources
• Client/Server network:- A Client/Server network contains the
centralized system. Therefore we can back up the data easily.
• A Client/Server network has a dedicated server that improves the
overall performance of the whole system.
• Security is better in Client/Server network as a single server
administers the shared resources.
• It also increases the speed of the sharing resources.
Components:
• 1) Network Interface Card(NIC) - It is a hardware component used to
connect a computer with another computer onto a network. It is a
circuit board installed in a computer that provides a dedicated
network connection to the computer.
• NIC allows both wired and wireless communications.
• NIC is both a physical layer and a data link layer device, i.e. it
provides the necessary hardware circuitry so that the physical
layer processes and some data link layer processes can run on
it.
In internal networks cards, motherboard has a slot for the
network card where it can be inserted. It requires network
cables to provide network access.
External network cards are of two types: Wireless and
USB based. Wireless network card needs to be inserted
into the motherboard, however no network cable is
required
Network Types

• A computer network can be categorized by their size.

• LAN(Local Area Network)
• Local Area Network is a group of computers connected to each other
in a small area such as building, office.
• LAN is used for connecting two or more personal computers through
a communication medium such as twisted pair, coaxial cable, etc.
• It is less costly as it is built with inexpensive hardware such as hubs,
network adapters, and ethernet cables.
• MAN(Metropolitan Area Network)
• A metropolitan area network is a network that covers a larger
geographic area by interconnecting a different LAN to form a larger
network.
• Government agencies use MAN to connect to the citizens and private
industries.
• In MAN, various LANs are connected to each other through a
telephone exchange line.
• WAN(Wide Area Network)
• A Wide Area Network is a network that extends over a large
geographical area such as states or countries.
• A Wide Area Network is quite bigger network than the LAN.
• A Wide Area Network is not limited to a single location, but it spans
over a large geographical area through a telephone line, fibre optic
cable or satellite links.
• The internet is one of the biggest WAN in the world.
Topologies:
• Done briefly in class.
Transmission modes

• The way in which data is transmitted from one device to another

device is known as transmission mode.
• The transmission mode is also known as the communication mode.
• The transmission mode is defined in the physical layer.
• The transmission mode is also known as a directional mode.
The Transmission mode is divided into three
categories:
• Simplex mode
• Half-duplex mode
• Full-duplex mode
Simplex mode

• In Simplex mode, the communication is unidirectional, i.e., the data flow in one
direction.
• A device can only send the data but cannot receive it or it can receive the data
but cannot send the data.
• This transmission mode is not very popular as mainly communications require the
two-way exchange of data. The simplex mode is used in the business field as in
sales that do not require any corresponding reply.
• The radio station is a simplex channel as it transmits the signal to the listeners but
never allows them to transmit back.
• Keyboard and Monitor are the examples of the simplex mode as a keyboard can
only accept the data from the user and monitor can only be used to display the
data on the screen.
• The main advantage of the simplex mode is that the full capacity of the
communication channel can be utilized during transmission.
Half-Duplex mode

• In a Half-duplex channel, direction can be reversed, i.e., the station

can transmit and receive the data as well.
• Messages flow in both the directions, but not at the same time.
• The entire bandwidth of the communication channel is utilized in one
direction at a time.
• In half-duplex mode, it is possible to perform the error detection, and
if any error occurs, then the receiver requests the sender to
retransmit the data.
• A Walkie-talkie is an example of the Half-duplex mode.
Full-duplex mode

• In Full duplex mode, the communication is bi-directional, i.e., the data

flow in both the directions.
• Both the stations can send and receive the message simultaneously.
• Full-duplex mode has two simplex channels. One channel has traffic
moving in one direction, and another channel has traffic flowing in
the opposite direction.
• The Full-duplex mode is the fastest mode of communication between
devices.
• The most common example of the full-duplex mode is a telephone
network.
Different Transmission Modes

• The primary concern in the transmission of data from one device to

another is the wiring and how to send the data stream. Do we send 1
bit at a time or group bits into larger groups. The transmission of
binary data across a link can be accomplished in either parallel or
serial mode. In parallel mode, multiple bits are sent with each clock
tick. In serial mode, 1 bit is sent with each clock tick. The different
transmission modes are as shown in the following figure.
Parallel Transmission:

• In Parallel Transmission, data consisting of 1s and 0s, may be organized into groups of
n bits each. Computers produce and consume data in groups of bits. By grouping, we
can send data n bits at a time instead of 1bit. This is called parallel transmission.
• In parallel transmission we use n wires to send n bits at one time. That way each bit
has its own wire, and all n bits of one group can be transmitted with each clock tick
from one device to another. The following figure shows how parallel transmission works
for n =8. Typically, the eight wires are bundled in a cable with a connector at each end.
• The advantage of parallel transmission is speed. All else being equal, parallel
transmission can increase the transfer speed by a factor of n over serial
transmission. But the disadvantage is cost. Parallel transmission requires n
communication lines just to transmit the data stream. Because this is expensive,
parallel transmission is usually limited to short distances.

•
Serial Transmission

• In serial transmission one bit follows another, so we need only one

communication channel rather than n to transmit data between two
communicating devices. The following figure shows serial
transmission.
The advantage of serial over parallel transmission is that
with only one communication channel, serial
transmission reduces the cost of transmission over
parallel by roughly a factor of n. Serial transmission
occurs in one of three ways: asynchronous, synchronous,
and isochronous.
a). Asynchronous Transmission:

• In Asynchronous transmission, the timing of a signal is

unimportant. Instead, information is received and
translated by agreed upon patterns. As long as those
patterns are followed, the receiving device can retrieve
the information without regard to the rhythm in which it
is sent. Patterns are based on grouping the bit stream
into bytes. Each group, usually 8 bits, is sent along the
link as a unit. The sending system handles each group
independently, relaying it to the link whenever ready,
without regard to a timer.
• Without synchronization, the receiver cannot use timing to predict
when the next group will arrive. To alert the receiver to the arrival of
a new group, therefore, an extra bit is added to the beginning of each
byte. This bit, usually a 0, is called the start bit. To let the receiver
know that the byte is finished, 1 or more additional bits are appended
to the end of the byte. These bits, usually 1 s, are called stop bits.
• By this method, each byte is increased in size to at least 10 bits, of
which 8 bits is information and 2 bits or more are signals to the
receiver. In addition, the transmission of each byte may then be
followed by a gap of varying duration. This gap can be represented
either by an idle channel or by a stream of additional stop bits. The
start and stop bits and the gap alert the receiver to the beginning and
end of each byte and allow it to synchronize with the data stream.
• This mechanism is called asynchronous because, at the byte level, the
sender and receiver do not have to be synchronized. But within each
byte, the receiver must still be synchronized with the incoming bit
stream.
b). Synchronous Transmission:

• In synchronous transmission, the bit stream is combined into longer "frames," which
may contain multiple bytes. Each byte, however, is introduced onto the transmission
link without a gap between it and the next one. It is left to the receiver to separate the
bit stream into bytes for decoding purposes.
The following figure show illustration of synchronous transmission.
• The sender puts its data onto the line as one long string. If the sender wishes to send
data in separate bursts, the gaps between bursts must be filled with a special
sequence of 0s and 1s that means idle. The receiver counts the bits as they arrive and
groups them in 8-bit units.
• The advantage of synchronous transmission is speed. With no extra bits or gaps to
introduce at the sending end and remove at the receiving end, and, by extension, with
fewer bits to move across the link, synchronous transmission is faster than
asynchronous transmission. For this reason, it is more useful for high-speed
applications such as the transmission of data from one computer to another.
c. Isochronous:
• In real-time audio and video, in which uneven delays
between frames are not acceptable, synchronous
transmission fails. For example, TV images are
broadcast at the rate of 30 images per second; they
must be viewed at the same rate. If each image is sent
by using one or more frames, there should be no delays
between frames. For this type of application,
synchronization between characters is not enough; the
entire stream of bits must be synchronized. The
isochronous transmission guarantees that the data
arrive at a fixed rate.
Protocols and Standards in Network:
• Computer networks are dependent on protocols and standards which
plays a vital role, which enables communication between different
devices and systems with one another and share data seamlessly.
Network protocol ensures that different technologies and
components of the network are compatible with one another,
reliable, and able to function together.
• In Order to make communication successful between devices , some
rules and procedures should be agreed upon at the sending and
receiving ends of the system. Such rules and procedures are called as
Protocols . Different types of protocols are used for different types of
communication.
Key Element
• Syntax : syntax refers to the structure or the format of the data that
gets exchanged between the devices. Syntax of message includes the
type of data, composition of message and sequencing of message.
The starting 8 bits of data is considered as the address of the sender.
The next 8 bits is considered to be the address of the receiver. The
remaining bits are considered as the message itself.
• Semantics : Semantics defines data transmitted between devices. It
provides rules and norms for understanding message or data element
values and actions.
• Timing : Timing refers to the synchronization and coordination
between devices while transferring the data. Timing ensures at what
time data should be sent and how fast data can be sent. For example,
If a sender sends 100 Mbps but the receiver can only handle 1 Mbps,
the receiver will overflow and lose data. Timing ensures preventing
data loss, collisions and other timing related issues.
• Sequence control : Sequence control ensures the proper ordering of
data packets. The main responsibility of sequence control is to
acknowledge the data while it get received, and the retransmission of
lost data.
• Flow Control : Flow control regulates device data delivery. It limits the
sender’s data or asks the receiver if it’s ready for more. Flow control
prevents data congestion and loss.
• Error Control : Error control mechanisms detect and fix data
transmission faults. They include error detection codes, data resend,
and error recovery. Error control detects and corrects noise,
interference, and other problems to maintain data integrity.
• Security : Network security safeguards data confidentiality, integrity,
and authenticity. which includes encryption, authentication, access
control, and other security procedures.
Protocol
• to make communication successful between devices , some rules and
procedures should be agreed upon at the sending and receiving ends
of the system. Such rules and procedures are called as Protocols .
Different types of protocols are used for different types of
communication.
Types of Protocol
Transmission Control Protocol (TCP)
Internet Protocol (IP)
User Datagram Protocol (UDP)
Post office Protocol (POP)
Simple mail transport Protocol (SMTP)
File Transfer Protocol (FTP)
Hyper Text Transfer Protocol (HTTP)
Hyper Text Transfer Protocol Secure (HTTPS)
• Transmission Control Protocol (TCP): TCP is a popular communication
protocol which is used for communicating over a network. It divides
any message into series of packets that are sent from source to
destination and there it gets reassembled at the destination.
• Internet Protocol (IP): IP is designed explicitly as addressing protocol.
It is mostly used with TCP. The IP addresses in packets help in routing
them through different nodes in a network until it reaches the
destination system. TCP/IP is the most popular protocol connecting
the networks.
• User Datagram Protocol (UDP): UDP is a substitute communication
protocol to Transmission Control Protocol implemented primarily for
creating loss-tolerating
• Simple mail transport Protocol (SMTP): SMTP is designed to send and
distribute outgoing E-Mail.
• File Transfer Protocol (FTP): FTP allows users to transfer files from one
machine to another. Types of files may include program files, multimedia
files, text files, and documents, etc.
• Hyper Text Transfer Protocol (HTTP): HTTP is designed for transferring a
hypertext among two or more systems. HTML tags are used for creating
links. These links may be in any form like text or images. HTTP is designed
on Client-server principles which allow a client system for establishing a
connection
Standard in Network:
• A networking standard is a document that's been developed to
provide technical requirements, specifications, and guidelines that
must be employed consistently to ensure devices, equipment, and
software which govern networking are fit for their intended purpose.
• Types of Standards
• Standards are of two types
• De Facto Standard.
• De Jure Standard.
• De facto −The meaning of the work ” De Facto ” is ” By Fact ”. These
are the standards that are followed without any formal plan or
approval by any organization. They have come into existence due to
traditions or facts. For example, the HTTP had started as a de facto
standard.
• De jure − The meaning of the word “De Jure” is “By Law”. These
standards are the ones which have been adopted through legislation
by any officially recognized standards organization. Most of the
communication standards that are used today are de jure standards.
Some of the noted standards organizations are:

• International Standards Organization (ISO)

• International Telecommunication Union (ITU)
• Institute of Electronics and Electrical Engineers (IEEE)
• American National Standards Institute (ANSI)
• The commonly used standards at each layer are −
• Application layer − HTTP, HTML, POP, H.323, IMAP
• Transport layer − TCP, SPX
• Network layer −IP, IPX
• Data link layer − Ethernet IEEE 802.3, X.25, Frame Relay
• Physical layer −RS-232C (cable), V.92 (modem)
Protocol Hierarchies :

• Generally, Computer networks are comprised of or contain a large

number of pieces of hardware and software. To just simplify network
design, various networks are organized and arranged as a stack of
layers of hardware and software, one on top of another. The number,
name, content, and function of each layer might vary and can be
different from one network to another. The main purpose of each of
layers is just to offer and provide services to higher layers that are
present. Each and every layer has some particular task or function.
Design issues of the layer
Reliability
• Network channels and components may be unreliable, resulting in
loss of bits while data transfer. So, an important design issue is to
make sure that the information transferred is not distorted.
Scalability
• Networks are continuously evolving. The sizes are continually
increasing leading to congestion. Also, when new technologies are
applied to the added components, it may lead to incompatibility
issues. Hence, the design should be done so that the networks are
scalable and can accommodate such additions and alterations.
Addressing
• At a particular time, innumerable messages are being transferred between large
numbers of computers. So, a naming or addressing system should exist so that each layer
can identify the sender and receivers of each message.

Error Control
• Unreliable channels introduce a number of errors in the data streams that are
communicated. So, the layers need to agree upon common error detection and error
correction methods so as to protect data packets while they are transferred.

Flow Control
• If the rate at which data is produced by the sender is higher than the rate at which data is
received by the receiver, there are chances of overflowing the receiver. So, a proper flow
control mechanism needs to be implemented.
Routing
• There may be multiple paths from the source to the destination. Routing
involves choosing an optimal path among all possible paths, in terms of
cost and time. There are several routing algorithms that are used in
network systems.

Security
• A major factor of data communication is to defend it against threats like
eavesdropping and surreptitious alteration of messages. So, there should
be adequate mechanisms to prevent unauthorized access to data through
authentication and cryptography.
OSI(Open System Interconnection)
• OSI stands for Open Systems Interconnection. It has been developed
by ISO – (International Organization for Standardization), in the year
1984. It is a 7-layer architecture with each layer having specific
functionality to perform. All these 7 layers work collaboratively to
transmit the data from one person to another across the globe.
Layers of OSI Model

• Physical Layer
• Data Link Layer
• Network Layer
• Transport Layer
• Session Layer
• Presentation Layer
• Application Layer
The seven layers of the OSI model are:
•7. Application layer: Data generated by and usable by software applications. The main protocol
used at this layer is HTTP.
•6. Presentation layer: Data is translated into a form the application can accept. Some authorities
consider HTTPS encryption and decryption to take place at this layer.
•5. Session layer: Controls connections between computers (this can also be handled at layer 4 by
the TCP protocol).
•4. Transport layer: Provides the means for transmitting data between the two connected parties, as well
as controlling the quality of service. The main protocols used here are TCP and UDP.
•3. Network layer: Handles the routing and sending of data between different networks. The most
important protocols at this layer are IP and ICMP.
•2. Data link layer: Handles communications between devices on the same network. If layer 3 is like the
address on a piece of mail, then layer 2 is like indicating the office number or apartment number at that
address. Ethernet is the protocol most used here.
•1. Physical layer: Packets are converted into electrical, radio, or optical pulses and transmitted as bits
(the smallest possible units of information) over wires, radio waves, or cables.
The OSI model is useful for helping people talk about networking equipment and protocols,
determining which protocols are used by which software and hardware, and showing roughly
how the Internet works. But it is not a rigid step-by-step definition of how Internet
connections always function.
OSI model vs. TCP/IP model

• The TCP/IP model is an alternative model of how the Internet works. It

divides the processes involved into four layers instead of seven. Some
would argue that the TCP/IP model better reflects the way the Internet
functions today, but the OSI model is still widely referenced for
understanding the Internet, and both models have their strengths and
weaknesses.
• In the TCP/IP model, the four layers are:
• 4. Application layer: This corresponds, approximately, to layer 7 in the OSI model.
• 3. Transport layer: Corresponds to layer 4 in the OSI model.
• 2. Internet layer: Corresponds to layer 3 in the OSI model.
• 1. Network access layer: Combines the processes of layers 1 and 2 in the OSI model.
• Some sources hold that the processes at OSI layers 5 and 6 either are
no longer necessary in the modern Internet, or actually belong
to layers 7 and 4 (represented by layers 4 and 3 in the TCP/IP model).
• For instance, since the TCP protocol opens and maintains sessions at
OSI layer 4, one could consider OSI layer 5 (the "session" layer) to be
unnecessary — and it is not represented in the TCP/IP model.
Additionally, HTTPS encryption and decryption can be considered an
application layer (OSI layer 7 or TCP/IP layer 4) process instead of a
presentation layer (OSI layer 6) process.
Multiplexing
• Multiplexing is a technique by which different analog and
digital streams of transmission can be simultaneously
processed over a shared link. Multiplexing divides the high
capacity medium into low capacity logical medium which is
then shared by different streams.
• Communication is possible over the air (radio frequency), using
a physical media (cable), and light (optical fiber). All mediums
are capable of multiplexing.
Concept of Multiplexing
Frequency Division Multiplexing

• When the carrier is frequency, FDM is used. FDM is an analog

technology. FDM divides the spectrum or carrier bandwidth in logical
channels and allocates one user to each channel. Each user can use
the channel frequency independently and has exclusive access of it.
All channels are divided in such a way that they do not overlap with
each other. Channels are separated by guard bands. Guard band is a
frequency which is not used by either channel.
Time Division Multiplexing

• TDM is applied primarily on digital signals but can be applied on

analog signals as well. In TDM the shared channel is divided among its
user by means of time slot. Each user can transmit data within the
provided time slot only. Digital signals are divided in frames,
equivalent to time slot i.e. frame of an optimal size which can be
transmitted in given time slot.
Wavelength Division Multiplexing

• Light has different wavelength (colors). In fiber optic mode, multiple

optical carrier signals are multiplexed into an optical fiber by using
different wavelengths. This is an analog multiplexing technique and is
done conceptually in the same manner as FDM but uses light as
signals.
Code Division Multiplexing

• Multiple data signals can be transmitted over a single

frequency by using Code Division Multiplexing. FDM divides
the frequency in smaller channels but CDM allows its users to
full bandwidth and transmit signals all the time using a unique
code. CDM uses orthogonal codes to spread signals.
• Each station is assigned with a unique code, called chip.
Signals travel with these codes independently, inside the
whole bandwidth.The receiver knows in advance the chip code
signal it has to receive.
Switching

• In large networks, there can be multiple paths from sender to

receiver. The switching technique will decide the best route for data
transmission.
• Switching technique is used to connect the systems for making one-
to-one communication
Circuit switching
• In circuit switching network resources (bandwidth) are divided into
pieces and bit delay is constant during a connection. The dedicated
path/circuit established between sender and receiver provides a
guaranteed data rate. Data can be transmitted without any delays
once the circuit is established.
• Telephone system network is one of the example of Circuit switching.
TDM (Time Division Multiplexing) and FDM (Frequency Division
Multiplexing) are two methods of multiplexing multiple signals into a
single carrier.
Disadvantage:
• 1) Inefficient use of resources
• 2) Limited scalability
• 3) Vulnerability to failures
• 4) Delay
• 5) High cost
• 6) Limited mobility
• 7) limited capacity
• 8) High setup time
Advantage:
• 1) guaranteed the data flow point to point
• 2) Quality of service
• 3) security
• 4) easy to maintain
• 5) no delay in data flow
• Transmission rate = Link Rate or Bit rate /
• no. of slots = R/h bps
• Transmission time = size of file /
• transmission rate
• = x / (R/h) = (x*h)/R second
• Total time to send packet to destination =
• Transmission time + circuit setup time
Packet Switching?
• Packet switching is a communication method where data is divided
into smaller units called packets and transmitted over the network.
Each packet contains the source and destination addresses, as well as
other information needed for routing. The packets may take different
paths to reach their destination, and they may be transmitted out of
order or delayed due to network congestion.
Advantages

• Efficient use of bandwidth: Packet switching is efficient because

bandwidth is shared among multiple users, and resources are
allocated only when data needs to be transmitted.
• Flexible: Packet switching is flexible and can handle a wide range of
data rates and packet sizes.
• Scalable: Packet switching is highly scalable and can handle large
amounts of traffic on a network.
• Lower cost: Packet switching is less expensive than circuit switching
because resources are shared among multiple users.
Disadvantages

• Higher latency: Packet switching has higher latency than circuit

switching because packets must be routed through multiple nodes,
which can cause delay.
• Limited QoS: Packet switching provides limited QoS guarantees,
meaning that different types of traffic may be treated equally.
• Packet loss: Packet switching can result in packet loss due to
congestion on the network or errors in transmission.
• Unsuitable for real-time communication: Packet switching is not
suitable for real-time communication, such as voice and video,
because of the potential for latency and packet loss.
Approaches Of Packet Switching:
There are two approaches to Packet Switching:
Datagram Packet switching:
It is a packet switching technology in which packet is known as a datagram, is considered as an
independent entity. Each packet contains the information about the destination and switch uses this
information to forward the packet to the correct destination.
The packets are reassembled at the receiving end in correct order.
In Datagram Packet Switching technique, the path is not fixed.
Intermediate nodes take the routing decisions to forward the packets.
Datagram Packet Switching is also known as connectionless switching.
Virtual Circuit Switching
Virtual Circuit Switching is also known as connection-oriented switching.
In the case of Virtual circuit switching, a preplanned route is established before the messages are
sent.
Call request and call accept packets are used to establish the connection between sender and
receiver.
In this case, the path is fixed for the duration of a logical connection.
Similarities:
• Both methods involve the transmission of data over a network.
• Both methods use a physical layer of the OSI model for transmission
of data.
• Both methods can be used to transmit voice, video, and data.
• Both methods can be used in the same network infrastructure.
• Both methods can be used for both wired and wireless networks.
Differences:

Circuit Packet
1)In-circuit switching has there 1)In Packet switching directly data
are 3 phases: transfer takes place.
• i) Connection Establishment.
• ii) Data Transfer.
• iii) Connection Released.
2)In-circuit switching, each data 2) In Packet switching, each data
unit knows the entire path unit just knows the final
address which is provided by the destination address intermediate
source. path is decided by the routers.
3) In-Circuit switching, data is 3) In Packet switching, data is
processed at the source system processed at all intermediate
only nodes including the source
4) Circuit switching is more system.
reliable. 4) Packet switching is less reliable.
5) Wastage of resources is more in 5) Less wastage of resources as
Circuit Switching compared to Circuit Switching
6) In-Circuit switching, the charge 6) In Packet switching, the charge
depends on time and distance, is based on the number of bytes
not on traffic in the network. and connection time.
Message Switching

• Message Switching is a switching technique in which a message is

transferred as a complete unit and routed through intermediate
nodes at which it is stored and forwarded.
• In Message Switching technique, there is no establishment of a
dedicated path between the sender and receiver.
• Message switches are programmed in such a way so that they can
provide the most efficient routes.
• Each and every node stores the entire message and then forward it to
the next node. This type of network is known as store and forward
network.
Advantages Of Message Switching

• Data channels are shared among the communicating devices that improve the
efficiency of using available bandwidth.
• Traffic congestion can be reduced because the message is temporarily stored in
the nodes.
• Message priority can be used to manage the network.
• The size of the message which is sent over the network can be varied. Therefore,
it supports the data of unlimited size.
• Disadvantages Of Message Switching
• The message switches must be equipped with sufficient storage to enable them
to store the messages until the message is forwarded.
• The Long delay can occur due to the storing and forwarding facility provided by
the message switching technique.