Unit 1: Introduction and Physical Layer Topic 8: Switching I - Circuit Switch

1. SNS COLLEGE OF ENGINEERING
Kurumbapalayam(Po), Coimbatore – 641 107
Accredited by NAAC-UGC with ‘A’ Grade
Approved by AICTE, Recognized by UGC & Affiliated to Anna University, Chennai
SNSCE / IT/ Sem V / S Rijutha / AP / IT
Unit 1: Introduction and Physical Layer
Topic 8: Switching I - Circuit Switch
Department of Information Technology
Course Name : CS8591 Computer Networks
III Year / V Sem

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Introduction
Network - set of
connected devices
Multiple devices
One to One
Communication

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Solution!
Topology
Large Network
Infrastructure
Idle

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Solution!
➢ Series of interlinked nodes - Switches
➢ Create temporary connection between two or more
devices
➢ Node connected to end system - telephone
➢ others, only for routing
Switching

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Switched Network
⮚ End system - Communicating device - (A, B,C,D . . . .)
⮚ Switches - (I, II, III & IV)
⮚ Each switch connected to multiple links

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Three Methods of Switching
⮚ Circuit Switching
⮚ Packet Switching
⮚ Message Switching

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Message Switching
⮚ Connectionless network switching
⮚ No dedicated path between two stations
⮚ Message routed, source to destination
⮚ Intermediate nodes
⮚ Hop-by-hop systems

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Message Switching
Characteristics:
⮚ Store and forward - forwards a message only if sufficient resources are
available and the next hop is accepting data
⮚ Message delivery - wrapping the entire information in a single message and
transferring it from the source to the destination node.

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⮚ Message switching network consists of
transmission links (channels)
⮚ Store-and-forward switch nodes and end
stations
Message Switching

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Disadvantages:
⮚ Cannot be used for real time
applications
⮚Intermediate devices - large
storing capacity.
Message Switching
Advantages:
⮚ Reduce the traffic congestion in
network
⮚ Data channels are shared by the
network devices.
⮚ Traffic management - priorities to
the messages.

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PUZZLE
Choose the correct answer
What is network switching?
1. The process of labeling network hops from any number of input ports to another designated port
2. The process of channeling network routers received from any number of input ports to another
designated port that will transmit the router to its desired destination
3. The process of channeling data messages or data packets received from any number of input ports to
another designated port that will transmit the data to its desired destination
4. A switching device that controls the volume of network traffic in a system

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Circuit Switched Networks
⮚ Switches connected by physical link
⮚ Dedicated path, one or more links
⮚ Connection, only one dedicated
channel on each link
⮚ Data is not stored
Circuit Switching

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Switching Process
⮚ End system A need to communicate with end system M
⮚ A request connection to M
⮚ Accepted by all switches as well M itself - Setup Phase
⮚ Channel reserved on each link
⮚ Dedicated path, connection established
⮚ Data transferred

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Switching Process
⮚ Sender communicate with receiver
⮚ Sender - request connection to receiver
⮚ That must be accepted by all switches as well receiver itself
⮚ Acknowledge send to receiver from sender
⮚ Sender receives ack, connection established

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Three Phases
⮚ Set up Phase - Connection establishment
⮚ Data Transfer Phase - No data packets, no
addressing
⮚ Teardown Phase - Connection disconnect.

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Efficiency and Delay
Channel remain idle
for 5 min
Low efficiency
Minimal Delay
⮚ Efficiency
○ Not efficient - resource allocated
entire duration
○ Resource unavailable to other
connection
⮚ Delay
○ Low efficiency
○ Delay, minimal
○ Data transfer not
delayed,resource allocated entire
duration of the connection

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Advantages of Circuit
Switching
Advantages
⮚ It uses a fixed bandwidth.
⮚ A dedicated communication channel increases the quality of communication.
⮚ Data is transmitted with a fixed data rate.
⮚ No waiting time at switches.
⮚ Suitable for long continuous communication.

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Disadvantages:
⮚ Dedicated connection makes it impossible to transmit other data even if the channel is
free.
⮚ Resources are not utilized fully.
⮚The time required to establish the physical link between the two stations is too long.
⮚circuit switching is more expensive.
⮚channel remains idle for a long time thereby making circuit switching inefficient.
⮚Dedicated channels require more bandwidth.
Disadvantages of Circuit Switching

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PUZZLE
Mention the phases of Circuit switching by seeing this picture
Connection
Setup
Data Transfer Connection
Teardown

20. THANK YOU !
SNSCE / IT/ Sem V / S Rijutha / AP / IT
SNSCE / IT/ Sem V / S Rijutha / AP / IT