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Circuit Switching vs Packet Switching | Circuit Switched Network vs Packet switched network

hey guys this is dg today we will learn

the difference between

circuit switching and packet switching

or

circuit switch networks and packet

switching networks

so let's start suppose there are two

restaurants

a and b restaurant a accepts reservation

while restaurant b does not if i want to

go to restaurant a

i will have to book a table so when i

arrive at the restaurant

i can immediately be seated and can

order my meal

on the other hand restaurant b does not

accept reservation

so when i arrive at the restaurant i may

have to wait in queues

before i can be seated circuit switching

is analogous to resident a which accepts

reservation

on the other hand packet switching is

analogous to restaurant b

which does not accept preservation that

is

in circuit switching resources are

reserved for the communication session

on the other hand resources are not

reserved in packet switching

in a computer network the devices are

connected via communication links

every link has a maximum rate at which

it can transmit data

for example 1 mbps it is called the

link's transmission capacity

for data transfer the transmission

capacity of the link

is shared among the devices present in

the network

with circuit switching all connected

devices get a constant transmission rate

for example if there are 4 devices every

device gets a dedicated transmission

rate

of 250 kbps that is circuit switching

pre allocates the transmission capacity

of the link

regardless of the demand even if the

device is not transmitting data

it has the dedicated transmission

capacity reserved that cannot be used by

any other ongoing communication on the

other hand

packet switching allocates the

transmission capacity

based on demand if there are four

devices present in the network

but only two devices have data to

transmit

then the link's transmission capacity is

shared among two devices only

so packet switching offers better

sharing of links transmission capacity

than circuit switching packet switching

is more efficient than circuit switching

because if one sender to receiver pair

is not using the resources

then it can be used by any other ongoing

communication

which is not the case with circuit

switching

let us understand the two points in more

detail with example

first point is packet switching is more

efficient than circuit switching

and the second point is packet switching

offers better sharing of the link's

transmission capacity

than circuit switching starting with the

first point

why packet switching is more efficient

suppose users share a common link

the transmission capacity of the link is

1 mbps

every user remains active for 10 percent

of the time

and transmits data at the rate of 100

kbps

for the remaining 90 percent of the time

the users remain

inactive and do not transmit data

with circuit switched networks the

transmission rate of 100 kbps

must be reserved for all users since

the transmission capacity of the link is

1 mbps

so the number of users that can be

supported is 1 mbps

divided by 100 kbps that is 10 raised to

power 6

bits per second divided by 10 raise to

power 5

bits per second which is equal to 10 so

circuit switch networks can support 10

users simultaneously

with packet switching the probability

that a user is active

is 0.1 because each user is active for

10 percent of the time

suppose there are 35 users therefore

the probability of having 10

simultaneously active users

can be found by using binomial

distribution

where x ranges from 0 to 10

p is 0.1 and n is 35

it comes out to be 0.9996

approximately which is the probability

of having

10 simultaneously active users therefore

the probability of having 11 or more

simultaneously active users

is 1 minus 0.9996

that is 0.0004

when the users who are transmitting data

are less than

or equal to 10 the total arrival rate of

data

is less than or equal to 1 mbps which is

the transmission capacity of the link

hence the data from users flow through

the link without any delay

as in the case of circuit switching when

the number of simultaneously active

users

is more than 10 the total arrival rate

of data

is more than 1 mbps since the

transmission capacity of the link

is 1 mbps so the output queue begins to

grow

until the incoming data rate goes below

1 mbps

however the probability of 11 or more

simultaneously active users

is 0.0004 which is extremely small

so packet switching or packet switch

network

offers the same performance as that of

circuit switching

along with supporting 35 users which is

more than three times of the users

supported by circuit switched networks

now let us start with the second point

which is packet switching offers better

sharing of links transmission capacity

than circuit switching suppose out of 10

users

only one user is active and suddenly it

generates 1 million bits

with time division multiplexed circuit

switched network

every user has a dedicated channel

capacity of 100 kbps

or 10 raised to power 5 bits per second

so the total time taken to transmit 10

raised to power 6 bits

is 10 raised to power 6 divided by 10

raised to the power 5 bits per second

that is 10 seconds circuit switching

pre-allocates the link's transmission

capacity

among the connected users while packet

switching

allocates the transmission capacity

based on the demand therefore

in the packet switch network if only one

user is transmitting data

the links capacity of 1 mbps is

allocated

to one active user only hence the user

can send

1 million bits in just 1 second which is

10 times faster than the circuit switch

network

so the performance of packet switching

is better than circuit switching

however because packet switching gives

variable and unpredictable delays

it is often argued that packet switching

is not suitable for the real-time

services

for example telephone and video

conferencing calls

at last the difference between the

switching techniques can be summarized

as

circuit switch network or circuit

switching reserve channels

before the data transfer packet switched

network

or packet switching does not reserve

resources before the data transfer

in circuit switching the idle reserved

resources

or channels cannot be used by any other

ongoing communication

in packet switching the idle resources

are allocated to other ongoing

communication

circuit switching does not involve

waiting at the switches

in packet switching the output queues

can grow if the incoming data rate

is more than the link's transmission

capacity

circuit switching is less efficient as

ideal resources

cannot be used by any other sender

receiver pair

packet switching is more efficient than

circuit switching

circuit switching is suitable for

real-time services

for example telephone and video

conferencing calls

packet switching is not considered

suitable for real-time services

as it involves variable and

unpredictable delays

circuit switching is connection oriented

packet switching is connection less

circuit switched networks

can support less number of users

simultaneously

packet switched networks can support

more users simultaneously

circuit switch network allocates

dedicated transmission rate for each

connection

packet switch network allocates variable

transmission rate

based on the demand if you have learned

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