Communication Switching Techniques

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A
Switched
Network
consists
interlinked nodes called Switches.
of
Switches
are hardware and software that
are
capable
of
creating
temporary
connections between two or more devices
linked to the switch.
In
a Switched network, some of nodes are
connected
to
the
end
system
or
communication devices like computer or
telephone.
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A,B,C,D,E and so on are end systems or communication
devices.
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Switches are labeled as I,II,III,IV,V and so on.
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Dedicated
physical connection or path is
established between the sending and
receiving device.
Dedicated
path made of one or more links.
Routing
is made when the path or link is
set up across the network. After the has
been set between the sender and receiver,
the information is forwarded continuously
over the link.
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Dedicated
path establish
guaranteed data rate.
provides
Data
a
is transmitted without any delay, as
there is no waiting time at each switch.
Suitable
for long continuous transmission.
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It
cannot be used to transmit any other
data even if the channel is free.
Inefficient
resources.
Long
in
time is
physical link.
terms
of
required
utilization
to
establish
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of
a
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Packet
node.
are sent over network node to
At
each node, packet is stored briefly and
then routed according to information in its
header. These types of networks are called
store and forward networks.
Individual
packets may follow different
routes to reach destination.
Two
types of Packet Switching:-Datagram Packet Switching
-Virtual Packet Switching
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Datagram Packet Switching
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Datagram approach is used to deliver four
packets from station A to X. All the four
packets belong to same message but they
travel via different paths to reach the
destination.

It
can cause the datagram to arrive out
of order at their destination with
different delays between the packets.
Packets
may also be lost because of lack
of resources.
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Circuit
connection called virtual circuit is
set up between sender and receive before
any data transfer takes place.
Virtual
circuit approach has a set up, data
transfer and tear down phase.
Resources
can be allocated during set up
phase or on demand.
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All
the packets of a message follow the
same path establish during the connection.
It
is implemented in the data link layer.
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Packets
may be lost on their route, so
sequence numbers are required to identify
the missing packets.
Large
amount RAM is required to handle
the large quantities of packets.
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When
message reaches a node, the channel
on which it came is released for use by
another message.
Message
M1 is transmitted from A to D
and M2 is transmitted from C to B. Message
M1 follows route A->I->II->D and M2
follows route C->IV->II->B depending upon
availability of free path at that particular
moment.
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No
physical connection is required between
source and destination.
Reduces
traffic congestion on network
because of store and forward facility.
Support
message length of unlimited size.
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Parameter
Circuit Switching
Packet Switching
Message
Switching
Path or Route
Path
is
created Virtual
circuit
is No need
to
between two points created
between create a link or
by setting switches. two points.
path.
Dedicated or
sharing
Links that make a
path are dedicated
and
cannot
be
used
other
connections.
In virtual circuit , links
that make a route
can be shared by
other connections.
Message
reaches a node
the channel on
which it came is
released
by
another
message.
Store and forward
transmission
No use
Each node may
store
incoming
packet temporarily
&
forward
them
later.
Store
and
forward
transmission
is
used.
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Parameter
Circuit Switching
Packet Switching
Message
Switching
Path followed by
packets
It is always same.
May or may not May or may not
be different
be same.
Call setup
It is required.
Not required.
Application
Real time transfer Internet
for Telegraph network
of voice signal.
datagram
and for transmission of
reliable
stream telegrams.
service between
computers.
Layer used for
implementation
It is implemented Virtual
circuit
at physical layer.
network
is
implemented
at
data link layer and
datagram network
at network layer.
Not required.
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