Introduction:
Switched Network
Circuit-Switched Network
Datagram Networks
Virtual-Circuit Network
In large networks we need some
means to allow one-to-one communication between any two nodes.
In LANs this is achieved using one
of three methods:
Direct point-to-point connection
(mesh)
Via central controller (star)
Connection to common bus in a
multipoint configuration (bus/hub)
None of the previous works in larger
networks with large physical separation or consisting of a large number of
computers.
The solution is a switching
network
Consists of a
series of interlinked nodes called switches.
Switches are
capable to create temporary connections between two or more devices
Circuit switched network:
A
circuit-switched network consists of a set of switches connected by physical
links.
A connection
between two stations is a dedicated path made of one or more links
Each connection
uses only one dedicated channel on each link
Each link is
normally divided into n channels.
The link can be
permanent (leased line) or temporary (telephone)
Switching take
place at physical layer
Resources
Such as channels
(bandwidth in FDM and time slot in TDM)
Switch buffer
Switch
processing time
Switch I/O
ports
Data
transferred are not packetized, continuous flow
No addressing
involved during data transfer
Transmission phase:
Data transfer
phase
After the
establishment of dedicated circuit, two parties can transfer data
Teardown phase
Signal is sent
to each switch to release resources, when one of the parties needs to
disconnect
Delay:
Delay is
minimal, no waiting time
Total delay is
due to time needed to create the connection, transfer data, and disconnect the
connection.
The delay
caused by set up is the sum of four things:
Propagation
time of the source computer request,
Request signal
transfer time,
Propagation
time of acknowledgement from the destination and
Signal transfer
time of the acknowledgement
The delay due
to data transfer is sum of two:
Propagation
time and
Data transfer
time
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