Switching: Circuit Switching and Packet Switching, Lecture notes of Computer science

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SWITCHING

CIRCUIT SWITCHING & PACKET SWITCHING

UNIT II: CHAPTER III

Switched Network

 A network is a set of connected devices. Whenever we have multiple devices, we have the

problem of how to connect them to make one-to-one communication possible. One solution

is to make a point-to-point connection between each pair of devices. But these methods,

however, are impractical and wasteful when applied to very large networks. The number

and length of the links require too much infrastructure to be cost-efficient, and the majority

of those links would be idle most of the time.

 A better solution is switching. A switched network consists of a series of interlinked nodes,

called switches. Switches are devices capable of creating temporary connections between

two or more devices linked to the switch. In a switched network, some of these nodes are

connected to the end systems (computers or telephones, for example). Others are used

only for routing.

 Every time in computer network you access the internet or another computer

network outside your immediate location, your messages are sent through a

maze of transmission media and connection devices.

The mechanism for moving information between different computer

network and network segment is called switching in computer

Circuit-Switched Network

Circuit-switched is a type of

network in which a physical

path is obtained for and

dedicated to a single

connection between two end-

points in the network for the

duration of the connection.

Ordinary voice phone service

is circuit-switched.

The telephone company

reserves a specific physical

path to the number you are

calling for the duration of your

call.

Circuit-Switched Network: Three

Phases

A circuit S witched

communication system involves three

phases :

Circuit establishment

(setting up dedicated links

between the source and

destination);

Data transfer (transmitting

the data between the source

and destination); and

Circuit disconnect (removing

the dedicated links).

CIRCUIT SWITCHING

 A crossbar switch connects n inputs to m outputs in a grid, using electronic

micro-switches (transistors) at each crosspoint.

 The major limitation of this design is the number of crosspoints required.

 To connect n inputs to m outputs using a crossbar switch requires n x m

crosspoints.

Crossbar Switch ( Space-Division Switch)

Switching Path

Switching Path

TDM with TSI

The most popular technology is called the time-slot interchange (TSI).

Time-Slot Interchange shows a system connecting four input lines to four

output lines. Imagine that each input line wants to send data to an output

line according to the pattern.

Time-Slot Interchange

Datagram Approach

Datagram Approach, Multiple Channels

A virtual-circuit network is a cross between a circuit-

switched network and a datagram network. It has some

characteristics of both.

Switched Virtual Circuit

Thank you