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Circuit-Switched Networks

In this tutorial, we will be covering Circuit-Switched Networks in detail.

A network consists of a set of switches that are connected by the physical links commonly known as Circuit-Switched Network.

  • Whenever one device communicates with another device then a dedicated communication path is established between them over the network.

  • There is only a dedicated channel on each link used by each connection. Also, each link can be easily divided into n channels by using the TDM(Time Division Multiplexing)or FDM( Frequency Divison Multiplexing)technique.

  • The Circuit Switching technique is mainly used in the public telephone network for voice communication as well as for data communication.

  • Data communication is less efficient than voice communication.

  • The Circuit switching technique mainly takes place at the physical layer.

  • In Circuit-switched networks, the data transfer mode mainly involves a dedicated end-to-end connection. Until the end of the communication, this dedicated path is maintained. After the communication is over the link is released.

The figure shows a trivial circuit-switched Network

Phases in Circuit Switching

In order to transfer data using Circuit switching there is a need to establish a circuit(these circuits can either be permanent or temporary) so that data transfer can take place smoothly. Given below are three phases that are used in Circuit Switching for actual communication:

  • Setup Phase

  • Data Transfer Phase

  • Teardown Phase

1.Setup Phase

It is the first phase of the Circuit switching technique and in this, there is an establishment of the circuit that simply means a dedicated link is established between the sender and the receiver with the help of several switching centers or nodes.

2.Data Transfer Phase

After the establishment of the circuit, the connection is established which means that data transfer can take place between sender and receiver.

3.Teardown Phase

On the completion of communication between the sender and receiver the circuit disconnects. In order to disconnect a signal is sent either by the sender or receiver

One of the best examples of Circuit switching is a telephone. Suppose there are two persons Person A and Person B; they both want to communicate with each other and located at a distance far from each other.

Person A makes a call to Person B this phase is the setup phase of circuit switching. After the establishment of the connection and after call pick up by Person B; they both can communicate with each other. This is the data transfer phase of Circuit switching

Once the communication is complete one of them can cut the call or break the connection. This is a teardown phase.

Circuit Switching can be further classified into two:

1. Space-Division Switching

2. Time-Division Switching

Let us cover the above given two types one by one.

1. Space-Division Switching

Space-Division switching is a technique of Circuit Switching where the paths in the circuits are separated from each other spatially.

  • This technology is used for analog as well as digital networks.

  • In this following switches are used for the connection:

    • Crossbar Switch: This switch contains n input lines and n output lines and it has n2 intersection points

    • Multistage Switch: The Multistage is made just by first splitting the crossbar switches into smaller units and then interconnecting them. In case of failure of one path, there is the possibility of another path.

  • The speed of Space Division switching is high and it has a high capacity.

  • Space division switching contains nonblocking switches.

2. Time-Division Switching

It is a digital switching technique. There is no need for crosspoints in this switching. In Time-Division Switching, the incoming signals, as well as outgoing signals, are received and re-transmitted in a different time slot.

  • One of the main differences between space-division multiplexing and time-division multiplexing is the sharing of Crosspoints. There are no Crosspoints shared in space division switching, whereas crosspoints can be shared for shorter periods in time-division multiplexing.

  • The Time-Division switches are used by modern devices.

  • In this technique, there is the use of time-division multiplexing inside the switch and it is known as Time Slot Interchange(TSI).

Examples of Circuit Switched Networks

Given below are some examples of Circuit-Switched Networks:

  • Public Switched Telephone Network(PSTN)

  • Optical Mesh Network

  • ISDN B-channel

  • Circuit-Switched Data(CSD) and High-speed Circuit-Switched Data(HSCSD) services in the cellular system like GSM

Advantages of Circuit Switching

Given below are some of the benefits of Circuit Switching:

1.Offers Dedicated Transmission

As there is a dedicated link between the sender and the receiver. Thus Circuit-Switched network provides a guarantee of dedicated transmission.

2.No Delay in Transmission

There is a dedicated path between sender and receiver thus there are no chances for the delay.

3. The Circuit Switching technique is best for long transmission because it facilitates a dedicated link between sender and receiver.

Disadvantages of Circuit Switching

There are some drawbacks of Circuit Switching and these are as follows:

  • One of the main disadvantages of Circuit switching is that as there is a dedicated path between sender and receiver; thus this path is received for these two particular devices and cannot be used by any other device.

  • There is a need for more bandwidth as a dedicated path requires more bandwidth.

  • Utilization of resources is not done properly as resources are allocated to a connection for the entire duration and thus became unavailable for all other connections.

  • It becomes inefficient in the case if the connection is established between sender and receiver but there is no data transfer between them.

  • Sometimes it takes a long time to establish the connection between sender and receiver.

  • As there is a dedicated path between sender and receiver; thus, this technique is expensive.