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Computer Networks · Class 12 · Data Communication · Switching Techniques
networksdata communication⏱️ 8 min read

Circuit Switching

Remember the mesh topology? Joining every device to every other took a cable for each pair, and that was only four computers. Nobody could cable every phone in India to every other phone. So large networks share: devices connect to switches, the switches connect to each other, and data finds its way across them.

1What a switching technique is

Switching technique
A switching technique is the method used to send data from a sender to a receiver through the shared switches and links of a network.

There are two switching techniques in your syllabus: circuit switching, in this lesson, and packet switching, in the next. The network below is used for both: three phones on the left, three on the right, and four switches (S1–S4) with two ways across — over S2 or through S3.

2Circuit switching

Circuit switching
In circuit switching, before communication starts, a dedicated path is set up between the sender and the receiver. The path stays reserved for the whole communication, and all the data follows it. When the communication ends, the path is released.

Every circuit-switched call has three steps:

  1. Set up — a path is found and reserved, switch by switch, from sender to receiver.
  2. Send data — everything travels along that one path, in order.
  3. Release — when the communication ends, the path is freed for others.

The old landline telephone worked this way. When you dialled, the telephone exchange connected a line all the way to the other phone, and it was yours until you hung up.

Circuit switching: a path reserved for each call

Press ▶ Play, or dial and hang up yourself. Drag sideways to turn.

Press ▶ Play to watch three calls, or make the calls yourself. Each call reserves a whole path before anyone speaks.

Simplified: here each link carries one call. Real telephone lines carry thousands at once, but each call still has its own reserved share for as long as it lasts.

Look at step five of the story. E’s call is refused, although A and B are not saying anything. Their path is reserved, not used, and in circuit switching reserved is enough to keep everyone else out.

Think of a reserved railway coach

A school books a whole coach for a trip. Nobody else may sit in it for the entire journey — even if half the seats stay empty, and even while the students are asleep. The students always have a seat, and the empty ones are wasted.

3Advantages and disadvantages

✅ Advantages
  • Once connected, the path is always there: a steady, reliable connection.
  • All data follows the same path, so it arrives in order.
  • Nobody else’s data slows the call down.
❌ Disadvantages
  • Setting up the path takes time before any data can be sent.
  • The reserved path is wasted whenever nothing is being sent.
  • Others are refused when the paths are taken, even if they are silent.
  • If a link on the path breaks, the whole call is cut off.

4From the board papers

1
Fill in the blank: In case of ________ switching, before a communication starts, a dedicated path is identified between the sender and the receiver.CBSE sample paper 2023-24 · also CBSE compartment exam 2023, as an MCQ
1 mark
▶Show the answer

Circuit. “Before communication starts” and “dedicated path” both point to circuit switching.

2
Which switching technique ensures a continuous, reliable connection for the duration of the communication session, uses all the bandwidth of the transmission channel and doesn’t share it until the communication session is over?KV practice paper, Jaipur region
1 mark
▶Show the answer

Circuit switching. “Doesn’t share it” is the reserved path.

5Check yourself

Quick Check

In circuit switching, when is the path between sender and receiver set up?

Quick Check

A and B are connected by circuit switching but have stopped talking. Can another call use their path?

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🔢 IPv4 and IPv6
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Packet Switching 📦