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What is the difference between circuit switching and packet switching?

In this Ask the Expert, John Burke explains the difference between packet switching and circuit switching and compares the two models.

What is the difference between circuit-switched and packet-switched networks?

Both circuit switching and packet switching are methods of transferring data between two nodes in a network.

Circuit switching

In a circuit-switched network, when two nodes need to communicate, a direct and continuous connection is established between them. It carries only the one conversation, for as long as it lasts.

For example, in the old, analog phone system, a strand of copper connected a telephone to a phone line to a switching facility. A physical link would then be made to a line to another switching station. And, from there, it would go through a strand of copper all the way to the other phone.

Packet switching

On a packet-switched network, data is divided into chunks, or packets. The packets have headers attached to them to identify them -- e.g., by source, destination and sequence number -- and are intermingled with the packets of other conversations on a shared network.

In a typical computer data network, computers send packets to a switch, which combines them with packets from many other computers. The combined stream may go to another switch -- an aggregation switch -- bringing together traffic from many switches or to a router that will send them on their way across the internet to other networks. Only the first connection, from computer to switch, is dedicated; all the rest are shared.

Comparing circuit switching and packet switching

There are some key differences between the two models, as illustrated in this chart:

Circuit switching vs. packet switching
This was last published in December 2018

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