Circuit Switching :
Standard Terminology :A type of communications in which a dedicated channel (or circuit) is established for the duration of a transmission. The most ubiquitous circuit-switching network is the telephone system, which links together wire segments to create a single unbroken line for each telephone call.
Explanation : you might have seen this in old movies in which they used to have one speaker in front of their mouth to send the message over the network and one speaker in their ear to hear from other side its mean that it is half Duplex.means you can either send the message in one direction or receive it As i have shown in the diagram that only one Telephone is connected to the telephone exchange at a time and these telephone exchange will be connected to other telephone Exchange here i have shown only one telephone exchange is connected to other one but in general one telephone exchange can be connected to many others at the same time .Lets consider a scenario that I want to talk to you using Circuit Switching .Now what happens is
There will be a telephone operator at every telephone exchange if I want to talk to you i'll call the nearest telephone exchange operator and tell him that i want to talk to you but he will not let me directly talk to you so what he will do is he will write my name in a log saying that i want to talk to you and whenever my no comes he will call the next operator saying i want to talk to you same for next exchange So every telephone operator will take a telephone wire and connect us over this network then only i'll get a chance to talk to you
And worst part of this is when I am talking to you any telephone Operator can Listen our conversation and can say in middle that we are not talking anything important and they can disconnect us anytime........Lol
Good thing is, it is obsolete now.
Points about Circuit Switching
We don't need Header in circuit switching
No reordering of Data is done means all data goes in in-order.
it is not applied at network Layer .It is applied at Physical Layer .
Packet Switching :
Standard Terminology : The other common communications method is packet switching, which divides messages into packets and sends each packet individually. The Internet is based on a packet-switching protocol, TCP/IP.
Explanation : To overcome the manual intervention of circuit switching we invented this switching .In Packet switching if i send a message to you then it will not be directly send to you it will be saved first with a header attached to it and looking at the header it will decide which way to send dynamically here no one need to connect any wire because it uses multiplexers means many to one and one to many connections .
Circuit-switching networks are sometimes called connection-oriented networks. Note, however, that although packet switching is essentially connection-less, a packet switching network can be made connection-oriented by using a higher-level protocol. TCP, for example, makes IP networks connection-oriented.
Reference : You can look at this