Thursday 15 December 2011

Packet Switching & Circuit Switching



Circuit switching and packet switching both are used in high-capacity networks. In circuit-switched networks, network resources are static, set in “copper” if you will, from the sender to receiver before the start of the transfer, thus creating a “circuit”. The resources remain dedicated to the circuit during the entire transfer and the entire message follows the same path. In packet-switched networks, the message is broken into packets, each of which can take a different route to the destination where the packets are recompiled into the original message.

packet switching. Fact is, there’s at least one other way, circuit switching.While the majority of switched networks today get data across the network through packet switching, the concept of circuit switching should be no mystery to the average tech, let alone the tech wannabe. There are at least two good reasons to learn the difference. First of all, there is plenty of legacy hardware out there to support. Second, and perhaps more or at least very important, it could well turn up on the test. If one question stands between you and passing, don’t make this the one you miss.



In Circuit Switching networks, when establishing a call a set of resources is allocated for this call. These resources are dedicated for this call, and can be used by any of the other calls. Circuit Switching is ideal when data must be transmitted quickly, must arrive in sequencing order and at a constant arrival rate. There for when transmitting real time data, such as audio and video, Circuit Switching networks will be used.

Packet switching main difference from Circuit Switching is that that the communication lines are not dedicated to passing messages from the source to the destination. In Packet Switching, different messages can use the same network resources within the same time period. Since network resources are not dedicated to a certain session the protocol avoid from waste of resources when no data is transmitted in the session. Packet Switching is more efficient and robust for data that is burst in its nature, and can withstand delays in transmission, such as e-mail messages, and Web pages.


Consider the two following examples to answer your question:

Example of Circuit Switching:-

 You pick up your land phone and dial your friend. At that point, the TELCO provider creates a dedicated Circuit for that session and connects you to your friend's telephone. No matter how long you keep the line open with your friend, the circuit will remain, and packets flowing between both telephones will always follow the same path. This is an example of a circuit-switched network.

Example of packet-switching:-

 In the second example, you switch on your PC and connect to your favorite site that offers a number of applications you can download from, so you begin downloading one application at a time. Each packet has to find its own route to the destination, i.e., your computer. Each packet finds its way using the information it carries, such as the source and destination IP Address. If network congestion occurs, the routers responsible for routing packet between networks will automatically select different paths to ensure data is transferred as required. This is an example of a packet-switched network.


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