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Difference between Datagram Switching & Virtual Circuit

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  • Difficulty Level : Easy
  • Last Updated : 08 Jun, 2021
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1. Datagram switching :
Datagram packet switching is a packet switching method that treats each packet, or datagram, as a separate entity. Each packet is routed via the network on its own. It is a service that does not require a connection. Because there is no specific channel for a connection session, there is no need to reserve resources. As a result, packets have a header with all the destination’s information. The intermediate nodes assess a packet’s header and select an appropriate link to a different node closer to the destination.

2. Virtual Circuit :
Virtual packet switching approach in which a path is built between the source and the final destination through which all packets are routed throughout a call is known as virtual circuit switching. Because the connection looks to the user to be an infatuated physical circuit, this path is referred to as a virtual circuit. Other communications, on the other hand, may be sharing parts of the same path. Before the data transmission can commence, the source and destination must agree on a virtual circuit path. For the decision, all intermediary nodes between the two places add a routing entry to their routing database. Additional parameters, like the utmost packet size, also are exchanged between the source and therefore the destination during call setup. The virtual circuit is cleared after the info transfer is completed.

Difference between Datagram switching & Virtual circuit switching :

Datagram Switching

Virtual Circuit

It is connection less service. There is no need for reservation of resources as there is no dedicated path for a connection session. Virtual circuits are connection-oriented, which means that there is a reservation of resources like buffers, bandwidth, etc. for the time during which the new setup VC is going to be used by a data transfer session.
All packets are free to use any available path. As a result, intermediate routers calculate routes on the go due to dynamically changing routing tables on routers. The first sent packet reserves resources at each server along the path. Subsequent packets will follow the same path as the first sent packet for the connection time.
Data packets reach the destination in random order, which means they need not reach in the order in which they were sent out. Packets reach in order to the destination as data follows the same path.
Every packet is free to choose any path, and hence all the packets must be associated with a header containing information about the source and the upper layer data. All the packets follow the same path and hence a global header is required only for the first packet of connection and other packets will not require it. 
Datagram networks are not as reliable as Virtual Circuits. Virtual Circuits are highly reliable.
Efficiency high, delay more Efficiency low and delay less
But it is always easy and cost-efficient to implement datagram networks as there is no need of reserving resources and making a dedicated path each time an application has to communicate. Implementation of virtual circuits is costly as each time a new connection has to be set up with reservation of resources and extra information handling at routers.
A Datagram based network is a true packet switched network. There is no fixed path for transmitting data. A virtual circuit network uses a fixed path for a particular session, after which it breaks the connection and another path has to be set up for the next session.
Widely used in Internet Used in X.25, ATM(Asynchronous Transfer Mode)


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