Computer networks that provide connection-oriented service are called Virtual Circuits while those providing connection-less services are called as Datagram networks. For prior knowledge, the Internet which we use is actually based on Datagram network (connection-less) at the network level as all packets from a source to a destination do not follow the same path.
Let us see what are the highlighting differences between these two hot debated topics here:
- It is connection-oriented simply meaning that there is a reservation of resources like buffers, CPU, bandwidth, etc. for the time in which the newly setup VC is going to be used by a data transfer session.
- First packet goes and reserves resources for the subsequent packets which as a result follow the same path for the whole connection time.
- Since all the packets are going to follow the same path, a global header is required only for the first packet of the connection and other packets generally don’t require global headers.
- Since data follows a particular dedicated path, packets reach inorder to the destination.
- In Virtual Circuit Switching, it is sure the all the packets will definitely reach to the Destination. No packet will discard due to unavailability of resources.
- From the above points, it can be concluded that Virtual Circuits are highly reliable means of transfer.
- Since each time a new connection has to be set up with reservation of resources and extra information handling at routers, its simply costly to implement Virtual Circuits.
- It is used by the ATM (Asynchronous Transfer Mode) Network, which is used for the Telephone calls.
Datagram Networks :
- It is connectionless service. There is no need for reservation of resources as there is no dedicated path for a connection session.
- All packets are free to go to any path on any intermediate router which is decided on the go by dynamically changing routing tables on routers.
- Since every packet is free to choose any path, all packets must be associated with a header with proper information about the source and the upper layer data.
- The connectionless property makes data packets reach the destination in any order, means they need not reach in the order in which they were sent.
- Datagram networks are not reliable as Virtual Circuits.
- The major drawback of Datagram Packet Switching is if the Buffer, CPU, and Bandwidth are available then the only Packet will be forwarded. Otherwise, Packet will discard.
- But it is always easy and cost-efficient to implement datagram networks as there is no extra headache of reserving resources and making a dedicated each time an application has to communicate.
- Its is generally used the IP network, which is used for Data services like Internet.