Question

Differentiate between ‘Datagram Packet Switching’ and ‘Virtual Circuit Packet Switchi

Answer 1

Virtual Circuits:

1. It is connection-oriented, 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.
2. 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.
3. AS all the packets are going to follow the same path, a global header is required. Only the first packet of the connection requires a global header, the remaining packets do not  require any type of  global headers.
4. Since all packets follow a specific path, packets are received in-order at the destination.
5. Virtual Circuit Switching ensures that all packets successfully reach the Destination. No packet will be discarded due to unavailability of resources.
6. they are a highly reliable method of data transfer.
7. The issue with virtual circuits is that each time a new connection is set up, resources and extra information have to be reserved at every router along the path, which becomes problematic if many clients are trying to reserve a routers resources simultaneously.
8. It is used by the ATM (Asynchronous Transfer Mode) Network, specifically for Telephone calls.

Datagram Packet Switching

1. t is a connection-less service. There is no need for reservation of resources as there is no dedicated path for a connection session.
2. 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.
3. all packets must be associated with a header with correct  information about the source and the upper layer data.
4. The connection-less property makes data packets reach the destination in any order, which means that they can potentially be received out of order at the receivers end.
5. not reliable as Virtual Circuits.
6. The major drawback of Datagram Packet switching is that a packet can only be forwarded if resources such as the buffer,CPU and bandwidth are available. Otherwise, the packet will be discarded.
7. 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.
8. Its is generally used by the IP network, which is used for Data services like Internet.