What is the difference in virtual packet switching and datagram switching? what information does packets hold?
Virtual Circuit Packet Switching
1. Virtual circuits allow packets to contains circuit number instead of full destination address so less router memory and bandwidth require. Thus cost wise it is cheaper.
2. Virtual circuit requires a setup phase, which takes time and consume resources.
3. In virtual circuit, router just uses the circuit number to index into a table to find out where the packet goes.
4. Virtual circuit has some advantages in
avoiding congestion within the subnet
Because resources can be reserved in advance, when the connection is established.
5. Virtual circuit have some problem.
It a router crashes and loses its memory,
even it come back up a second later, all the
virtual circuits passing through it will have
to be aborted.
6. The loss fault on communication line
vanishes the virtual circuits.
7. In virtual circuit a fixed path is used during
transmission so traffic throughout the
subnet can not balanced. It cause congestion problem.
8. A virtual circuit is a implementation of connection oriented service.
Datagram Packet Switching
1. Datagram circuits allow packets to contains full address instead of circuit number so each packet has significant amount of overhead, and hence wasted band width. Thus it is costly.
2. Datagram circuit does not require setup phase , so no resources are consumed.
3. In datagram circuit, a more complicated procedure is required to determine where the packet goes.
4. In a datagram subnet, congestion avoidance is more difficult.
5. In datagram circuit if a router goes down only those user whose packets were queued up in the router at the time will suffer.
6. The loss or fault on communication line can be easily compensated in datagram circuits.
7. Datagram allow the router to balance the traffic throughout the subnet, since router can be changed halfway through a connection.
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