a) Datagram packet delivery and Virtual circuit packet delivery are two approaches to the delivery of packets by the network layer. Explain.
b) What is the meaning of" tunnelling?
c) Differentiate between UDP datagram communication and TCP stream communication.
d) Explain how it is possible for a sequence of packets transmitted through a wide area network to arrive at their destination in an order that differs from that in which they were sent. Why can't this happen in a local network? Can it happen in an ATM network? Give at least one reason for your answer.