Which of the following delays are present in packet switching?

The correct answer is D, All of the options. In a packet switched network a packet meets four kinds of delay at every router on its path, and transmission, processing and queuing delays are three of them. Processing delay is the time a router takes to read the header and decide the outgoing link. Queuing delay is the time the packet waits in the output buffer while earlier packets are sent, so it grows as traffic grows. Transmission delay is the time needed to push all the bits of the packet onto the link, equal to packet length divided by link bandwidth. The fourth is propagation delay, the time the signal takes to travel the length of the link. A, B and C are each wrong only because they name a single delay, while all three are present together in packet switching. Exam tip: total delay = processing + queuing + transmission + propagation.