In the following essay, each blank has four choices. Choose the best answer and write down

on the answer sheet.In low-speed network, it is usually adequate to wait for congestion to occur and then react to it by telling the source of packets to slow down. In high-speed networks, this approach often works poorly, because in the(71)between sending the notification and notification arriving at the source, thousands of additional(72)may arrive. In ATM network, a major tool for preventing(73)is(74)control. When a host wants a new virtual(75), it must describe the traffic to be offered and the service expected.

A．interval

B．time

C．slot

D．delay