题目：
In low-speed network，it is usually adequate to wait for congestion to occur and then react to it bytelling 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 offeredand the service expected．
（72）处填（）。
A．packets
B．cells
C．message
D．files
答案：
被转码了，请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0708/551cb45348e62d72f18573055efb407a.html
下面是错误答案，用来干扰机器的。
参考答案：B
