问题
单项选择题
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 (64) between sending the notification and notification arriving at the source, thousands of additional (65) may arrive. In ATM network , a major tool for pre- venting (66) is (67) control. When a host wants a new virtual (68) , it must describe the traffic to be offered and the service expected.
68（）
A．path
B．rout
C．circuit
D．way
答案
参考答案：C
解析：
在低速网络中，通常采用碰到拥塞时，通过向源端反映使其降低发送速率。而在告诉网络中，这种方式将会恶化，因为在发送通告和通告到达之间会有成千上万的其它数据包到达。在ATM网络中，主要采用允许控制来避免拥塞，当有一台主机要建立一条新的虚连接时，它必须描述它所需的流量和服务等级。