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 (71) between sending the notification and notification arriving at the source thousands of additional (72) may arrive．InATMnetwork，amajortoolfor preventing (73) is (74) control. When ahostwants a new virtual (75) , it must describe the traffic to be offered and the service expected.
A．interval
B．time
C．slot
D．delay
答案
参考答案：A
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。而在高速网络中，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他数据包到达。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。