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 (1) between sending the notification and notification arriving at the source, thousands of additional (2) may arrive. In ATM network, a major tool for preventing (3) is (4) control. When a host wants a new virtual (5) ,it must describe the traffic to be offered and the service expected.
5（）
A．path
B．rout
C．circuit
D．way
答案
参考答案：C
解析：
(1)～(5)在低速的网络里，等拥塞发生了然后再作出响应，通知报文的发送源减缓发送速度就足够了。然而，在高速网络里面，这样的方法常常是没用的，因为在发送通知到通知到报文发送方这段时间里，成千上个更多的报文已经到达了接收方。在ATM网络中，主要的控制拥塞的工具就是控制允许进入网络的报文，当一个主机需要建立一个新的虚电路时，它必须描述将要出现的通信量和期待的服务。