未知题型 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.

单项选择题 下列哪些电商网站还未上市？（）

未知题型 有一个操作系统需要控制1千兆字节的地址空间，为了表示其地址，所需要的二进位数至少为(1)。