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.

65（）

A．packets

B．cells

C．message

D．files

男性，62岁，在打麻将时突感剧烈头痛，视物成双，同时颈部明显僵硬，急诊头颅CT提示脑池内高密度影。该患者的临床诊断最有可能为（）

A.脑血栓形成

B.脑栓塞

C.蛛网膜下腔出血

D.椎基底动脉系统TIA

E.颈内动脉系统TIA