FDDI的基本编码方法是(30)，在此基础上采用(31)编码以获得足够多的同步信息，这样使编码效率提高到(32)。为了消除环网中的时钟偏移，FDDI使用了(33)方案，并规定进入站点缓冲器的数据时钟由输入信号的时钟确定，缓冲器的输出时钟信号由(34)确定。

(70)

(71)

(69)

(68)

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 pre- venting(73)is(74)control. When a host wants a new virtual(75), it must describe the traffic to be offered and the service expected.

(66)

(64)

(65)

(63)

For each blank, choose the best answer from the four choices and write down on the answer sheet.

  (66) is a six bytes OSI layer 2 address which is burned into every networking device that provides its unique identity for point to point communication.

  (67) is a professional organization of individuals in multiple professions which focuses on effort on lower-layer protocols.

  (68) functions with two layers of protocols. It Can connect networks of different speeds and can be adapted to an environment as it expands.

  (69) is the popular LAN developed under the direction of the IEEE 802.5.

  (70) is the popular backbone technology for transmitting information at high speed with a high level of fault tolerance which is developed under the direction of ANSI.