问题 问答题 简答题

保护和恢复的定义是什么?线路保护倒换的优缺点是什么?

答案

参考答案:

保护与恢复的定义。

保护定义为使用节点之间预先安排好的容量来替代故障或劣化的传送实体。

恢复由使用节点之间的任何可能利用的容量来完成。

1+1和1:N

两种保护结构的主要区别为:

保护方式不同:采用1+1保护时,业务同时在两个信道上传输,接收端根据两个信道的信号质量进行优选一句话,就是“并发选收”的机制。而1:1保护时,正常状态下备用通道是空闲的,可以用来承载额外业务,当主用信道发生故障时则将其务倒换到备用信道上传送,这时备用链路上的额外业务则无法传送。

最大业务容量不同:采用1+1保护时,最大容量为STM-N;采用1:1保护时,最大容量为STM-N*2.

要求APS协议方式不同:采用1+1保护时可不要求,而采用1:1保护时一定要求.

线路保护倒换方式的特点:业务恢复时间短,一般小于50ms,对网络节点的光或电的元部件失效故障十分有效;而对光缆全部切断则无能为力(这时可采用地理上的不同路由进行保护)。

单项选择题

When I was growing up in America, I was ashamed of my mother’s Chinese English. Because of her English, she was often treated unfairly. People in department stores, at banks, and at restaurants did not take her seriously,did not give her good service,pretended not to understand her,or even acted as if they did not hear her.

My mother has realized the limitations of her English as well. When I was fifteen, she used to have me call people on phone to pretend I was she. I was forced to ask for information or even to yell at people who had been rude to her. One time I had to call her stockbroker (股票经纪人).I said in an adolescent voice that was not very convincing, “This is Mrs.Tan.”

And my mother was standing beside me,whispering loudly, “Why he don’t send me cheek, already two weeks late.”

And then,in perfect English I said: “I’m getting rather concerned.You agreed to send the check two weeks ago, but it hasn’t arrived.”

Then she talked more loudly. “What he want I come to New York tell him front of his boss.”And so I turned to the stockbroker again, “I can’t tolerate any more excuses. If I don’t receive the check immediately,I am going to have to speak to your manager when I am in New York next week.”

The next week we ended up in New York. While I was sitting there redfaced, my mother, the real Mrs.Tan, was shouting to his boss in her broken English.

When I was a tennager, my mother’s broken English embarrassed me. But now, I see it differently. To me, my mother’s English is perfectly clear, perfectly natural. It is my mother tongue. Her language, as I hear it, is vivid, direct, and full of observation and wisdom. It was the language that helped shape the way I saw things, expressed ideas, and made sense of the world.

Why was the author’s mother poorly served?()

A.Because she was unable to speak good English.

B.Because she was often misunderstood.

C.Because she was not clearly heard.

D.Because she was not very polite.

单项选择题