SNMPv1是一个不安全的协议，管理站(Manager)与代理(Agent)之间通过 (8) 进行身份认证，由于认证信息没有加密，所以是不安全的。1998年公布的SNMPv3定义了基于用户的安全模型USM，其中的认证模型块结合 (9) 算法形成认证协议，产生了一个96位的报文摘要。SNMPv3还定义了基于视图的访问控制模型VACM。在这个模型中，用户被分成组，属于同一组的用户可以有不同的安全级别，其中 (10) 是最高安全级别。RFC1757定义的RMON管理信息库是对MIB-2的扩充，其中的统计组记录 (11) 的管理信息，而矩阵组则记录 (12) 的通信情况。
A．RC6和SHA
B．RC6和MD5
C．MD5和RC6
D．MD5和SHA
参考答案：D
| 阅读理解。 | ||
Dear Editor, I am writing to ask what has happened to the young. They are not as polite, hardworking or clever as my generation (一代人). I'll give you an example. Last Friday I got on the underground at 9:15 a. m. It was very busy so there were no free seats. There were some teenagers (青少年) sitting on the seats near me. I don't know why they were not at school. They were talking loudly and laughing. It was difficult to read my newspaper with all the noise. A heavily pregnant (怀孕的) woman and her daughter got on at the next stop, with lots of shopping bags. I expected the teenagers to let them sit down. They slowly did so but gave me an impolite look. I got off at the next stop and was glad that the teenagers didn't follow me. I worried about the future of our country. How could these young people become responsible (有责任心的) workers and parents? They sit around McDonald's after school instead of going to the library as I did at their age. Maybe they have too much money. Perhaps another reader can give us an idea about what to do with this "lost generation". Franz Johnson
Dear Editor, I read Mr. Johnson's letter about the problem of today's youth (青少年) with much interest. He described teenagers on a train not giving seats to a pregnant woman and her daughter. I was the woman. We must have seen things differently. I found the teenagers helpful and kind. Did Mr. Johnson see the teenagers help me off the train? Did he see them carry my shopping bags to a taxi for me? Did he see them friendly to my daughter? Obviously (明显地) not. "Older" people often say today's youth isn't as good as their generation. Their parents said that about them. Mr. Johnson must accept (接受) that the world is changing and young people are changing with it. I find today's youth mostly kind and more friendly than my generation. Perhaps Mr. Johnson should really try to get to know some young people before he calls them the "lost generation". Linda Black | ||
| 1. Mr. Johnson wrote the letter to _____. | ||
| A. ask for help-from the newspaper B. find the way to solve the problem C. show his worry towards the young D. teach the young a lesson | ||
| 2. When Mr. Johnson was young, he usually _____ after school. | ||
| A. went to the library B. read newspapers C. went to McDonald's D. helped people in trouble | ||
| 3. In the second letter, Mrs. Black _____. | ||
| A. discussed the youth problem with the old B. told another story about the young people C. warned to show her thanks to the young people D. wanted the "older" people to understand the young | ||
| 4. Which of the following is the correct order of what happened? ① Mrs. Black wrote to the newspaper. ② Mrs. Black took a taxi with her daughter. ③ Mrs. Black got on the train with her daughter. ④ Mr. Johnson asked the young people to give her a seat. ⑤ Mr. Johnson thought the young people might follow him. | ||
| A. ②③④⑤① B. ②④⑤③① C. ③④⑤②① D. ⑤③①④② | ||
| 5. From the two letters we can learn that _____. | ||
| A. Mrs. Black didn't like the old like Johnson B. people have different ideas about the young C. older people are more helpful than the youth D. people should talk more about the same story |