问题 问答题

【说明】
某学校欲构建校园网,根据实际情况,计划在校园总部采用有线网络和无线网络相结合的接入方式,校园分部通过Internet采用VPN技术与校园总部互联,该校园网采用了分层设计结构,其网络拓扑结构如图2-5所示。


1.【问题1】
该校园网的部分区域部署了无线网络(WLAN),采用符合IEEE 802.11g标准的无线网络设备,该校园网无线网络部分的最大数据传输速率为 (1)

  • A.11Mb/s
  • B.54Mb/s
  • C.100Mb/s
  • D.108Mb/s

答案

参考答案:(7)B,或汇聚层
(8)B,或汇聚层提供访问控制功能

解析:[要点解析]
这是一道要求读者选择ACL规则部署位置的综合分析题。本题的解答思路如下。
在大型网络方案设计时,核心层为汇聚层、接入层提供优化的数据转移功能,即尽可能快地交换数据。应尽量不要使核心层交换机卷入到具体数据包的运算中(如ACL过滤等),否则会增加核心层交换机的负载,降低整个网络的数据包交换速度。
汇聚层提供基于统一策略的互连性,负责对数据包的复杂运算、ACL访问策略的控制、地址的聚集、 VLAN的划分、组播域的定义等功能。可见,图2-5的校园网根据需求使用ACL实现各个单位之间的访问控制,在能够实现预定功能的前提下,应将ACL交给汇聚层交换机实现,其理由是汇聚层提供访问控制功能。
接入层为终端用户提供网络访问的途径,如带宽共享、交换带宽、MAC层过滤和网段微分等功能。

问答题
阅读理解

The following are introductions to some programs that BBC I London will show on TV.
12:25 a.m.Tuesday
    The Real Swiss Robinson Family
Laura worried that her children have had their life too easy due to her husband’s career in big business, so she decides to take her teenagers to the Cook Islands to experience the simple life.They face storms and a lack of food, but Laura is happy as their local guide shows them the island’s wealth of rare fruits and foods.
11:00 a.m.Wednesday
Orangutan Diary
A Team have come across an armed man who is holding two baby apes who were captures one of them, David, is sent to a medical emergency in the forest.Later a center director, Nielsen, finds a suitable place to set free more rescued animals.
7:50 p.m.Thursday
Lost Buildings of Britain
Simon Thurley visits the ruins of Glastonbruy Abbey(修道院),which , before its destruction by Henry VIII, was famous for some of the most amazing stained-glass of its age.It also had a great deal of financial power, acting as the center of an influential business empire.Eventually, it was the king’s envy of the abbey’s wealth that changed the abbey’s fate.
10:35 p.m.Thursday
Nigella Express
Nigella presents ideas for impromptu(即兴的)cooking, from new recipes and suggestions for taking advantage of the food you have to making quick, simple and impressive meals.
68.Why is Laura worried?
A.Life on the Cook Islands is too simple.
B.Her husband faces difficulties in his business.
C.Storms are approaching her hometown.
D.Her children may not know how to cherish life.
69.Jim enjoys TV programmes of people or organizations that take care of animals. He should probably watch TV at       .
A.10:35 p.m. on Thursday  B.7:50 p.m. on Thursday
C.11.00 a.m. on Wednesday       D.12:25 a. m. on Tuesday
70.We can learn from the text that        .
A.David is a farmer          
B.Henry VIII set up a business empire in the Abbey
C.Nielsen is an animal-lover
D.Glastonbury Abbey is famous today for its stained-glass
71.Elizabeth, who likes trying out new recipes, may be most interested in        .
A.Nigella Express              B.Lost Buildings of Britain
C.Orangutan Diary             D.The Real Swiss Robinson Family