2009本科生计算机网络考试B卷

北京化工大学2008 ——2009 学年第二学期

《计算机网络》期末考试试卷（B）

班级：姓名：学号：分数：

一、Explain following terms. (40 points)

1、QoS：

2、TCP/UDP：

3、Slotted ALOHA：

4、Computer Networks：

5、Date Link Layer：

6、B/S and C/S models：

7、ARP：

8、DNS：

二、Answer questions. (60 points)

1、What are differences between computer networks and distributed systems?

2、What is the main difference between TCP and UDP?

3、Comparison of Fiber Optics and Copper Wire.

4、The following character encoding is used in a data link protocol: A: 01000111; B: 11100011;

FLAG: 01111110; ESC: 11100000 Show the bit sequence transmitted (in binary) for the

four-character frame: A B ESC FLAG when each of the following framing methods are used:

a)Character count.

b)Flag bytes with byte stuffing.

c)Starting and ending flag bytes, with bit stuffing.

5、What is the essential difference between message switching and packet switching?

6、Two networks each provide reliable connection-oriented service. One of them offers a reliable

byte stream and the other offers a reliable message stream. Are these identical? If so, why is the distinction made? If not, give an example of how they differ.

7、Please explain following figure about TCP Congestion control.

8、In Ethernet protocol design, why does a frame need a minimum frame length.?

9、A simple telephone system consists of two end offices and a single toll office to which each

end office is connected by a 1-MHz full-duplex trunk. The average telephone is used to make eight calls per 8-hour workday. The mean call duration is 10 min. Twenty percent of the calls are long-distance (i.e., pass through the toll office). What is the maximum number of telephones an end office can support? (Assume 4 kHz per circuit.)

10、What is the Count-to-Infinity Problem of routing? Give example to explain it.

三、Experiment

1、What are user mode, privileged mode, and global configuration mode when you configure CISCO network devices? Explaining them in details.

2、Assign FastEthernet 0/0 IP address to 192.168.1.1, and open this interface. Fill following space.

router> //进入特权模式

router# //配置模式

router(config)# //对以太0/0口的配置

router(config-if)# // 0/0的IP地址

router(config-if)# //打开端口