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《计算机网络》期末题库——简答题

• 2017 年 07 月 04 日 • 闲言碎语

天津理工大学《计算机网络》期末复习——简答题
中文答案

1.(3points) What is the difference between a host and end system? List the types of end systems. Is a Web Server an end system?
答:

  • 没有区别
  • 个人计算机、工作站、邮件服务器等

2.(1points) Why is there a Web cache?
答:减少接入网络的流量、减小延迟

3.(3points) Please briefly describe the function of the five layers in TCP/IP architecture
(NOTE: include the protocol data unit)
答:

功能PDU
应用层提供各种网络应用,运行网络应用程序Message 报文
运输层提供端到端进程之间的数据传输Segment 报文段
网络层主机到主机的传输Datagram 数据报
链路层节点间建立数据链路连接frame 帧
物理层在物理线路上传输原始的二进制数据bit stream 数据位

4.(2points) What are the services of TCP?
答:
面向连接的服务
可靠的数据传输
有序的字节流数据传输
流量控制
拥塞控制

5.(2points) What is the difference between routing and forwarding?
答:
转发是将数据包从路由器的输入链路转移到输出链路
选路是决定源到端的路径

6.(3points) How big is MAC address space? The IPv4 address space? The IPv6 address space?
答:MAC: 48位,IPv4:32位;IPv6:128位

7.(3points) Where can queuing occur in a router? Briefly explain the conditions that lead to such queuing.
答:
排队时延发生在路由的入口和出口

数据到达Buffer的速度比出去时快

8.(3points) Describe why an application developer might choose to run an application over UDP rather than TCP.

UDP速度快

  • 没有重传机制
  • 没有拥塞控制和流量控制
  • 分组首部开销小
  • 无需建立连接、也无需维护连接

9.(3points)If all the links in the Internet were to provide the reliable delivery service, would the TCP reliable delivery service be redundant? Why or Why not?

答:不会,TCP提供有序的字节流数据传输,保证接收端接收到正确顺序的字节流

10.The difference between UDP and IP packets is minimal. Why shouldn’t applications use IP directly? (2 points)

答:
传输层需要向上层隐藏下层的实现细节
IP没有实现端口,应用程序不能直接发送或接收IP数据包

11.Can two computers that have a different implementation of the same protocol exchange messages? Explain your answer. (2 points)

是的,协议规定了消息的格式,以及消息交换的准确规则。 您可以轻松地使用相同协议的不同实现。

12.Explain the difference between a connection-oriented messaging service and a connectionless messaging service. (2 points)

面向连接的服务要求在传输数据之前建立连接;无连接的服务直接向向目标发送消息,每个消息都包含地址。

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