发布时间 : 星期日 文章计算机网络原理期末试卷2012级更新完毕开始阅读
Ⅰ、Choose the best answer( 1 points each problems, total 10 points)
1．TCP stands for （ A ）．
A. Transmission Control Protocol B. Trivial Connecti on Protocol C. Telephony Connection Protocol D. Traffic Control Protocol
2．（ B ）of the following higher-level protocols typically operate on top of UDP. A．ARP B．DNS C．Telnet D．OSPF
3．The Sender of TCP protocol will take ( D ) to void the longer time delay of the missing TCP segment before the segment’s timer expires. A. sending ACKs B. flow control C. responsing timeout event D. fast retransmit. 4．（ D ）is the subnet mask of the IP address block of 192.169.15.136/29. A. 255.255.255.192 B. 255.255.255.240 C. 255.255.255.224 D. 255.255.255.248 5．（ A ）should be used for enabling a host to communicate with another host on a different IP network. A. switch B. hub C. router D. host
6．In CSMA/CD, after the third collision, the probability is （ D ） that the value of K that a node chooses is 2. A. 0 B. 0.33 C. 0.25 D. 0.125
7．If the sequence number has k bits, what the maximum of slide window is （ C ）in Selective Repeat protocol. A. 2k B. 2k-1 C. 2k-1 D. 2k+1 8．The retransmission timeout(超时) interval(间隔) in TCP expressed by TimeoutInterval, which satisfies the equation of ‘TimeoutInterval = EstimatedRTT + 4*DevRTT’. The meaning of ‘EstimatedRTT’ is （c） .
A. The predicted value of RTT of last transferred packet B. SAMPLE RTT
C. The predicted value of RTT of packet to be immediately sent D. The average value of all RTT
9．An Ethernet switch reads the entire data frame, completes the data frame error checking and then forwards, this switch method is called （ A ）. A. store-and-forward switch B. cut-through switch C. No-fragment switch D. No-error switch 10．( B ) is an class B IP address in following IP addresses? ( ) A. 223.1.1.1 B. 191.1.1.1 C. 192.1.1.1 D. 228.1.1.1
Ⅱ、Fill in blanks (1 points each blank, total 5 points)
1．Coaxial cable, 光纤 and radio are the physical media that network can run over. 2．IP address and 端口号 are used by a process running on one host to identify a process running on another host。
3．Consider sending a 3000 byte datagram into a link that has an MTU of 500 bytes. How many fragments are generated 7 .
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4．There are two broad classes of packet-switched networks: virtual circuit and 数据报 network. 5．A bit time is equal to 1/10^7 seconds for a 10 Mbps Ethernet.
Ⅲ、True or false（1 points for each item, total 10 points）
1．The Data: header in the HTTP response message indicates when the object in the response was last modified. （ F ） 2．The receive window size of GBN protocol is greater than 1. （ F ） 3．Link layer protocol is implemented by Ethernet Adapter(书上写的是Network
information card,Network Adapter)(以太网适配器，网卡) in Ethernet Network. （ T ）
4．ARP tables in nodes are established by self-learning themselves(不是self-learning). （ F ）
5．The slotted ALOHA protocol makes more efficient in using of the network bandwidth than the pure ALOHA protocol. （ T ） 6．The OSPF is a route protocol related to distance vector routing algorithm. （ F ） 7．The PPPoE is a PPP（PtoP Protocol） protocol that it runs over Ethernet. （ T ）
8．The UDP header checksum is recomputed at every routers. （ F ） 9．There are no collisions in CSMA protocol because it has detected that the channel is idle before transmits frame . （F ） 10．In general, efficiency（效率） of the CSMA protocol channel is better than the Slotted ALOHA.
（ T ）
Ⅳ、Please answer following question( total 30 points）
1. What are the five layers in the Internet protocol stack? What are the principal
responsibilities for each of these layers? （5 points）
１．应用层：应用层是网络应用程序及其应用程协议停留的地方；
２．运输层：运输层提供了在应用程序端点之间传送应用层报文的服务；
３．网络层：因特网的网络层负责将称为数据报的网络层分组从一台主机移动到另一台主机； ４．链路层：链路层将网络层传来的数据报沿着路径将数据传递给下一个结点；
５．物理层：物理层的任务是将链路层传来的帧中的数据一个比特一个比特从一个节点移动到下一个结点；
2. Which protocols are inter-ASs and intra-ASs protocols respectively(各自的) used in the
Internet（5 points）
Inter-ASs:OSPF,BGP Intra-Ass:RIP,OSPF,IGRP
3. Consider the generator, G=1001, and suppose that D has the value of 11001001. What
are the bits of CRC R? What is the data for transferring with CRC code? （5 points）. 011,11001001011
4. UDP and TCP use 1s complement for their checksums. Suppose you have the following
three 8-bit bytes 01101010, 01001111, 01110011. What is the checksum of these 8-bit bytes ? (5 points)
01101010 01001111
-------------------- 10111001 01110011 ---------------------
100101100
1
---------------------- 00101101
5. What is the different between MAC address and IP address? （5 points）
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mac是在在生产是就确认的，由网卡生产厂家烧入网卡的EPROM（一种闪存芯片，通常可以通过程序擦写），它存储的是传输数据时真正赖以标识发出数据的电脑和接收数据的主机的地址。 IP地址就是给每个连接在Internet上的主机分配的一个32bit地址。
32-bit IP address: network-layer address
used to get datagram to destination IP network
MAC (Media Access Control or LAN or physical or Ethernet) address:
used to get frame from one interface to another physically-connected interface (same network) 48 bit MAC address (Ethernet) burned in the adapter ROM
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Ⅴ、Comprehensive problems (total 45 points)
2. According to the network shown below, please analyze how the link-state algorithm builds the routing table at node D.(15 points)
A8D3C6B2E1F2
Answer:
(1) Computing the shortest path from D to all other network nodes according link-state algorithm N’ D DE DEC DECB DECBA DECBAF D(A), p(A) 8，D 8，D 6，C 6，C D(B), p(B) ∞ 4，E 4，E D(C), p(C) ∞ 3，E D(E), p(E) 2，D D(F), p(F) ∞ ∞ 9，C 9，C 9，C
(2) D vector and p vector in node D (3) forwarding table in D D? A B C E F Destination link D(j) 6 4 3 2 9 A (D,E) p(j) C E E D C B (D,E) C (D,E) E (D,E) F (D,E)
3. Please answer the following questions.(9 points)
(1) Consider the following HTTP GET message. Answer the following questions, indicating where in the message below you find the answer. (4 points)
GET /info/2012-10-18/0-1-411.html http/1.1
Host: www.ynu.edu.cn User-agent: Mozilla/4.0
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