2022年2022年计算机网络A卷 3.pdf

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1、本试卷共 4 页第1 页东北大学考试试卷 （A卷）2009 2010 学年第 一 学期课程名称：计算机网络（Computer Networks ）总分一二三四五学院班级学号姓名密封线. Multiple Choice（20 points,1 point for each ）Directions: Choose the correct answer for each question and fill it in the corresponding blank. There is ONLY ONE correct answer for each question. ( )1There are t

2、wo kinds of coaxial cables usually used. One is the baseband cable and the other is the broadband cable. The impedance of the baseband cable is: A. 50B. 70C. 75D. 90( )2According to the ISO/OSI reference model, the Ethernet switch works on: A. Data link layerB. Network layer C. Transport layer D. Pr

3、esentation layer ( )3 Which device extends the LAN on network layer? A. Repeater B. Hub C. Switch D. Router ( )4 How many network segments can be there at most for network connected by hubs? A. 5 B. 4 C. 3 D. 2 ( )510BaseT network takes: A. thick coaxial cable, bus topology B. twisted pair, ring top

4、ology C. thin coaxial cable, star topology D. twisted pair, star topology ( )6When two computers communicate via a telephone line, which of the following device is necessary? A. network adapter B. MODEMC. repeater D. coaxial cable ( )7If a package is to be broadcasted to the local network, then the

5、destination IP address of the package should be: A. 255.255.255.255B. 0.0.0.0 C. the lowest address of the subnet D. the highest address of the subnet ( )8What many bytes are there in the payload of an ATM cell? A. 48 B. 53 C. 64 D. 36 ( )9The core of the Internet protocols is: A. IPX/SPX B. PPP C.

6、TCP/IPD. SLIP ( )10With respect to protocol layer, the ARP protocol in TCP/IP corresponds to: A. physical layer B. data link layerC. network layer D. transport layer ( )11The lower layer of OSPF protocol uses: A. UDPB. TCP C. ARP D. IP( )12Which port on sever does the POP3 protocol use? A. 20 B. 23

7、C. 25D. 110 ( )13What is the mask for a smallest subnet usable in practice? A. 255.255.255.0 B. 255.255.255.254 C. 255.255.255.252D. 255.255.255.255 ( )14Which of the following IP address CANNOT be assigned to a host? A. 141.107.255.80/16 B. 201.255.0.11/24 C. 116.1.0.255/16 D. 198.121.254.255/24 (

8、)15When installing a MODEM to a PC, the interface standard we take is: A. X.25 B. RJ11C. RS232D. RJ45 ( )16Which of the following is NOT an advantage of a layer model? A. Dividing the complex network operation into a more manageable layer approach. B. Allowing changes to occur in one layer without h

9、aving to change all layers. C. Allowing changes to occur in all layers without having to change one layer. D. Defining a standard interface for the plug-and-play multivendor integration. ( )17How many bits are there for an Ethernet MAC address? A. 32 B. 48C. 64 D. 128 ( )18The protocol for two compu

10、ters to transport files is: A. FTPB. WWW C. Telnet D. SMTP ( )19The Internet can be traced back to its origin: A. ARPANET B. ALOHA C. NEFNET D. Ethernet ( )20Which of the following IPv6 address is correct? A. 2001:8:417A B. 12.20.3.3:0:0:0:0:0:FFFF C. :145.20.15.29D. 145.20.15.29:名师资料总结 - - -精品资料欢迎下

11、载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 1 页，共 4 页 - - - - - - - - - 本试卷共 4 页第2 页学院班级学号姓名密封线1The length of an IPv6 header is _ 60_ bytes. 2. The TCP/IP protocol consists of _ 5_ (how many) layers. 3 ping 127.0.0.1 command will test the internal loopback of a computer. (Fill the c

12、omplete command with parameters) 4. _254_ (how many) usable subnets are created by applying the subnet mask 255.255.255.0 to a Class B network. 5. FF-FF-FF-FF-FF-FF is a Layer-2 broadcast address. 6. The switching method that traditional telephone takes is circuit switching, while the method that IP

13、 telephone takes is_ packet switching_. 7. The common used guided transmission media are_coaxial cable_, _twisted pair_, and _optical fiber_. 1Make a comparison among the three network interconnection devices: hubs, routers and switches. Fill in “ Yes” or “ No” in the blanks of the following form to

14、 say whether the device can perform the corresponding function. (6 points) Hubs Routers Switches Traffic Isolation No Yes Yes Plug & Play Yes No Yes Optimal Routing No Yes No Cut Through Yes No Yes 2. Consider the TCP/IP protocol suite: (1) Fill the names of protocol data units corresponding to each

15、 layer in the PDU colunm. (4 points) (2) Match the following functions to one of the five layers in the Function colunm. (10 points) Reliable process-to-process message delivery Packet switching Defines frames Provides user services such as email and file transfer Transmission of bit stream across p

16、hysical medium Mechanical, electronical, and functional interface Reassembly of data packets Ensure reliable transmission of data Network selection Route determination Layer PDU Functions Application Layer Message Transport Layer Segment Network Layer Packet Data Link Layer Frame Physical Layer Bits

17、 on the wire . Fill in the Blanks （10 points, 1 point for each blank ）Directions: Fill proper contents into the blanks according to the context. . True or False （10 points, 1 point for each ）Directions: Answer the following using T (True)/F (False). You do not need to explain your answers. ( T)1 Car

18、rier Sense Multiple Access with Collision Detection uses first-come, first-served approach. ( T) 2Ethernet provides unreliable, connectionless service. ( T) 3The feature of a Token Ring network is collisionless environment. ( F) 4 8 broadcast domains are created when you segment a network with an 8-

19、port switch. ( T) 5Packet-switching networks place a tight upper limit on block size. ( T) 6Network Address Translation technology is a solution to expand the number of IP addresses available for public use. ( T) 7Latency through the store-and-forward switch varies with frame length. ( F) 8Security

20、is one of the advantages of using static routes over dynamic routes. ( F) 9OSPF is an inter-AS routing protocol, while BGP is an intra-AS routing protocol. ( F) 10In Time-Division Multiplexing, each user cannot get all of the bandwidth periodically during its slot. . Fill in the Forms （20 points ）Di

21、rections : Fill proper contents into the forms. 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 2 页，共 4 页 - - - - - - - - - 本试卷共 4 页第3 页. 学院班级学号姓名密封线3(6 points) Use Dijkstra Algorithm to find out the shortest paths from origin E to every other node in the following gr

22、aph, and calculate corresponding costs. Solution: EA: EA, cost(E,A)=4 EB: EDB, cost(E,B)=4 EC: EDC, cost(E,C)=4 ED: ED, cost(E,D)=2 1(5 points) How long does it take to send a file of 640K bits from host A to host B over a circuit-switched network? All links are 1.536 Mbps Each link uses TDM with 24

23、 slots/sec 500 milliseconds to establish end-to-end circuit Solution: Transmission Speed: 1.536Mbps24=64Kbps Transmission Time: 640K64Kbps=10s Connection Establishment Time: 0.5s File sending time: 10.5s 2. (5 points) The distance between host A and host B is L 10000Km. The bandwidth of the link is

24、R1Mbps (220 bps). Suppose the propagation speed over this link is V2.5108m/s. (1) What is the propagation time Tp? (2) During this time, how many bits have been sent to the link by host A? (3) What is the distance d between two adjacent bits? Solution: TpLV0.04s NumbTpR=41943 dL Numb238m . Comprehen

25、sive Calculation （40 points ）A C B D E 4 2 1 2 2 1 2 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 3 页，共 4 页 - - - - - - - - - 本试卷共 4 页第4 页学院班级学号姓名密封线4(9 points) An organization is granted an IP address 211.17.185.0. The network administrator wants to create 32 subn

26、ets. (1) Find out the subnet mask. (2) Find out the number of host addresses in each subnet. (3) Find out the network address of the first subnet. (4) Find out the first and last host addresses in the first subnet. (5) Find out the subnet directed broadcast address and limited broadcast address in t

27、he first subnet. Solution: (1) 255.255.255.252 (2) 2 (3) 217.17.185.4 (4) 217.17.185.5 217.17.185.6 (5) 211.17.185.7 255.255.255.255 5(15 points) Consider a router with the following routing table: Destination Address Subnet Mask Next Hop 128.96.57.0 255.255.255.128 Interface 0 128.96.39.128 Interfa

28、ce 1 128.96.90.0 255.255.255.128 R2 192.4.131.0 255.255.255.192 R3 Default R4 This router can forward packets directly through Interface 0 and Interface 1, and it can also forward packets through neighboring routers R2, R3, or R4. Suppose the router received 5 packets with the following IP addresses

29、 respectively: (1) 128.96.57.10 (2) 128.96.90.12 (3) 128.96.39.128 (4) 192.4.131.17 (5) 192.4.131.90 Try to calculate the next hop of each packet. Solution: (1) The result of 128.96.57.0 AND 255.255.255.128 is 128.96.57.0, so Packet 1 is forwarded to Interface 0. (3 points) (2) The result of 128.96.

30、90.12 AND 255.255.255.128 is 128.96.90.0, so Packet 2 is forwarded to R2. (3 points) (3) 128.96.39.128 has the single IP entry, so Packet 3 is forwarded to Interface 1. (3 points) (4) The result of 192.4.131.17 AND 255.255.255.192 is 192.4.131.0, so Packet 4 is forwarded to R3. (3 points) (5) The result of 192.4.131.90 AND MASK cannot match any entry, so Packet 5 is forwarded to R4. (3 points) 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 4 页，共 4 页 - - - - - - - - -