计算机网络试卷英语版

1、注意：1. 可以用英文答题，也可以用中文答题。2. 答案请写在每种类型题目的答题区中！一 multiple choice(20 points, 2 points each problem)1、ospf routing protocol typically runs over:a. ip b. tcp c. udp d. none of the above2、the transfer of an web document from one host to another is:a. loss-intolerant and time insensitiveb. loss-tolerant and

2、time sensitivec. loss-intolerant and time sensitived. none of the above3、consider sending a 999 byte datagram into a link that has an mtu of 500 bytes.a. 2 fragments are created with offset field value 0, 500, respectivelyb. 3 fragments are created with offset field value 0, 480,960, respectivelyc.

3、3 fragments are created with offset field value 0, 60,120, respectivelyd. none of the above4、suppose an application generates chunks of 120 bytes of data every second, and each chunk gets encapsulated in a tcp segment and then an ip datagram(no options fields). what percentage of each datagram will

4、contain application data?a. 80% b. 75% c. 60% d. 25%5、we are sending a 30 mbit mp3 file from a source host to a destination host. suppose there is only one link between source and destination and the link has a transmission rate of 10 mbps. assume that the propagation speed is 2 * 108 meters/sec, an

5、d the distance between source and destination is 10,000 km. also suppose that message switching is used, with the message consisting of the entire mp3 file. how many bits will the source have transmitted when the first bit arrives at the destination?a. 1 bit b. 30,000,000 bits c. 500,000 bits d. non

6、e of the above6、in routing among ass, which of the following issues dominantsa. policy b. geographical distance between assc. current congestion levels in the ass d. number of ass traversed7、an arp query packet is encapsulated ina. a link-layer frame addressed to a specific adapterb. a link-layer br

7、oadcast framec. an ip datagramd. none of the above8、a taking-turns protocol has which of the following characteristicsa. there is no single point failure.b. it does not generate collisionsc. there is no master noded. all of the above9、tcp has which of the following characteristics:a. flow control b.

8、 connection establishmentc. congestion control d. all of the above10、which of the following statements is true?a. a network adapter (nic) is an autonomous unit.b. in a distance-vector routing algorithm, each node has a map of the entire network and determines the shortest path from itself to all oth

9、er nodes in the network.c. an adapters mac address has a flat structure and doesnt change no matter where the adapter goes.d. none of the above二 fill in the blanks(24 points, 2 points each problem)1、as a packet travels from one node to the subsequent node along the path, the packet suffers from seve

10、ral types of delays at each node along the path. the most important of these delays are the _delay, _delay, _ delay, and _delay.2、the internet mail system has three major components: _, _, and _.3、_ is called transport- layer multiplexing and demultiplexing.4、computer networks that_ are called virtu

11、al-circuit networks; computer networks that _ are called datagram networks.5、there are 4 components in routers architecture. they are input ports, _, output ports and _. and _connects the routers input ports to its output ports; _ executes the routing protocols.6、historically, two routing protocols

12、have been used extensively for routing within an autonomous system in the internet: rip protocol and _ protocol. and _ is a distance-vector protocol. and _ is a link-state protocol.7、tcp provides a _service to its applications to eliminate the possibility of the sender overwhelming the receiver.8、we

13、 can classify just about any multiple access protocol as belonging to one of three categories. csma/cd belongs to _ protocol. polling belongs to _ protocol.9、a hub is a _-layer device, and switches are _-layer devices.10、cookie technology has four components: a cookie header line in http response me

14、ssage; a cookie header line in the http request message; _; _.11、two basic approaches toward pipelined error recovery can be identified: _and _. and in _ protocol, the receiver discards out-of-order-packets. .12、there are two fundamental approaches to building a network core: _ switching and _ switc

15、hing. and in _ switched networks, the resources are not reserved; a sessions messages use the resources on demand, and as a consequence, may have to wait for access to a communication link.三 true or false(10 points, 1 point each problem)1、when a user request a web page that consists of some text and

16、 two images. for this page, the client will send one request message and receive three response messages.2、it is possible for a mail client to send e-mail messages over http rather than smtp.3、in tcp, the acknowledgement number that a host puts in a segment is the sequence number of the next byte th

17、e host is expecting from the sender.4、tcp applies fast retransmit to a segment when it estimates unusually large rtt.5、local dns name servers cache resource records, but discard them after a period of time that is on the order of a few days.6、for the web application, the user agent is the users keyb

18、oard.7、suppose that host a wants to send data over tcp to host b, and host b wants to send data to host a over tcp. two separate tcp connections - one for each direction - are needed.8、when a tcp segment arrives to a host, the socket to which the segment is directed depends on the source ip address

19、of the datagram encapsulated the segment，the source port number，the destination port number and the destination ip address.9、the stop-and-wait protocol is highly inefficient when there is a large distance between source and destination and the transmission rate is high.10、suppose a router has n inpu

20、t ports each with identical line speeds, n output ports each with identical line speeds, and the line speed of an output port is at least n times as that of an input port. further suppose that the switching fabric speed is at least n times as fast as an input line speed. then queuing can occur in an

21、 output port.四、answer the following questions briefly.(33 points)1、how many layers are there in the internet protocol stack? what are they? what are the principal responsibilities of each of these layers?(7 points)2.what is the difference between persistent http with pipelining and persistent http w

22、ithout pipelining? (4 points)3. consider a subnet with prefix 4/26. give an example of one ip address (of form xxx.xxx.xxx.xxx) that can be assigned to an interface in this network. suppose an isp owns the block of addresses of the form 4/26. and suppose it wants to create

23、four subnets from this block, with each block having the same number of ip addresses. what are the prefixes (of form a.b.c.d/x) for the four subnets? (5 points)4. in the table, there are six reliable data transfer mechanisms. give the use of each mechanism. (6 points)mechanismusetimersequence number

24、acknowledgmentnegative ackwindow, pipeliningchecksum5. list six access technologies and classify each one as residential access, company access, or mobile access. (6 points)6. in csma/cd, after the sixth collision, what is the probability that a node chooses k=3? the result k=3 corresponds to a delay of how many seconds on a 10mbps ethernet? (5 points)五、computing problems (13 points)1、 consider the network shown below, the link costs are c(x,y)=5, c(y,z)=6, c(z,x)=2. compute the dista