1、网络工程师-计算机专业英语(五)及答案解析(总分：100.00，做题时间：90 分钟)一、单项选择题(总题数：8，分数：100.00)Traditional IP packet forwarding analyzes the _ IP address contained in the network layer header of each packet as the packet travels from its source to its final destination. A router analyzes the destination IP address independentl
2、y at each hop in the network. Dynamic _ protocols or static configuration builds the database needed to analyze the destination IP address (the routing table). The process of implementing traditional IP routing also is called hop-by-hop destination-based _ routing. Although successful, and obviously
3、 widely deployed, certain restrictions, which have been realized for some time, exist for this method of packet forwarding that diminish its _. New techniques are therefore required to address and expand the functionality of an IP-based network infrastructure. This first chapter concentrate on ident
4、ifying these restrictions and presents a new architecture, known as multipleprotocol _ switching, that provides solutions to some of these restrictions.（分数：12.50）(1).A. datagram B. destination C. connection D. service（分数：2.50）A.B.C.D.(2).A. routing B. forwarding C. transmission D. management（分数：2.50
5、）A.B.C.D.(3).A. anycast B. multicast C. broadcast D. unicast（分数：2.50）A.B.C.D.(4).A. reliability B. flexibility C. stability D. capability（分数：2.50）A.B.C.D.(5).A. const B. cast C. mark D. label（分数：2.50）A.B.C.D.The de facto standard application program interface _ for TCP/IP applications is the “socket
6、s“ interface. Although this API was developed for _ in the early 1980s. it has also been implemented on a wide variety of non-Unix systems. TCP/IP _ written using the sockets API have in the past enjoyed a high degree of portability and we would like the same _ with IPv6 applications. But changes ar
7、e required to the sockets API to support IPv6 and this memo describes these changes. These include a new socket address structure to carry IPv6 _, new address conversion functions, and some new socket options. These extensions are designed to provide Access to the basic IPv6 features required by TCP
8、 and UDP applications, including multicasting, while introducing a minimum of change into the system and providing complete _ for existing IPv4 applications.（分数：12.50）(1).A. Windows B. Linux C. Unix D. DoS（分数：2.50）A.B.C.D.(2).A. applications B. networks C. protocols D. systems（分数：2.50）A.B.C.D.(3).A.
9、 portability B. availability C. capability D. reliability（分数：2.50）A.B.C.D.(4).A. connections B. protocols C. networks D. addresses（分数：2.50）A.B.C.D.(5).A. availability B. compatibility C. capability D. reliability（分数：2.50）A.B.C.D.The TCP protocolis a _ layer protocol. Each connection connects two TCP
10、s that may be just one physical network apart or located on opposite sides of the globe. In other words, each connection creates a _ witha length that may be totally different from another path created by another connection. This means that TCP cannot use the same retransmission time for all connect
11、ions. Selecting a fixed retransnussion time for all connections can result in serious consequences. If the retransmission time does not allow enough time for a _ to reach the destination and an acknowledgment to reach the source, it can result in retransmission of segments that are still on the way.
12、 Conversely, if the retransmission time is longer than necessary for a short path, it may result in delay for the application programs. Even for one single connection, the retransmission time should not be fixed. A connection may be able to send segments and receive _ faster during nontraffic period
13、 than during congested periods. TCP uses the dynamic retransmission time, a transmission time is different for each connection and which may be changed during the same connection. Retransmission time can be made _ by basing it on the round-trip time (RTT). Several formulas are used for this purpose.
14、（分数：12.50）(1).A.physical B.network C.transport D.application（分数：2.50）A.B.C.D.(2).A.path B.window C.response D.process（分数：2.50）A.B.C.D.(3).A.process B.segment C.program D.user（分数：2.50）A.B.C.D.(4).A.connections B.requests C.acknowledgments D.datagrams（分数：2.50）A.B.C.D.(5).A.long B.short C.fixed D.dynam
15、ic（分数：2.50）A.B.C.D.Let us now see how randomization is done when a collision occurs. After a _, time is divided into discrete slots whose length is equal to the worst-case round-trip propagation time on the ether (2t). To accommodate the longest path allowed by Ethernet, the slot tome has been set t
16、0 512 bit times, or 51.2sec.After the first collision, each station waits either 0 or 1 _ times before trying again. If two stations collide and each one picks the same random number, they will collide again. After the second collision, each one picks either 0, 1, 2, or3 at random and waits that num
17、ber of slot times. If a third collision occurs (the probability of this happening is 0.25), then the next time the number of slots to wait is chosen at _ from the interval 0 to 23-1.In general, after i collisions, a random number between 0 and 2i-1 is chosen, and that number of slots is skipped. How
18、ever, after ten collisions have been reached, the randomization _ is frozen at a maximum of 1023 slots. After 16 collisions, the controller throws in the towel and reports failure back to the computer. Further recovery is up to _ layers.（分数：12.50）(1).A.datagram B.collision C.connection D.service（分数：
19、2.50）A.B.C.D.(2).A.slot B.switch C.process D.fire（分数：2.50）A.B.C.D.(3).A.rest B.random C.once D.odds（分数：2.50）A.B.C.D.(4).A.unicast B.multicast C.broadcast D.interval（分数：2.50）A.B.C.D.(5).A.local B.next C.higher D.lower（分数：2.50）A.B.C.D.Border Gateway Protocol(BGP) is inter-autonomous system _ protocol.
20、 BGP is based on a routing method called path vector routing. Distance vector routing is not a good candidate for inter-autonomous system routing because there are occasions on which the route with the smallest _ count is not the preferred route. For example, we may not want a packet through an auto
21、nomous system that is not secure even though it is shortest route. Also, distance vector routing is unstable due to the fact that the routers announce only the number of hop counts to the destination without defining the path that leads to that _. A router that receives a distance vector advertiseme
22、nt packet may be fooled if the shortest path is actually calculated through the receiving router itself. Link _. routing is also not a good candidate for inner-autonomous system routing because an internet is usually too big for this routing method. To use link state routing for the whole internet w
23、ould require each router to have a huge link state database. It would also take a long time for each router to calculate its routing _ using the Dijkstra algorism.（分数：12.50）(1).A. routing B. switching C. transmitting D. receiving（分数：2.50）A.B.C.D.(2).A. path B. hop C. route D. packet（分数：2.50）A.B.C.D.
24、(3).A. connection B. window C. source D. destination（分数：2.50）A.B.C.D.(4).A. status B. search C. state D. research（分数：2.50）A.B.C.D.(5).A. table B. state C. metric D. cost（分数：2.50）A.B.C.D.A transport layer protocol usually has several responsibilties. One is to create a process-to-process communicatio
25、n UDP uses _ numbers to accomplish this. Another responsibility is to provide control mechanisms at the transport level UDP does this task at a very minimal level. There is no flow control mechanism and there is no _ for received packet. UDP, however, does provide error control to some extent. If UD
26、P detects an error in the received packet, it will silently drop it.The transport layer also provides a connection mechanism for the processes. The _ must be able to send streams of data to the transport layer. It is the responsibility of the transport layer at _ station to make the connection with
27、the receiver chop the stream into transportable units, number them, and send them one by one. it is the responsibility of the transport layer at the receiving end to wait until all the different units belonging to the same process have arrived, check and pass those that are _ free, and deliver them
28、to the receiving process as a stream.（分数：12.50）(1).A.hop B.port C.route D.packet（分数：2.50）A.B.C.D.(2).A.connection B.window C.acknowledgement D.destination（分数：2.50）A.B.C.D.(3).A.jobs B.processes C.programs D.users（分数：2.50）A.B.C.D.(4).A.sending B.routing C.switching D.receiving（分数：2.50）A.B.C.D.(5).A.c
29、all B.state C.cost D.error（分数：2.50）A.B.C.D.Although a given waveform may contain frequencies over a very broad range, as a practical matter any transmission system will be able to accommodate only a limited band of _. This, in turn, limits the data rate that can be carried on the transmission _. A s
30、quare wave has an infinite number of frequency components and hence an infinite _. However, the peak amplitude of the kth frequency component, kf, is only l/k, so most of the _ in this waveform is in the first few frequency components. In general, any digital waveform will have _ bandwidth. If we at
31、tempt to transmit this waveform as a signal over any medium, the transmission system will limit the bandwidth that can be transmitted.（分数：12.50）(1).A. frequencies B. connections C. diagrams D. resources（分数：2.50）A.B.C.D.(2).A. procedures B. function C. route D. medium（分数：2.50）A.B.C.D.(3).A. source B.
32、 bandwidth C. energy D. cost（分数：2.50）A.B.C.D.(4).A. frequency B. energy C. amplitude D. phase（分数：2.50）A.B.C.D.(5).A. small B. limited C. infinite D. finite（分数：2.50）A.B.C.D.The metric assigned to each network depends on the type of protocol.Some simple protocol, like RIP, treats each network as equal
33、s. The _ of passing through each network is the same; it is one _ count. So if a packet passes through 10 network to reach the destination, the total cost is 10 hop counts. Other protocols, such as OSPF, allow the administrator to assign a cost for passing through a network based on the type of serv
34、ice required. A _ through a network can have different costs (metrics). For example, if maximum _ is the desired type of service, a satellite link has a lower metric than a fiber-optic line. On the other hand, if minimum _ is the desired type of service, a fiber-optic line has a lower metric than a
35、satellite line. OSPF allow each router to have several routing table based on the required type of Service.（分数：12.50）(1).A. number B. connection C. diagram D. cost（分数：2.50）A.B.C.D.(2).A. process B. hop C. route D. flow（分数：2.50）A.B.C.D.(3).A. flow B. window C. route D. cost（分数：2.50）A.B.C.D.(4).A. pac
36、ket B. throughput C. error D. number（分数：2.50）A.B.C.D.(5).A. delay B. stream C. packet D. cost（分数：2.50）A.B.C.D.网络工程师-计算机专业英语(五)答案解析(总分：100.00，做题时间：90 分钟)一、单项选择题(总题数：8，分数：100.00)Traditional IP packet forwarding analyzes the _ IP address contained in the network layer header of each packet as the packe
37、t travels from its source to its final destination. A router analyzes the destination IP address independently at each hop in the network. Dynamic _ protocols or static configuration builds the database needed to analyze the destination IP address (the routing table). The process of implementing tra
38、ditional IP routing also is called hop-by-hop destination-based _ routing. Although successful, and obviously widely deployed, certain restrictions, which have been realized for some time, exist for this method of packet forwarding that diminish its _. New techniques are therefore required to addres
39、s and expand the functionality of an IP-based network infrastructure. This first chapter concentrate on identifying these restrictions and presents a new architecture, known as multipleprotocol _ switching, that provides solutions to some of these restrictions.（分数：12.50）(1).A. datagram B. destinatio
40、n C. connection D. service（分数：2.50）A.B. C.D.解析：(2).A. routing B. forwarding C. transmission D. management（分数：2.50）A. B.C.D.解析：(3).A. anycast B. multicast C. broadcast D. unicast（分数：2.50）A.B.C.D. 解析：(4).A. reliability B. flexibility C. stability D. capability（分数：2.50）A.B. C.D.解析：(5).A. const B. cast
41、C. mark D. label（分数：2.50）A.B.C.D. 解析：The de facto standard application program interface _ for TCP/IP applications is the “sockets“ interface. Although this API was developed for _ in the early 1980s. it has also been implemented on a wide variety of non-Unix systems. TCP/IP _ written using the sock
42、ets API have in the past enjoyed a high degree of portability and we would like the same _ with IPv6 applications. But changes are required to the sockets API to support IPv6 and this memo describes these changes. These include a new socket address structure to carry IPv6 _, new address conversion f
43、unctions, and some new socket options. These extensions are designed to provide Access to the basic IPv6 features required by TCP and UDP applications, including multicasting, while introducing a minimum of change into the system and providing complete _ for existing IPv4 applications.（分数：12.50）(1).
44、A. Windows B. Linux C. Unix D. DoS（分数：2.50）A.B.C. D.解析：(2).A. applications B. networks C. protocols D. systems（分数：2.50）A. B.C.D.解析：(3).A. portability B. availability C. capability D. reliability（分数：2.50）A. B.C.D.解析：(4).A. connections B. protocols C. networks D. addresses（分数：2.50）A.B.C.D. 解析：(5).A. a
45、vailability B. compatibility C. capability D. reliability（分数：2.50）A.B. C.D.解析：The TCP protocolis a _ layer protocol. Each connection connects two TCPs that may be just one physical network apart or located on opposite sides of the globe. In other words, each connection creates a _ witha length that
46、may be totally different from another path created by another connection. This means that TCP cannot use the same retransmission time for all connections. Selecting a fixed retransnussion time for all connections can result in serious consequences. If the retransmission time does not allow enough ti
47、me for a _ to reach the destination and an acknowledgment to reach the source, it can result in retransmission of segments that are still on the way. Conversely, if the retransmission time is longer than necessary for a short path, it may result in delay for the application programs. Even for one si
48、ngle connection, the retransmission time should not be fixed. A connection may be able to send segments and receive _ faster during nontraffic period than during congested periods. TCP uses the dynamic retransmission time, a transmission time is different for each connection and which may be changed
49、 during the same connection. Retransmission time can be made _ by basing it on the round-trip time (RTT). Several formulas are used for this purpose.（分数：12.50）(1).A.physical B.network C.transport D.application（分数：2.50）A.B.C. D.解析：(2).A.path B.window C.response D.process（分数：2.50）A. B.C.D.解析：(3).A.proce
