计算机网络教程自顶向下方法选择题及问题详解 Chapt 4 Network Layer-QUIZZ

Chapter 4 Network Layer1.Packetizing at the network layer involvesA) Encapsulating the payload at the sourceB) Adds a header that contains the source and destination informationC) Decapsulating the payload at the destinationD) All of the choices are correct2.Routers in the path are not allowed to ___________________________.A) fragment the packet they receiveB) decapsulate the packetC) change source or destination addressD) All of the choices are correct3.The network layer in the Internet provides _________________.A) comprehensive error and flow control.B) limited error control, but no flow control.C) comprehensive error control but limited flow control.D) All of the choices are correct4.In a virtual-circuit approach, the forwarding decision is based on the value of the _____________ field in the packet header.A) source addressB) destination addressC) labelD) None of the choices are correct5.In a datagram approach, the forwarding decision is based on the value of the _____________ field in the packet header.A) source addressB) destination addressC) labelD) None of the choices are correct6.The performance of a network can be measured in terms of ________.A) delayB) throughputC) packet lossD) all of the choices are correct7.Transmission delay (time) is the ratio of ______________________.A) transmission rate to packet lengthB) transmission rate to distanceC) packet length to transmission rateD) processing time to transmission rate8.Propagation delay (time) is the ratio of ______________________.A) transmission rate to propagation speedB) propagation speed to distanceC) packet length to propagation speedD) distance to propagation speed9.When the load in the network reaches the network capacity, the packet delay ___________ and the network throughput reaches ______________.A) increases sharply; its minimumB) increases sharply; its maximumC) decreases sharply; its minimumD) decreases sharply; its maximum10.In open-loop congestion control, policies are applied ____________________.A) to prevent congestion before it happensB) to alleviate congestion after it happensC) to either prevent congestion before it happens or to alleviate congestion after it happensD) None of the choices are correct11.The __________________ technique is one of the open-loop congestion policyA) backpressureB) choke packetC) implicit signalingD) None of the choices are correct12.The __________________ technique is one of the close-loop congestion policyA) acknowledgment policyB) choke packetC) discarding policyD) None of the choices are correct13.IP is a _________ protocol.A) connection-oriented unreliableB) connection-oriented reliableC) connectionless unreliableD) connectionless reliable14.An HLEN value of decimal 10 means _______.A) there are 10 bytes of optionsB) there are 10 bytes in the headerC) there are 40 bytes of optionsD) there are 40 bytes in the header15.If the fragment offset has a value of 100, it means that _______.A) the datagram has not been fragmentedB) the datagram is 100 bytes in sizeC) the first byte of the datagram is byte 800D) None of the choices are correct16.What is needed to determine the number of the last byte of a fragment?A) offset numberB) total lengthC) both offset number and the total lengthD) None of the choices are correct17.The IP header size is _______ bytes long.A) 20 to 60B) 20C) 60D) None of the choices are correct18.Packets in the IP layer are called _________.A) segmentsB) datagramsC) framesD) None of the choices are correct19.The total length field defines the total length of the datagram _________.A) including the headerB) excluding the headerC) excluding the option lengthD) None of the choices are correct20.When a datagram is encapsulated in a frame, the total size of the datagram must be lessthan the _______.A) MUTB) MATC) MTUD) None of the choices are correct21.An IPv4 address is normally represented in base ____ in dotted-decimal notation.A) 16B) 256C) 10D) None of the choices are correct22.In classful addressing, the IPv4 address space is divided into _______ classes.A) 3B) 4C) 5D) None of the choices are correct23.The number of addresses assigned to an organization in classless addressing _______.A) can be any numberB) must be a multiple of 256C) must be a power of 2D) None of the choices are correct24.The first address assigned to an organization in classless addressing _______.A) must be evenly divisible by the number of addresses in the organizationB) must be divisible by 128C) must belong to one of the A, B, or C classesD) None of the choices are correct25.In subnetting, the number of addresses in each subnet must _______.A) be a power of 2B) be a multiple of 128C) be divisible by 128D) None of the choices are correct26.What is the default prefix length for class A in CIDR notation?A) 9B) 8C) 16D) None of the choices are correct27.What is the default prefix length for class B in CIDR notation?A) 9B) 8C) 16D) None of the choices are correct28.What is the default prefix length for class C in CIDR notation?A) 24B) 8C) 16D) None of the choices are correct29.DHCP is a (an) ___________ layer protocol.A) applicationB) transportC) networkD) data-link30.In DHCP, the client uses ________ port and the server uses _________ port.A) an ephemeral; a well-knownB) a well-known; a well-knownC) a well-known; an ephemeralD) None of the choices are correct31.DHCP uses the services of _______.A) UDPB) TCPC) IPD) None of the choices are correct32._________ allows a site to use a set of private addresses for internal communication and a set of global Internet addresses for communication with the rest of the world.A) DHCPB) NATC) IMCPD) None of the choices are correct33.The idea of address aggregation was designed to alleviate the increase in routing table entries when using ________ addressing.A) classfulB) classlessC) classful or classlessD) None of the choices are correct34.The use of hierarchy in routing tables can ________ the size of the routing tables.A) reduceB) increaseC) neither reduce nor increaseD) None of the choices are correct35.ICMP is a (an) _________ layer protocol.A) application-layer protocol that helps TCP/IP at the network layerB) transport-layer protocol that helps TCP/IP at the network layerC) network-layer protocol.D) data-link layer protocol that helps TCP/IP at the network layer36.Which of the following is true about ICMP messages?A) An ICMP error message may be generated for an ICMP error message.B) An ICMP error message may be generated for a fragmented datagram.C) An ICMP error message may be generated for a multicast datagram.D) None of the choices are correct37.Routing inside an autonomous system is referred to as ________ routing.A) interdomainB) intradomainC) out-of-domainD) None of the choices are correct38.Routing between autonomous systems is referred to as ______ routing.A) interdomain routingB) intradomain routingC) out-of-domainD) None of the choices are correct39.In _______ routing, the least cost route between any two nodes is the route with the minimum distance.A) path vectorB) distance vectorC) link stateD) None of the choices are correct40.In ________, each node maintains a vector (table) of minimum distances to every node.A) path vectorB) distance vectorC) link stateD) None of the choices are correct41.In distance vector routing, each node periodically shares its routing table with _________ and whenever there is a change.A) every other nodeB) its immediate neighborsC) one neighborD) None of the choices are correct42.The Routing Information Protocol (RIP) is an intradomain routing based on _________ routing.A) distance vectorB) link stateC) path vectorD) None of the choices are correct43.The metric used by _______ is the hop count.A) OSPFB) RIPC) BGPD) None of the choices are correct44.In RIP, the ________ timer controls the advertising of regular update messages.A) garbage collectionB) expirationC) periodicD) None of the choices are correct45.In RIP, the ________ timer is used to purge invalid routes from the table.A) garbage collectionB) expirationC) periodicD) None of the choices are correct46.In RIP, the ________ timer controls the validity of the route.A) garbage collectionB) expirationC) periodicD) None of the choices are correct47.RIP uses the services of _______.A) TCPB) UDPC) IPD) None of the choices are correct48.The _________ routing uses the Dijkstra algorithm to build a routing table.A) distance vectorB) link stateC) path vectorD) None of the choices are correct49.The Open Shortest Path First (OSPF) protocol is an intradomain routing protocol based on _______ routing.A) distance vectorB) link stateC) path vectorD) None of the choices are correct50.The _______ protocol allows the administrator to assign a cost, called the metric, to each route.A) OSPFB) RIPC) BGPD) None of the choices are correct51.In OSPF, a ________ link connects two routers without any other host or router in between.A) point-to-pointB) transientC) stubD) None of the choices are correct52.In OSPF, a _______ link is a network with several routers attached to it.A) point-to-pointB) transientC) stubD) None of the choices are correct53.In OSPF, a ________ link is a network connected to only one router.A) point-to-pointB) transientC) stubD) None of the choices are correct54.In OSPF, a ________ defines the links of a network.A) network linkB) router linkC) summary link to networkD) None of the choices are correct55.___________ is an interdomain routing protocol using path vector routing.A) BGPB) RIPC) OSPFD) None of the choices are correct56.A one-to-all communication between one source and all hosts on a network is classified as a _______ communication.A) unicastB) multicastC) broadcastD) None of the choices are correct57.A one-to-many communication between one source and a specific group of hosts is classified as a _______ communication.A) unicastB) multicastC) broadcastD) None of the choices are correct58.A one-to-one communication between one source and one destination is classified as a _______ communication.A) unicastB) multicastC) broadcastD) None of the choices are correct59.In ______, the router forwards the received packet through only one of its interfaces.A) unicastingB) multicastingC) broadcastingD) None of the choices are correct60.In multicast routing, each involved router needs to construct a ________ path tree for each group.A) averageB) longestC) shortestD) None of the choices are correct61.In the _______ tree approach to multicasting, each router needs to create a separate tree for each source-group.A) group-sharedB) source-basedC) destination-basedD) None of the choices are correct62.The Multicast Open Shortest Path First (MOSPF) routing uses the _______ tree approach.A) source-basedB) group-sharedC) destination-basedD) None of the choices are correct63.The Multicast Open Shortest Path First (MOSPF) protocol is an extension of the OSPF protocol that uses multicast routing to create source-based trees. The protocol is based on _______ routing.A) distance vectorB) link stateC) path vectorD) None of the choices are correct64.In RPF, a router forwards only the copy that has traveled the _______ path from the source to the router.A) shortestB) longestC) averageD) None of the choices are correct65.RPF eliminates the ________ in the flooding process.A) forwardingB) backwardingC) floodingD) None of the choices are correct66.RPB creates a shortest path _______ tree from the source to each destination.A) unicastB) multicastC) broadcastD) None of the choices are correct67.RPB guarantees that each destination receives _________ of the packet.A) only one copyB) no copiesC) multiple copiesD) None of the choices are correct68.In ________, the multicast packet must reach only those networks that have active members for that particular group.A) RPFB) RPBC) RPMD) None of the choices are correct69._______ adds pruning and grafting to _______ to create a multicast shortest path tree that supports dynamic membership changes.A) RPM; RPBB) RPB; RPMC) RPF; RPMD) None of the choices are correct70.__________ is an implementation of multicast distance vector routing. It is a source-based routing protocol, based on RIP.A) MOSPFB) DVMRPC) CBTD) None of the choices are correct71.DVMRP is a ________ routing protocol, based on RIP.A) source-basedB) group-sharedC) destination-basedD) None of the choices are correct72.Pruning and grafting are strategies used in _______.A) RPFB) RPBC) RPMD) None of the choices are correct73.PIM-DM is used when the number of routers with attached members is ______ relative to the number of routers in the internet.A) largeB) smallC) moderateD) None of the choices are correct74.PIM-SM is used when the number of routers with attached members is ______ relative to the number of routers in the internet.A) largeB) smallC) moderateD) None of the choices are correct75.An IPv6 address is _________ bits long.A) 32B) 64C) 128D) 25676.An IPv6 address consists of ________ bytes (octets);A) 4B) 8C) 16D) None of the choices are correct77.In hexadecimal colon notation, a 128-bit address is divided into _______ sections, each _____ hexadecimal digits in length.A) 8; 2B) 8; 3C) 8; 4D) None of the choices are correct78.An IPv6 address can have up to __________ hexadecimal digits.A) 16B) 32C) 8D) None of the choices are correct79.In IPv6, the _______ field in the base header restricts the lifetime of a datagram.A) versionB) priorityC) hop limitD) None of the choices are correct80.The _________ in IPv6 is designed to provide special handling for a particular flow of data.A) flow labelB) next headerC) hop limitD) None of the choices are correct81.When two computers using IPv6 want to communicate but the packet must pass through an IPv4 region, which transition strategy should be used?A) tunnelingB) header translationC) either tunneling or header translationD) None of the choices are correct82.When the majority of the Internet has moved to the IPv6 but some still use IPv4, which transition strategy should be used?A) tunnelingB) header translationC) either tunneling or header translationD) None of the choices are correct83.The protocols __________________________ in version 4 are combined into one single protocol, ICMPv6.A) ARP and IGMPB) ICMP and IGMPC) ICMP, ARP, and IGMPD) None of the choices are correctDCBCB DCCBA DBCDC CABAC BCCAA BCAAB ABBAC DBABB BABCA BBBBA ABCAA CBAAC BABAD CACAB ACABC CCBCA ABC。