计算机网络教程自顶向下方法选择题及答案 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 less than 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)4