计算机网络题库

计算机网络题库c h a p t e r4(总15
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Chapter 4 The Network Layer
1．What is the name of a network-layer packet（）
A.message
B.segment
C.datagram
D.frame
2．What are the two most important network-layer functions in a datagram network
（）
A.forwarding & routing
B.forwarding & filtering
C.routing & detecting
D.routing & checking
3．When a packet arrives at a router’s input link, the router must move the packet to the appropriate output link, this action is called ____
（）
A.Forwarding
B.routing
C.cut through
D.filtering
4．The network layer must determine the path taken by packets as they flow from a sender to a receiver. This action is called____ （）
A.Forwarding
B.routing
C.cut through
D.examine
5．A router forwards a packet by examining the value of a field in the arriving packet’s header, and then using this value to index into the router’s forwarding table, this value is
（）
A.destination IP address
B.source IP address
C.destination MAC address
D.source MAC address
6．IP belongs to ____ layer （）
A.transport
work
C.data link
D.physical
7．Which layer provides host-to-host services? （）
A.transport
work
C.data link
D.physical
8．Which layer provides a connection service called virtual-circuit networks and a connectionless service called datagram networks? （）
A.transport
work
C.data link
D.physical
9．IPV4 has a ___ bit address （）
A.48
B.16
C.32
D.64
10．MAC address is ____ bits （）
A.48
B.16
C.32
D.64
11．The Internet’s network layer has three major component s, the first component is the IP protocol, the second component is the routing protocol, the final component
is____ （）
A.forwarding
B.address translation
C.check
D.ICMP
12．How many bits specify the IP protocol version in a datagram? （）
A. 1 bit
B. 2 bits
C. 4 bits
D.8 bits
13．Most IPV4 datagram do not contain option field, how many bytes a header has in a typical IP datagram? （）
A. 4 bytes
B.8 bytes
C.16 bytes
D.20 bytes
14．How many bits used in IP datagram express total length of the IP datagram? （）
A. 4 bits
B.8 bits
C.16 bits
D.20 bits
15．Data-grams are rarely larger than ____（）
A.1500 bytes
B.65535 bytes
C.500 bytes
D.1024 bytes
16．New version of IP----IPV6 does not allow fragment in ____
（）
A.Router
B.Host
C.Both of above
D.None of above
17．How does the TTL changed by one each time the datagram is processed by a router? （）
A.decrease
B.increase
C.no change
D.always 0
18．Which layer protocol is indicated by the value of protocol field in IP datagram? （）
A.application
B.transport
work
D.data link
19．IP option is dropped in the ____ header. （）
A.IPv6
B.IPv4
C.TCP
D.UDP
20．The data field in IP datagram can carry many types of data except ____. （）
A.TCP
B.UDP
C.ICMP
D.MAC
21．ICMP is used for____
（）
A.Reliable data transfer
B.Error reporting
C.Flow control
D.Congestion control
22．Suppose you receive an IP datagram from one link and check your forwarding table to determine the outgoing link, but this outgoing link has an MTU that is smaller than the length of IP datagram. Which technology will be used （）
A.resend
B.discard
C.fragment
D.none
23．The designer of IPv4 decided to put the job of datagram reassembly in____.
（）
A.r outer
B.s witch
C.h ub
D.e nd system
24．IP addressing assigns an address to /29, the network address for this network
is____.（）
A.
B.
C.
D.
25．If all data-grams arriving at the router from WAN have the same destination IP address, then how does the router know the internal host to which it should forward a given datagram? The trick is to use ____ table at router, and include port numbers as well as IP address in the table entries. （）
A.routing
B.forwarding
C.ARP
D.NAT translation
26．When running a Telnet, FTP, or HTTP session, you may have encountered an error message such as “Destination network un-reachable”, This message had its origin in ____. （）
A.IGMP
B.EGP
C.ICMP
D.BGP
27．The well-known ping program sends an (a) ____ type 8 code 0 message to the specified host. The destination hosts seeing the echo request, send back a type 0 code
0 ICMP echo reply. （）
A.ICMP
B.IGMP
C.TCP
D.UDP
28．Tracer-out is implemented with ____ messages. （）
A.IGMP
B.TCP
C.UDP
D.ICMP
29．The standard Tracer-out program actually sends sets of ____ packets with the same TTL. （）
A.one
B.two
C.three
D.four
30．IPv6 increases the size of the IP address from 32bit to ____ bit. （）
A.64
B.128
C.256
D.512
31．How many bytes are there in header of IPv6
（）
A.8
B.20
C.40
D.32
32．IPv6 does not allow for fragmentation and reassembly at inter-media ____.
（）
A.routers
B.switches
C.end system
D.hubs
33．From sender to receivers, all packets will take the same path, this is we use a
____ service. （）
A.datagram
B.VC
C.circuit
D.Ethernet
34．____ means moving packets from router’s input port to appropriate router output port
（）
A.forwarding
B.filtering
C.routing
D.switching
35．____ means determining route taken by packets from source to destination? （）
A.forwarding
B.filtering
C.routing
D.switching
36．A router works in ____ layer? （）
A.N etworking
B.D ata link
C.A pplication
D.P hysical
37．A switch works in ____ layer
（）
working
B.Data link
C.Application
D.Physical
38．Networking layer provides services between two ____.（）
A.Hosts
B.Processes
C.Applications
D.Machines
39．Link layer provides services between two ____. （）
A.Hosts
B.Processes
C.Applications
D.Machines
40．The internet’s network layer provides a single service----that is ____.（）
A.Reliable data transfer
B.Flow control
C.Congestion control
D.Best-effort-service
41．Datagram network provides network-layer____.（）
A.connectionless service
B.connection service
C.both of above
D.neither of A and B
42．VC network provides network-layer ____. （）
A.connectionless service
B.connection service
C.both of above
D.neither of A and B
43．In VC network, each packet carries ____. （）
A.VC identifier
B.destination host address
C.IP address
D.Mac address
44．A VC consists of three part, this three parts do not include____. （）
A.Path from source to destination
B.VC numbers, one number for each link along path
C.Entries in forwarding tables in routers along path
D.Destination address
45.In ____ networking, a series of packet may follow different paths and may arrive out of order? （）
A.Datagram
B.VC
C.TCP
D.None of above
46．The internet is a (an) ____ network
（）
A.Datagram
B.VC
C.Both of above
D.None of above
47．The four components of a router do not include____
（）
A.Input and output ports
B.Switch fabric
C.Routing processor
D.Switching processor
48．There are three kinds of switch fabric for a router normally, those three switch fabric do not includes____
（）
A.Switching via memory
B.Switching via a bus
C.Switching via an Interconnection-Network
D.Packet switching
49．Which of the following protocol is used for error reporting
（）
A.ICMP
B.TCP
C.IP
D.UDP
50．Which of the following is not a routing protocol
（）
A.TCP
B.RIP
C.OSPF
D.BGP
51．IPV4 has a ___ bits address? （）
A.32
B.64
C.16
D.128
52．IP address is identifier for ____. （）
A.Host
B.Router interface
C.Both of above
D.None of above
53．“/24”, where the /24 notation, so metimes known as a____. （）
A.Subnet mask
working address
C.Host address
D.None of above
54．Subnets with an 8-, ____-, and 24-bit subnet addresses were know as class A, B, and C networks respectively. （）
A.9
B.10
C.12
D.16
55．IPV6 has a ___ bits address
（）
A.32
B.64
C.16
D.128
56．____ means that IPv6 nodes also have a complete IPv4 implementation as well （）
A.Dual stack
B.Tunneling
C.Bridge connection
D.Forwarding
57．____ means that IPv6 carried as payload in IPv4 data-gram among IPv4 routers （）
A.Dual stack
B.Tunneling
C.Bridge connection
D.Forwarding
58．Typically a host is attached directly to one router, the ____ for the host. （）
A.Default router
B.Source router
C.Destination router
D.Core router
59．The default router of the source host is known as ____.（）
A.Default router
B.Source router
C.Destination router
D.Core router
60．The default router of the destination host is known as ____. （）
A.Default router
B.Source router
C.Destination router
D.Core router
61．A path between the source and destination that has beast cost is known as____. （）
A.Least cost path
B.Shortest path
rgest cost path
D.None of above
62．The path with the smallest number of links between the source and the destination is known as ____. （）
A.Least cost path
B.Shortest path
rgest cost path
D.None of above
63．Which of following about DV is not correct? （）
A.Iterative
B.Synchronous
C.Distributed
D.Self-terminating
64．Which of the following is not intra-AS routing protocol? （）
A.RIP
B.OSPF
C.IGRP
D.BGP
65．RIP is a kind of ____ algorithm. （）
A.DV
B.LS
C.Both of above
D.Neither of A and B
66．OSPF is a kind of ____ algorithm. （）
A.DV
B.LS
C.Both of above
D.Neither of A and B
67．The router in non-backbone areas and perform only intra-AS routing is known as ____. （）
A.Internal routers
B.Area border routers
C.Backbone routers
D.Boundary routers
68．____“summarize” distances to nets in own area, advertise to other Area Border routers. （）
A.Internal routers
B.Area border routers
C.Backbone routers
D.Boundary routers
69．____ runs OSPF routing limited to backbone. （）
A.Internal routers
B.Area border routers
C.Backbone routers
D.Boundary routers
70．____ connect to other AS’s. （）
A.Internal routers
B.Area border routers
C.Backbone routers
D.Boundary routers
71．Which of the following is an inter-autonomous system routing protocol? （）
A.RIP
B.OSPF
C.IGRP
D.BGP
72．____means sending a packet to all other nodes in the network. （）
A.Broadcast
B.Multicast
C.Any-cast
D.Uni-cast
73．A ____ packet is delivered to only a subset of network nodes. （）
A.Broadcast
B.Multicast
C.Any-cast
D.Uni-cast
74．Means that the switch must receive the entire packet before it can begin to transmit the first bit of the packet onto the outbound link. （）
A.store-and-forward transmission
B.FDM
C.End-to-end connection
D.TDM
75．Datagram networks and virtual-circuit networks differ in ____.（）
A.Datagram networks are circuit-switched networks, and virtual-circuit
networks are packet-switched networks.
B.Datagram networks are packet-switched networks, and virtual-circuit
networks are circuit-switched networks.
C.Datagram networks use destination addresses and virtual-circuit networks
use VC. Numbers to forward packets toward their destination.
D.Datagram networks use VC. Numbers and virtual-circuit networks use
destination addresses to forward packets toward their destination.
76．The Internet’s network layer is responsibl e for moving network-layer packets known as ____ from one host to another. （）
A.frame
B.datagram
C.segment
D.message
77．The protocols of various layers are called ____. （）
A.the protocol stack
B.TCP/IP
C.ISP
work protocol
78．The two important network-layer functions are ____. （）
A.multiplexing and de-multiplexing
B.routing and forwarding
C.lookup and forwarding
D.routing and IP addressing
79．The virtual circuit includes three identifiable phases but ____. （）
A.s etup
B.d ata transfer
C.f orwarding VC numbers
D.t eardown
80．There are some ways to accomplish the switching in the router, which one is not included
（）
A.switching via memory
B.switching via a bus
C.switching via hub
D.switching via an interconnection
81．In the router, the packet queues can form at ____.（）
A.institutional cache
B.switch fabric
C.input port
D.routing processor
82．In IPV4 datagram header, which field is to ensure that datagram do not circulate forever in the network? （）
A.type of service
B.time-to-live
C.header checksum
D.version
83．Suppose one IP datagram of 5,000 bytes (20 bytes of IP header) and it must be forwarded to a link with an MTU of 1,500 bytes, the offset and flag of the second fragment in header are ____. （）
A.185, 0
B.185, 1
C.370, 1
D.370,0
84．Given the IP address /20, its subnet address is ____. （）
A.
B.
C.
D.
85．If the subnet mask is , then how many bits indicate the host address? （）
A.20
B.24
C.12
D.16
86．In the following four fields, which is in IPV6 header but not in IPV4
（）
A.source address
B.destination address
C.version
D.flow label
87．One host is attached directly to one router, the router is ____.（）
A.NAT router
B.gateway router
C.first-hop router
D.interval router
88．The Internet’s network layer includes the following components but ____.（）
A.IP protocol
B.the Internet Message Control Protocol
C.Routing Protocol
D.Channel Partitioning Protocol
89．In the following protocols, which one is inter-AS routing protocol
（）
A.RIP
B.OSPF
C.BGP
D.ICMP
90．In the following four descriptions about autonomous system, which one is not correct
（）
A.An autonomous system is a collection of routers under the same
administrative and technical control.
B.All routers in an autonomous system run the same routing protocol.
C.The routing algorithm running within an autonomous system is called an
intra-AS routing protocol.
D.The routers that connect AS-s to each other are called default router. 91．In the loop of the Dijkstra’s algorithm, for node x, add y to N’, and update the cost of y’s neighbor v, then D(v) is ____. （）
A.c(x, v)
B.min{D(v), D(x)+c(x, v)}
C.min{D(v), D(y)+c(y, v)}
D.c(y, v)
92．Consider the data D is 001, if use even parity checking approach, the parity bit is ( ), if use odd parity checking approach, the parity bit is ____. （）
A.0, 0
B.0, 1
C.1, 0
D.1, 1
93．The ability to determine the interfaces to which a frame should be directed, and then directing the frame to those interfaces is ____.（）
A.filtering
B.forwarding
C.self-learning
D.optimal routing
94．Given that costs are assigned to various edge in the graph abstraction. In the following four descriptions, which one is not correct
（）
A.The shortest path is the path with smallest number of links between the
source and destination.
B.The least cost path is not always the shortest path.
C.If all edges have same cost, the least cost path must be the shortest path.
D.If all edges have various costs, the least cost path must not be the shortest
path.
95．Given the IP address /20, its broadcast address is ____. （）
A.
B.
C.
D.
96．If the subnet mask is , then how many bits indicate the host address? （）
A.20
B.12
C.24
D.16
97．In IPV6 datagram header, the field Next-header is equivalent to the field ( ) in IPV4. （）
A.upper-layer protocol
B.time-to-live
C.header checksum
D.version
98．For one host, its source router is also called ____. （）
A.NAT router
B.gateway router
C.first-hop router
D.interval router
99．In the following four descriptions about link-state (LS) algorithm, which one is not correct
（）
A.The LS algorithm must be aware of the cost of each link in the network.
B.The LS algorithm is a decentralized algorithm
C.The LS algorithm computes the least cost path between a source and
destination using complete global knowledge about the network
D.The calculation of LS algorithm can be run at one site or multiple sites 100．In the initialization of the Dijkstra’s algorithm, for node x, if y is not a ne ighbor of x, then D(y) is ____. （）
A.0
B. 1
C.∞
D.c(x, y)
101．In DV algorithm, when one node updates its distance vector, it must ____.
（）
A.send the updated routing table to its neighbors
B.send the updated routing table to all the nodes in the AS
C.send the updated routing table at random
D.do nothing
102．Now we had known IP address is /26, Please compute :
(1). Network address
(2). Broadcast address
(3). How many hosts are there in the network
(4). Fist host IP address
(5). Last host IP address
103．For the given topology of the network, use Dijstra’s shortest path algorithm to compute the shortest path from A to all network nodes. Give a shortest path tree and node A’s routing table.
104．The topology of a network shown as below. Using Link State routing algorithm to calculate the routing table in the node A. The vectors arrive to node C as bellow: B:( 4, 0, 8, 12, 6, 2 ); D:( 13, 10, 6, 0, 9, 10 ); E:( 7, 6, 3, 9, 0, 14 ). The delays measured from C to B, D, E are 4, 2, and 3 separately. Update router C’s route table please.。