chapter5 Network_Layer

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【Chapter4】Network Layer

4.6 Routing in the
Internet

Datagram format IPv4 addressing ICMP IPv6

RIP OSPF BGP
Network Layer 4-10
Network layer connection and connection-less service
Network Layer 4-12
VC implementation
A VC consists of:
1. 2.
3.
Path from source to destination VC numbers, one number for each link along path Entries in forwarding tables in routers along path
Datagram network provides network-layer
connectionless service VC network provides network-layer connection service Analogous to the transport-layer services, but:
intervening routers establish virtual connection

Routers get involved
Network and transport layer cnctn service: Network: between two hosts Transport: between two processes
Service: host-to-host No choice: network provides one or the other Implementation: in the core

计算机网络教程自顶向下方法选择题及答案

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 ofglobal 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。

计算机网络(第四版)课后习题(英文)+习题答案(中英文)

damaged is p, what is the mean number of transmissions required to send a frame? Assume that acknowledgements are never lost.(M) 假设某帧传到第 k 次才传输成功，起初 k-1 次传输皆尝试失败，概率为 pk-1 , 第 k 次传输成功，概率为(1-p) ，则发送一帧成功的平均传输次数为：
1. a.
Which of the OSI layers handles each of the following: (a) Dividing the transmitted bit stream into frames.
b. (b) Determining which route through the subnet to use.（E）把传输的比特流划分为帧——数据链路层决定使用哪条路径通过子网——网络层. 19. If the unit exchanged at the data link level is called a frame and the unit exchanged at the network level is called a packet, do frames encapsulate packets or do packets encapsulate frames? Explain your answer.（E）帧封装包。当一个包到达数据链路层时，整个数据包，包括包头、数据及全部内容，都用作帧的数据区。或者说，将整个包放进一个信封(帧)里面，( 如果能装入的话)。 21. List two ways in which the OSI reference model and the TCP/IP reference model are the same. Now list two ways in which they differ.（M）相似点：都是独立的协议栈的概念；层的功能也大体相似。不同点：OSI 更好的区分了服务、接口和协议的概念，因此比 TCP/IP 具有更好的隐藏性，能够比较容易的进行替换；OSI 是先有的模型的概念，然后再进行协议的实现，而 TCP/IP 是先有协议，然后建立描述该协议的模型；层次数量有差别； TCP/IP 没有会话层和表示层，OSI 不支持网络互连。OSI 在网络层支持无连接和面向连接的通信，而在传输层仅有面向连接的通信，而 TCP/IP 在网络层仅有一种通信模式（无连接），但在传输层支持两种模式。 22. What is the main difference between TCP and UDP?（E） TCP 是面向连接的，而 UDP 是一种数据报服务。

CCNA ENetwork Chapter 5

ENetwork Chapter 5 - CCNA Exploration: Network Posted by Space on Sunday, May 10, 20091In an IPv4 environment, what information is used by the router to forward data packets from one interface of a router to another?**destination network addresssource network addresssource MAC addresswell known port destination address2What information is added during encapsulation at OSI Layer 3?source and destination MACsource and destination application protocolsource and destination port number**source and destination IP address3In a connectionless system, which of the following is correct?The destination is contacted before a packet is sent.**The destination is not contacted before a packet is sent.The destination sends an acknowledgement to the source that indicates the packet was received. The destination sends an acknowledgement to the source that requests the next packet to be sent.4Which IP packet field will prevent endless loops?type-of-serviceidentificationflags**time-to-liveheader checksum5Which portion of the network layer address does a router use to forward packets?host portionbroadcast address**network portiongateway address6Refer to the exhibit. Using the network in the exhibit, what would be the default gateway address for host A in the 192.133.219.0 network?192.135.250.1192.31.7.1192.133.219.0**192.133.219.17If the default gateway is configured incorrectly on the host, what is the impact on communications? The host is unable to communicate on the local network.**The host can communicate with other hosts on the local network, but is unable to communicate with hosts on remote networks.The host can communicate with other hosts on remote networks, but is unable to communicate with hosts on the local network.There is no impact on communications.8What is the purpose of a default gateway?physically connects a computer to a networkprovides a permanent address to a computeridentifies the network to which a computer is connectedidentifies the logical address of a networked computer and uniquely identifies it to the rest of the network**identifies the device that allows local network computers to communicate with devices on other networks9What type of routing uses information that is manually entered into the routing table?dynamicinterior**staticstandard10When the destination network is not listed in the routing table of a Cisco router, what are two possible actions that the router might take? (Choose two.)The router sends an ARP request to determine the required next hop address.**The router discards the packet.The router forwards the packet toward the next hop indicated in the ARP table.The router forwards the packet to the interface indicated by the source address.**The router forwards the packet out the interface indicated by the default route entry.11What are the key factors to consider when grouping hosts into a common network? (Choose three.) gateways**purposephysical addressingsoftware version**geographic location**ownership12What is a component of a routing table entry?the MAC address of the interface of the routerthe destination Layer 4 port numberthe destination host address**the next-hop address13Which intermediary devices could be used to implement security between networks? (Choose two.) **routerhubswitch**firewallaccess pointbridge14What are three common problems with a large network? (Choose three.)too few broadcasts**performance degradation**security issueslimited management responsibility**host identificationprotocol compatibility15Refer to the exhibit. All devices shown in the exhibit have factory default settings. How many broadcast domains are represented in the topology that is shown?3**45781116Which three statements are true about routes and their use? (Choose three.)If no route to the destination network is found, the packet is returned to the previous router.**If the destination network is directly connected, the router forwards the packet to the destination host.If multiple network entries exist for the destination network, the most general route is used to forward the packet.**If no route exists for the destination network and a default route is present, the packet is forwarded to the next-hop router.**If the originating host has a default gateway configured, the packet for a remote network can beforwarded using that route.If a host does not have a route manually configured for the destination network, the host will drop the packet.17Refer to the exhibit. A network administrator is troubleshooting a connectivity problem and needs to determine the address that is used to forward network packets out the network. Using the netstat -r command, the administrator would identify which address as the address to which all hosts send packets that are destined for an outside network?10.10.10.26127.0.0.1**10.10.10.610.10.10.1224.0.0.018Refer to the exhibit. A network administrator notices that there are too many broadcasts on the network. What two steps can the network administrator take to resolve this problem? (Choose two.) **Replace S2 with a router.Place all servers on S1.Disable TCP/IP broadcasts.**Subnet the 192.168.0.0 /24 network.Disable all unused interfaces on the switches.19Refer to the exhibit. The network in the exhibit is fully operational. What two statements correctly describe the routing for the topology that is shown? (Choose two.)**192.168.0.2 is the next-hop address that is used by R3 to route a packet from the 10.0.0.0 network to the 172.16.0.0 network.10.0.0.1 is the next-hop address that is used by R1 to route a packet from the 192.168.12.0 network to the 10.0.0.0 network.192.168.0.1 is the next-hop address that is used by R1 to route a packet from the 192.168.12.0 network to the 172.16.0.0 network.172.16.0.1 is the next-hop address that is used by R3 to route a packet from the 10.0.0.0 to the 172.16.0.0 network.**192.168.0.1 is the next-hop address that is used by R2 to route a packet from the 172.16.0.0 network to the 192.168.12.0 network.192.168.0.2 is the next-hop address that is used by R2 to route a packet from the 172.16.0.0 network to the 192.168.12.0 network.20What two characteristics are commonly associated with dynamic routing protocols? (Choose two.) require no device configuration**provide routers with up-to-date routing tablesrequire less processing power than static routes require**consume bandwidth to exchange route informationprevent manual configuration and maintenance of the routing table21What statement describes the purpose of a default route?A host uses a default route to transfer data to another host on the same network segment.A host uses a default route to forward data to the local switch as the next hop to all destinations.A host uses a default route to identify the Layer 2 address of an end device on the local network. **A host uses a default route to transfer data to a host outside the local network when no other route to the destination exists.。

计算机网络-5_Transport_Layer(传输层协议)解析

network layer: logical
Household analogy:
12 kids sending letters to 12 kids
processes = kids
app messages = letters
relies on, enhances, network layer services
Computer Networking: A Top Down Approach Featuring the Internet,
2nd edition. Jim Kurose, Keith Ross Addison-Wesley, July 2002.
Transport Layer
3-1
Chapter 3: Transport Layer

32 bits source port # dest port #
other header fields
application data (message)
TCP/UDP segment format
Transport Layer 3-9
Connectionless demultiplexing
How demultiplexing works
host receives IP datagrams
each datagram has source IP address, destination IP address each datagram carries 1 transport-layer segment each segment has source, destination port number (recall: well-known port numbers for specific applications) host uses IP addresses & port numbers to direct segment to appropriate socket

计算机网络 Chapter_5_V6.01

datagram transferred by different link protocols over different links: e.g., Ethernet on first link, frame relay on intermediate links, 802.11 on last link each link protocol provides different services e.g., may or may not provide rdt over link
datagram controller datagram controller
sending host
datagram
receiving host
frame

sending side: encapsulates datagram in frame adds error checking bits, rdt, flow control, etc.
• Error detection not 100% reliable! • protocol may miss some errors, but rarely • larger EDC field yields better detection and correction
otherwise
Link Layer 5-11
transportation analogy:

trip from Princeton to Lausanne limo: Princeton to JFK plane: JFK to Geneva train: Geneva to Lausanne

tourist = datagram transport segment = communication link transportation mode = link layer protocol travel agent = routing algorithm

计算机网络课程介绍(Computer Networks)

IT行业发展状况

IT职业说明

以集中授课和课后学习,并配以实验教学和同学们网上查阅，多种方式来巩固所学知识点。考试方式分为
卷面答题方式的笔试考核网络项目方式的综合案例考核
笔试用于考核对面授理论、技术的掌握程度综合案例用于考核对网络整体的认识程度

教材：计算机网络 (谢希仁 Fifth Edition) 理论学时： 36(自动化) 39(信管网络) 实验学时： 14(自动化) 18(信管网络) 上课周次： 1-18(自动化) 3-18(信管网络) 实验地点：网络实验室
以教室、教师、知识为中心课程学习
OSI七层网络模型
TCP/IP协议
网络管理和应用
以太网络基础知识
网络布线和集成
学生运用教室中学到的知识
四不象
TCP/IP协议
网络布线和集成
网络管理和应用
OSI七层网络模型
以太网络基础知识
感受类型
听看听＋看听＋看＋做亲身实践
10
保持率
20% 30% 50% 90% 90% 20 30 40 50 60 70 80 90 100
教学过程给出特定教学内容和具有应用价值，具有轮廓清晰的任务说明；能将教学的理论知识和实践技能结合在一起；学生有独立工作机会，可以自行组织、安排自己的学习行为；有明确而具体的成果展示；学生自己克服处理在项目中出现的问题；具有一定难度，要求学生运用已有知识，在一定范围内学习新的知识技能，解决过去从未遇到过的实际问题；学习结束时，师生共同评价项目工作成果以及工作和学习的方法。
ห้องสมุดไป่ตู้
网络知识有“学懂容易掌握难”的特点.要随时

计算机网络英文题库(附答案)chapter5

Chapter 5 The Link Layer and Local Area Network1．A ( ) protocol is used to move a datagram over an individual link.A application-layerB transport-layerC network-layerD link-layer2．The units of data exchanged by a link-layer protocol are called ( ).A datagramsB framesC segmentsD messages3．Which of the following protocols is not a link-layer protocol? ( )A EthernetB PPPC HDLCD IP4．In the following four descriptions, which one is not correct? ( )A link-layer protocol has the node-to-node job of moving network-layer datagrams over a single link in the path.B The services provided by the link-layer protocols may be different.C A datagram must be handled by the same link-layer protocols on the different links in the path.D The actions taken by a link-layer protocol when sending and receiving frames include error detection, flow control and random access.5．Which of the following services can not offered by a link-layer protocol? ( )A congestion controlB Link AccessC Error controlD Framing6．( ) protocol serves to coordinate the frame transmissions of the many nodes when multiple nodes share a single broadcast link.A ARPB MACC ICMPD DNS7．In the following four descriptions about the adapter, which one is not correct? ( )A The adapter is also called as NIC.B The adapter is a semi-autonomous unit.C The main components of an adapter are bus interface and the link interface.D The adapter can provide all the link-layer services.8．Consider CRC error checking approach, the four bit generator G is 1011, and suppose that the data D is 10101010, then the value of R is( ).A 010B 100C 011D 1109．In the following four descriptions about random access protocol, which one is not correct? ( )A I n slotted ALOHA, nodes can transmit at random time.B I n pure ALOHA, if a frame experiences a collision, the node will immediately retransmit it with probability p.C T he maximum efficiency of a slotted ALOHA is higher than a pure ALOHA.D I n CSMA/CD, one node listens to the channel before transmitting.10．In the following descriptions about MAC address, which one is not correct? ( )A T he MAC address is the address of one node’s adapter.B N o two adapters have the same MAC address.C T he MAC address doesn’t change no matter where the adapter goes.D M AC address has a hierarchical structure.11．The ARP protocol can translate ( ) into ( ). ( )A h ost name, IP addressB h ost name, MAC addressC I P address, MAC addressD broadcast address, IP address12．The value of Preamble field in Ethernet frame structure is ( )A 10101010 10101010……10101010 11111111B 10101011 10101011……10101011 10101011C 10101010 10101010……10101010 10101011D 10101010 10101010……10101010 1010101013．There are four steps in DHCP, the DHCP server can complete ( ).A DHCP server discoveryB DHCP server offersC DHCP requestD DHCP response14．In CSMA/CD, the adapter waits some time and then returns to sensing the channel. In the following four times, which one is impossible? ( )A 0 bit timesB 512 bit timesC 1024 bit timesD 1028 bit times15．The most common Ethernet technologies are 10BaseT and 100BaseT. “10” and “100” indicate( ).A the maximum length between two adaptersB the minimum length between two adaptersC the transmission rate of the channelD the transmission rate of the node16．The principal components of PPP include but not( ).A framingB physical-control protocolC link-layer protocolD network-layer protocol17．In the following four options, which service can not be provided by switch? ( )A filteringB self-learningC forwardingD optimal routing18．In the following four services, which one was be required in PPP? ( )A packet framingB error detectionC error correctionD multiple types of link19．The ability to determine the interfaces to which a frame should be directed, and then directing the frame to those interfaces is( ).A filteringB forwardingC self-learningD optimal routing20．In ( ) transmission(s), the nodes at both ends of a link may transmit packets at the same time.A full-duplexB half-duplexC single-duplexD both full-duplex and half-duplex21．Consider the data D is 01110010001, if use even parity checking approach, the parity bit is( ① ), if use odd parity checking approach, the parity bit is( ② ). ( )A ①0 ②1B ①0 ②0C ①1 ②1D ①1 ②022．In the following four descriptions about parity checks, which one is correct? ( )A Single-bit parity can detect all errors.B Single-bit parity can correct one errors.C Two-dimensional parity not only can detect a single bit error, but also can correct that error.D Two-dimensional parity not only can detect any combination of two errors, but also can correct them.23．MAC address is ( ) bits long.A 32B 48C 128D 6424．Wireless LAN using protocol ( ).A IEEE 802.3B IEEE 802.4C IEEE 802.5D IEEE 802.1125．The following protocols are belonging to multiple access protocols except for ( ).A channel partitioning protocolsB routing protocolsC random access protocolsD taking-turns protocols26．Which of the following is not belonging to channel partitioning protocols? ( )A CSMAB FDMC CDMAD TDM27．In the following four descriptions about CSMA/CD, which one is not correct? ( )A A node listens to the channel before transmitting.B If someone else begins talking at the same time, stop talking.C A transmitting node listens to the channel while it is transmitting.D With CSMA/CD, the collisions can be avoided completely.28．( ) provides a mechanism for nodes to translate IP addresses to link-layer address.A IPB ARPC RARPD DNS29．A MAC address is a ( )address.A physical-layerB application-layerC link-layerD network-layer30．Which of the following is correct? ( )A No two adapters have the same MAC address.B MAC broadcast address is FF-FF-FF-FF-FF-FF.C A portable computer with an Ethernet card always has the same MAC address, no matter where the computer goes.D All of the above31．In the following four descriptions, which one is not correct? ( )A ARP resolves an IP address to a MAC address.B DNS resolves hostnames to IP addresses.C DNS resolves hostnames for hosts anywhere in the Internet.D ARP resolves IP addresses for nodes anywhere in the Internet.32．In the LAN, ( )protocol dynamically assign IP addresses to hosts.A DNSB ARPC DHCPD IP33．DHCP protocol is a four-step process: ①DHCP request. ②DHCP ACK. ③DHCP server discovery. ④DHCP server offer(s). The correct sequence is ( )A ①②③④B ③②①④C ③④①②D ①④③②34．In the Ethernet frame structure, the CRC field is ( )bytes.A 2B 4C 8D 3235．In the Ethernet frame structure, the Data field carries the ( ).A IP datagramB segmentC frameD message36．In the following four descriptions, which one is not correct? ( )A Ethernet uses baseband transmission.B All of the Ethernet technologies provide connection-oriented reliable service to the network layer.C The Ethernet 10Base2 technology uses a thin coaxial cable for the bus.D The Ethernet 10BaseT technology uses a star topology.37．Ethernet’s multiple access protocol is ( ).A CDMAB CSMA/CDC slotted ALOHAD token-passing protocol38．In the following four descriptions about CSMA/CD, which one is not correct? ( )A An adapter may begin to transmit at any time.B An adapter never transmits a frame when it senses that some other adapter is transmitting.C A transmitting adapter aborts its transmission as soon as it detects that another adapter is also transmitting.D An adapter retransmits when it detects a collision.39．Which of the following descriptions about CSMA/CD is correct? ( )A No slots are used.B It uses carrier sensing.C It uses collision detection.D All of the above.40．The Ethernet 10BaseT technology uses( )as its physical media.A fiber opticsB twisted-pair copper wireC coaxial cableD satellite radio channel41．For 10BaseT, the maximum length of the connection between an adapter and the hub is ( )meters.A 100B 200C 500D 1042．A ( )is a physical-layer device that acts on individual bits rather than on frames.A switchB hubC routerD gateway43．A hub is a ( )device that acts on individual bits rather than on frames.A physical-layerB link-layerC network-layerD ransport-layer44．A switch is a( )device that acts on frame.A physical-layerB link-layerC network-layerD transport-layer45．In the following four descriptions, which one is not correct? ( )A Switches can interconnect different LAN technologies.B Hubs can interconnect different LAN technologies.C There is no limit to how large a LAN can be when switches are used to interconnect LAN segments.D There is restriction on the maximum allowable number of nodes in a collision domain when hubs are used to interconnect LAN segments.46．The ability to determine whether a frame should be forwarded to some interface or should just be dropped is ( ).A f ilteringB f orwardingC s elf-learningD o ptimal routing47．Which of the following devices is not a plug and play device? ( )A hubB routerC switchD repeater48．Which of the following devices is not cut-through device? ( )A hubB routerC switchD repeater49．In the following four descriptions, which one is not correct? ( )A Switches do not offer any protection against broadcast storms.B Routers provide firewall protection against layer-2 broadcast storms.C Both switches and routers are plug and play devices.D A router is a layer-3 packet switch, a switch is a layer-2 packet switch. 50．Which device has the same collision domain? ( )A HubB SwitchC RouterD Bridge51．IEEE802.2 protocol belong to ( )layerA networkB MACC LLCD physical52．IEEE802.11 protocol defines ( )rules.A Ethernet BusB wireless WANC wireless LAND Token Bus53．In data link-layer, which protocol is used to share bandwidth? ( )A SMTPB ICMPC ARPD CSMA/CD54．When two or more nodes on the LAN segments transmit at the same time, there will be a collision and all of the transmitting nodes well enter exponential back-off, that is all of the LAN segments belong to the same( ).A collision domainB switchC bridgeD hub55．( )allows different nodes to transmit simultaneously and yet have their respective receivers correctly receive a sender’s encoded data bits.A CDMAB CSMAC CSMA/CDD CSMA/CA56．Because there are both network-layer addresses (for example, Internet IP addresses) and link-layer addresses (that is, LAN addresses), there is a need totranslate between them. For the Internet, this is the job of ( ).A RIPB OSPFC ARPD IP57．PPP defines a special control escape byte, ( ). If the flag sequence, 01111110 appears anywhere in the frame, except in the flag field, PPP precedes that instance of the flag pattern with the control escape byte.A 01111110B 01111101C 10011001D 1011111058．The device ( ) can isolate collision domains for each of the LAN segment.A modemB switchC hubD NIC59．In the following four descriptions about PPP, which one is not correct? ( )A PPP is required to detect and correct errors.B PPP is not required to deliver frames to the link receiver in the same order in which they were sent by the link sender.C PPP need only operate over links that have a single sender and a single receiver.D PPP is not required to provide flow control.60．In the PPP data frame, the( ) field tells the PPP receivers the upper-layer protocol to which the received encapsulated data belongs.A flagB controlC protocolD checksum61．PPP’s link-control protocols (LCP) accomplish ( ).A initializing the PPP linkB maintaining the PPP linkC taking down the PPP linkD all of the above62．The PPP link always begins in the ( ) state and ends in the ( ) state. ( )A open, terminatingB open, deadC dead, deadD dead, terminating63．For( ) links that have a single sender at one end of the link and a single receiver at the other end of the link.A point-to-pointB broadcastC multicastD all of the above64．With ( )transmission, the nodes at both ends of a link may transmit packets at the same time.A half-duplexB full-duplexC simplex(单工)D synchronous65．With ( ) transmission, a node can not both transmit and receive at the same time.A half-duplexB full-duplexC simplex(单工)D synchronous66．Which of the following functions can’t be implemented in the NIC? ( )A encapsulation and decapsulationB error detectionC multiple access protocolD routing67．Which of the following four descriptions is wrong? ( )A The bus interface of an adapter is responsible for communication with the adapter’s parent node.B The link interface of an adapter is responsible for implementing the link-layer protocol.C The bus interface may provide error detection, random access functions.D The main components of an adapter are the bus interface and the link interface. 68．For odd parity schemes, which of the following is correct? ( )A 011010001B 111000110C 110101110D 00011011069．( )divides time into time frames and further divides each time frame into N time slots.A FDMB TMDC CDMAD CSMA70．With CDMA, each node is assigned a different ( )A codeB time slotC frequencyD link71．Which of the following four descriptions about random access protocol is not correct? ( )A A transmission node transmits at the full rate of the channelB When a collision happens, each node involved in the collision retransmits at once.C Both slotted ALOHA and CSMA/CD are random access protocols.D With random access protocol, there may be empty slots.72．PPP defines a special control escape byte 01111101. If the data is b1b201111110b3b4b5, the value is( )after byte stuffing.A b1b20111110101111110b3b4b5B b1b20111111001111101b3b4b5C b5b4b30111111001111101b2b1D b5b4b30111110101111110b2b173．MAC address is in ( ) of the computer.A RAMB NICC hard diskD cache74．Which of the following is wrong? ( )A ARP table is configured by a system administratorB ARP table is built automaticallyC ARP table is dynamicD ARP table maps IP addresses to MAC addresses75．NIC works in ( )layer.A physicalB linkC networkD transport76．In LAN, if UTP is used, the common connector is( ).A AUIB BNCC RJ-45D NNI77．The modem’s function(s) is(are) ( ).A translates digital signal into analog signalB translates analog signal into digital signalC both translates analog signal into digital signal and translates digital signal into analog signalD translates one kind of digital signal into another digital signal78．( )defines Token-Ring protocol.A IEEE 802.3B IEEE 802.4C IEEE 802.5D IEEE 802.279．( )defines Token-Bus protocol.A IEEE 802.3B IEEE 802.4C IEEE 802.5D IEEE 802.280．( ) defines CSMA/CD protocol.A IEEE 802.3B IEEE 802.4C IEEE 802.5D IEEE 802.281．The computer network that concentrated in a geographical area, such as in a building or on a university campus, is ( )A a LANB a MANC a WAND the Internet82．The MAC address is ( ) bits long.A 32B 48C 128D 25683．Which of the following four descriptions about MAC addresses is wrong? ( )A a MAC address is burned into the adapter’s ROMB No two adapters have the same addressC An adapter’s MAC address is dynamicD A MAC address is a link-layer address84．Which of the following four descriptions about DHCP is correct? ( )A DHCP is C/S architectureB DHCP uses TCP as its underlying transport protocolC The IP address offered by a DHCP server is valid foreverD The DHCP server will offer the same IP address to a host when the host requests an IP address85．The ( )field permits Ethernet to multiplex network-layer protocols.A preambleB typeC CRCD destination MAC address86．For 10BaseT, the maximum length of the connection between an adapter and the hub is ( ) meters.A 50B 100C 200D 50087．An entry in the switch table contains the following information excepts for ( )A the MAC address of a nodeB the switch interface that leads towards the nodeC the time at which the entry for the node was placed in the tableD the IP address of a node88．Consider the 4-bit generator , G is 1001, and suppose that D has the value 101110000. What is the value of R?89．Consider the following graph of the network. Suppose Host A will send a datagram to Host B, Host A run OICQ on port 4000, Host B run OICQ on port 8000. All of ARP tables are up to date. Enumerate all the steps when message “Hello” is sent from host A to host B.。

layer加载例子

layer加载例子Layer是一种常用的深度学习框架，可以用来构建和训练神经网络模型。

通过使用不同类型的layer，可以实现各种不同的功能。

1. Input Layer（输入层）：输入层是神经网络模型的第一层，负责接收输入数据，通常是一个向量或矩阵。

例如，在图像分类任务中，输入层可以接收图像的像素值作为输入。

2. Convolutional Layer（卷积层）：卷积层是用来提取输入数据中的特征的。

它通过应用一系列滤波器（也称为卷积核）来扫描输入数据，生成一组特征映射。

每个特征映射代表输入数据中的一种不同的特征。

3. Activation Layer（激活层）：激活层是用来引入非线性性质的。

它将卷积层的输出作为输入，并将其传递到一个激活函数中，以生成非线性的特征表示。

常用的激活函数包括ReLU、Sigmoid和Tanh 等。

4. Pooling Layer（池化层）：池化层用来降低特征映射的维度，并减少计算量。

它通过将每个特征映射划分为不重叠的区域，并对每个区域进行汇总操作（如最大值池化或平均值池化）来实现。

池化层可以帮助模型对输入数据的平移和缩放不变性。

5. Fully Connected Layer（全连接层）：全连接层将前一层的所有神经元与当前层的所有神经元相连接。

它负责组合上一层的特征，并生成最终的输出。

在图像分类任务中，全连接层通常用于将卷积层的特征映射转换为类别概率。

6. Dropout Layer（随机失活层）：随机失活层用于减少模型的过拟合。

它通过在训练过程中随机将一些神经元的输出置为0来实现。

这样可以强迫模型学习到更加鲁棒的特征表示。

7. Batch Normalization Layer（批归一化层）：批归一化层用于加速模型的训练，并提高模型的鲁棒性。

它通过在每个小批量的数据上进行归一化操作，使得输入数据的分布更加稳定。

这样可以减少模型对输入数据分布的依赖，提高模型的泛化能力。

川大软院计网选择题答案Chapter4(含答案)

CHAPTER 4: NETWORK LAYER1.Which of the following groups belongs to network layer protocol? _____D____A.IP, TCP and UDPB.ARP, IP, and UDPC.FTP, IMAP and IPD.ICMP, BGP, and RIP2.The 3-PDU is named as ____C_____A.messageB.packetC.datagramD.segment3.In a datagram network, the forwarding decision is based on the value of the____B field in the packet header.A.source addressB.destination addressbelD.None of the choices are4.HOL blocking happens on ____A_____A.input portB.output portC.switching fabricsD.all of above5.If no free buffers in router, the arriving packets will be: AA.droppedB.queuedC.returnedD.marked6.During normal IP packet forwarding at a router, which of the following packetfields are updated? ____C____A.Source IP addressB.Destination IP addressC.ChecksumD.Destination port number7.Which of the following IP address doesn’t belong to the 202.115.32.0/25 network?______D___A.202.115.32.1B.202.115.32.11C.202.115.32.120D.202.115.32.1298.You are given an IP network of 192.168.5.0 and told that you need to separatethis network into sub networks that can support a maximum of 30 hosts per subnet.This will help alleviate congestion on the network. What subnet mask can you use to create the subnets necessary to meet the given criteria? ___C______A.255.255.255.0B.255.255.255.128C.255.255.255.224D.255.255.255.2409.An IP datagram of 1500 bytes (20 byte of IP header plus 1480 bytes of IP payload)arrives at a router and must be forwarded to a link with an MTU of 500 bytes.Thus the router has to fragment the datagram. To the last fragment, the value of offset should be _____D____A.1440B.1000C.186D.18010.IP is a ____C_____ protocol.A.connection-oriented unreliableB.connection-oriented reliableC.connectionless unreliableD.connectionless reliable11.Which ICMP message type is the basis for the Traceroute utility?BA.Echo RequestB.TTL expiredC.Host UnreachableD.Fragment Reassembly Time Exceed12.Routers in the path are not allowed to _________________B__________.A.fragment the packet they receiveB.change source or destination addressC.decapsulate the packetD.All of the choices are correct13.____B_____ allows a site to use a set of private addresses for internalcommunication and a set of global Internet addresses for communication with the rest of the world.A.DHCPB.NATC.ICMPD.None of the choices are correct14.How many bits are there in IPv6 ? ______C___A.32B.64C.128D.25615.In CIDR notation, which of the following networks contains host 192.168.14.2?CA.192.168.10.0/22B.192.168.11.0/21C.192.168.12.0/23D.192.168.13.0/2416.What is the limited broadcast address corresponding to the node with thefollowing IP address: 131.15.46.59?DA.131.15.46.255B.131.15.255.255C.255.255.255.255D.None of the above17.In classful IP addressing, how many network bits does 125.140.128.16 have?AA.8B.16C.24D.3218.What is the broadcast IP address for 193.140.141.128 / 26 ?DA.193.140.141.128B.193.140.141.127C.255.255.255.63D.193.140.141.19119.What’s a network? From IP address perspective they can physically reach eachother without intervening router and the device interfaces with: CA.same IP addressB.same TCP port #C.same network part of IP addressD.same host part of IP address20.The Internet’s network layer has three major components, the first component isthe IP protocol, the second component is the routing protocol, the final component is____.DA.forwardingB.address translationC.checkD.ICMP21.IP addressing assigns an address to 223.10.198.250/29, the network address forthis network is____.A（）A.223.10.198.248B.223.10.198.250C.223.10.198.0D.223.10.0.022.There are two 16-bit integers: 1110 0110 0110 0110, 1101 0101 0101 0101. Theirchecksum isA____.A.0100010001000011B.1011101110111100C.1111111111111111D.100000000000000023.The use of hierarchy in routing tables can __A______ the size of the routingtables.A.reduceB.increaseC.neither reduce nor increaseD.None of the choices are correct24.Which of the following protocol doesn’t belong to intra-AS routing protocol?_____B____A.RIPB.BGPC.OSPFD.IRAP25.Which of the following protocol belongs to intra-AS routing protocol?______A___A.RIPB.BGPC.DV (Distance Vector)D.LS (Link State)26.In OSPF network, a ____B_____ belongs to both an area and the backbone.A.internal routerB.area border routerC.boundary routerD.backbone router27._A___ is an inter-domain routing protocol using path vector routing.A.BGPB.RIPC.OSPFD.None of the choices are correct28.RIP uses the services of ___C____.A.TCPB.IPC.UDPD.None of the choices are correct29.The Routing Information Protocol (RIP) is an intra-domain routing based on_______A__ routing.A.distance vectorB.link stateC.path vectorD.all of the above30.Which of the following algorithm has the so called count-to-infinity problem?CA.Flooding algorithmB.Link-state algorithmC.Distance vector algorithmD.None of the above。

DUT-Chapter5(大连理工软件学院计算机网络课件)

widely used in practice (Ethernet, 802.11 WiFi, ATM)
5: DataLink Layer
5-13
5: DataLink Layer
5-14
CRC Example
Want: D.2r XOR R = nG
equivalently:
equivalently:
5.1 Introduction and

services 5.2 Error detection and correction 5.3Multiple access protocols 5.4 Link-layer Addressing 5.5 Ethernet
5.6 Link-layer switches 5.7 PPP 5.8 Link Virtualization:
5.6 Link-layer switches 5.7 PPP 5.8 Link virtualization:
ATM, MPLS
5: DataLink Layer
5-2
Link Layer: Introduction
Some terminology:
hosts and routers are nodes communication channels that
instantiation and implementation of various link
layer technologies
5: DataLink Layer
5-1
Link Layer
5.1 Introduction and

services 5.2 Error detection and correction 5.3Multiple access protocols 5.4 Link-layer Addressing 5.5 Ethernet

计算机网络_中英文名词术语对照表

Advanced Data Communication Control
Procedure
High-level Data Link Control
Point-to-Point Protocol
Link Control Protocol
Network Control Protocol
缩写 CRC
PAR ARQ
LAN
Metropolitan Area Networks
MAN
Wide Area Networks
WAN
对应的中文名称开放系统互连传输控制协议国际互联网络协议参考模型物理层数据链路层网络层传输层会话层表示层应用层异步传输模式国际电讯联盟国际标准化组织
美国国家标准学会（美国）国家标准与与技术学会
Physical layer coding violations
Hamming Code
Hamming Distance
Even
Odd
Parity bit
Codeword
Finite state machine models
Petri net models
Synchronous Data Link Control
缩写 MAC CSMA CSMA/CD MACA
TDR
FE FDDI GE LLC
VLAN NIC
对应的中文名称多路访问协议介质访问控制纯 ALOHA 协议分槽 ALOHA 协议载波侦听多路访问带冲突检测的载波侦听多路访问避免冲突的多路访问冲突窗口位图协议二进制倒计数适应树搜索协议时域反射计曼侧斯特编码差分曼侧斯特编码以太帧格式二进制指数回退算法快速以太网（100M）光纤分布式数据接口吉比特以太网（1G，1000M）逻辑链路控制透明网桥交换机逆向地址学习泛洪/广播转发丢弃过滤冲突域生成树虚拟局域网网络接口卡（网卡）存储转发交换直通交换无分片交换

计算机网络英文题库(附答案)chapter5

Chapter 5 The Link Layer and Local Area Network1．A ( ) protocol is used to move a datagram over an individual link.A application-layerB transport-layerC network-layerD link-layer2．The units of data exchanged by a link-layer protocol are called ( ).A datagramsB framesC segmentsD messages3．Which of the following protocols is not a link-layer protocol? ( )A EthernetB PPPC HDLCD IP4．In the following four descriptions, which one is not correct? ( )A link-layer protocol has the node-to-node job of moving network-layer datagrams over a single link in the path.B The services provided by the link-layer protocols may be different.C A datagram must be handled by the same link-layer protocols on the different links in the path.D The actions taken by a link-layer protocol when sending and receiving frames include error detection, flow control and random access.5．Which of the following services can not offered by a link-layer protocol? ( )A congestion controlB Link AccessC Error controlD Framing6．( ) protocol serves to coordinate the frame transmissions of the many nodes when multiple nodes share a single broadcast link.A ARPB MACC ICMPD DNS7．In the following four descriptions about the adapter, which one is not correct? ( )A The adapter is also called as NIC.B The adapter is a semi-autonomous unit.C The main components of an adapter are bus interface and the link interface.D The adapter can provide all the link-layer services.8．Consider CRC error checking approach, the four bit generator G is 1011, and suppose that the data D is 10101010, then the value of R is( ).A 010B 100C 011D 1109．In the following four descriptions about random access protocol, which one is not correct? ( )A I n slotted ALOHA, nodes can transmit at random time.B I n pure ALOHA, if a frame experiences a collision, the node will immediately retransmit it with probability p.C T he maximum efficiency of a slotted ALOHA is higher than a pure ALOHA.D I n CSMA/CD, one node listens to the channel before transmitting.10．In the following descriptions about MAC address, which one is not correct? ( )A T he MAC address is the address of one node’s adapter.B N o two adapters have the same MAC address.C T he MAC address doesn’t change no matter where the adapter goes.D M AC address has a hierarchical structure.11．The ARP protocol can translate ( ) into ( ). ( )A h ost name, IP addressB h ost name, MAC addressC I P address, MAC addressD broadcast address, IP address12．The value of Preamble field in Ethernet frame structure is ( )A 10101010 10101010……10101010 11111111B 10101011 10101011……10101011 10101011C 10101010 10101010……10101010 10101011D 10101010 10101010……10101010 1010101013．There are four steps in DHCP, the DHCP server can complete ( ).A DHCP server discoveryB DHCP server offersC DHCP requestD DHCP response14．In CSMA/CD, the adapter waits some time and then returns to sensing the channel. In the following four times, which one is impossible? ( )A 0 bit timesB 512 bit timesC 1024 bit timesD 1028 bit times15．The most common Ethernet technologies are 10BaseT and 100BaseT. “10” and “100” indicate( ).A the maximum length between two adaptersB the minimum length between two adaptersC the transmission rate of the channelD the transmission rate of the node16．The principal components of PPP include but not( ).A framingB physical-control protocolC link-layer protocolD network-layer protocol17．In the following four options, which service can not be provided by switch? ( )A filteringB self-learningC forwardingD optimal routing18．In the following four services, which one was be required in PPP? ( )A packet framingB error detectionC error correctionD multiple types of link19．The ability to determine the interfaces to which a frame should be directed, and then directing the frame to those interfaces is( ).A filteringB forwardingC self-learningD optimal routing20．In ( ) transmission(s), the nodes at both ends of a link may transmit packets at the same time.A full-duplexB half-duplexC single-duplexD both full-duplex and half-duplex21．Consider the data D is 01110010001, if use even parity checking approach, the parity bit is( ① ), if use odd parity checking approach, the parity bit is( ② ). ( )A ①0 ②1B ①0 ②0C ①1 ②1D ①1 ②022．In the following four descriptions about parity checks, which one is correct? ( )A Single-bit parity can detect all errors.B Single-bit parity can correct one errors.C Two-dimensional parity not only can detect a single bit error, but also can correct that error.D Two-dimensional parity not only can detect any combination of two errors, but also can correct them.23．MAC address is ( ) bits long.A 32B 48C 128D 6424．Wireless LAN using protocol ( ).A IEEE 802.3B IEEE 802.4C IEEE 802.5D IEEE 802.1125．The following protocols are belonging to multiple access protocols except for ( ).A channel partitioning protocolsB routing protocolsC random access protocolsD taking-turns protocols26．Which of the following is not belonging to channel partitioning protocols? ( )A CSMAB FDMC CDMAD TDM27．In the following four descriptions about CSMA/CD, which one is not correct? ( )A A node listens to the channel before transmitting.B If someone else begins talking at the same time, stop talking.C A transmitting node listens to the channel while it is transmitting.D With CSMA/CD, the collisions can be avoided completely.28．( ) provides a mechanism for nodes to translate IP addresses to link-layer address.A IPB ARPC RARPD DNS29．A MAC address is a ( )address.A physical-layerB application-layerC link-layerD network-layer30．Which of the following is correct? ( )A No two adapters have the same MAC address.B MAC broadcast address is FF-FF-FF-FF-FF-FF.C A portable computer with an Ethernet card always has the same MAC address, no matter where the computer goes.D All of the above31．In the following four descriptions, which one is not correct? ( )A ARP resolves an IP address to a MAC address.B DNS resolves hostnames to IP addresses.C DNS resolves hostnames for hosts anywhere in the Internet.D ARP resolves IP addresses for nodes anywhere in the Internet.32．In the LAN, ( )protocol dynamically assign IP addresses to hosts.A DNSB ARPC DHCPD IP33．DHCP protocol is a four-step process: ①DHCP request. ②DHCP ACK. ③DHCP server discovery. ④DHCP server offer(s). The correct sequence is ( )A ①②③④B ③②①④C ③④①②D ①④③②34．In the Ethernet frame structure, the CRC field is ( )bytes.A 2B 4C 8D 3235．In the Ethernet frame structure, the Data field carries the ( ).A IP datagramB segmentC frameD message36．In the following four descriptions, which one is not correct? ( )A Ethernet uses baseband transmission.B All of the Ethernet technologies provide connection-oriented reliable service to the network layer.C The Ethernet 10Base2 technology uses a thin coaxial cable for the bus.D The Ethernet 10BaseT technology uses a star topology.37．Ethernet’s multiple access protocol is ( ).A CDMAB CSMA/CDC slotted ALOHAD token-passing protocol38．In the following four descriptions about CSMA/CD, which one is not correct? ( )A An adapter may begin to transmit at any time.B An adapter never transmits a frame when it senses that some other adapter is transmitting.C A transmitting adapter aborts its transmission as soon as it detects that another adapter is also transmitting.D An adapter retransmits when it detects a collision.39．Which of the following descriptions about CSMA/CD is correct? ( )A No slots are used.B It uses carrier sensing.C It uses collision detection.D All of the above.40．The Ethernet 10BaseT technology uses( )as its physical media.A fiber opticsB twisted-pair copper wireC coaxial cableD satellite radio channel41．For 10BaseT, the maximum length of the connection between an adapter and the hub is ( )meters.A 100B 200C 500D 1042．A ( )is a physical-layer device that acts on individual bits rather than on frames.A switchB hubC routerD gateway43．A hub is a ( )device that acts on individual bits rather than on frames.A physical-layerB link-layerC network-layerD ransport-layer44．A switch is a( )device that acts on frame.A physical-layerB link-layerC network-layerD transport-layer45．In the following four descriptions, which one is not correct? ( )A Switches can interconnect different LAN technologies.B Hubs can interconnect different LAN technologies.C There is no limit to how large a LAN can be when switches are used to interconnect LAN segments.D There is restriction on the maximum allowable number of nodes in a collision domain when hubs are used to interconnect LAN segments.46．The ability to determine whether a frame should be forwarded to some interface or should just be dropped is ( ).A f ilteringB f orwardingC s elf-learningD o ptimal routing47．Which of the following devices is not a plug and play device? ( )A hubB routerC switchD repeater48．Which of the following devices is not cut-through device? ( )A hubB routerC switchD repeater49．In the following four descriptions, which one is not correct? ( )A Switches do not offer any protection against broadcast storms.B Routers provide firewall protection against layer-2 broadcast storms.C Both switches and routers are plug and play devices.D A router is a layer-3 packet switch, a switch is a layer-2 packet switch. 50．Which device has the same collision domain? ( )A HubB SwitchC RouterD Bridge51．IEEE802.2 protocol belong to ( )layerA networkB MACC LLCD physical52．IEEE802.11 protocol defines ( )rules.A Ethernet BusB wireless WANC wireless LAND Token Bus53．In data link-layer, which protocol is used to share bandwidth? ( )A SMTPB ICMPC ARPD CSMA/CD54．When two or more nodes on the LAN segments transmit at the same time, there will be a collision and all of the transmitting nodes well enter exponential back-off, that is all of the LAN segments belong to the same( ).A collision domainB switchC bridgeD hub55．( )allows different nodes to transmit simultaneously and yet have their respective receivers correctly receive a sender’s encoded data bits.A CDMAB CSMAC CSMA/CDD CSMA/CA56．Because there are both network-layer addresses (for example, Internet IPaddresses) and link-layer addresses (that is, LAN addresses), there is a need to translate between them. For the Internet, this is the job of ( ).A RIPB OSPFC ARPD IP57．PPP defines a special control escape byte, ( ). If the flag sequence, 01111110 appears anywhere in the frame, except in the flag field, PPP precedes that instance of the flag pattern with the control escape byte.A 01111110B 01111101C 10011001D 1011111058．The device ( ) can isolate collision domains for each of the LAN segment.A modemB switchC hubD NIC59．In the following four descriptions about PPP, which one is not correct? ( )A PPP is required to detect and correct errors.B PPP is not required to deliver frames to the link receiver in the same order in which they were sent by the link sender.C PPP need only operate over links that have a single sender and a single receiver.D PPP is not required to provide flow control.60．In the PPP data frame, the( ) field tells the PPP receivers the upper-layer protocol to which the received encapsulated data belongs.A flagB controlC protocolD checksum61．PPP’s link-control protocols (LCP) accomplish ( ).A initializing the PPP linkB maintaining the PPP linkC taking down the PPP linkD all of the above62．The PPP link always begins in the ( ) state and ends in the ( ) state. ( )A open, terminatingB open, deadC dead, deadD dead, terminating63．For( ) links that have a single sender at one end of the link and a single receiver at the other end of the link.A point-to-pointB broadcastC multicastD all of the above64．With ( )transmission, the nodes at both ends of a link may transmit packets at the same time.A half-duplexB full-duplexC simplex(单工)D synchronous65．With ( ) transmission, a node can not both transmit and receive at the same time.A half-duplexB full-duplexC simplex(单工)D synchronous66．Which of the following functions can’t be implemented in the NIC? ( )A encapsulation and decapsulationB error detectionC multiple access protocolD routing67．Which of the following four descriptions is wrong? ( )A The bus interface of an adapter is responsible for communication with the adapter’s parent node.B The link interface of an adapter is responsible for implementing the link-layer protocol.C The bus interface may provide error detection, random access functions.D The main components of an adapter are the bus interface and the link interface. 68．For odd parity schemes, which of the following is correct? ( )A 011010001B 111000110C 110101110D 00011011069．( )divides time into time frames and further divides each time frame into N time slots.A FDMB TMDC CDMAD CSMA70．With CDMA, each node is assigned a different ( )A codeB time slotC frequencyD link71．Which of the following four descriptions about random access protocol is not correct? ( )A A transmission node transmits at the full rate of the channelB When a collision happens, each node involved in the collision retransmits at once.C Both slotted ALOHA and CSMA/CD are random access protocols.D With random access protocol, there may be empty slots.72．PPP defines a special control escape byte 01111101. If the data is b1b201111110b3b4b5, the value is( )after byte stuffing.A b1b20111110101111110b3b4b5B b1b20111111001111101b3b4b5C b5b4b30111111001111101b2b1D b5b4b30111110101111110b2b173．MAC address is in ( ) of the computer.A RAMB NICC hard diskD cache74．Which of the following is wrong? ( )A ARP table is configured by a system administratorB ARP table is built automaticallyC ARP table is dynamicD ARP table maps IP addresses to MAC addresses75．NIC works in ( )layer.A physicalB linkC networkD transport76．In LAN, if UTP is used, the common connector is( ).A AUIB BNCC RJ-45D NNI77．The modem’s function(s) is(are) ( ).A translates digital signal into analog signalB translates analog signal into digital signalC both translates analog signal into digital signal and translates digital signal into analog signalD translates one kind of digital signal into another digital signal78．( )defines Token-Ring protocol.A IEEE 802.3B IEEE 802.4C IEEE 802.5D IEEE 802.279．( )defines Token-Bus protocol.A IEEE 802.3B IEEE 802.4C IEEE 802.5D IEEE 802.280．( ) defines CSMA/CD protocol.A IEEE 802.3B IEEE 802.4C IEEE 802.5D IEEE 802.281．The computer network that concentrated in a geographical area, such as in a building or on a university campus, is ( )A a LANB a MANC a WAND the Internet82．The MAC address is ( ) bits long.A 32B 48C 128D 25683．Which of the following four descriptions about MAC addresses is wrong? ( )A a MAC address is burned into the adapter’s ROMB No two adapters have the same addressC An adapter’s MAC address is dynamicD A MAC address is a link-layer address84．Which of the following four descriptions about DHCP is correct? ( )A DHCP is C/S architectureB DHCP uses TCP as its underlying transport protocolC The IP address offered by a DHCP server is valid foreverD The DHCP server will offer the same IP address to a host when the host requests an IP address85．The ( )field permits Ethernet to multiplex network-layer protocols.A preambleB typeC CRCD destination MAC address86．For 10BaseT, the maximum length of the connection between an adapter and the hub is ( ) meters.A 50B 100C 200D 50087．An entry in the switch table contains the following information excepts for ( )A the MAC address of a nodeB the switch interface that leads towards the nodeC the time at which the entry for the node was placed in the tableD the IP address of a node88．Consider the 4-bit generator , G is 1001, and suppose that D has the value 101110000. What is the value of R?89．Consider the following graph of the network. Suppose Host A will send a datagram to Host B, Host A run OICQ on port 4000, Host B run OICQ on port 8000. All of ARP tables are up to date. Enumerate all the steps when message “Hello” is sent from host A to host B.。

The Network Layer

IP Addresse formats
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
a)
The Internet is an interconnected collection of many networks.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
a) b) c) d) e) f) g) h) i) The IP Version 4 Protocol IP Addresses IP Version 6 Internet Control Protocols Label Switching and MPLS OSPF—An Interior Gateway Routing Protocol BGP—The Exterior Gateway Routing Protocol Internet Multicasting Mobile IP
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
The Network Layer Principles (2)
a) . . . 6. Avoid static options and parameters 7. Look for good design (not perfect) 8. Strict sending, tolerant receiving 9. Think about scalability 10. Consider performance and cost

letnet5结构

letnet5结构LeNet-5是一种经典的卷积神经网络结构，由加拿大著名科学家Yann LeCun等人在1998年提出，用于手写数字的识别，是深度学习的奠基之作。

1. 整体结构LeNet-5由7个层次构成，包括输入层，卷积层，池化层，卷积层，池化层，全连接层和输出层。

其中，卷积层和池化层是基本模块，用来提取特征。

全连接层和输出层则用于分类。

2. 输入层输入层接收输入的图像，经过像素化处理，将图像转化为28×28的矩阵。

输入层即为图像的原始数据。

3. 卷积层第一层卷积层使用6个大小为5×5的过滤器，通过卷积操作来提取局部特征，得到6张特征图。

每个过滤器的权重均需要训练得到。

4. 池化层卷积后得到的特征图比原图小，通过下采样操作可以得到更小的特征图，提高模型的性能和计算效率。

第一层池化层使用2×2的最大池化操作，将每个2×2的区域中取最大值作为该区域的值，得到6张下采样后的特征图。

5. 卷积层第二层卷积层使用16个大小为5×5的过滤器，得到16张特征图。

6. 池化层第二层池化层同样使用2×2的最大池化操作，得到16张下采样后的特征图。

7. 全连接层经过池化层后，将16张特征图展开为一个一维向量，再经过全连接层即可对特征进行分类。

LeNet-5共有3个全连接层，分别包括120个神经元，84个神经元和10个神经元。

8. 输出层输出层使用softmax函数将前面三个全连接层输出的结果映射到10个类别中，得到最终的分类结果。

总之，LeNet-5是一种经典的卷积神经网络结构，具有良好的性能和可解释性，为后来深度学习的发展奠定了基础。

计算机网络英文题库附答案chapter3解析

计算机网络英文题库（附答案）chapter3解析-CAL-FENGHAI.-(YICAI)-Company One 1Chapter 3 Transport Layer1.A transport-layer protocol provides for logical communication between ____________・A Application processesB HostsC RoutersD End systems2.Tran sport-layer protocols run in _______ ・A ServersB ClientsC RoutersD End systems3.In transport layer, the send side breaks application messages into ___________ , passes to network layer.A FramesB SegmentsC Data-gramsD bit streams4.Services provided by transport layer inelude _________ ・A HTTP and FTPB TCP and IPC TCP and UDPD SMTP5.Which of the following services is not provided by TCPA Delay guarantees and bandwidth guaranteesB Reliable data transfers and flow controlsC Congestion controlsD In-order data transfers6.These two minimal transport-layer services——_______ and ______ ——are the only two services that UDP provides!A process-to-process data delivery, error checkingB congestion control, reliable data transferC flow control, congestion controlD In-order data transfer, error checking7.Port number's scope is _______ t o _______ ・A 0, 1023B 0. 65535C 0, 127D 0,2558.The port numbers ranging from _______ t o _____ are called well-known port numberand are restricted・A 0,1023B 0, 65535C 0, 127D 0,2559.UDP socket identified by two components, they are _________ ・A source IP addresses and source port numbersB source IP addresses and destination IP addressesC destination IP address and destination port numbersD destination port numbers and source port numbers10.TCP socket identified by a (an) _________ ・A 1-tupleB 2-tupleC 3-tupleD 4-tuple11.Which of the following applications normally uses UDP servicesA SMTPB Streaming multimediaC FTPD HTTP12.Reliable data transfer protocol over a perfectly reliable channel is __________ ・A rdt 1.0B rdt2.0C rdt3.0D rdt2.113.Reliable data transfer protocol over a channel with bit errors and packet losses isA rdt 1.0B rdt2.0C rdt3.0D rdt2.114.Which of Hie following about reliable data transfer over a channel with bit errors i s not correct?A RDT2.0: assuming ACK and NAK will not be corniptedB RDT2.1: assuming ACK and NAK can be corruptedC RDT2.2: only use ACK-sD RDT2.2: use both ACK-s and NAK-s15.Which of the following protocols is not pipelining protocols?A TCPB rdt3.0C GO-BACK-ND selective repeat16.Which of the following is not correct about GBN protocol?A Only using ACK-sB Using cumulative ACK-sC Receiver discards all out-of-order packetsD It is not pipelined protocol17.Which of the following is not correct about SR protocol?A receiver individually acknowledges all correctly received packetsB sender only resends packets for which ACK not receivedC It limits sequence number of sent but un-ACK-ed packetsD It is not a pipelined protocol18.Which of the following about TCP connection is not correctA It is a broadcast connectionB It is a point-to-point connectionC It is a pipelined connectionD It is a full duplex connection19.The SYN segment is used for ______ ・A TCP connection setupB TCP flow controlC TCP congestion controlD Closing a TCP connection20.The FIN segment is used for _______ ・A TCP connection setupB TCP flow controlC TCP congestion controlD Closing a TCP conn ection21 ・ How does TCP sender perceive congestionA Through a timeout eventB Through a receiving duplicate ACK-s eventC Both A and BD Either A or B22.Extending host-to-host delivery to process-to-process delivery is called transportlayerand _.A multiplexing and de-multiplexingB storing and forwardingC forwarding and filteringD switching and routing23.UDP is a ______ sendee while TCP is a connection-oriented service・A ConnectionlessB ReliableC Connection-orientedD In-order24.The UDP header has only four fields, they are _________ ・A Source port numbei; destination port number, length and checksumB Source port number, destination port number, source IP and destination IPC source IP, destination IP, source MAC address and destination MAC addressD source IP, destination IP, sequence number and ACK sequence number25.There are two 16七it integers: 1110 0110 0110 0110, 1101 0101 0101 0101. Their checksum is _______ ・A 0100010001000011B 1011101110111100C 1111111111111111D 100000000000000026.The maximum amount of data that can be grabbed and placed in a segment is limited by the _____ ・A Maximum segment size (MSS)B MTUC ChecksumD Sequence number27.The MSS is typically set by first determining the length of the largest linklayer frame that can be sent by the local sending host——the so-called ____________________ ・A Maximum transmission unit (MTU)B MSSC ChecksumD Sequence number2& A File size of 500,000bytes5 MSS equals lOOObytes. When we want to transmit this file with TCP, the sequence number of the first segment is 0, and the sequence number of the second segment is _______________________ ・A 1000B 999C 1001D 50000029.Because TCP only acknowledges bytes up to the first missing byte in thestream, TCP is said to provide _______ ・A Cumulative acknowledgementsB Selective acknowledgementsC 3 duplicate ACKsD positive ACKs30.Provided a=0・125, current value of Estimated-RTT is 0.4s, Saniple-RTT is 0.8s,then the new value of Estimated-RTT is __________ s.A 0.45B 0.6C 0.7D 0.831.Provided RcvBuffer=20,LastByteRcvd=20,LastByteRead= 15, thenRev Window 二・A 14B 15C 16D 1032.TCP service does not provide _______ ・A Reliable data transferB Flow controlC Delay guaranteeD Congestion control33.There are two states in TCP congestion control, which are __________ ・A slow start and congestion avoidanceB safe start and congestion avoidanceC slow start and congestion abandonD safe start and congestion abandon34.The transport-layer protocol provides logical communication between __________ , and the network-layer protocol provides logical communication __________ ・A hosts, processesB processes, hostsC threads, processesD processes, threads35.To implement the multicast services the Internet employs the _________ protocol.A FTPB TCPC IGMPD UDP36.If an application developer chooses ________ protocol, then the application process is almost directly talking with IP.A HTTPB RIPC CSMA/CDD UDP37. ____ maintains connection-state in the end systems. This connection stateincludes receive and send buffers, congestion-control parameters, and sequence and acknowledgment number parameters・A UDPB TCPC DNSD HTTP38.The host that initiates the session in the Internet is labeled as__________ .A serverB user agentC clientD router39.With TCP there is no _________ b etween sending and receiving transport-layer entities ・A flow controlB handshakingC・ congestion control D VC setup40.Tlie Internet's ______ s ervice helps prevent the Inteniet fi*om entering a state of gridlock ・A datagramB congestion controlC sliding windowD timeout event41 ・ Connection setup at the transport layer involves _______ ・A serverB only the two end systemsC clientD router42. A _____ layer protocol provides for logical communication between applications.A transportB applicationC networkingD MAC43.In static congestion window, if it satisfies W*S/R > RTT + S/R, the Latency isA W*S/R-( RTT+ S/R)B 2RTT + O/RC 2RTT + O/R + (k-1 )[W* S/R- (RTT + S/R)]D 2RTT + S/R44.The receive side of transport layer reassembles segments into messages, passes to l ayer.A ApplicationB NetworkingC PhysicalD MAC45.In the following four options, which one is correct?A The variations in the SampIeRTT are smoothed out in the computation of the Esti mated RTTB The timeout should be less than the connection's RTTC Suppose that the last SampIeRTT in a TCP connection is equal to 1 sec. Then the current value of Timeoutinterval will necessarily be>l secD Suppose that the last SampIeRTT in a TCP connection is equal to 1 sec. Then the current value of Timeoutinterval will necessarily be<l sec46.The port number used by HTTP is ________ .A 80B 25C 110D 5347.The port number used by SMTP is ________ .A 80B 25C 110D 534& The port number used by pop3 is _________A 80B 25C 110D 5349.The port number used by DNS is _________A 80B 25C 110D 5350.The port number used by FTP is ________ .A 20 and 21B 20C 21D 5351. A UDP socket identified by a ________ tuple(s).A 2B 4C 1D 352. A TCP socket identified by a _________ tuple(s).A 2B 4C 1D 353. A TCP socket does not include ______ .A Source MAC addressB Source port numberC Destination IP addressD Destination port number54.Which of following about UDP is not correct.A It is a reliable data transfer protocolB It is connectionlessC no handshaking between UDP sender, receiverD it is a best effort service protocol55.DNS uses ______ service・A TCPB UDPC Both TCP and UDPD None of above56.Which of following about UDP is correctA Finer application-level control over what data is sent, and whenB No connection establishment (which can add delay), so no delay for establish a connectionC No connection state (so, UDP can typically support many active clients)D Large packet header overhead (16・B)57.Streaming media uses a ______ service normally・A TCPB UDPC Both TCP and UDPD None of above58.The UDP header has only ________fields.A 2B 4C 1D 359.Which of the following does not included in UDP header.A Source port numberB Destination port numberC ChecksumD Sequence number60.Which of Hie following is not a pipelining protocol.A Rdtl.OB Go-Back-NC Selective repeatD TCP61.In the following four descriptions about MSS and MTU, which one is not correctA The MSS is the maximum amount of application-layer data in the segmentB The MSS is the maximum size of the TCP segment including headersC The MSS is typically set by MTUD The MTU means the largest link-layer frame62.The job of gathering data chunks, encapsulating each data chunk with header information to create segments and passing Hie segments to the network is called___________A multiplexingB de-multiplexingC forwardingD routing63.In the following four descriptions about the relationship between the transport layer and the network layer, which one is not correctA The transport-layer protocol provides logical communication between hostsB The transport-layer protocol provides logical communication between processesC The services that a transport-layer protocol can provide are often constrained by the service model of the network-layer protocolD A computer network may make available multiple transport protocols64.Suppose the following three 8-bit bytes: 01010101, 01110000, 01001100. Whaf s the Is complement of the sum of these 8-bit bytesA 00010001B 11101101C 00010010D 1000100065.The following four descriptions about multiplexing and de-multiplexing, which one is correctA A UDP socket is identified by a two-tuples consisting of a source port number and a destination port number・B If two UDP segment have different source port number, they may be directed to the same destination process・C If two TCP segments with different source port number, they may be directed to the same destination process・D If two TCP segments with same destination IP address and destination port number, they must be the same TCP connection・66.UDP and TCP both have the fields except _________ ・A source port numberB destination port numberC checksumD receive window67.If we define N to be the window size, base to be the sequence number of theoldest unacknowledged packet, and next-seq-num to be the smallest unused sequence number, then the interval [nextseqnum.base+N-1 ] corresponds to packet that __________ ・A can be sent immediatelyB have already been transmitted and acknowledgedC cannot be usedD have been sent but not yet acknowledged68.Which of the following about TCP is not correctA It is a connectionless protocolB Point-to-point protocolC Reliable, in-order byte steam protocolD Pipelined protocol69.Which of the following about TCP is not correctA It is a connectionless protocolB full duplex data transfer protocolC connection-oriented protocolD flow controlled protocol70.The maximum amount of data that can be grabbed and placed in a segment is limited by the ______ ・A Maximum segment size (MSS)B MTUC Sequence numberD Check sum71.The MSS is typically set by first determining the length of the largest link-layer frame that can be sent by the local sending host (the so-called _________ ), and then will fit into a single link-layer frame・A Maximum segment size (MSS)B MTUC Sequence numberD Check sum72.The MSS is the maximum amount of _________ l ayer data in the segment, not the maximum size of the TCP segment including headers・A ApplicationB TransportC NetworkingD Link73.Which of the following field is not used for connection setup and teardownA Sequence numberB TSTC SYND FIN74. ____ is the byte stream number of first byte in the segment・A Sequence numberB ACK numberC ChecksumD port number75. ____ is the byte sequence numbers of next byte expected from odier side・A Sequence numberB ACK numberC ChecksumD port number76.Because TCP only acknowledges bytes up to the first missing byte in the stream, TCP is said to provide ________ acknowledgements・A CumulativeB SelectiveC SingleD Negative77.Fast retransmit means in the case that _______ duplicate ACK-s are received, the TCP sender resend segment before timer expires・A 3B 4C 5D 67& TCP ______ means sender won't ov©rflow receivei^s buffer by transmitting too much, too fast.A Flow controlB Congestion controlC Reliable data transferD Connection-oriented service79.TCP provides flow control by having the sender maintain a variable called theA Receive windowB Congestion windowC Sliding windowD buffer80.How does TCP sender perceive congestionA TimeoutB 3 duplicate ACK-sC Both A and BD None of above81 ・ Transport protocols run in ______・A ServersB ClientsC RoutersD End systems82.Which of the following services is not provided by TCPA Delay guarantees and bandwidth guaranteesB Reliable data transfers and flow controlsC Congestion controlsD In-order data transfers83.Which service does UDP not provideA multiplexingB de-multiplexingC error-detectionD error-correction84.There are three major events related to data transmission and retransmission in the TCP sender, which one is not in it?A data received from application aboveB de-nmltiplexing segmentC timer timeoutD ACK receipt85.Which of the following applications normally uses UDP services?A SMTPB Streaming multimediaC FTPD HTTP86.Which of the following about TCP connection is not correct?A It is a broadcast connectionB It is a point-to-point connectionC It is a pipelined connectionD It is a full duplex connection87.The SYN segment is used for _______ ・A TCP connection setupB TCP flow controlC TCP congestion controlD Closing a TCP connection8& Which service helps prevent the internet from entering a state of gridlockA reliable data transferB flow controlC congestion controlD handshaking procedure89.Tlie Internet's ________ is responsible fbr moving packets from one host to another.A application layerB transport layerC network layerD link layer90.In the following applications, which one is a bandwidth-sensitive application?A E-mailB web applicationC real-time audioD file transfer91.In the following applications, which one uses UDP?A E-mailB web applicationC file transferD DNS92.In the following four descriptions, which one is correct?A If one host's transport layer uses TCP, then its network layer must use \-iitiial- circuit network・B Datagram network provides connection serviceC The transport-layer connection service is implemented in the routerD The network-layer connection service is implemented in the router as well as in the end system.93.____ is a speeding-matching service一-matching the rate which the sender is sending against the rate at which the receiving application is reading・A congestion controlB flow controlC sliding-window controlD variable control94.In the following four descriptions about Rev-Window, which one is correct?A The size of the TCP RcvWindow never changes throughout the duration of the connectionB The size of the TCP RcvWindow will change with the size of the TCP RcvBufferC The size of the TCP RcvWindow must be less than or equal to the size of the TCP RcvBufferD Suppose host A sends a file to host B over a TCP connection, the number of unacknowledged bytes that A sends cannot exceed the size of the size of the RcvWindow. 95.There are 6 flag fields. Which one is to indicate that the receiver should pass the data to the upper layer immediately?A PSHB URGC ACKD RST96.Suppose the TCP receiver receives the segment that partially or completely fills ingap in received data, it will ________ .A immediately send ACKB immediately send duplicate ACKC wait some time for arrival of another in-order segmentD send single cumulative97. _____ imposes constrain on the rate at which a TCP sender can send traffic intothe network・A sliding windowB congestion windowC receive windowD variable window98.Flow control and congestion control are same at that they all limit the rate of the sender, but differ in that _______ ・A flow control limits its rate by the size of RcvWindow, but congestion control by the traffic on the linkB congestion control limits its rate by the size of RcvWindow, but flow control by the traffic on the linkC flow control mainly is accomplished by the sender, but congestion control by the receiver.D flow control mainly is accomplished by the receiver, but congestion control by the link.99.This job of delivering the data in a transport-layer segment to the correct socket is called ______ ・A multiplexingB de-muitiplexingC forwardingD routing100.If we define N to be the window size, base to be the sequence number of theoldest unacknowledged packet, and next-seq-num to be the smallest unused sequence number, then the interval [base, nextseqnunvl] corresponds to packet 什lat ____________ ・A can be sent immediatelyB have already been transmitted and acknowledgedC cannot be usedD have been sent but not yet acknowledged101.____ are the two types of transport services that the Internet provides to the applications.A TCP and UDPB connection-oriented and connectionless serviceC TCP and IPD reliable data transfer and flow control102.In the following descriptions about persistent connection, which one is not correct?A The server leaves the TCP connection open after sending a responseB Each TCP connection is closed after the server sending one objectC There are two versions of persistent connection: without pipelining and with pipeliningD The default mode of HTTP uses persistent connection with pipelining103.The field of Length in UDP segment specifies the length of __________ ・A the UDP segment, not including the headerB the UDP segment, including the headerC the UDP seginenf s headerD the Length field104.In TCP segment header, which field can implement the reliable data transfer?A source port number and destination port numberB sequence nuniber and ACK numberC urgent data pointerD Receive window105.In the following four descriptions about TCP connection management, which one is not correct?A Either of the two processes participating in a TCP connection can end the connectionB If the FIN bit is set to 1, it means that it wants to close the connectionC In the first two step of the three-way handshake, the client and server randomly choose an initial sequence numberD In the three segments of the three-way handshake, the SYN bit must be set to 1106.Suppose host A sends two TCP segments back to back to host B over a TCP connection. The first segment has sequence number 42, and the second has sequence number 110. If the l sl is lost and 2nd arrives at host B. What will be the acknowledgment number?A 43 C 109B ACK42 D ACK110Choices:1 〜5 ADBCA 6-10 ABACD11〜15 BACDB16〜20 DDAAD 21~25DAAAA 26 〜30 AAAAA31 〜35 BCABC 36-40DBCDB 41V5 BACAA46 〜50 AB CD A 51 〜55ABAAB 5640 DBBDA6145 BAABB 66 〜DAAAA 71-75 BAAAB76-80 AAAAC 81 〜85DADBB 86®AACCC91 〜95 DDBCB 95 〜CBABD 101-106 ABABDB1.Consider sending an object of size 0=500,OOObytes from server to client. Let S=500bytes and RTT=0.2s. Suppose the transport protocol uses static windows with window size 5. For a transmission rate of 100Kbps, determine the latency for sending the whole object. Recall the number of windows K=O/ WS), and there is K-l stalled state (that is idle time gaps).1- SolutionK=0/'(\VS)=500*8* 1000/(5 * 5 000*8)=200Latency=2RTT+ORKK-l )(S,R+RTT-WS‘R)=0.4+500*1000*8'100000+(200-1>(5 00*8/100000+02-5*500*8/1000QQ)=48.36s2.Consider the following plot of TCP congestion window size as a function of time.Fill in the blanks as follow:a) The initial value of Threshold at the first transmission round is ____________ b) The value of Threshold at the 11st transmission round is __________ ・ c) The value of Threshold at the 21st transmission round is __________ ・ d) After the 9th transmission round, segment loss detected by __________ ・(A) Timeout(B) Triple duplicate ACKe) After the 19lh transmission round, segment loss detected by _________ ・(A) Timeout(B) Triple duplicate ACKf) During_______ t ransmission round, the 18lh segment is sent ・2. Solutiona) 12 b) Sc) 7d)Ae)Bf)53. Consider the TCP reliable data transfer in the given graph ・ If in Segment l ，s Sequence number =10,data=u AC'\ please fill in the following blanks ・ a) In Segment 2, ACK number 二：b) In Segment 3, Sequence number =_______ ; data=u 0123456789^c) If there are some bits corrupted in segment 3 when it arrives Host B, then the ACKnumber in Segment 5 is : and the ACK number in Segment 6 is ,Transmission roundb n 8congestion、f4. The client A wants to request a Web page from Server B ・ Suppose the URL of the page is 172.16.0.200/experiment, and also it wants to receive French version of object. The time-sequence diagram is shown below, please fill in the blanks ・Packet® to Packet③ are TCP connection's segment, then: Packet ①：SYN flag bit 二 aACK flag bit=_b Sequence number= 92 Packet ®: SYN flag bit=l3. Solution:a) 12b)12 c) 12; 22ACK flag bit=_cSequence number= 100 Packet ®: SYN flag bit=_dACK flag bit=l Sequence number= e 4. Solution:a)l b)0 c)l d)0 e)935・ Consider sending an object of size 0=100 Kbytes from server to client. Let S=536 bytes and RTT= 100msec ・ Suppose the transport protocol uses static windows with window size W ・(1) For a transmission rate of 25 kbps, determine the minimum possible latency. Determine the minimum window size that achieves this latency. (2) Repeat (1) for 100 kbps. 5. Solution:(1) Latency=2RTT + OR =2*0.1+100*8/25= 0.2+32=32.2 (s)W* S R > S.R+RTT —- W>L6= so W=2 (2)Latency =2RTT+ O,R=2«0.1+100*8/'100=0.2+8=82 (s) W* S,R> SR+RTT —-W3.3, so W=46. Consider the following plot of TCP congestion window size as a function of time. Please fill in the blanks as below.Aa) The initial value of Threshold at the first transmission round is b) The value of Threshold at die 11th transmission round is ___________ ・ c) The value of Threshold at the 21st transmission round is・congestion window﹃4︱TITIT丄|︱rlrL ︱lrlrL ︱︱LILILIklklrlrlrL ︱IL ︱﹂︱﹂︱ J.IJ.1/Transmission roundd)After the 9th transmission round, _________e)After the 19th transmission round, ________6. Solution:a) 12 b) 8 c) 7 d) timeouttriple ACK occurs・ are detected.e) 321。

lenet5结构

lenet5结构LeNet-5网络结构是一种经典的卷积神经网络，它是由Yann LeCun等人于1998年提出的，用于手写数字识别任务。

LeNet-5由七层组成，包括两个卷积层、两个池化层和三个全连接层。

我们来介绍LeNet-5的网络结构。

LeNet-5的输入是一个32x32的灰度图像，经过第一层卷积层后，图像尺寸变为28x28。

该卷积层使用了6个5x5的卷积核，每个卷积核与输入图像进行卷积运算，得到6个特征图。

然后，经过一个2x2的池化层，将特征图的尺寸减小为14x14。

接下来，经过第二层卷积层，图像尺寸再次减小为10x10，该卷积层使用了16个5x5的卷积核，得到16个特征图。

然后，再经过一个2x2的池化层，将特征图的尺寸减小为5x5。

接着，将得到的16个5x5的特征图展开成一个400维的向量，传入第一个全连接层。

该全连接层有120个神经元，每个神经元与400维的输入向量进行全连接操作，得到一个120维的输出向量。

然后，将第一个全连接层的输出传入第二个全连接层。

该全连接层有84个神经元，每个神经元与120维的输入向量进行全连接操作，得到一个84维的输出向量。

将第二个全连接层的输出传入第三个全连接层，该全连接层有10个神经元，每个神经元与84维的输入向量进行全连接操作，得到一个10维的输出向量。

这个输出向量表示了输入图像属于10个不同类别的概率分布，可以通过softmax函数进行归一化处理，得到最终的分类结果。

LeNet-5的网络结构简洁而高效，它采用了卷积层和池化层的组合，能够有效地提取图像的局部特征，并通过全连接层将这些特征组合起来进行分类。

另外，LeNet-5还使用了sigmoid函数作为激活函数，使得网络能够进行非线性映射，提高了分类的准确性。

LeNet-5的网络结构在手写数字识别任务上取得了很好的效果，成为了卷积神经网络发展的里程碑。

它的设计思想和网络结构对后来的深度学习模型有着重要的影响。

lenet5模型结构

lenet5模型结构Lenet-5模型是一种经典的卷积神经网络，由Yann LeCun于1998年提出，被广泛应用于手写数字识别任务。

它的结构包括卷积层、池化层和全连接层，具有较强的特征提取和分类能力。

Lenet-5模型的整体结构可以分为7个主要的层次：输入层、C1层、S2层、C3层、S4层、F5层和输出层。

下面将对每个层次的功能和作用进行介绍。

1. 输入层：Lenet-5模型的输入层接收手写数字图片作为输入。

手写数字图片的大小为32×32像素，黑白图像。

每个像素的灰度值范围在0到255之间。

2. C1层：C1层是卷积层，使用6个5×5的卷积核对输入图像进行卷积操作，得到6个特征图。

每个卷积核与输入图像的一个局部区域进行卷积操作，通过滑动窗口的方式遍历整个输入图像。

卷积操作可以提取图像的局部特征。

3. S2层：S2层是池化层，使用2×2的池化核对C1层的特征图进行下采样操作，得到6个下采样后的特征图。

池化操作能够降低特征图的维度，减少后续计算量，并保持特征的位置不变性。

4. C3层：C3层是卷积层，使用16个5×5的卷积核对S2层的特征图进行卷积操作，得到16个特征图。

与C1层类似，C3层的卷积操作也是通过滑动窗口的方式实现的。

5. S4层：S4层是池化层，使用2×2的池化核对C3层的特征图进行下采样操作，得到16个下采样后的特征图。

6. F5层：F5层是全连接层，将S4层的特征图展开成一维向量，并与权重矩阵相乘得到长度为120的特征向量。

F5层可以综合全局特征，并将其输入到输出层进行分类。

7. 输出层：输出层是全连接层，将F5层的特征向量与权重矩阵相乘，并经过softmax函数得到最终的分类结果。

在手写数字识别任务中，输出层有10个神经元，分别对应数字0到9。

Lenet-5模型通过卷积和池化操作，能够提取图像的局部特征，并通过全连接层将特征综合起来进行分类。