Shortest-hop Based Reliable Network Multicast
计算机网络英文版习题答案
P63 #5 Consider sending a packet of F bits over a path of Q links. Each link transmits at R bps. The network is lightly loaded so that there are no queuing delays. Propagation delay is negligible.a.Suppose the network is a packet-switched virtual-circuit network. Denote the VC setup time by t s seconds. Suppose the sending layers add a total of h bits of header to the packet. How long does it take to send the file from source to destination?t s+[(F+h)/R]Qb.Suppose the network is a packet-switched datagram network and a connectionless service is used. Now suppose each packet has 2h bits of header. How long does it take to send the packet?[(F+2h)/R]Qc.Finally, suppose that the network is a circuit-switched network. Further suppose that the transmission rate of the circuit between source and destination is R bps. Assuming ts setup time and h bits of header appended to the packet, how long does it take to send the packet?t s+(F+h)/RP64 #6 This elementary problem begins to explore propagation delay and transmission delay, two central concepts in data networking. Consider two hosts, A and B, connected by a single link of rate R bps. Suppose that the two hosts are separated by m meters and suppose that the propagation speed along the link is s meters/sec. Host A sends a packet of size L bits to host B.[a] Express the propagation delay, d prop, in terms of m and s.[b] Determine the transmission time of the packet, d trans, in terms of L and R.[c] Ignoring processing and queueing delays, obtain an expression for the end-to-end delay.[d] Suppose Host A begins to transmit the packets at time t=0. At time t=d trans, where is the last bit of the packet?[e] Suppose d prop is greater than d trans. At time t=d trans, where is the first bit of the packet?[f] Suppose d prop is less than d trans. At time t=d trans, where is the first bit of the packet?[g] Suppose s=2.5 x 108, L=100 bits and R=28kbps. Find the distance m so that d prop = d trans.[a] d prop = m/s[b] d trans = L/R[c] end-to-end delay = d prop + d trans=m/s+L/R[d] The beginning position of the link.[e] On the channel between A and B.[f] On the host B.[g] m/s = L/R = > m = sL/R = > m = 892.86 kmP65 #10 Consider the queueing delay in a router buffer. Suppose that all packets are L bits, the transmission rate is R bps, and that N packets simultaneously arrive at the buffer every LN/R seconds. Find the average queueing delay of a packet (in terms of L, R and N). (Hint: The queueing delay for the first packet is zero; for the second packet L/R; for the third packet 2L/R. The Nth packet has already been transmitted when the second batch of packets arrives.)As the Nth packet has already been transmitted when the next batch of packets arrive, we only need to consider the delay for a single batch of packets.Average delay = Total delay / Number of packetsDelay for 1st packet = 0Delay for 2nd packet = L/RDelay for 3rd packet = 2L/R......Delay for Nth packet = (N-1)L/RTotal delay for N packets = (0 + 1 + 2 ... +(N-1) ) * (L/R)Using the formulas for sum of integer series, this can be written as: Total delay for N packets = (N-1) * (N/2) * (L/R)Therefore, average delay for N packets = ((N-1) * L) / 2RP170 #12 What is the difference between persistent HTTP with pipelining and persistent HTTP without pipelinning? Which of the two is used by HTTP/1.1?For the persistent connection without pipelining, the client issues a new request only when the previous has been received. In this case, the client experiences one RTT in order to request and receive each of the referenced objects.For the persistent connection with pipelining, the client issues a request as soon as it encounters a reference. It is possible for only RTT to be expended for all the referenced objects.P170 #14 Telnet into a Web server and send a multiline request message. Include in the request message theIf-modified-since: header line to force a response message with the 304 Not Modified status code.GET/somedir/exp.html HTTP/1.1Host: Connection: closeUser-agent: Mozilla/4.0If-Modified-Since: Thu, 30 May 2007 12:00:00 GMTAccept-language: frP172 #6 Suppose within your web browser you click on a link to obtain a web page. The IP address for the associated URL is not cached in your local host, so a DNS look-up is necessary to obtain the IP address. Suppose that n DNS servers are visited before your host receives the IP address from DNS; the successive visits incur an RTT (Round Trip Time) of RTT1, ... RTTn. Further suppose that the web page associated with the link contains exactly one object, consisting of a small amount of HTTP text. Let RTT0 denote the RTT between the local host and the remote server containing the object. Assuming zero transmission time of the object, how much time elapses from when the client clicks on the link until the client receives the object? (Hint: read pages 90 .. 93)Time to visit DNS servers and get IP address = RTT1 + RTT2 + ... + RTTnTime to establish TCP connection (SYN and SYNACK) = RTT0Time to send HTTP request and receive reply = RTT0Total time = 2 * RTT0 + (RTT1 + RTT2 + ... + RTTn)P171 #16 Suppose Alice with a Web-based e-mail account (such as Yahoo! Mail or Hotmail) sends a message to Bob, who accesses his mail from his mail server using POP3. Discuss how the message gets from Alice’s host to Bob’s host. Be sure to list the series of application-layer protocols that are used to move the message between the two hosts.The series of application-layer protocols: HTTP、SMTP、POP3Suppose that you send an e-mail message whose only data is a Microsoft Excel attachment. What might the header lines (including MIME lines) look like?From:***********To:***********Subject: helloMIME-Version: 1.0Content-Transfer-Encoding: base64Content-Type: Application/MS-ExcelP286 #5 Suppose host A sends two TCP segments back to back to host B over a TCP connection. The first segment has sequence number 90: the second has sequence number 110.a.How much data is in the first segment?a.20 bytesb.Suppose that the first segment is lost but the second segment arrives at B. In the acknowledgement that host B sends to host A, what will be the acknowledgement number?b.ACK90P291 #27 Consider the following plot of TCP window size as a function of time. (reproduced below for you) Assuming TCP Reno is the protocol experiencing the behavior shown above, answer the following questions. In all cases, you should provide a short discussion justifying your answer.a. Identify the intervals of time when TCP slow start is operating.b. Identify the intervals of time when TCP congestion avoidance is operating.c. After the 16th transmission round, is segment loss detected by a tripleduplicate ACK or by a timeout?d. After the 22nd transmission round, is segment loss detected by a triple duplicate ACK or by a timeout?e. What is the initial value of Threshold at the first transmission round?f. What is the value of Threshold at the 18th transmission round?g. What is the value of Threshold at the 24th transmission round?h. During what transmission round is the 70th segment sent?i. Assuming a packet loss is detected after the 26th round by the receipt of a triple duplicate ACK, what will be the values of the congestion-window size and of Threshold?Solution:a.1-6, 23-26b.6-16, 17-22c.a triple duplicate ACKd.timeoute.32f.21g.13h.7i.4, 4P293 #34 Consider sending an object of size O = 100 Kbytes from server to client. Let S = 536 bytes and RTT = 100 msec. suppose the transport protocol uses static windows with window size W. (See Section 3.7.2)a.For a transmission rate of 28 kbps, determine the minimum possible latency. Determine the minimum window size that achieves this latency.b.Repeat (a) for 100 kbps.tency=28.8s W=2tency=8.2s W=4P405 #8 Consider a datagram network using 8-bit host addresses. Suppose a router uses longest prefix matching and has t he following forwarding table:-----------------------------------------------------Prefix Match Interface-----------------------------------------------------00 001 110 211 3-----------------------------------------------------For each of the four interfaces, give the associated range of destination host addresses and the number of addresses in the range.6P407 #15 Consider sending a 3000-byte datagram into a link that has a MTU of 500 bytes. Suppose the original datagram is stamped with the identification number 422. How many fragments are generated? What are their characteristics?there are「2980/480」=7 fragments be generatedP408 #22 Consider the network shown in Problem 21 (reproduced below). Using Dijkstra’s algorithm, and showing your work using a table similar to Table 4.3, do the following:a. Compute the shortest path from s to all network nodesSteps D(t),P(t) D(u),P(u)D(v),P(v)D(w),P(w)D(x),P(x)D(y),P(y)D(z),P(z)0 1,s 4,s ∞∞∞∞∞1 3.t 10,t ∞∞5,t 3,t2 4,u 6,u ∞5,t 3,t3 4,u 6,u ∞5,t4 5,v 7,v 5,v5 6,w 5,v6 6,wPlease fill in the following tables using DV algorithm:For the node Z in the graph shown in the 22nd topic (P408), please fill in the following routing table in the router z about the initial distance-vector Destination node Next hop Current shortest distancevalue-DzS —∞T T 2U —∞V —∞W —∞X —∞Y Y 14Z Z 0following rout-ing table in the node z to update this routing tableDestination node Currentdistance-DyDestination node Current distance-DtS 5 S 1 T 4 T 0 U 2 U 2P493 #7 How big is the MAC address space？The IPv4 address space？The IPv6 address space?MAC address: 6 bytes, MAC address space 2^48IPV4 address: 4 bytes, IPV4 address space 2^32IPV6 address: 16 bytes, IPV6 address space 2^128P494 #4 Consider the 4-bit generator, G, shown in Figure 5.8, and suppose the D has the value 10101010. What is the value of R?G=1001, D=10101010, R=101。
Secure Multi-Hop Infrastructure Access
Secure Multi-Hop Infrastructure Access Baruch Awerbuch1Reza Curtmola1David Holmer1Cristina Nita-Rotaru2Herbert Rubens1I.I NTRODUCTIONWireless networking today is predominantly used to provide mobile users with untethered access tofixed infrastructure. This allows users to move freely throughout the office or warehouse while remaining continuously connected with the office network and the Internet.While traditional access point devices currently provide this capability,they have a limited coverage range and thus many access points are required to provide coverage of a given area.One solution to this problem is to use a routing protocol that allows the users to traverse multiple hops to the nearest access point.This greatly expands the coverage range of each access point while simultaneously reducing costs and simplifying deployment.Multi-hop infrastructure access has previously been pro-posed by[1]and[2].However,the proposed solutions have only focused on routing without considering security.In this work we provide several extensions to the Pulse protocol[1] that defend against a large class of external attacks.The main contribution is providing strong adversarial resilience while maintaining low overhead.The Pulse protocol was originally evaluated with an in-frastructure only traffic ter work[3]evaluated the protocol under a more general mobile ad hoc network model with peer-to-peer traffic.The protocol was shown to achieve high delivery ratios under a wide range of network densities, mobilities,and traffic loads.The protocol operates with a periodicflood initiated by the infrastructure access gateway, which is referred to as the pulse source.This creates a pro-actively updated spanning tree throughout the network.The periodic pulseflood exploits the communication concentration at the pulse source by providing every node in the network with a continuously updated route.The proactive pulseflood provides scalability to high levels of mobility.As the mobility level increases,many failures begin to occur throughout the network.In the Pulse protocol,all broken routes are repaired simultaneously within one pulse interval using oneflood.In contrast,an on-demand protocol may initiate oneflood for every broken active route,and a proactive link-state protocol may generate oneflood per link failure.As the number of failures increases,this results in congestion due to the additional routing overhead,limiting the scalability of these protocols to high levels of mobility.While the performance and scalability of the protocol has been validated in existing studies,no existing work to our 1Department of Computer Science,Johns Hopkins University,3400N. Charles St.Baltimore,MD21218USA.410-516-5298{baruch,crix,dholmer, herb}@2Department of Computer Science,Purdue University,250N.University Street,West Lafayette,IN47907.765-496-6757crisn@ knowledge has addressed securing the protocol against adver-sarial attacks.In this work we present an efficient security framework for protecting the Pulse protocol operation from external adversarial attacks.II.P ROBLEM D ESCRIPTIONWe consider an ad hoc network in which nodes obtain multi-hop access tofixed infrastructure(such as the wired network or Internet)by reaching the gateway(the pulse source).We consider the following adversarial model:the gateway and all authenticated nodes are trusted to perform the routing protocol correctly.The adversaries are unauthenticated nodes that can perform arbitrary attacks(e.g.drop,inject or modify packets)and may collude to perform even stronger attacks (e.g.tunnel packets).The protocol should offer a level of security comparable to state of the art single-hop protocols(e.g.802.11i[4]).In addition,it has to offer protection against multi-hop routing attacks.Specifically,the routing protocol has to withstand the following attacks:packet injection,modification,replay,black holes,flood rushing,and wormholes.These are well-known attacks against wireless networks.We assume that each node in the network has a unique pre-established shared secret(PSK)with the infrastructure access gateway,which is used for authentication.The PSK can be manually entered(as in WEP or WPA/WPA2personal mode), or it can be automatically generated by an authentication server(as in802.1x/EAP).The system must efficiently support adding and revoking nodes from the network.III.P ROTOCOL O VERVIEWWe present a modified version of the Pulse protocol,which ensures packets are securely routed under the described ad-versarial model.In order to provide a secure routing service, all the nodes in the network share a network wide symmetric key(NSK).This key is used to provide packet authenticity and integrity.It is established and maintained using the key management scheme discussed below.Our protocol establishes a reliability metric based on past history and uses it to select the best path.The metric is represented by link weights where high weights correspond to low reliability.Each node in the network monitors the performance of its links to its neighbors,and uses the resulting weights for selecting the shortest path.Faulty links are identi-fied using secure acknowledgements on each link.Faulty links are avoided as their cost increases.IV.P ROTOCOL O PERATIONThe protocol operates similarly to the original Pulse proto-col,however all packets include a nonce for replay protection, and are encrypted and authenticated using the NSK.This prevents external adversaries from participating as nodes in the routing protocol.However,external adversaries can still execute several attacks against the protocol.For example,a pair of adversaries may create a wormhole,performflood rushing on routing packets to increase the probability of being selected on a route,and then drop any drawn in data packet in a black hole attack.In order to protect against these types of attacks,a cryptographic acknowledgement is required for each data packet that traverses a link.This strategy is similar to the one used in ODSBR[5],however our adversarial model is different in that it excludes insider attacks.These acknowledgements allow the protocol to establish a secure loss-rate history for each link in the network.This secure loss-rate information is then used as a routing metric,similarly to ETX[6],which allows the protocol to select paths composed of reliable links.V.K EY M ANAGEMENTIn this section we briefly describe some issues related to the management of keys in the system.All the participating nodes share a network wide symmetric key,NSK,which is used to provide packet authenticity and integrity.While the set of participating nodes is dynamic,the network wide key NSK should be shared only by non-revoked nodes. Whenever nodes are revoked,the gateway needs to generate a new NSK and distribute it to the the set of valid nodes, so that revoked nodes are no longer able to participate in the protocol.Since each node in the network has a pre-established indi-vidual shared key(PSK)with the gateway,the trivial solution would be for the gateway to unicast the new network key encrypted with the individual key to each node.However,this solution is inefficient.Instead,we use a broadcast encryption technique(e.g.LSD[7]),in which the gateway plays the role of the center.Specifically,we define the join and revoke operations for nodes:•join-to join the network,a node communicates with the gateway using its individual ing this secure channel,the gateway provides the node with both the current network key NSK,and a number of subset keys.The subset keys are used by the broadcast encryption scheme,and will allow the node to decrypt updated versions of NSK in the future.•revocation&key refresh-to update the network key, the gateway generates a new NSK,encrypts it using the broadcast encryption scheme,andfloods it through the network.The broadcast encryption semantics ensure that revoked nodes will not be able to decrypt the new network key,even if they collude.In the LSD broadcast encryption algorithm,the number of subset keys stored by each node is O(log3/2(n))(where n is the number of nodes in the network),the length of the broadcast message is O(r)(where r is the number of revoked nodes),while each node will have to perform O(log(n)) inexpensive operations to decrypt the broadcast message.For example,even with264millon(228)potential nodes,the LSD scheme needs less than3kilobytes of storage per node(with 128-bit keys),and requires no more than27operations for any node to recover the key.VI.A TTACK A NALYSISPacket Injection or Modification:An HMAC with the NSK prevents an adversary from creating or tampering with valid packets.Packet Replay:A nonce prevents an adversary from re-transmitting previously transmitted packets on the network. The nonce is unique per node and replaced at every hop. Black Hole:Black hole attacks are mitigated using the secure reliability metric to avoid unreliable links. Wormhole:Wormhole creation is not prevented,however, the reliability metric allows nodes to avoid using wormhole links that do not deliver data packets.Flood Rushing:Theflood rushing attack exploits the timing sensitivity of routing protocols.Our protocol always prefers paths of lower metric regardless of timing,and is thus immune toflood rushing attacks.VII.C ONCLUSIONWe presented a secure version of the Pulse Protocol for multi-hop infrastructure access.The protocol prevents a wide variety of external adversarial attacks.The protocol is light-weight and relies solely on symmetric cryptography.R EFERENCES[1] B.Awerbuch,D.Holmer,and H.Rubens,“The pulse protocol:Energyefficient infrastructure access,”in Proceedings of The23rd Conference of the IEEE Communications Society INFOCOM,2004.[2]S.Lee,S.Banerjee,and B.Bhattacharjee,“The case for a multi-hopwireless local area network,”in Proceedings of The23rd Conference of the IEEE Communications Society INFOCOM,March2004.[3] B.Awerbuch,D.Holmer,and H.Rubens,“The pulse protocol:Mobile adhoc network performance evaluation,”in Wireless On-demand Network Systems and Services2005.[4]IEEE Std802.11i-2004./getieee802/802.11.html.[5] B.Awerbuch,D.Holmer,C.Nita-Rotaru,and H.Rubens,“An on-demandsecure routing protocol resilient to byzantine failures,”in ACM Workshop on Wireless Security(WiSe)2002,2002.[6] D.S.J. D.Couto, D.Aguayo,J.Bicket,and R.Morris,“A high-throughput path metric for multi-hop wireless networks,”in9th annual international conference on mobile computing and networking(MobiCom03),September2003.[7] D.Halevy and A.Shamir,“The LSD broadcast encryption scheme,”inAdvances of Cryptology-Crypto’02,vol.2442of LNCS,pp.47–60, Springer-Verlag,2002.。
基于最短依存路径与神经网络的关系抽取
基于最短依存路径与神经网络的关系抽取温政; 段利国; 李爱萍【期刊名称】《《计算机工程与设计》》【年(卷),期】2019(040)009【总页数】6页(P2672-2676,2696)【关键词】关系抽取; 最短依存路径; 双通道; 卷积神经网络; 双向长短期记忆网络【作者】温政; 段利国; 李爱萍【作者单位】太原理工大学信息与计算机学院山西太原030024; 武汉大学软件工程国家重点实验室湖北武汉430072【正文语种】中文【中图分类】TP3910 引言实体关系抽取广泛应用于知识图谱构建、智能信息处理、自动问答系统等领域。
具有极其重要的研究价值[1]。
关系类型确定的关系抽取可以看成分类问题，先定义好关系所属的类别，然后将句子划分到它所属的类别中，从而完成关系抽取任务。
本文首先对句子进行依存句法分析，从依存句法分析的结果中找出给定实体之间的最短依存路径，然后将最短依存路径上的每个词分别用Word2vec和GloVe进行向量表示，分别输入卷积神经网络和双向长短期记忆网络，将网络学习到的特征拼接并通过softmax进行分类。
最后通过Adam优化器最小化交叉熵损失函数训练出关系抽取模型。
本文的主要贡献如下：(1)提出了一种基于最短依存路径的双通道神经网络关系抽取模型；(2)在关系抽取领域使用两种不同的词向量表示最短依存路径。
并且通过拼接的方式将CNN(卷积神经网络)和LSTM(长短期记忆网络)抽取的特征融合；(3)在SemEval-2010 Task 8数据集上取得了很好的关系抽取效果。
1 相关工作近年来，关系抽取成为了自然语言处理中广受研究的内容。
目前的研究分别基于知识工程和机器学习展开。
基于知识工程的研究有：Aone等首先用人工编写对应关系类型的抽取规则，然后将规则与文本进行匹配，进而得出关系类型。
由于两个实体之间的谓词对关系类型有很强的表征作用，Fukumoto等将谓词作为了关系抽取的重要特征。
基于知识工程的方法通过构建规则集，然后将待识别的句子与规则集进行匹配，匹配成功则认为该句子具有对应规则的关系。
计算机英语词汇.doc
TFTP=trival file transfer protocol简单文件传输协议
FTP＝file transfer protocol文件传输协议
SNMP＝simple network mangement protocol 简单网络管理协议
GARP=generic attribute registration protocol 通用属性注册协议
import-route 路由引入
traffic classification 流分类
VRRP=virtul router redundancy protocl 虚拟路由备份协议
port aggregation 端口捆绑
CEP
Connection end point连接端点
hdlc＝high-level data link control 高级数据链路控制
ppp ＝point to point protocol 点到点协议
stack 栈
connect-oriented 面向联接
mulitiplex 多路复用
buffering 缓存
source quench messages 源抑制报文
Campus network校园网
CNNIC中国互联网络信息中心
ChinaNET中国公用计算机互联网
CERNET中国教育科研网
CSTNET中国科学技术网
CHINAGBN国家公用经济信息能信网络
CCITT
Consultative committee international telegraph and telephone
网络路由协议外文翻译文献
网络路由协议外文翻译文献Network Routing Protocol: Foreign Language Translation LiteratureIntroductionIn the ever-expanding digital era, networking plays a crucial role in connecting and exchanging information between various devices. One of the fundamental components of network communication is routing protocols. These protocols determine the path that data packets take from source to destination, ensuring efficient and reliable transmission. This article aims to provide a high-quality translation of a foreign language literature regarding network routing protocols.1. Historical OverviewTo understand the significance of network routing protocols, it is essential to explore their historical development. Routing protocols have evolved significantly over the years, adapting to the growth and complexity of networks. The literature discusses the early adoption of distance-vector protocols, such as Routing Information Protocol (RIP), followed by the advancements to link-state protocols like Open Shortest Path First (OSPF). This evolution has been driven by the need for better scalability, faster convergence, and improved fault tolerance.2. Basic ConceptsThe translation literature provides an in-depth understanding of the basic concepts related to network routing protocols. It introduces key terms such as autonomous systems, routing tables, next-hop determination, and metrics.It also explains the difference between interior gateway protocols (IGPs) and exterior gateway protocols (EGPs) and their respective significance in intra-domain and inter-domain routing.3. Routing AlgorithmsUnderstanding the routing algorithms employed by routing protocols is crucial for comprehending their operation. The literature addresses several popular routing algorithms, including Distance Vector, Link State, Hybrid, and Path Vector. It describes the algorithms' mechanisms, advantages, and limitations, enabling readers to grasp their nuances when selecting an appropriate protocol for a specific network environment.4. Protocol Types and ComparisonThe translation provides a comprehensive overview of various network routing protocols, accompanied by a comparative analysis. It sheds light on interior gateway protocols such as RIP, OSPF, and Intermediate System to Intermediate System (IS-IS), highlighting their characteristics, advantages, and areas of application. Additionally, it covers exterior gateway protocols like Border Gateway Protocol (BGP) and describes their role in connecting autonomous systems.5. Protocol Convergence and ScalabilityThe efficient convergence of network routing protocols is crucial for maintaining network stability and minimizing downtime. The literature presents an analysis of protocol convergence mechanisms, exploring techniques such as split horizon, triggered updates, and route poisoning. Furthermore, it delves into the scalability challenges faced by routingprotocols in large networks, discussing the employment of techniques like route summarization, fast hellos, and areas in OSPF.6. Security ConsiderationsAs network security continues to be a concerning issue, the translation literature sheds light on the security considerations associated with network routing protocols. It discusses common threats and vulnerabilities, such as spoofing, route hijacking, and Denial of Service (DoS) attacks. The significance of authentication mechanisms, such as MD5 key authentication and IPsec, is emphasized to ensure secure routing protocol operation.ConclusionIn conclusion, network routing protocols serve as the backbone for efficient and reliable data transmission. This high-quality translation of foreign language literature provides a comprehensive understanding of routing protocol concepts, algorithms, types, convergence mechanisms, scalability, and security considerations. By assimilating this knowledge, network administrators and professionals can make informed decisions while implementing and managing routing protocols in their networks, ultimately enhancing overall network performance and security.。
MNMU-RA
Wireless Sensor Network, 2012, 4, 162-166doi:10.4236/wsn.2012.46023 Published Online June 2012 (/journal/wsn)MNMU-RA: Most Nearest Most Used Routing Algorithm for Greening the Wireless Sensor NetworksHafiz Bilal Khalil, Syed Jawad Hussain ZaidiSchool of Electrical Engineering & Computer Sciences, National University of Sciences and Technology, Islamabad, PakistanEmail: {10mseetkhalil, 10mseejzaidi}@.pkReceived February 22, 2012; revised March 22, 2012; accepted April 10, 2012ABSTRACTWireless sensors are widely deployed in military and other organizations that significantly depend upon the sensed in-formation in any emergency situation. One of the main designs issues of the wireless sensor network (WSN) is the con-servation of energy which is directly proportional to the life of the networks. We propose most nearest most used rout-ing algorithm (MNMU-RA) for ad-hoc WSNs which vitally plays an important role in energy conservation. We find the best location of MNMU node for energy harvesting by apply our algorithm. Our method involves the least number of nodes in transmission of data and set large number of nodes to sleep in idle mode. Based on simulation result we shows the significant improvement in energy saving and enhance the life of the network.Keywords: Energy Efficiency; Wireless Sensor Networks; Routing1. IntroductionThe growth in wireless sensor networks and its applica- tions dramatically increased in last decade. Wireless sen- sor nodes are widely used in military surveillance, intel- ligence and targeting in war operations. Energy available at each sensor for sensing and communications is limited because of the cost constraints and smaller size, which affects the sensor application and network lifetime. The purpose of green networking is to overcome the carbon foot print, reduce the energy consumption and energy losses. Energy efficiency is an important issue to enhance the life time of the network. To achieve the green net- working every component of the network is integrated with energy efficient protocols, e.g., energy-aware rout- ing on network layer, energy-saving mode on MAC layer, etc. One of the most important components of the sensor node is the power source. In sensor networks generally there are three modes of power consumption: sensing, data processing, and communication. Compared to sensing and data processing, much more energy is required for data communication in a typical sensor node [1]. These are also categorized as sleep (idle) and wakeup (trans-mission) mode.In ad-hoc WSNs (Wireless Sensor Networks) always the nodes are cooperative, they sense and transmit their own data and also act as router to route the sensed infor- mation of other nodes towards the data center or gateway node which is connected to the internet. Most of the nodes consumed their power resource while transmitting the data of neighboring nodes. The scope of this paper is to minimize the power consumption in transmitting or routing process and set large number of nodes into sleep mode. The remaining sections of this paper organized as follows. Section 2 explains related work and current en-ergy efficient techniques for sensor networks. Section 3 introduces some problems and research issues in current work. Section 4 describes overview of network model, our proposed algorithm and proposed solution respec-tively. In Section 5 experiment, Results and comparisons are given.2. Related WorkEnergy efficiency is already achieved by many appro- aches. These approaches include energy aware protocol development and hardware optimizations, such as sleep- ing schedules to keep electronics inactive most of the time, dynamic optimization of voltage, and clock rate. In[2] Smart Dust motes are designed that are not more thana few cubic millimeters. They can float in the air, keep sensing and transmitting for hours or days. In [3] authors described the µAMPS wireless sensor node, it is hard- ware based solution in which they simultaneously con- sider the features of the microprocessors and transceivers to reduce the power consumption of the each wireless sensor node in network. Routing algorithms also play an important role to reduce the energy consumption during the routing of data. A lot of work is done in MAC layer and Mac protocols;MAC protocol for wireless sensorH. B. KHALIL, S. J. H. ZAIDI163networks is not like the traditional wireless MACs such as IEEE 802.11. One of the most important goals is en-ergy conservation, fairness and latency is less important [4].SMAC/AL (Sensor MAC with Adaptive Listening) is a famous MAC protocol for WSNs proposed by Ye et al. [5,6]. Main purpose of SMAC/AL is to reduce energy consumption. But in SMAC/AL without considering the distance among the nodes, all nodes unnecessarily con- sume the energy by transmitting information with con- stant power level. An energy efficient MAC protocol with adaptive transmit power scheme named ATPM (Adap- tive Transmit Power MAC) is proposed in [7]. By meas- uring the received power ATPM can calculate the dis- tance between the sender and the receiver, and then adap- tively choose the suitable transmit power level according to the propagation model and distance. The ATMP can not only conserve the energy source, but also decrease the collision probability. A Novel Clustering Algorithm for Energy Efficiency in Wireless Sensor Networks (AN-CAEE) has been proposed [8]. It minimizes energy utili-zation during data transmission and energy consumptions are distributed uniformly among all nodes. Each cluster contains cluster head, each node send its data to cluster head with single hop transmission. And cluster transmits the combined data to the base station with multi hope transmission. This approach reduces energy consumption of nodes within the cluster.3. Problem StatementSensor nodes which are one hope away or closest to the gateway node always consume their power more quickly than others because they have to transmit the data of other nodes in addition to transmission of their own sensed information. In [9] a solution was proposed for such type of scenario by implementing the multiple base stations and periodically changing their positions. But the prob- lem is that if every time the most far away sensor trans- mits its data then major part of overall network energy will be consumed. Another solution for prolong the sen- sor network lifetime is to divide sensors nodes into dis- joint sets, such that all the targets completely covered by every set [3]. Authors consider that within an active sen- sor’s operational range a target is covered. These disjoint sets are activated in round robin fashion, such that at a time only one set is active. Sensors are into the active state in an active set and all other sensors are in a low- energy sleep state. According to this method almost half of the sensor remains active and remaining half goes to sleep mode which reduce energy down to 50%. To make it more efficient and conserve the larger amount of en- ergy we proposed an algorithm named as MNMU-RA (Most nearest most used routing algorithm). That algo- rithm finds the efficient placement of active sensor nodes and set other nodes into sleep mode. An issue is also re- solved by our algorithm, reducing the number of multiple base stations by finding out the best location for the base station without changing its location periodically.4. Synopsis of Our Network ModelIn this paper we deal with the issue of energy efficiency in wireless sensor networks for surveillance of a set of targets with known locality. Scenario of the network is chosen for armed forces purposes like surveillance of the boarder, battle fields and no go areas to acquire the in- formation about enemies and their locations without tak- ing the risk for human personal. We consider that a large number of sensors are distributed randomly in close prox- imity for monitoring and send the monitored information to a gateway node. All nodes are static and makes ad-hoc wireless sensor network. Every sensor nodes must moni-tor the area all the time in its operational range and each sensor has fixed transmission range. In network model we assume that each sensor has unique pre configured Id and Global/proactive routing algorithms are used. Main advantage of proactive algorithm is not route latency but drawback is the high maintenance overhead when many of the routes are never used.Proactive routing is appro-priate for networks with: Small size, low mobility and high communication rates. We proposed an algorithm called as most nearest most used routing algorithm for this purpose. By using MNMU-RA we can find the per-fect location of node for energy harvesting which also reduce the overall energy consumption and cost.4.1. Most Nearest Most Used Routing Algorithm Run shortest path routing algorithm or link state routing to find the shortest path for each node in the wireless sensor network. Calculate all the possible shortest paths for each node. Then find the MNMU node (Figure 1).∙ A node which is most nearest to the gateway node.∙Select a node which is used in maximum number of shortest paths.Figure 1. Location of selected MNMU node.H. B. KHALIL, S. J. H. ZAIDI 164In above network model we assumed that sensed in- formation is equally probable for all the nodes. Then we calculate the shortest path for the nodes A, B and C. Then we find out the nodes which are most nearest to the gate way node. In above network model there are only two nodes X and Y which are closer to the gateway node. Then for selection we give the preference to the node which is most used in shortest paths. In above model Y is node which is most used in all shortest paths. If nodes A, B and C transmit their data the entire time node Y will be included in their path. Then every node keeps its routes information towards the node Y for future communica- tions. Flow chart of our algorithm is given in Figure 2. 4.2. Proposed SolutionWe used our algorithm to find most nearest most used node in a network, that node should be active all the time while other sensors remain in sleep mode and keep sens- ing. As we use proactive routing so each sensor knows its path towards the MNMU node. If a node has to send its information before sending it will wake up the nodes along his route. When MNMU nodes receive the infor- mation it will forward the data to the gateway and sets all the nodes into sleep mode. The critical issue in this solu- tion is that if a node (MNMU node) remains active all the time then its energy source will be empty soon. We re- solve this issue by using the energy harvesting concept at MNMU node [1]. We can also use secondary batteryFigure 2. MNMU routing algorithm flow chart. which is rechargeable and coupled with photovoltaic cell[10]. If all the nodes can generate energy from light, vi-bration, heat etc [11,12] it will increase the system cost.We don’t need to replace all the nodes with secondary sources. By replacing only one node (MNMU node) re-solves the issue and slightly increases the cost of theoverall system. But effectively prolong the life time ofsensor network. A solution given by Gandham et al. [9]can be more energy efficient if we implement our pro-posed algorithm with every new location of mobile basestation. Split the network in equal parts and periodicallychange the position of base station in each part. Basestation can be easily implemented at the place of MNMUnode in each part of the network instead of replacing itoutside the network. MNMU node will reduce the multihop and number of transmission which directly reducethe energy consumption.5. ExperimentWe done the experiment by implementing our proposedalgorithm in a network and calculate the amount of en-ergy utilization using MATLAB. Then implement theconcept of disjoint set and analyze the values at same network. For simulation 20 nodes containing one gate-way node are distributed randomly in 30 meter squarearea. We consider the features of MICA2 mote platform.It is third generation mote specifically built for WSNs [4].MICA2 have selectable transmission power range whichoffers adjustable communication ranges, selected trans-mission range for each node is 10 meters. The packetlength is fixed at 200 bits. MICA2 usually operated with3 V battery and other features mentioned in Table 1.We divided our analysis in three parts; first we calcu-late the power consumption using disjoint sets methods[3], then we apply our algorithm and calculate & com-pare power consumption. Same network and topologytaken in which each node remains active all the time andno energy saving protocol and technique is implemented.Energy calculated during the 20 rounds, all nodes areactive in first five rounds in which they sense and trans-mit the data. After ten rounds there is no activity andnodes go to sleeping mode according to implemented Table 1. Features of MICA2 motes platform [12,13].Operation/Features UnitListening 8mA Receiving 10mA Transmission 17mA Sleep 19µA Radio Frequency 900 MHzCPU 8 bit Atmel at 8 MHzBandwidth 40KbpsH. B. KHALIL, S. J. H. ZAIDI165methodology. Calculated results are given in Figures3 and 4.Simulation ResultsFigure 3 shows the result comparison of energy con- sumption in different modes; sensing, Transmission and sleeping of network. In Figure 3(a) set of all the active nodes shown by blue line are transmitting the data with- out applying any energy saving protocol. During the transmission if all nodes are active they will keep trans- mitting the information to each other and maximum amount of energy is consumed. In disjoint system only active set take part in transmission and inactive nodesFigure 3. Power consumptions in different modes. (a) Trans- mission mode; (b) Power consume by sleeping nodes; (c)Power consume by active nodes in sleep mode. Figure 4. Result and comparison of energy consumption in different modes.remain inactive during the transmission of active set. Our proposed algorithm gives lowest amount of energy con- sumption because only the MNMU node and less number of nodes take part in transmission. Energy consumed by inactive nodes in sleeping modes is shown in Figure 3(b). Energy consumption of sleeping nodes is in µwatts. Ac- cording to our algorithm 19 nodes set to sleep mode and only one MNMU node is active. While Figure 3(c) shows the separately calculated energy consumption by active nodes when there is no activity and network is in idle mode. Similarly in sleeping mode only MNMU node remains active and rest of the network sets to sleep mode. Figure 4 shows the result of energy consumption of entire network in different rounds. In first 5 rounds we assume that there is no sensed information to send; all the nodes are active in listening mode and keep sensing. In 5 to 10 rounds nodes are transmitting their sensed in- formation to the gateway. After round 10 there is no ac- tivity and nodes set to sleep mode in sleep mode only energy consumed by active nodes are calculated and en- ergy consumed by sleeping nodes which is in µwatts is neglected. Our algorithm gives the minimum energy con- sumption during the transmission in which fewer num- bers of nodes take part in routing and also in sleep mode by keeping only MNMU node active.6. ConclusionWe presented the most nearest most used routing algo- rithm to reduce the energy utilization in wireless sensor networks. Using this algorithm we find the best location of energy harvested node in a network. Our algorithm involves least number of nodes during transmission and keeps one node active in sleep mode. That significantly reduces the energy consumption during the transmissionH. B. KHALIL, S. J. H. ZAIDI 166and sleep mode when there is no activity. An open re- search issue is the heterogeneity of energy resources of the nodes that must be resolved after practical imple- mentation in any network. In our solution there is uneven energy consumption due to the topology of the network and nature of data flow. But that uneven energy con- sumption is helpful to reduce the energy consumption of entire network7. Future DirectionDesired goal in wireless networks is energy efficiency to maximize the network life. Our algorithm can be used to find the location of cluster header quickly in novel clus- tering algorithm for energy efficiency in wireless sensor networks [8]. Further we can implement coding tech- niques to reduce the number of transmissions at MNMU node. Energy consumes per bit or per packet transmis- sion can be reduce. Number of packets can be transmit- ted as a single packet by applying x-or Operations which reduces the energy but may cause of slighter delay. To apply this technique sensor nodes must be smarter and have ability to do this quickly.REFERENCES[1]I. F. Akyildiz, T. Melodia and K. Chowdhury, “A Surveyon Wireless Multimedia Sensor Networks,” ComputerNetworks, Vol. 51, No. 4, 2007, pp. 921-960.doi:10.1016/net.2006.10.002[2]J. M. Kahn, R. H. Katz and K. S. J. Pister, “EmergingChallenges: Mobile Networking for Smart Dust,” Inter-national Journal of Communication Networks, Vol. 2, No.3, 2000, pp. 188-196.[3]M. Cardei and D. Z. Du, “Improving Wireless SensorNetwork Lifetime through Power Aware Organization,”Wireless Networks, Vol. 11, No. 3, 2005, pp. 333-340.doi:10.1007/s11276-005-6615-6[4]Q. Hu and Z. Z. Tang, “An Adaptive Transmit PowerScheme for Wireless Sensor Networks,” 3rd IEEE Inter-national Conference on Ubi-Media Computing, Jinhua, 5-7 July 2010, pp. 12-16.[5]W. Ye, J. Heidemann and D. Estrin, “An Energy-EfficientMAC Protocol for Wireless Sensor Networks,” Proceed- ings of the IEEE INFOCOM, New York, 23-27 June 2002, pp. 1567-1576.[6]W. Ye, J. Heidemann and D. Estrin, “Medium AccessControl with Coordinated Adaptive Sleeping for Wireless Sensor Networks,” IEEE/ACM Transactions on Network- ing, Vol. 12, No. 3, 2004, pp. 493-506.doi:10.1109/TNET.2004.828953[7]Q. Hu and Z. Tang, “ATPM: An Energy Efficient MACProtocol with Adaptive Transmit Power Scheme for Wire- less Sensor Networks,” Journal of Multimedia, Vol. 6, No.2, 2011, pp. 122-128. doi:10.4304/jmm.6.2.122-128[8] A. P. Abidoye and N. A. Azeez, “ANCAEE: A Novel Clus-tering Algorithm for Energy Efficiency in Wireless Sen- sor Networks,” Journal of Wireless Sensor Networks, Vol.3, No. 9, 2011, pp. 307-312. doi:10.4236/wsn.2011.39032 [9]S. R. Gandham, M. Dawande, R. Prakash and S. Venkate-san, “Energy Efficient Schemes for Wireless Sensor Net- works with Multiple Mobile Base Stations,” Global Tele- communications Conference, San Francisco, 1-5 Decem- ber 2003, pp. 377-381.[10]M. A. M. Vieira, C. N. Coelho, D. C. Silva and J. M. Mata,“Survey on Wireless Sensor Network Devices,” Proceed- ings of IEEE International Conference on Emerging Tec- hnologies and Factory Automation (ETFA’03), Lisbon, 16-19 September 2003, pp. 537-544.[11]J. Paradiso and T. Starner, “Energy Scavenging for Mo-bile and Wireless Electronics,” Pervasive Computing, Vol.4, No. 1, 2005, pp. 18-27. doi:10.1109/MPRV.2005.9 [12]V. Gungor and G. Hancke, “Industrial Wireless SensorNetworks: Challenges, Design Principles, and Technical Approaches,” IEEE Transactions on Industrial Electron- ics, Vol. 56, No. 10, 2009, pp. 4258-4265.doi:10.1109/TIE.2009.2015754[13]CrossBow, Mica2 Data Sheet./Products/Product_pdf_files/MICA%20data%20sheet.pdf。
天津理工大学 计算机网络题库
PART Ⅰ: ChoiceB 1. Which of the following services does not the transport layer provide for the application layer?A.In-order delivery of data segments between processesB.Best effort delivery of data segments between communicating hostsC.Multiplexing and demultiplexing of transport layer segmentsD.Congestion controlA 2. What are the two of the most important protocols in the Internet?A. TCP and IPB. TCP and UDPC. TCP and SMTPD. ARP and DNSC 3. The Internet provides two services to its distributed applications: a connection oriented reliable service and a ( ).A. connection oriented unreliable serviceB. connectionless reliable serviceC. connectionless unreliable serviceD. In order data transport serviceD 4. Processes on two different end systems communicate with each other by exchanging ( ) across the computer network.A. packetsB. datagramC. framesD. messagesA 5. The job of delivering the data in a transport-layer segment to the correct socket is called ( ).A. demultiplexingB. multiplexingC. TDMD. FDMC 6. Two important reasons that the Internet is organized as a hierarchy of networks for the purposes of routing are:A.Least cost and maximum free circuit availabilityB.Message complexity and speed of convergenceC.Scale and administrative autonomyD.Link cost changes and link failureB 7. Which of characters is not distance-vector algorithm’s characters？（）A. iterativeB. globalC. asynchronousD. distributedD 8. The length of IPV6 address is （）bits.A. 32B. 48C. 64D. 128C 9. The host component of a CIDR address of the form a.b.c.d/25 can contain addresses for:A.225 hosts (minus “special” hosts)B.512 hosts (minus “special” hosts)C.2(32-25) hosts (minus “special” hosts)D.25 hosts (minus “special” hosts)C 10. The primary function of the address resolution protocol (ARP) that resides in Internet hosts androuters is:A.To provide LAN router functionsB.To translate between LAN addresses and physical interface addressesC.To translate IP addresses to LAN addressesD.To calculate the shortest path between two nodes on a LANA 11. The POP3 protocol runs over ____ and uses port ____.A. TCP 110B. UDP 110C. UDP 25D. TCP 25D 12.When a destination host transport layer receives data from the network layer, it unambiguouslyidentifies the appropriate process to pass the data to by using a triplet consisting of:A. Source port #, destination IP address, and source IP addressB. Destination port #, source port #, process ID#C. Destination port #, source port #, destination IP addressD. Destination port #, source port #, source IP addressD 13. From the list below, select the items found in the TCP segment structure that are not found in theUDP segment structure:A. Application Generated DataB. Destination Port #C. Source Port #D. Sequence #A 14. The RIP routing protocol is based on an algorithm that is:A. Based on information received only from link “neighbors”B. A link state algorithmC. An OSPF algorithmD. A centralized routing algorithmB 15. With an exterior routing protocol, which of the following issues generally dominates the routing decisions?A. Geographical distance between AS’sB. PolicyC. Number of AS’s traversedD. Current congestion levels in the AS’sA 1. End system are connected together by ____.A. communication linksB. application layerC. transport layerD. the network layerC 2. Which application’s NOT using TCP?A. SMTPB. HTTPC. DNSD. All of themB 3. In the polling protocols, the master node polls each of the nodes in a/an ____ fashion.A. randomB. appointedC. round-robinD. uncirculatedC 4. The DNS protocol runs over ____ and uses port ____.A. UDP 36B. TCP 36C. UDP 53D. TCP 53A 5. TCP provides a ____ service to its applications to eliminate the possibility of the sender over-flowingthe receiver’s buffer.A. flow-controlB. congestion controlC. reliability controlD. data connectionD 6. We can classify just about any multiple access protocol as belonging to one of three categories: channel partitioning protocols, random access protocols, and ____.A. address resolution protocolsB. Dynamic host configuration protocolsC. link-control protocolsD. taking-turns protocolsB 8. The maximum transfer unit(MTU) in Ethernet frame structure is ()byte .A. 1000B. 1500C. 800D. 2000B 9. The socket of UDP is identified by _____ and _______.A. source IP address and source port numberB. destination IP address and destination port number.C. source IP address and destination port number.D. destination IP address and source IP address.C 10. Which is not plug and play in the following four items?A. DHCPB. HubsC. RoutersD. SwitchesD 11．Which of routers is not default routers ?A. first-hop routerB. source routerC. destination routerD. second-hop routerB 13. ICMP is_____.A. the protocol of Application layerB. the protocol of network layerC. the protocol of transport layerD. not a part of TCP/IP protocolsB 14. As general, we has following channel partitioning protocols except ____.A. TDMB. CSMAC. FDMD.CDMAD 15. ____ is most used for error reporting.A. UDPB. SMTPC. FTPD. ICMPB 16. The header of IPV6 is ____byte.A. 20B. 40C. 60D. 80B 17. In the network layer these service are host-to-host service provided by ____. （B）A. the transport layer to the network layerB. the network layer to the transport layerC. the network layer to the network layerD. the transport layer to the transport layerA 18. If there is not enough memory to buffer an incoming packet , a policy that drop the arriving packet called ____.A. drop-tailB. packet lossC. protocolD. encapsulationC 19. In either case, a ____ receives routing protocol messages, which are used to configure its forwarding table.A. serverB. hostC. routerD. ModemD 20. Which of the following functions does not belong to PPP___.A. framingB. link-control protocolsC. network-control protocolsD. error correctionB 1. Which of the following services does the Internet network layer provide for the Internet transport layer?A.In-order delivery of data segments between processesB.Best effort delivery of data segments between communicating hostsC.Multiplexing and demultiplexing of transport layer segmentsD.Congestion controlD 2. The main task of the Internet’s Domain Name System (DNS) is to:A.Translate port numbers to IP addressesB.Specify the standards for Internet domain namesC.Provide an authority for registering domain namesD.Translate mnemonic（记忆的）names to IP addressesA 10. The FTP protocol runs over ____ and uses port ____.A. TCP 21B. TCP 80C. UDP 20D. TCP 110C 3.RDT3.0’s receiver FSM is same to:a) RDT1.0 b) RDT2.1 c) RDT2.2 d) RDT2.0B 4.The Transmission Control Protocol (TCP) provides which of the following services?a)End-to-end station addressingb)Application multiplexingc)Inter network routingd)Medium access control (MAC)D 6.Given that the requested information is not available at any intermediate databases, a non-iterated DNS query from a requesting host would follow the path:a)Root name server, local name server, authoritative name serverb)Authoritative name server, root name server, host name serverc)Local name server, root name server, local name server, authoritative name servere)Local name server, root name server, authoritative name serverA 8.lect the four essential steps, briefly described, for terminating a TCP connection between a client and a server, assuming that the initiating host is the client:(1)Client sends TCP segment with ACK0 and final sequence number(2)Client sends TCP segment with FIN =1 and goes into FIN_WAIT state(3)Server sends TCP segment to ACK the client’s FIN request and enters CLOSE_WAIT state(4)Server sends TCP segment with FIN=0(5)Server sends TCP segment with FIN=1(6)Client sends TCP segment with to ACK server’s FIN and enters second FIN_WAIT state(7)Client sends TCP segment with FIN=0a) 2，3，5，6 b) 5，1，2，3 c) 1，3，5，7 d) 2，3，4，6B 10.When compensating for link cost changes in the distance vector algorithm, it can generally be said that:a)Increased costs are propagated quickly, i.e., “bad news” travels fastb)Decreased costs are propagated rapidly, i.e., “good news” travels fastc)Decreased costs do not converged)None of the aboveB 14.As an IP datagram travels from its source to its destination:a)the source IP address is changed at each router to identify the sending routerb)the router uses the destination IP address to consult its routing tablec)the router does not use the IP addresses in the datagramd)the destination IP address is changed at each router to reflect the next hopC 15.From the list below, choose the bit pattern which could be a valid generator value for the CRC code (R) 11010:a)1110b)011010c)100101d)10011A 16.Consider sending a 1300 byte IPv4 datagram into a link that has an MTU of 500 bytes:a)Three fragments are created.b)Four fragments are created.c)Three fragments are created with offsets 0, 500 1000d)The last fragment consists of exactly 300 bytes of data from the original datagramC 17.Suppose one IPv6 router wants to send a datagram to another IPv6 router, but the two are connected together via an intervening IPv4 router. If the two routers use tunneling, then:a)The sending IPv6 router creates an IPv4 datagram and puts it in the data field of an IPv6datagram.b)The sending IPv6 router creates one or more IPv6 fragments, none of which is larger than themaximum size of an IPv4 datagram.c)The sending IPv6 router creates an IPv6 datagram and puts it in the data field of an IPv4datagram.d)The sending IPv6 router creates an IPv6 datagram and intervening IPv4 router will reject theIPv6 datagramD 18.Which of the following was an important consideration in the design of IPv6a)fixed length 40-byte header and specified options to decrease processing time at IPv6 nodesb)128-bit addresses to extend the address spacec)different types of service (flows) definedd)all of the aboveD 19.A network bridge table is used to perform the following:a)Mapping MAC addresses to bridge port numbersb)Forwarding frames directly to outbound ports for MAC addresses it handlesc)Filtering (discarding) frames that are not destined for MAC addresses it handlesd)All of the abovePART Ⅱ: True / False (1 points per question – total:20 points)1. The DNS server can update the records. (T)2. The TCP connection is a direct virtual pipe between the client’s socket and the server’s connection socket. （T）3. SMTP protocol connect the sender’s mail server and receiver’s mail server (T)4. Whereas a transport-layer protocol provides logical communication between processes running on different hosts, a network-layer protocol provides logical communication between hosts. (T)5. UDP and TCP also provide integrity checking by including right-detection fields in their headers. (F)6. If the application developer chooses UDP instead of TCP, then the application is not directly talking with IP. ( F )7. When we develop a new application, we must assign the application a port number. ( T )8. Real-tine applications, like Internet phone and video conferencing, react very poorly to TCP’s congestion control. ( T )9. The sender knows that a received ACK or NAK packet was generated in response to its most recently transmitted data packet. (T)10. To simplify terminology, when in an Internet context, we refer to the 4-PDU as a unit. (F)11. DV algorithm is essentially the only routing algorithm used in practice today in the Internet。
全国计算机等级考试三级网络技术英文单词
第一章计算机基础Computer计算机Client客户机Server服务器Peer To Peer对等，P2P计算机辅助工程：Computer Aided Design CAD计算机辅助设计Computer Aided Manufacturing CAM计算机辅助制造Computer Aided Engineering CAE计算机辅助工程Computer Aided Instruction CAI计算机辅助教学Computer Aided Testing CAT计算机辅助测试GIS地理信息系统计算机分类：Mainframe大型主机Minicomputer小型计算机/迷你电脑Personal Computer个人计算机，Microcomputer微型计算机Workstation工作站Supercomputer巨型计算机/超级计算机Minisuper小巨型计算机/小超级计算机服务器按处理器体系结构划分：Complex Instruction Set Computer CISC复杂指令集计算机Reduced Instruction Set Computer RISC精简指令集计算机Very Long Instruction Word VLIW超长指令字Explicitly Parallel Instruction Computing EPIC清晰并行指令计算/简明平行指令计算Intel Architecture IA英特尔架构Blade Serer刀片式服务器计算机分类：Server服务器Workstation工作站Desktop PC台式机Notebook笔记本，Mobile PC便携机/移动PCHandheld PC掌上电脑，Sub-Notebook亚笔记本Ultra Mobile PC UMPC超便携计算机PDA个人数字助理LCD液晶显示器Serial Advanced Technology Attachment SATA串行高级技术附件Serial Attached SCSI串行SCSI硬盘Redundant Array Of Independent Disks RIAD独立磁盘冗余阵列，Disk Array磁盘阵列计算机的技术指标：Million Instruction Per Second,MIPS,单字长定点指令的平均执行速度Million Floating Instruction Per Second,MFLOPS,单字长浮点指令的平均执行速度Bits Per Second,Bps,每秒传输位数Mean Time Between Failure,MTBF,平均无故障时间Mean Time To Repair,MTTR,平均故障修复时间奔腾芯片的技术特点：Superscalar超标量Superpipeline,超流水线Peripheral Component Interconnect,PCI,外围部件互联Video Electronic Standard Association,VESA,视频电子标准协会Streaming SIMD Extension,SSE,流式的单指令流、多数据流扩展指令Mainboard主板、主机板，Motherboard,母版Adapter Card网卡、适配卡软件按授权方式分类：Commercial-Ware商业软件Share Ware共享软件Freeware自由软件信息的形式：Number数字Text文本Graphic图形Image图像Sound声音Media媒体Multimedia多媒体Videodisk视频光盘Speech语音Audio音响Multimedia PC,MPC,多媒体计算机Media Player媒体播放器Sound Recorder录音机Object Linking And Embedding,OLE,对象链接和嵌入数据压缩编码方法：Source Coding源编码Hybrid Coding混合编码Entropy Coding信息熵编码法Huffman Coding哈尔曼编码Run Length Coding游程编码Arithmetic Coding算术编码Prediction Coding预测编码法Differential Pulse Code Modulation,DPCM,微分脉码调制Delta Modulation,DM,Δ调制Transformation Coding变换编码法Discrete Fourier Transform,DFT,离散傅里叶变换Discrete Cosine Transform,DCT,离散余弦变换Discrete Hadamard Transform,DHT,离散哈达玛变换Vector Quantization Coding矢量量化编码法Joint Photographic Experts Group,JPEG,联合图像专家组International Organization For Standardization,ISO,国际标准化组织CCITT国际电报电话咨询委员会Baseline Sequential Codec基线顺序编解码Moving Picture Experts Group,MPEG,运动图像专家组HDTV高清晰度电视ITU国际电信联盟ISDN综合业务数字网IECNode结点Link链接Streaming Media流媒体第二章网络技术基础Advanced Research Projects Agency,ARPA,美国国防部高级研究计划局System Network Architecture,SNA,系统网络体系结构Distributed Computer Architecture,DCA,数字网络体系结构Open System Interconnection,OSI,开放系统互连Ethernet以太网Token Bus令牌总线Token Ring令牌环Fiber Distributed Data Interface,FDDI,光纤分布式数据接口National Information Infrastructure,NII,国家信息基础设施Global Information Infrastructure Committee,GIIC,全球信息基础设施委员会B-ISDN宽带业务综合数据网ATM异步传输模式IEEE美国电子电气工程师协会PSTN公用电话交换网CNNIC中国互联网网络信息中心计算机网络按覆盖的地理范围分类：Local Area Network,LAN,局域网Metropolitan Area Network,MAN,城域网Wide Area Network,WAN,广域网CATV有线电视网Nyquist奈奎斯特Shannon香农Circuit Switching电路交换Store-And-Forward Switching存储转发交换Message Switching报文交换Packet Switching报文分组交换Datagram,DG,数据报Virtual Circuit,VC,虚电路Message报文Packet报文分组Protocol协议Network Architecture计算机网络体系结构Implementation实现Interconnection互连性Interoperation互操作性Portability可移植性Service Definition服务定义Protocol Specification协议规格说明Physical Layer物理层Data Link Layer数据链路层Network Layer网络层Transport Layer传输层Session Layer会话层Presentation Layer表示层Application Layer应用层End-To-End端到端User Agent用户代理FTAM文件传送访问和管理VT虚拟终端TP事务处理RDA远程数据库访问MMS制造业报文规范Intercommunication互通Internet Layer互联层Host-To-Network Layer主机-网络层Transport Control Protocol,TCP,传输控制协议User Datagram Protocol,UDP,用户数据报协议Byte Stream字节流Byte Segment字节段Telnet远程登录协议File Transfer Protocol,FTP,文件传输协议Simple Mail Transfer Protocol,SMTP,简单邮件传输协议Domain Name Service,DNS,域名服务Router Information Protocol,RIP,路由信息协议Network File System,NFS,网络文件系统Hypertext Transfer Protocol,HTTP,超文本传输协议Page页面Web Site Web站点CERN欧洲粒子物理实验室Podcast播客Blog,Weblog博客，网络日志，网志Internet Protocol Television,IPTV,互联网协议电视/网络电视：Video On Demand,VOD,视频点播技术Live TV直播电视Time Shift TV时移电视Instant Messaging,IM,即时通信Wireless MAN,WMAN,无线城域网Bluetooth蓝牙Personal Operating Space,POS,个人操作空间Personal Area Network,PAN,个人区域网络Wireless Personal Area Network,WPAN,无线个人区域网络Mobile Ad Hoc Network,MANET,移动Ad Hoc网络Wireless Sensor Network,WSN,无线传感器网络Packet Radio Network,PRNET,分组无线网第三章局域网基础Fast Ethernet,FE,快速以太网Gigabit Ethernet,GE,千兆以太网Collision冲突Media Access Control,MAC,介质访问控制Logical Link Control,LLC,逻辑链路控制WG工作组TAG技术行动组Carrier Sense Multiple Access With Collision Detection,CSMA/CD,带冲突检测的载波侦听多路访问Truncated Binary Exponential Backoff截止二进制指数后退延迟Unicast Address单一节点地址Multicast Address多点地址Broadcast Address广播地址FCS帧校验字段CRC循环冗余校验Registration Authority Committee,RAC,注册管理委员会Company-Id公司标识Organizationally Unique Identifier,OUI,机构唯一标识符Extended Unique Identifier扩展的唯一标识符EPROM网卡的只读存储器Share LAN共享式局域网Switched LAN交换式局域网Media Independent Interface,MII,介质独立接口Gigabit Media Independent Interface,GMII,千兆介质独立接口High Speed Study Group,HSSG,高速研究组Switched Ethernet交换式以太网Ethernet Switch以太网交换机Hub集线器Cut Through直通Store And Forward存储转发Virtual Network虚拟网络Virtual LAN,VLAN,虚拟局域网Nomadic Access漫游访问Infrared Radio,IR,红外无线Channel Encoder信道编码器Frequence Hopping Spread Spectum,FHSS,跳频扩频通信Direct Sequence Spread Spectrum,DSSS,直接序列扩频Point Coordination Function,PCF,点协调功能Distributed Coordination Function,DCF,分布协调功能Collision Avoidance,CA,冲突避免Interframe Space,IFS,帧间间隔Bridge网桥网桥按路由表的建立方法分类：Transparent Bridge透明网桥Source Routing Bridge源路由网桥Spanning Tree生成树Discovery Frame发现帧第四章服务器操作系统Network Operating System,NOS,网络操作系统Process进程File Handle文件句柄File Allocation Table,FAT,文件表Virtual File Allocation Table,VFAT,虚拟文件表High Performance File System,HPFS,高性能文件系统Basic Input/Output System,BIOS,基本输入/输出系统Graphics Device Interface,GDI,图形设备接口Application Programming Interface,API,应用编程接口Kernel内核Monolithic Kernel单内核Microkernel微内核Nanokernel超微内核Exokernel外核Hardware Abstract Layer,HAL,硬件抽象层Directory Service,DS,目录服务Network Server网络服务器Network Station网络工作站网络操作系统的基本功能：File Service文件服务Print Service打印服务Database Service数据库服务Communication Service通信服务Message Service信息服务Distributed Service分布式服务Network Management Service网络管理服务IntranetSQL结构化查询语言Graphic User Interface,GUI,图形用户界面Domain域Primary Domain Controller主域控制器Backup Domain Controller备份域控制器Thread线程Preemptive抢占式NDIS网络驱动接口规范TDI传输驱动接口Netbeui扩展用户接口Active Directory Manager活动目录管理Tree域树Forest域森林Organizational Unit,OU,组织单元Role角色DEP数据执行保护NAP网络访问保护NAT自动网络地址转换Server Core服务器内核Powershell外壳Business Intelligence,BI,商务智能Netware Core Protocol,NCP,Netware核心协议System Failure Tolerance,SFT,系统容错File Server Mirroring文件服务器镜像Transaction Tracking System,TTS,事物跟踪系统Novell Directory Services,NDS,Novell目录服务Swapping对换Independent Software Vendors,ISV,独立软件厂商Dynamic Logic Partition动态处理器备用SWA软件助手OE操作环境第五章Internet基础ISP互联网服务提供商Remote Access Server远程访问服务器Modem调制解调器ADSL非对称数字用户线路Hybrid Fiber Coaxial,HFC,混合光纤同轴电缆网Cable TV,CATV,有线电视网DDNATMNetid网络号Hosted主机号NATAddress Resolution Protocol,ARP,地址解析协议Dynamic Binding动态绑定Cache缓存区Datagram数据报Maximum Transmission Unit,MTU,最大传输单元源路由选项的分类：Strict Source Route严格源路由选项Loose Source Route松散源路由选项Time Stamp时间戳Universal Time格林尼治时间Internet Control Message Protocol,ICMP,互联网控制报文协议Source Quench源站抑制Routing路由选择Router路由器Metric度量值度量值中经常使用的特征：Hop Count跳数Bandwidth带宽Delay延迟Load负载Reliability可靠性Cost开销应用最广的路由选择协议：Routing Information Protocol,RIP,路由信息协议Open Shortest Path First,OSPF,开放式最短路径优先协议Vector-Distance,V-D,向量-距离，Bellman-FordLink-Status,L-S,链路-状态Convergence收敛CIDR无类域间寻址DHCP动态主机配置协议Qos服务质量保证TCP提供的服务的特征：Connection Orientation面向连接Complete Reliability完全可靠性Full Duplex Communication全双工通信Stream Interface流接口Reliable Connection Startup&Graceful Connection Shutdown连接的可靠建立和优雅关闭Retransmission重发Acknowledgement确认Round Trip Time,RTT,往返时间3-Way Handshake3次握手Window窗口Well-Known Port著名端口第六章Internet基本服务服务器处理多个并发请求的方案：Iterative Server重复服务器Concurrent Server并发服务器First In,First Out先进先出Daemon守护进程Master主服务器Slave从服务器Worm蠕虫互联网的命名机制：Flat Naming无层次命名机制Hierarchy Naming层次型命名机制Label标号Domain域域名解析的两种方式：Recursive Resolution递归解析Iterative Resolution反复解析资源记录的组成：Domain Name域名Time To Live,TTL,最大生存周期，有效期Type类型Class类别Value（域名的）具体值Network Virtual Terminal,NVT,网络虚拟终端Real Terminal实终端数据连接建立的模式：Active主动模式Passive被动模式电子邮件传输协议：Simple Mail Transfer Protocol,SMTP,简单邮件传输协议Post Office Protocol,POP,邮局协议Interactive Mail Access Protocol,IMAP,RFC822将电子邮件报文分为两部分：Mail Header邮件头Mail Body邮件体Multipurpose Internet Mail Extensions,MIME,多用途Internet邮件扩展MIME-Version版本号Content-Type数据类型Content-Transfer-Encoding数据编码类型Quoted-Printable打印编码World Wide Web,WWW,European Center For Nuclear Research,CERN,欧洲核物理研究中心Hyper Text Markup Language,HTML,超文本标记语言Uniform Resource Locator,URL,统一资源定位符History历史Bookmark书签Default默认状态Tag标记Attitude属性Secure Sockets Layer,SSL,安全套接层NTFS第七章网络管理与网络安全网络管理的功能：Configuration Management配置管理Fault Management故障管理Accounting Management计费管理Performance Management性能管理Security Management安全管理NME网管代理模块IETF Internet工程任务组SNMP简单网络管理协议Manager管理者Agent代理者Polling轮询Interrupt-Based基于中断MIB管理信息库Trap-Directed Polling陷入制导轮询方法CIMP公共管理信息协议Association Control Protocol,ACP,联系控制协议Remote Operation Protocol,ROP,远程操作协议Protocol Data Unit,PDU,协议数据单元NCSC国家计算机安全中心Trusted Computer Standard Evaluation Criteria可信任计算机标准评估准则Orange Book橘皮书Dos拒绝服务Ddos分布式拒绝服务DES数据加密标准DEA数据加密算法AES高级加密算法RSANIST美国国家标准和技术研究所Key Distribution Center,KDC,密钥分发中心Certification Authority,CA,认证中心信息完整性认证方法：Massage Authentication Code,MAC,消息认证码Manipulation Detection Code,MDC,篡改检测吗认证函数：Message Encryption Function,MEF,信息加密函数Massage Authentication Code,MAC,信息认证码Hash Function散列函数DSS数字签名标准Token持证MIT麻省理工学院安全电子邮件常用技术：Pretty Good Privacy,PGP,非常好的私密性Secure/Multipurpose Internet Mail Extension,S/MIME,安全/通用Internet邮件扩充Passphrase口令短语Clear-Signed透明签名Ipsec IP安全协议：Authentication Head,AH,身份认证头Encapsulation Security Payload,ESP,封装安全负载TLS运输层安全Internetwork Security Monitor,互联网安全监视器HAR主机审计记录Generic Decryption,GD,类属解密第八章网络应用技术Multicast Backbone,Mbone,组播主干网Unicast单播Broadcast广播Multicast组播IANA管理局组播的相关协议：Internet Group Management Protocol,IGMP,互联网组管理协议CGMPRouter-Port Group Management Protocol,RGMP,路由器-端口组管理协议Dense-Mode Multicast Routing Protocol密集模式组播路由协议Flooding洪泛Distance Vector Multicast Routing Protocol,DVMRP,距离矢量组播路由协议Multicast For Open Shortest Path First,MOSPF,开放最短路径优先的组播扩展协议Protocol Independent Multicast-Dense Mode,PIM-DM,独立组播密集模式Core Based Trees,CBT,基于核心的Multiprotocol Border Gateway Protocol,MBGP,多协议边界网关协议Multicast Source Discovery Protocol,MSDP,组播源发现协议Centralized Topology集中式拓扑结构Decentralized Unstructured Topology分布式非结构化拓扑Distributed Hash Table,DHT,分布式散列表Node ID结点标识符Object ID资源标识符Chum波动Hybrid Structure混合式结构Instant Messaging And Presence Protocol Working Group,IPPWG,IMPP工作小组Request For Comment,RFC,请求评论Internet Engineering Task Force,IETF,Internet工程任务组IM系统的附加功能：Voice/Video Chat音频/视频聊天Application Sharing应用共享File Transfer文件传输File Sharing文件共享Game Request游戏邀请Remote Assistance远程助理Whiteboard白板Session会话Session Initiation Protocol,SIP,会话初始化协议SIP For Instant Messaging And Presence Leverage Extension,SIMPLEExtensible Messaging And Presence Protocol,XMPP,SIP系统的组成：User Agent用户代理User Agent Client,UAC,用户代理客户机User Agent Server,UAS,用户代理服务器Proxy Server代理服务器Redirect Server重定向服务器Registrar注册服务器SIP消息的类型：Request请求Response响应SIP消息的组成：Start-Line起始行Field字段Message Body消息体Entity Header实体头Request-Line请求行Status-Line状态行Message Session Relay Protocol,MSRP,消息中断协议Presence Information呈现信息Presence Service呈现服务呈现服务包括：Presence User Agent,PUA,呈现用户代理Presence Agent,PA,呈现代理Presence Server,PS,呈现服务器Watcher申请者Set Top Box机顶盒Near Video On Demand,NVOD,就近式点播电视True Video On Demand,TVOD,真实点播电视Interactive Video On Demand,IVOD,交互式点播电视Voice Over IP,Voip,IP电话，Internet Protocol PhoneIP电话的实现方法：PC-to-PCPC-to-PhonePhone-to-PhoneIP电话的组成：Terminal终端设备Gateway网关Multipoint Control Unit,MCU,多点控制单元Gatekeeper网守Common Gate Interface,CGI,公共网关接口Page Rank网页等级Store Server存储服务器Searcher搜索器Spiders蜘蛛/搜索器Robot机器人/搜索器Crawlers爬虫/搜索器Indexer索引器Sorter排序器Repository知识库Work Stemming词干法Word Truncation截词Link popularity链接流行度Hyperlink超链接。
三层交换机实现三层互联的方法
三层交换机实现三层互联的方法英文回答：To implement layer 3 connectivity using a layer 3 switch, there are several methods that can be used. One common method is to configure the switch with multiple VLANs (Virtual Local Area Networks) and then use a routing protocol to enable communication between the VLANs.Firstly, the layer 3 switch needs to be configured with the appropriate VLANs. VLANs are used to separate network traffic into different logical networks, allowing forbetter network management and security. Each VLAN will have its own subnet and IP address range.Once the VLANs are configured, the layer 3 switch needs to be configured with a routing protocol. A routing protocol is used to exchange routing information between routers and switches, allowing them to dynamically update their routing tables and determine the best path for datapackets to reach their destination.One commonly used routing protocol is OSPF (Open Shortest Path First). OSPF is a link-state routing protocol that uses the concept of areas to scale large networks. By configuring OSPF on the layer 3 switch, it can exchange routing information with other OSPF-enabled devices in the network, allowing for layer 3 connectivity between VLANs.Another method to achieve layer 3 connectivity with a layer 3 switch is to use static routes. Static routes are manually configured routes that specify the next hop for a particular destination network. By configuring static routes on the layer 3 switch, it can forward packets between VLANs based on the static route entries.In addition to VLANs and routing protocols, layer 3 switches can also support other layer 3 features such as access control lists (ACLs) and quality of service (QoS). ACLs can be used to filter traffic based on specific criteria, such as source IP address or protocol, while QoS can prioritize certain types of traffic to ensure optimalperformance.In summary, to implement layer 3 connectivity using a layer 3 switch, VLANs need to be configured to separate network traffic, and a routing protocol or static routes need to be configured to enable communication between VLANs. Other layer 3 features such as ACLs and QoS can also be utilized to enhance network security and performance.中文回答：使用三层交换机实现三层互联的方法有多种。
多径路由协议AOMDV的改进与性能分析
XIAO Kejiang, XIONG Zhongyang, ZHANG Yufang. Improvement and performance analysis of multipath AOMDV routing protocol. Computer Engineering and Applications, 2012, 48（6）：99-101. Abstract：Mobile Ad hoc Network（MANET）is a mobile, multihop wireless network in which effective routing algorithm is critical. Because of the mobility of Ad hoc network, the active route of Ad hoc On-demand Multipath Distance Vector Routing（AOMDV）is no longer the shortest routing. An improved approach to the mentioned deficiencies is proposed：two-hop route is constructed and then the two-hop route information is used to optimize the active route dynamically, making the route distance more shorter. NS-2 simulation results indicate that the improved AOMDV can obtain lower route discovery frequency, lower end-to-end average delay, smaller normalized routing load and more packet delivery ratio than those of the AOMDV. Key words：Mobile Ad hoc Network; routing algorithm; Ad hoc On-demand Multipath Distance Vector Routing（AOMDV）; NS-2 simulation
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At IEEE Communication Networks and Services Research (CNSR 2005), Halifax, Canada.
Shortest-hop Based Reliableຫໍສະໝຸດ Network Multicast
†
K.L. Eddie Law†, Daniel Siu‡ Ryerson University, Toronto, Canada. Email: eddie@ee.ryerson.ca ‡ IBM Canada, Toronto, Canada. Email: siud@sympatico.ca Abstract
Although many multicast communication protocols have been recommended at IETF, reliable multicast communications currently rely on programs built at the application layer, e.g., multicast overlay. This is because there is a lack of reliable multicast protocols. This is even harder for the multicast capable routers to offer transparent reliable multicast services if receivers are on paths with drastically different path characteristics. In this paper, concept of multicast reliability integrated within routing algorithm is discussed. It is important to map reliability from transport layer to network layer, and subsequently from network layer to data link layer. The novelty of the proposed design is to offer packet recovery mechanisms between every two intelligent routers. The resulting shortest-hop based reliability eliminates the retransmission request implosion problem and shortens the error recovery session time along any multicast tree. Consequently, the proposed design offers high goodput performance for multicasting important information in wired and wireless networks.
end-to-end packet recovery techniques. In Section 3, the design details on integrating both positive acknowledgment (ACK) and negative acknowledgment (NACK) techniques in a multicast tree infrastructure are discussed. Packet loss rate is analyzed to determine the operating choice of NACK and ACK mechanisms. Each router has a soft-store for calculating packet loss rate between next intelligent multicast routers and storing temporary packets. In the design, the numbers of retransmission requests between leaves and root are reduced which improve the bandwidth utilization. In Section 4, goodput per link is measured to compare different reliable multicast scheme. In Section 5, extensive experiments have been done in a prototype testbed. Performance results are discussed. Section 6 concludes the paper.