Datacenter Networks
2023年-2024年网络系统软件应用与维护考试题库(含答案)
2023年-2024年网络系统软件应用与维护考试题库（含答案）一、单选题1.管理员要为服务器增加内存。
系统启动后,显示为升级前的内存容量。
以下哪种原因有可能()A、内存不是正确的CAS延迟。
B、内存未安装在正确的插槽内。
C、内存没有正确计时。
D、内存速度不正确参考答案:B2.Linux之父是谁?()A、比尔盖茨B、LinusTorvaldsC、马云D、ElonMusk参考答案:B3.如果网络中只建立了一个域,那么可以称其为()。
A、父域结构B、单域结构C、组织单位D、多域结构参考答案:B4.RPM(Redhatpackagemanager)是由哪个公司提出的一种软件包管理标准?()A、三星B、微软C、甲骨文D、红帽参考答案:D5.()用来存储ActiveDirectory的更改日志。
A、SYSVOL文件夹B、数据库文件夹C、日志文件文件夹D、站点参考答案:C6.用ls–al命令列出下面的文件列表,问那一个文件是符号连接文件。
()A、-rw2hel-susers56Sep0911:05helloB、-rw2hel-susers56Sep0911:05goodbeyC、drwx1helusers1024Sep1008:10zhangD、lrwx1helusers2024Sep1208:12cheng参考答案:D7.在应用程序起动时,如何设置进程的优先级?()A、priorityB、niceC、reniceD、setpri参考答案:B8.NTFS允许长达()个字符的文件名。
A、16B、63C、127D、255参考答案:D9.创建新用户的时候会将这个目录下的文件自动复制到新用户的主目录下,这个目录是。
()A、/etc/skel/B、/etc/default/C、/etc/defaults/D、/etc/profile.d/参考答案:A10.()目录存放的是Linux系统管理的配置文件。
A、etcB、usrC、homeD、var参考答案:A11.Windows系统默认情况防火墙状态是启用的,并且入站连接默认是(),出站连接是允许A、允许B、连接C、阻止D、断开参考答案:C12.()一般翻译做散列,是把任意长度的输入通过散列算法变换成固定长度的输出,该输出就是散列值。
数据中心网络组网架构的趋势
数据中心网络组网架构的趋势作者：赵红来源：《中华建设科技》2017年第08期【摘要】数据中心是数据的传输、计算和存储的中心，集中了各种软硬件资源和关键业务系统，面临异构环境问题、业务融合问题、管理规范等非常复杂的问题，给数据中心的管理带来了巨大挑战，如何构建新一代数据中心网络成为时代主题。
【关键词】数据中心；网络结构；无线DDN；SDN网络Trends in Data Center Network ArchitectureZhao Hong（Tianyuan Ruixin Communication Technology Co.， LtdXi'anShaanxi710075）【Abstract】The data center is the center of data transmission， computing and storage， which focuses on various hardware and software resources and key business systems， which are faced with problems such as heterogeneous environment problems， business integration problems and management specifications， and bring data management to the data center. A great challenge， how to build a new generation of data center network to become the theme of the times.【Key words】Data center；Network structure；Wireless DDN；SDN network1. 前言（1）“数据中心”是一整套复杂的设施，它不仅仅包括计算机系统和其它与之配套的设备（例如通信和存储系统），还包含冗余的数据通信连接、环境控制设备、监控设备以及各种安全装置。
广域存储的一致性和稳定性COPS理论
Princeton University, † Intel Labs, ‡ Carnegie Mellon University
ABSTRACT
To appear in Proceedings of the 23rd ACM Symposium on Operating Systems Principles (SOSP’11)
Don’t Settle for Eventual:
Scalable Causal Consistency for Wide-Area Storage with COPS1.INTRODUCTION
Categories and Subject Descriptors
C.2.4 [Computer Systems Organization]: Distributed Systems
General Terms
Design, Experimentation, Performance
Distributed data stores are a fundamental building block of modern Internet services. Ideally, these data stores would be strongly consistent, always available for reads and writes, and able to continue operating during network partitions. The CAP Theorem, unfortunately, proves it impossible to create a system that achieves all three [13, 23]. Instead, modern web services have chosen overwhelmingly to embrace availability and partition tolerance at the cost of strong consistency [16, 20, 30]. This is perhaps not surprising, given that this choice also enables these systems to provide low latency for client operations and high scalability. Further, many of the earlier high-scale Internet services, typically focusing on web search, saw little reason for stronger consistency, although this position is changing with the rise of interactive services such as social networking applications [46]. We refer to systems with these four properties—Availability, low Latency, Partition-tolerance, and high Scalability—as ALPS systems. Given that ALPS systems must sacrifice strong consistency (i.e., linearizability), we seek the strongest consistency model that is achievable under these constraints. Stronger consistency is desirable because it makes systems easier for a programmer to reason about. In this paper, we consider causal consistency with convergent conflict handling, which we refer to as causal+ consistency. Many previous systems believed to implement the weaker causal consistency [10, 41] actually implement the more useful causal+ consistency, though none do so in a scalable manner. The causal component of causal+ consistency ensures that the data store respects the causal dependencies between operations [31]. Consider a scenario where a user uploads a picture to a web site, the picture is saved, and then a reference to it is added to that user’s album. The reference “depends on” the picture being saved. Under causal+ consistency, these dependencies are always satisfied. Programmers never have to deal with the situation where they can get the reference to the picture but not the picture itself, unlike in systems with weaker guarantees, such as eventual consistency. The convergent conflict handling component of causal+ consistency ensures that replicas never permanently diverge and that conflicting updates to the same key are dealt with identically at all sites. When combined with causal consistency, this property ensures that clients see only progressively newer versions of keys. In comparison, eventually consistent systems may expose versions out of order. By combining causal consistency and convergent conflict handling, causal+ consistency ensures clients see a causally-correct, conflict-free, and always-progressing data store. Our COPS system (Clusters of Order-Preserving Servers) provides causal+ consistency and is designed to support complex online applications that are hosted from a small number of large-scale datacenters, each of which is composed of front-end servers (clients of
思科数据中心Datacenter解决方案
思科数据中心Datacenter解决方案简介数据中心(Datacenter)是企业内部或外部的一个设备空间，它是用于存储、管理和分发数据和应用程序的集中式资源。
随着数字化时代的到来，企业的数据量不断增长，对数据中心的要求也随之提高。
思科(Datacenter)作为全球领先的网络设备供应商，提供了一系列的数据中心解决方案，以满足不同企业的需求。
本文将介绍思科数据中心(Datacenter)解决方案的主要特点和优势。
主要特点1. 扩展性思科数据中心解决方案具有高度的扩展性，可以根据企业的需求进行灵活的扩展。
无论是需要增加存储容量、计算能力还是网络带宽，都可以通过简单的配置和升级来实现。
这使得企业能够根据业务需求快速响应，并在不断变化的市场环境中保持竞争优势。
2. 高可靠性思科数据中心解决方案采用了多种技术来确保高可靠性和服务可用性。
例如，通过多个服务器和存储设备的冗余配置，以及利用虚拟化技术来实现灵活的服务器资源分配，以降低系统故障和数据丢失的风险。
此外，思科数据中心解决方案还提供了强大的网络安全功能，以保护企业的数据免受恶意攻击和数据泄露的威胁。
3. 灵活性思科数据中心解决方案支持多种应用和部署模式。
它可以适应不同的工作负载，包括虚拟化、容器化和云计算等。
企业可以根据自己的业务需求选择适合的部署方式，并通过思科的解决方案轻松实现平滑的迁移和扩展。
4. 性能优化思科数据中心解决方案提供了高性能的硬件和软件组件，以满足企业对数据处理和网络传输的需求。
例如，采用了高速网络交换机、光纤通道和固态硬盘等先进技术，以提高存储和计算的速度和效率。
优势1. 统一管理思科数据中心解决方案通过集中的管理平台，提供了对整个数据中心的统一管理和监控。
管理员可以通过该平台对服务器、存储、网络和安全等组件进行集中管理，以提高管理效率和操作便捷性。
2. 节约成本思科数据中心解决方案通过虚拟化和自动化等技术，可以减少硬件设备和人力资源的需求，从而降低企业的运营成本。
数据中心网络架构浅谈（四）
数据中心网络架构浅谈（四）通常来说，如果一个数据中心服务器规模超过10万台，就可以称large-scale datacenter，也就是常说的大规模数据中心。
大规模数据中心对于网络的要求有很多，但是最突出的就在于稳定和简单。
这两点要求本身也有一定的关联性。
比如，大规模数据中心因为网络设备数量多，所以从统计学的角度来说，出故障的频率也更高。
这里说的故障，不仅包括设备本身出现的硬件软件问题，还包括因为运维过程中对设备误操作引起的故障。
因此，一个简单的网络设计，例如采用统一的硬件连接方式，使用有限的软件功能，能减少故障概率，从而一定程度提升整个网络架构的稳定性。
但是，或许不只对于IT行业，对于任何领域，用简单的方法去解决一个复杂的问题，本身就不简单。
因此，这一次分析一下如何用CLOS架构，来“简单的”管理大规模数据中心的网络。
CLOS架构CLOS架构被广泛应用在现代的数据中心，因为它提供了数据中心的水平扩展能力和大规模数据中心所需要的稳定和简单。
下图就是一个最基本的CLOS单元，Spine和Leaf交换机共同组成数据中心网络，其中Leaf交换机作为TOR交换机，连接服务器；Spine交换机，为Leaf交换机提供网络连接。
水平扩展能力--想要扩展一个CLOS网络架构，通常有两种方法，第一就是增加设备的端口数；第二就是增加更多的层级。
通过增加交换机端口数量，可以连接更多的服务器，如下图所示，端口数量扩大一倍，数据中心规模也扩大了一倍。
也可以增加CLOS架构的层级数。
上面图中都是3-stages CLOS 架构，虽然只有两层交换机，但是因为对应CLOS的理论，是一个对折了的架构，所以被称为3-stages。
在现有的spine-leaf基础上，再增加一层super-spine交换机，就可以构成一个5-stages CLOS架构。
如下图所示，增加了一层super-spine交换机，数据中心规模也水平扩大了一倍。
计算机期刊大全
计算机期刊大全【前言】随着计算机技术的快速发展，越来越多的人开始关注计算机期刊，以获取最新的科研成果和技术进展。
本文旨在介绍全球范围内主要的计算机期刊，帮助读者了解各期刊的主题范围、影响因子、最新收录论文等信息，以提高论文发表效率和科研成果的质量。
【一、计算机科学顶级期刊】计算机领域的顶级期刊，对于任何一位计算机科学家来说，都是非常重要的。
这些期刊的文章水平高、质量优，其发表文章往往具有一定的权威性和影响力。
以下是全球最著名的计算机科学顶级期刊：1.《ACM Transactions on Computer Systems》（ACM TOCS）主题范围：该期刊关注计算机系统的设计、分析、实现和评估等方面，特别是操作系统、网络、分布式系统、数据库管理系统和存储系统等方面的最新研究成果。
影响因子：3.612发行周期：每年4期最新收录论文：Content-Based Data Placement for Efficient Query Processing on Heterogeneous Storage Systems, A Framework for Evaluating Kernel-Level Detectors, etc.2.《IEEE Transactions on Computers》（IEEE TC）主题范围：该期刊刊登计算机科学领域的创新性研究成果，重点关注计算机系统、组件和软件的设计、分析、实现和评估等方面的最新进展。
影响因子：4.804发行周期：每月1期最新收录论文：A Comprehensive View of Datacenter Network Architecture, Design, and Operations, An Efficient GPU Implementation of Imperfect Hash Tables, etc.3.《IEEE Transactions on Software Engineering》（IEEE TSE）主题范围：该期刊涉及软件工程领域的各个方面，包括软件开发、可靠性、维护、测试等方面的最新研究成果。
中国建筑论文参考文献范例
中国建筑论文参考文献一、中国建筑论文期刊参考文献[1].空间维视角下中国建筑产业竞争力形成机理差异化研究.《系统工程理论与实践》.被中信所《中国科技期刊引证报告》收录ISTIC.被EI收录EI.被北京大学《中文核心期刊要目总览》收录PKU.被南京大学《核心期刊目录》收录CSSCI.2013年5期.刘炳胜.王雪青.陈晓红.张帅.[2].亚洲视野下的中国建筑研究.《建筑学报》.被中信所《中国科技期刊引证报告》收录ISTIC.被北京大学《中文核心期刊要目总览》收录PKU.2015年11期.赖德霖.[3].基于SEM与SD组合的中国建筑产业竞争力动态形成机理仿真.《系统工程理论与实践》.被中信所《中国科技期刊引证报告》收录ISTIC.被EI收录EI.被北京大学《中文核心期刊要目总览》收录PKU.被南京大学《核心期刊目录》收录CSSCI.2010年11期.刘炳胜.王雪青.曹琳剑.[5].走向“合”——20042014年中国建筑历史研究动向.《建筑学报》.被中信所《中国科技期刊引证报告》收录ISTIC.被北京大学《中文核心期刊要目总览》收录PKU.2014年9期.陈薇.[6].“中国建筑”不是"Architecture"——反思150年Architecture对中国建筑的冲击.《新建筑》.被中信所《中国科技期刊引证报告》收录ISTIC.2014年4期.杨涛.滕军红.[7].中国建筑推进绿色建筑最新进展.《施工技术》.被中信所《中国科技期刊引证报告》收录ISTIC.被北京大学《中文核心期刊要目总览》收录PKU.2013年1期.毛志兵.[8].经学、经世之学、新史学与营造学和建筑史学——现代中国建筑史学的形成再思.《建筑学报》.被中信所《中国科技期刊引证报告》收录ISTIC.被北京大学《中文核心期刊要目总览》收录PKU.2014年9期.赖德霖.[9].近代西方学者对中国建筑的研究.《建筑学报》.被中信所《中国科技期刊引证报告》收录ISTIC.被北京大学《中文核心期刊要目总览》收录PKU.2015年2期.程枭翀.徐苏斌.[10].全球化视野下的当代中国建筑——2014年德班世界建筑师大会中国建筑展回顾.《建筑学报》.被中信所《中国科技期刊引证报告》收录ISTIC.被北京大学《中文核心期刊要目总览》收录PKU.2014年11期.邵韦平.二、中国建筑论文参考文献学位论文类[1].以《中国建筑》与《建筑月刊》为资料源的中国建筑现代化进程研究.被引次数：5作者：钱海平.建筑设计及其理论浙江大学2010（学位年度）[2].阿卡汗奖与中国建筑传媒奖及其作品解读.被引次数：1作者：吴珊珊.建筑历史与理论华中科技大学2012（学位年度）[3].论当代中国建筑中传统文化精神的回归——兼论王澍获普利兹克奖的思考.作者：张璇.设计艺术学河南大学2013（学位年度）[4].早期现代中国建筑规则创立初探——结合陪都时期重庆城市讨论.作者：刘宜靖.建筑学重庆大学2014（学位年度）[5].来华西方人游记中的中国建筑认识初探——从“建筑之树”说起.作者：李洪.建筑历史与理论浙江大学2011（学位年度）[6].当代中国建筑思潮研究.被引次数：38作者：郝曙光.建筑历史与理论东南大学2006（学位年度）[7].解读近代日本学者对中国建筑的考察与图像记录.作者：贺美芳.建筑历史与理论天津大学2013（学位年度）[8].中国建筑遗产的话语生成.被引次数：1作者：谢洁怡.英语语言文学浙江大学2010（学位年度）[9]. 企业集团公司人力资源管控研究——以中国建筑为例.作者：王杰.工商管理对外经济贸易大学2013（学位年度）[10].中国建筑二局财务控制研究.作者：刘冬.企业管理哈尔滨工业大学2009（学位年度）三、相关中国建筑论文外文参考文献[1]ICA~3DIntelligentcomputeraidedancientChinesearchitecturedesign .SongmaoZhangRuqianLu《Advancedengineeringinformatics》,被EI收录EI.被SCI收录SCI.20124[2]Tingtools:interactiveandproceduralmodelingofChineseting. ChunYenHuangWenKaiTai《Thevisualcomputer》,被EI收录EI.被SCI收录SCI.201312[3]TheSmartArchitect:ScalableOntologyBasedModelingofAncientChines eArchitectures.YongLiuCongfuXuQiongZhangYunhePan《IEEEintelligentsystems》,被EI收录EI.被SCI收录SCI.20081[4]MESOZOICINTRAPLATEGRANITICMAGMATISMINTHEALTAIACCRETIONARYOROGE N,NWCHINA:IMPLICATIONSFORTHEOROGENICARCHITECTUREANDCRUSTALGROWTH. TAOWANGBORMINGJAHNVICTORP.KOVACH《AmericanJournalofScience》,被EI收录EI.被SCI收录SCI.20141[5]AnovelVLSIarchitectureofmotioncompensationformultiplestandards .JunhaoZhengWenGaoDavidWuDonXie 《IEEETransactionsonConsumerElectronics》,被EI收录EI.被SCI收录SCI.20082[6]GenomewidebindinganalysisofthetranscriptionactivatorIDEALPLANT ARCHITECTURE1revealsacomplexnetworkregulatingriceplantarchitecture.. LuZefuYuHongXiongGuoShengWangJingJiaoYongQingLiuGuiFuJingYanHuiMengXi angBingHuXingMingQianQianFuXiangDongWangYongHongLiJiaYang 《ThePlantCell》,被EI收录EI.被SCI收录SCI.201310[7]HighlyTransparentandConductiveStretchableConductorsBasedonHier archicalReticulateSingleWalledCarbonNanotubeArchitecture. LeCaiJinzhuLiPingshanLuanHaiboDongDuanZhaoQiangZhangXiaoZhangMinTuQin gshengZengWeiyaZhouSishenXie《Advancedfunctionalmaterials》,被EI收录EI.被SCI收录SCI.201224[8]HighStrengthLaminatedCopperMatrixNanocompositesDevelopedfromaS ingleWalledCarbonNanotubeFilmwithContinuousReticulateArchitecture. ZhiqiangNiuWenjunMaJinzhuLiHaiboDongYanRenDuanZhaoWeiyaZhouSishenXie 《Advancedfunctionalmaterials》,被EI收录EI.被SCI收录SCI.201224[9]AuxinbiosyntheticgeneTAR2isinvolvedinlownitrogenmediatedreprog rammingofrootarchitectureinArabidopsis..MaWenYingLiJingJuanQuBaoYuanHeXueZhaoXueQiangLiBinFuXiangDongTongYiPi ng《ThePlantJournal》,被EI收录EI.被SCI收录SCI.20141[10]AScalableMulticastSourceRoutingArchitectureforDataCenterNetwo rks.Jia,WenKang《IEEEJournalonSelectedAreasinCommunications》,被EI收录EI.被SCI收录SCI.20141四、中国建筑论文专著参考文献[1]当代中国建筑话语源流与传播[4]中国建筑不只木.右史，2007第四届中国建筑史学国际研讨会[5]近代中国建筑史学初创与国外汉学背景述要——以中国营造学社古建筑调查活动的展开为例.段智钧.赵娜冬，20092009世界建筑史教学与研究国际研讨会。
数据中心网络系统技术白皮书
主编单位： 中国工程建设标准化协会信息通信专业委员会数据中心工作组 参编单位： 思科系统（中国）信息技术服务有限公司 华为技术有限公司
心工 中 杭州华三通信技术有限公司 数据 国 中 世源科技工程有限公司
国际商业机器公司 美国康普公司 美国西蒙公司
CC） D C （ 作组
所有 权 版
泛达网络产品国际贸易（上海）有限公司 罗森伯格亚太电子有限公司
数据中心网络系统技术白皮书
Data Center Network System Technology White Paper
（试读）
China Data Center Committee Information Communications Expert Commission China Association for Engineering Construction Standardization
2012. 11
序
言
为促进数据中心的技术发展，2010年2月，数据中心工作组开始编制《数据中 心网络技术白皮书》。在编写过程中，编写组根据国内外相关技术标准和规范的 要求，进行了多次专题研究和调查分析，广泛征求各方面的意见，总结归纳国内 外数据中心网络技术在工程应用中的实践经验，经多次修改和专家审查，于2012 年9月定稿。 本白皮书作为数据中心建设的参考文献，技术内容的解释由中国工程建设标 准化协会信息通பைடு நூலகம்专业委员会数据中心工作组负责。在应用过程中如有需要修改 和补充的建议，请将有关资料 Email：service@。
课题技术负责人：钟景华 主要起草人：汪澍 参编人：孙玉武 庞俊英 王宏亮 王为 兴嘎 陈宇通 王喆 梁俊 孙慧永 谭俊
主要审查人：庞俊英
李必胜
DataCenter 韌體 軟體更新步驟說明说明书
DataCenter firmware update procedureDataCenter has a built-in remote firmware server that can update firmware automatically when internet connection is present.In situations that a manual firmware update is required, please follow the below update procedure.STEP 1.Browse and upload firmware ZIP file (no need to unzip) into DC01 directly.STEP 2After firmware is uploaded, please click refresh button to check firmware version and process update.DataCenter韌體更新步驟說明DataCenter內建韌體自動檢查功能，當系統處於網路連線狀態時，會自動更新為最新版本。
若使用者須手動跟新韌體時，請依下方步驟執行。
步驟1：請在DC01系統畫面下，瀏覽並上傳韌體檔案（無須解壓縮）。
步驟2：韌體上傳完畢，請點擊「refresh」按鍵，此時系統會自動檢查韌體版本並自動執行更新作業。
DataCenter软件更新步骤说明DataCenter内建软件自动检查功能，当系统处于网络联机状态时，会自动更新为最新版本。
若使用者须手动跟新软件时，请依下方步骤执行。
步骤1：请在DC01系统画面下，浏览并上传软件档案（无须解压缩）。
步骤2：软件上传完毕，请点击「refresh」按键，此时系统会自动检查软件版本并自动执行更新作业。
思科CCNA DC DCICT PPT
© 2012 Cisco and/or its affiliates. All rights reserved.
DCICT v1.0—15
Cisco Data Center Network Services
© 2012 Cisco and/or its affiliates. All rights reserved.
DCICT v1.0—10
https:///community/netpro
© 2012 Cisco and/or its affiliates. All rights reserved.
DCICT v1.0—11
https://
Lost Packets
Data Data
Tx
Rx
Pause
Flow Control in Ethernet
© 2012 Cisco and/or its affiliates. All rights reserved.
DCICT v1.0—20
• Fibre Channel uses a credit-based strategy:
- The transmitter does not send a frame until the receiver tells the transmitter that the receiver can accept another frame.
- The receiver is always in control.
Course Introduction
2012 Cisco a d/or Its afflllates. AII nghts ese ed
DCICT v 1 . 0 - 2
IT人员可以提高自身价值的六个证书
IT行业有哪些含金量高的证书。
如果相关IT人员希望通过学习数据中心管理技能来提升自己的水平，以下是一些可以掌握基本知识所提供的教育和认证机会一、VMWARE专家认证(VMWARE Certified Professional)如果IT人员对数据中心管理的兴趣是围绕移动性进行的，那么VMware认证的专业认证就是其最佳选择。
在当代的商业运作中，员工通常需要在某种意义上具有移动性。
他们可以被要求执行工作和活动，并且还在各种网络上的多个设备上执行职责。
为此，这些员工需要大量的协作和沟通，以获得更好的工作体验。
实质上，这导致了对移动性问题有着良好基础的员工的需求增加。
获得VMware认证的专业人员可以具备出色的移动技能。
通过VCP6-DCV计划，专业人员的移动技能将得到加强。
该程序主要向人们介绍虚拟化数据中心的安装程序、管理和控制。
并可以确保获得高度的移动技能，从而提高其在数据中心技术方面的实力。
二、CCNP数据中心认证(Cisco Certified Network Professional DataCenter)思科公司的认证是全球最受欢迎的专业数据中心认证之一。
获得思科公司的认证对任何专业人员的职业发展都有很大的促进作用。
它是全球公认的具有一定权威性的认证。
思科网络专业数据中心为数据中心设备的设计、安装过程，以及最佳维实践提供了全面的知识基础。
他们的教育内容非常广泛，涵盖思科操作系统和各种数据中心技术等方面知识。
事实上，IT人员可以将这个认证证书与大学学位或大学文凭一起使用，以促进其职业前景的发展。
获得这个专业数据中心认证的人士会获得巨大的投资回报。
三、数据中心设计专家认证(Certified DataCenter Design Professional)这个认证在太平洋地区很受欢迎。
这是一个重要的数据中心认证。
对于拥有数据中心的组织来说，这是数据中心专业人员为了高效顺利地运营数据中心而应该具备的最好的教育培训之一。
无线数据传输模块(DTU)外文翻译
外文文献：A Detailed Implementation and Analysis of Data Center of GPRS DTUZhen Yu Dept. of Automation Xiamen UniversityXiamen, China****************.cnZhong Zheng Dept.of AutomationXiamen UniversityXiamen, China*********************Abstract—This paper gives an overview of the architecture of the telecontrol system based on GPRS. The objectives of this paper are two fold. One is to present the design and implement of the data center of GPRS DTU. The other is to investigate its performance. According to the features of GPRS DTU, data center provides reliable communication between members of a group by implementing the telecontrol system in the client/server model. With the use of the data center, it is of practical significance to implement multiple master stations to receive data from all slave stations simultaneously and to control all slave stations in parallel. The data center design parameters include real- time control, deployment simplification and the ability to provide high availability, scalability and reliability.Keywords-GPRS DTU; data center; telecontrol system; master station; slave stationI.I NTRODUCTIONIn recent years, it is a major trend to use wireless networks in the large-scale industrial production systems to control and manage the components which scattered in the different remote areas. In order to ensure the appropriate operation of the system, these components must be operated under the unified command to coordinate the work among them through the scheduling agencies.The scheduling agencies should keep abreast of the actual production situations of the various parts. On this basis it can make regulation and control strategies on time. With the rapid development of network technology, the telecontrol technology which is the combination of scheduling management and modern control technology can not only meet the real-time dispatch, but also ensure high reliability. For implementing efficient measuring and monitoring processes, it’s facility for the telecontrol system to transmit the information through the use of wireless networks. One prominent communication technology for this service is the GPRS. Thus, under the premise of lowering the cost and enhancing the competitiveness, more and more enterprises are applying the GPRS technology to replace the traditional long distance leased line. In this paper, we give a detailed implementation of public network access solution and analyze its performance.II.C HARACTERISTIC OF GPRS NETWORK The most widely deployed public mobile data network, which enables the integration of IP with mobile networks and constitutes a migration step toward third-generation communication systems, is the General Packet Radio Service (GPRS) [1]. GPRS attempts to reuse the existing Global System for Mobile Communication (GSM)network elements as much as possible, but in order to effectively build a packet-based mobile cellular network,some new network elements, interfaces, and protocols are required [1]. The new network nodes are called GPRS support nodes (GSNs). The SGSN is responsible for the delivery of data packets from and to the mobile station(MS) within its service area [2]. The GGSN acts as an interface between the GPRS backbone network and the external packet data network [2]. GPRS supports applications based on standard protocols for packet-switch data communication. The standards include interworking procedures with IP and X.25 networks [3]. This makes the realization of the GPRS services feasible, when GPRS exchanges information with the external networks which based on the IP protocol suite, such as Internet.The traffic characteristic of the packet-mode data effectively supported by GPRS ranges from intermittent, bursty data transfer, to frequent transmission of “sma ll”amount of data, to occasional transmission of “large”amount of data [3]. An important benefit of GPRS is that the radio channels in GPRS are shared between multiple Mobile Stations (MS). Second, multiplexing on the air interface permits efficient support of bursty traffic [3]. GPRS transmission rate can be raised to 56 or even 114 Kbps. Moreover, connections and transmission will be more convenient and easier, for they no longer need the intermediary converters among the existing wireless applications [3]. More importantly, once activate the GPRS applications, it will always remain online. However,mobile subscribers only pay according to the amount of information transferred, not in terms of the occupied time.III.D EMAND ANALYSIS FOR THE TELECONTROLSYSTEMThe telecontrol system is a broad term which refers to the system of monitoring and controlling the production process. The equipments which constitute the telecontrol system include the factory station, the scheduling station and the telecontrol channel. Traditionally and customarily, we call the factory station and the scheduling station as the slave station and the master station respectively.In the sequel, the proposed telecontrol system based on GPRS deployment scenario is presented and analyzed. The system requires to provide with the conveniences for easy installation, easy usage, remote manageable, easilyexpand, and only takes up little bandwidth for transmitting monitorFigure 1. The architecture of the telecontrol systemand management information, etc. As shown in Fig. 1, some of the key components of the architecture are as following:GPRS DTU is the abbreviation for GPRS Data Terminal Unit. In simple terms, DTU is the GPRS wireless device which specially applied to transmit the serial data through the GPRS networks. DTU provides serial communication interface, such as RS-232 or RS-485. Every station connects with the GPRS DTU through RS- 232. In practice, each GPRS DTU needs a build-in SIM card which was used to apply for GPRS services.The master station is the monitor and management center, which provides a convenient and integrated user interface; with easy installation and usage, as well as allowing for telecontrol and teleadjusting. Relatively, the slave station is the remote terminal unit, which is responsible for data acquisition and transmission.The data center implements the communication among numbers of DTUs though the use of Client/Server model. The data center acts as a server, maintaining and managing bidirectional communication between the master stations and slave stations though DTUs. In such a communication model, where all stations are connecting to the data center, and data transfer is carried out using mobile devices (such as GPRS DTU), stability and real-time are considered paramount.IV.F UNDAMENTALS OF GPRS DTUA.Working ProcessOnce the GPRS DTU powers on, it firstly reads out the internal flash saved operating parameters which include GPRS dial-up parameters, serial port baud rate, the data center IP address and port number, and so on. After the success of a dial-up, a internal IP address will be randomly allocated to GPRS DTU. In other words, GPRS works in a mobile network, but its network IP addresses are not usually fixed but changed along with each dial-up.It means that GPRS DTU is a mobile device within the internal LAN (Local Area Network) and communicates with the external public Internet network through the mobile gateway (GGSN). So it is impossible to communicate between the master station and the slave station directly. But DTU can connect to the data center with a fixed public network IP address or domain name automatically and keep this communication link on line. Therefore, GPRS DTU needs to take the initiative to connect to the data center.Specifically, GPRS DTU initiates a TCP (Transmission Control Protocol) or UDP (User Datagram Protocol) communication request to the data center though the data center IP address and port number which were configured in advance. After receiving the response from the data center, GPRS DTU makes a successful handshake with the data center and maintains the communication link. If the communication link was interrupted, GPRS DTU would immediately re-handshake with the data center.Then the TCP/UDP bidirectional communication links between GPRS DTU and the data center have been set up.GPRS DTU have integrated TCP/IP protocol stack, so it’s relatively simple to complete the conversion between user serial data and GPRS network packet. While receiving the user’s serial data, GPRS DTU immediately encapsulates the serial data into a TCP/UDP packet and sends it to the data center. Conversely, when GPRS DTU receives the TCP/UDP packet from the data center, it will extract useful data from the packet, and send the data to the user equipment through the serial port at once.More importantly, one of the advantages of GPRS networks is that it supports GPRS terminal equipments to keep online permanently, so typically GPRS DTU is designed to support this function. It requires that the features of GPRS DTU include automatically dial-up, maintaining a permanent online, supporting re-connection automatically, and so on.B.Heartbeat PacketWhen there is no data transmission for a certain time, the mobile gateway will disconnect the communication link between the data center and GPRS DTU automatically. For maintaining the connection online,DTU heartbeat packet would be send before this link is disconnected. The problem is how long did DTU heart packet be send. If the send-time interval was set too long,there is no data transmission. Then the mobile gateway interrupts the link. On the contrary, the data center ca n’t receive the heartbeat packet on time because of the wireless network delay. On the earth, GPRS DTU will determine that the communication link has disconnected and re-connect automatically. No matter what kind of situations, it will increase instability to the telecontrol system.Fig. 2 shows the experimental results for setting the send-time interval of the heartbeat packet analysis. One observation is that GPRS DTU always re-connects to the data center per 160 seconds more or less, when the send-time interval of the heartbeat packet was set as 60 seconds in Xiamen, China. So we reset the time parameter as 160seconds, it greatly improve the reliability and stability of the system.Figure 2. The reconnected time intervalFigure 3. The frame format of DTU register packetC.Register PacketOnce the TCP communication link between GPRS DTU and the data center was set up successfully, the DTU sends the register packet to the data center at first. As shown in Fig. 3, the content of the register packet includes identification (ID) number to identify GPRS DTU, SIM card number for opening GPRS services, and dynamic IP address being allocated. After the data center receives the register packet, it will get hold of the basic information of GPRS DTU. Since the ID number is unique and fixed, it can be used as the station address to identify DTUs or stations naturally. By extracting the ID number from the register packet, it’s easy to establish and maintain a DTU list to record the connection status of the all stations.The aforementioned discussions are both necessary and sufficient for designing and implementing the telecontrol system. It is the data center that the normal communication between the master station and slave station depends entirely on through the use of GPRS DTU.V.DESIGN AND IMPLEMENT OF DATA CENTERA.Design ScenarioThe work in this paper primarily implements the functions of communication for the data center of GPRS DTU on the platform of VC++6.0 SP4 and Windows XP, which was built to evaluate the performance of remote access GPRS-Internet networks. For reaching a desired quality of service and maintaining the system in a reliable and stable operation, design and implement of the data center is very important. Furthermore, the aforementioned telecontrol system network topology is a star network. In a star network, the failure of a single link can not affect the performance of the whole system. However, if the data center fails, each station in the system will become disconnected. As shown in the Fig. 4, combining with the knowledge of network programming, the data center refers to as a socket interface which is a virtual interface that can be established between the transport layer and application layer of the TCP/IP Suite of protocol. From the perspective of reliability, the socket program should choose the SOCK_STREAM which based on reliable connection TCP (Transmission Control Protocol).The data center is fairly meaningless if it cannot service multiple clients at the same time, usually asynchronous I/O calls and multithreading is used for this purpose. By definition, an asynchronous I/O call returns immediately, leaving the I/O call pending. Nowadays, It is commonly known that asynchronous Input/Output Completion Ports (IOCP) is one of the most efficient ways. By using IOCP, we can overcome the “one-thread-per-client”problem. Threads are system resources that are neither unlimited nor cheap. IOCP provides a way to have a few I/O workers thread handle multiple client s’input/output “f airly”. The threads are suspended, and do n’t use the CPU cycles until there is something to do.When using asynchronous I/O calls, we have to provide a private buffer to be used with the I/O operation.There are some considerations that are to be taken into account when we allocate buffers to use. From the storage structure point of view, to allocate and free memory is expensive, therefore we should reuse buffers which have been allocated. We save buffers in the linked list structures. A list container represents noncontiguous memory. It is efficient to insert or erase an element at any point.Inserting or removing an element in a list container does not move any other elements. It significantly improved the efficiency of the data center.Figure 4. Flows of the data center softwareFigure 5. The frame format of the telecontrol informationmunication ProtocolIn the telecontrol system, in order to send and receive information correctly, there must a set of rules on the information transmission sequence, information format, information content and so on. Usually we call this set of rules as communication protocol. As shown in the Fig. 5, the telecontrol information of each frame begins with the synchronization word, as well as the control and information words. The most important thing is that the control word contains the ID numbers of the source station and destination station. The data center can properly forward the frame though the ID numbers of the destination station.C.Measurement ProceduresThe telecontrol system deploys two master stations and eight slave stations. We measure some metric performance in TCP mode. These metrics are used in our experiments as they have a direct impact on the ultimate performance. During our experiments, the following parameters were used to quantify the services provided.Overall transfer time: is the amount of time it takes one packet to travel from one station to another; the parameter is measured in seconds.Overall response time: consists of subtracting the time at which the telecontrol segment is sent from the time at which the acknowledgement arrives; the parameter is measured in seconds.D.Design issuesIn the telecontrol system, given a real-time control has been a key challenge to many designers. Real-time is an important design parameter in the whole system. There are two main factors that have a great impact on the real-time control.One is bandwidth of the communication channel. In GPRS, DTU can access the public data networks directly and easily using their standard protocol address. A GPRS MS (mobile station) can use between one and eight channels over the air interface. GPRS system has a very short access time to the network. The theoretical maximum throughput of the GPRS system is 160 kbps per MS when using all eight time slots without any error correction [4]. To fully exploit the high capacity of GPRS, the slave stations can periodically take the initiative to send the telecontrol messages to the master stations in accordance with a given order. And the master station transmit “larg e”amount of telecontrol information to all slave stations occasionally.Another key element is the forwarding rate of the data center. Deciding on the process structure of the data center is a major problem in the design of any service. The data center is required to operate efficiently in peek periods, when dozens of active stations need to be simultaneously. One of the best solutions for the data center architecture is the use of IOCP which has been discussed above. The real-time of the telecontrol system can be illustrated by overall transfer time and overall response time. As shown in the Fig. 6, overall transfer time is less than 5 seconds. And overall response time is approximately no more than 10 seconds. It basically reaches the ministerial standard real-time control.Another design issue involves fault tolerance. Communication faults, malicious attack, access violation should all be tolerated to some extent. A fault-tolerant system should continue to function, perhaps in a degraded form, when faced with these failures. In a typical connection, The GPRS DTU sends a message asking the data center to accept it, once it connected to the datacenter. The data center returns the accept approval to the GPRS DTU. The GPRS DTU acknowledges this approval and then is allowed onto the data center. A “denial-of-servi ce” attack is characterized by an explicit attempt by attackers to prevent legitimate users of a service from using that service or accessing information. Usually one GPRS DTU connects to the data center for a long time, but it does n’t send a message asking the data center to accept it. Consequently prevent other GPRS DTUs from connecting to the data center on time, even disable the data center. One of the more common methods of blocking this attack is to set up a timer. The time of GPRS DTU connecting to the data center ca n’t exceed a given time(such as 60 seconds), or else the data center will close this vicious connection compulsorily.Still another issue is scalability –the capability of a system to adapt to increased service load. Systems have bounded resources and can become completely saturated under increased load. Even worse, expanding the system can call for expensive design modifications. A scalable system should have the potential to grow without these problems. In the telecontrol system, the ability to scale up gracefully is of special importance, since expanding the system by adding one or more new stations is commonplace. At first, No matter how many the number of slave station or master station increases, we can solve scalability and availability though the use of the forwarding function of the data center. The data center can forward the telecontrol information which received from the master station to all the slave stations, and vice versa. Secondly, with introducing the thread pooling and IOCP into Windows XP, Server applications make extensive use of thread pooling techniques to delegate client requests to worker threads, which is implemented as a thread pool so that they can achieve better throughput. After serving a client request, the thread goes back into the thread pool and gets ready to serve the next pending client’s request. Thread pooling will give better throughput, as less time is wasted in creating and destroying threads, because the application already has an idle pool of threads. The Fig. 7 (a) and (b) indicate clearly the purpose of this article is to cover a design that can be used to develop scalable data center without impacting performance.The last issue is parallel control. It is of practical significance to implement multiple master stations to receive data from all slave stations simultaneously and to control all slave stations in parallel. Each station can beuniquely identified with a physical address (ID number).Figure 6. The overall transfer time and overall response time But during the packet transmission, we can define that the all master stations deployed a unified virtual address to send and receive data. Once receiving a telemetering or teleindication packet whose destination address is the virtual address, the data center should forward the packet to all master stations. The virtual address plays as a multicast address. Similarly, for controlling all slave stations in parallel, we can define another virtual address.When the data center receives a telecontrol or teleadjusting packet with the defined address, it must multicast this packet to all slave stations. It is convenient and easy to carry out the parallel control though the data center.VI.CONCLUSION In this paper, a telecontrol system deployment scenario over the GPRS-Internet networks has been proposed and discussed in regard to real-time control, scalability, fault tolerance and parallel control. The primary objective of this paper is to present the design and implementation of the data center. In practice, it has been normally run for more than 7*24 hours. This work should be expanded to analyze from a security point of view. A key element of secure networking is the proper design and configuration of virtual private networks (VPNs) [5].R EFERENCES[1] GSM 03.60, “GPRS Service Description”, Stage 2, 1998.[2] Amitabh Mishra, “Performance and Architecture of SGSN andGGSN of General Packet Radio Service (GPRS)”, IEEE Press, pp.3494–3498 January 2001.[3] Christos Xenakis, Lazaros Merakos, “On Demand Network-wide VPNDeployment in GPRS”, IEEE Press, vol. 16, pp. 28–37, Nov.- Dev.2002.[4] Xiangguang Che, Hamalainen .S, Ryynanen.J, Moisio.M, “GPRSradio network performance simulation and optimization with dynamic simulator”, Proc. IEEE Symp. Communication Technology Proceedings (ICCT 2003), IEEE Press, pp. 935-939, doi: 10.1109/ICCT.2003.1209684.[5] B. Gleeson et al.,”A Framework for IP Based Virtual PrivateNetworks”, RFC 2764, Feb. 2000.Figure 7. The experiment results: (a) increase one master station (b) increase two slave stations中文译文：GPRS DTU 数据中心的详细实施及分析摘要:本文给出了一种基于GPRS远程控制系统体系结构的概述。
datadirectnetworks介绍-概述说明以及解释
datadirectnetworks介绍-概述说明以及解释1.引言1.1 概述在datadirectnetworks介绍的概述部分，我们将对datadirectnetworks进行简要的介绍和概述。
datadirectnetworks是一家领先的数据存储解决方案提供商，致力于帮助企业有效地管理和处理海量数据。
datadirectnetworks的核心理念是通过创新的技术和高性能的存储系统，为全球各行业的企业提供可靠、高效的数据存储解决方案。
作为一家拥有多年经验和丰富实践经验的公司，datadirectnetworks深知数据对企业的重要性，因此不断致力于研发和提供先进的存储产品和解决方案，以满足企业日益增长的存储需求。
datadirectnetworks的产品和服务涵盖了从硬件到软件的全方位存储解决方案。
通过其自主研发的高速网络存储设备和多种存储软件，datadirectnetworks能够为企业提供高度可扩展的存储平台，支持多种数据类型和应用场景。
无论是大型企业还是中小型企业，datadirectnetworks都能够提供定制化的解决方案，满足客户不同的需求和预算。
除了产品和解决方案，datadirectnetworks还拥有一支专业的技术团队，能够为客户提供全面的咨询、部署和维护服务。
无论是在数据中心内部还是云环境中，datadirectnetworks的专家都能够为客户提供快速响应和高效解决问题的支持。
综上所述，datadirectnetworks作为一家领先的数据存储解决方案提供商，以其创新的技术、高性能的存储系统和全面的服务，为企业提供可靠、高效的数据存储解决方案。
通过选择datadirectnetworks，企业可以更好地管理和处理海量数据，提升其数据存储和处理的能力，实现业务的持续增长和发展。
1.2 文章结构文章结构部分的内容如下：文章结构部分主要介绍了本篇文章的整体组织和章节安排。
数据中心网络架构和底层协议演进
数据中心网络架构和底层协议演进作者：魏月华陈晓张征来源：《中兴通讯技术》2021年第03期摘要：受计算规模的驱动，数据中心物理拓扑从接入-汇聚-核心三级网络架构演进到基于Clos的Spine-and-Leaf架构。
计算资源的基本单位经历了物理服务器、虚拟机、容器化3个阶段。
数据中心底层（underlay）连接协议逐步从以二层协议为主演进到以IP路由协议为主。
但传统路由协议存在可扩展性、拓扑可见性、自动化部署能力等诸多问题。
结合链路状态和距离矢量的胖树路由协议，解决了超大规模数据中心部署的痛点问题，有望逐渐成为超大规模数据中心底层网络的主流技术。
关键词：Spine-and-Leaf；路由；数据中心Abstract： Driven by the scale of computing， the physical topology of the data center has evolved from an access-aggregation-core three-level network architecture to a Closbased Spine-and-Leaf architecture. The basic unit of computing resources has gone through three stages： physical server， virtual machine， and containerization. The underlay connection protocol of the data center has gradually evolved from layer 2 protocol to IP routing protocol. However， traditional routing protocols have many problems， such as scalability， topology visibility， and automated provision capabilities. The fat-tree routing protocol， which combines link state and distance vector， solves the pain points of ultralarge-scale data center deployment， and is expected to gradually become the mainstream technology for ultra-large-scale data center underlay networks.Keywords： Spine-and-Leaf； routing； data center1 接入-匯聚-核心三级网络架构协议方案演进受计算规模的驱动，数据中心的网络架构和解决方案，在过去20年里发生了很大变化。
1+X网络培训第一次测试试题及答案
1+X网络培训第一次测试试题及答案本张试卷共100道单选题，每道题1分，共100分。
您的姓名： [填空题] *_________________________________1. Linux至少定义了 7 个“运行级”,其中运行级（）代表单用户模式｡ [单选题] *A.0B.6C.2D.1(正确答案)2.下列哪项是符合密码复杂性要求（）。
[单选题] *A．Acd@132(正确答案)B．Abc@123C．123456D．a@1233.默认密码最长使用时间是（） [单选题] *A．30天B．42天(正确答案)C．35天D．48天4.密码必须符合复杂性要求密码至少（） [单选题] *A．3位B．5位C．6位(正确答案)D．9位5.Windows系统在默认的情况下已经防火墙已经（） [单选题] *A．关闭B．开启(正确答案)C．禁用D．还没安装6.下列哪种方式可以以批处理的方式创建组织单元和其他的活动目录对象（）｡[单选题] *A.ActiveDirectory 用户和计算机B.活动目录服务工具C.轻型目录访问协议互换格式目录交换(正确答案)D.Windows 脚本主机7.在 DNS 中定义了不同类型的记录，但常用的不到 10 种，IPv6 又增加了几种｡试问下列哪条记录属于 IPv6 的（） [单选题] *A.SOAB.NSC.AD.AAAA(正确答案)8.通常 Linux 支持的网卡类型不包括:（）｡ [单选题] *A.令牌网卡B.以太网卡C.PCMCIAD.PS/2(正确答案)9.Windows系统默认情况防火墙状态是启用的，并且入站连接默认是阻止，出站连接是允许（） [单选题] *A．允许B．连接C．断开D．阻止(正确答案)10.MBR分区中每块磁盘最多被划分为（）个分区。
[单选题] *A.4(正确答案)B.8C.64D.12811.在Linux中如何用命令查找一个二进制命令 xcmd 的路径?（） [单选题] * A．apropos xcmdB．which xcmd(正确答案)C．where xcmdD．find xcmd12.下面哪一条命令用来装载所有在 /etc/fstab 中定义的文件系统?（） [单选题] * A．amountB．mount -a(正确答案)C．fmountD．mount –f13.在linux中，如何标识接在ide0上的slave硬盘的第2个逻辑分区?（） [单选题] *A．/dev/hdb2B．/dev/hd1b2C．/dev/hdb6(正确答案)D．/dev/hd1b614.在应用程序起动时，如何设置进程的优先级?（） [单选题] *A．priorityB．nice(正确答案)C．reniceD．setpri15.下面哪条命令可以把f1．txt复制为f2．txt? （） [单选题] *A．cp f1．txt | f2．txtB．cat f1．txt | f2．txtC．cat f1．txt > f2．txt(正确答案)D．copy f1．txt | f2．Txt16.在Users组中的成员不能执行一些任务（） [单选题] *A．运行程序B．使用本地网络C．锁定服务器D．关闭系统(正确答案)17.显示一个文件最后几行的命令是:（） [单选题] *A．tacB．tail(正确答案)C．rearD．last18.如何快速切换到登录用户的主目录下? （） [单选题] *A．cd(正确答案)B．cd #homeC．cd /homeD．cd ~home19.如何装载(mount)，在 /etc/fstab 文件中定义的所有文件系统? （） [单选题] * A．mount -a(正确答案)B．mount /mnt/*C．mountD．cat /etc/fstab | mount20.如果使用ln命令生成了一个指向文件old的符号链接new，如果你将文件old删除，是否还能够访问new文件中的数据? （） [单选题] *A．不可能再访问(正确答案)B．仍然可以访问C．能否访问取决于new的所有者D．能否访问取决于old的权限21.如何在文件中查找显示所有以“ *”开头的行? （） [单选题] *A．grep \* file(正确答案)B．wc -l *C．grep -n * fileD．find \* file22.在ps命令什么参数是用来显示所有用户的进程的? （） [单选题] *A．a(正确答案)B．bC．uD．x23.在一行结束位置加上什么符号，表示未结束，下一行继续? （） [单选题] * A．/B．\(正确答案)C．;D．|24.在大多数linux发行版本中，图形方式的运行级定义为? （） [单选题] * A．1B．2C．3D．5(正确答案)25.如何删除一个非空子目录/tmp? （） [单选题] *A．del /tmp/*B．rm -rf /tmp(正确答案)C．rm -ra /tmp/*D．rm -rf /tmp/*26.对所有用户的变量设置，应当放在哪个文件下? （） [单选题] *A．/etc/bashrcB．/etc/profile(正确答案)C．~/．bash_profileD．/etc/skel/．Bashrc27.下面哪种写法表示如果cmd1成功执行，则执行cmd2命令? （） [单选题] * A．cmd1&&cmd2(正确答案)B．cmd1|cmd2C．cmd1;cmd2D．cmd1||cmd228.命令 kill 9 的含义是: （） [单选题] *A．结束pid是9的进程(正确答案)B．杀死所有uid为9的用户进程C．发送kill信号给pid是9的进程D．发送term型号给pid是9的进程29.在vi中退出不保存的命令是? （） [单选题] *A．:qB．:wC．:wqD．:q!(正确答案)30.光盘所使用的文件系统类型是（） [单选题] *A．vfatB．ext4C．swapD．iso9660(正确答案)31.（）目录存放的是Linux系统管理的配置文件。
基于松弛时间与累计发送量的数据中心网络混合流调度机制
止时间流的 平 均 完 成 时 间 （ＡｖｅｒａｇｅＦｌｏｗＣｏｍｐｌｅｔｅＴｉｍｅ，ＡＦＣＴ）同 时 维 持 低 截 止 时 间 错 失 率 （ＤｅａｄｌｉｎｅＭｉｓｓＲａｔｅ，
ＤＭＲ），本文提出了一种基于 松 弛 时 间 与 累 计 发 送 量 的 混 合 流 调 度 机 制 （ＳｌａｃｋＴｉｍｅａｎｄＡｃｃｕｍｕｌａｔｉｏｎｂａｓｅｄＭｉｘｆｌｏｗ
收稿日期：２０１７１２２７；修回日期：２０１９０２２８；责任编辑：孙瑶 基金项目：国家网络空间安全专项课题（Ｎｏ．２０１７ＹＦＢ０８０３２０４）；国家 ８６３高技术研究发展计划（Ｎｏ．２０１５ＡＡ０１６１０２）；国家自然科学基金创新研 究群体科学基金（Ｎｏ．６１５２１００３）
２０６２
电 子 学 报
ＳｌａｃｋＴｉｍｅａｎｄＡｃｃｕｍｕｌａｔｉｏｎＢａｓｅｄＭｉｘｆｌｏｗ ＳｃｈｅｄｕｌｉｎｇｉｎＤａｔａＣｅｎｔｅｒＮｅｔｗｏｒｋｓ
ＺＡＮＧＷｅｉｆｅｉ，ＬＡＮＪｕｌｏｎｇ，ＨＵＹｕｘｉａｎｇ
（ＮａｔｉｏｎａｌＤｉｇｉｔａｌＳｗｉｔｃｈｉｎｇＳｙｓｔｅｍ Ｅｎｇｉｎｅｅｒｉｎｇ＆ ＴｅｃｈｎｏｌｏｇｉｃａｌＲｅｓ）
Ａｂｓｔｒａｃｔ： Ａｐｐｌｉｃａｔｉｏｎｓｄｅｐｌｏｙｅｄｉｎｄａｔａｃｅｎｔｅｒｎｅｔｗｏｒｋｓｇｅｎｅｒａｔｅａｍｉｘｏｆｆｌｏｗｓｗｉｔｈａｎｄｗｉｔｈｏｕｔｄｅａｄｌｉｎｅｓ．Ｔｏｒｅ ｄｕｃｅｔｈｅａｖｅｒａｇｅｆｌｏｗｃｏｍｐｌｅｔｅｔｉｍｅ（ＡＦＣＴ）ｗｈｉｌｅｍａｉｎｔａｉｎａｌｏｗｄｅａｄｌｉｎｅｍｉｓｓｒａｔｅ（ＤＭＲ），ａｓｌａｃｋｔｉｍｅａｎｄａｃｃｕｍｕｌａ ｔｉｏｎｂａｓｅｄｍｉｘｆｌｏｗｓｃｈｅｄｕｌｉｎｇｍｅｃｈａｎｉｓｍ （ＳＴＡＭ）ｉｓｐｒｏｐｏｓｅｄｉｎｔｈｉｓｐａｐｅｒ．Ｆｉｒｓｔｌｙ，ｔｈｅｄｅｌａｙｔｏｌｅｒａｎｃｅｏｆｄｅａｄｌｉｎｅｆｌｏｗｓ ｏｎｎｏｎｄｅａｄｌｉｎｅｆｌｏｗｓｉｓｍｅａｓｕｒｅｄｗｉｔｈｔｈｅｉｎｔｒｏｄｕｃｔｉｏｎｏｆＳｌａｃｋＴｉｍｅ．Ｔｈｅｎｔｈｅｃｏｓｔｏｆｃｏｍｐｌｅｔｅｔｉｍｅｏｆｎｏｎｄｅａｄｌｉｎｅ ｆｌｏｗｓｉｓｒｅｄｕｃｅｄｂｙｃｏｍｐｌｅｔｉｎｇｄｅａｄｌｉｎｅｆｌｏｗｓｂａｒｅｌｙｂｅｆｏｒｅｔｈｅｉｒｄｅａｄｌｉｎｅｓ．Ｌａｓｔｌｙ，ｎｏｎｄｅａｄｌｉｎｅｆｌｏｗｉｓｓｃｈｅｄｕｌｅｄａｃｃｏｒｄｉｎｇ ｔｏｔｈｅｎｕｍｂｅｒｏｆｂｙｔｅｓｉｔｈａｓｓｅｎｔｔｏｒｅｄｕｃｅｔｈｅａｖｅｒａｇｅｆｌｏｗ ｃｏｍｐｌｅｔｉｏｎｔｉｍｅ．Ｅｘｐｅｒｉｍｅｎｔｒｅｓｕｌｔｓｓｈｏｗ ｔｈａｔｔｈｅｐｒｏｐｏｓｅｄ ｍｅｃｈａｎｉｓｍ ｃａｎｅｆｆｅｃｔｉｖｅｌｙｒｅｄｕｃｅｔｈｅａｖｅｒａｇｅｆｌｏｗ ｃｏｍｐｌｅｔｉｏｎｔｉｍｅｏｆｎｏｎｄｅａｄｌｉｎｅｆｌｏｗｓｗｈｉｌｅｍａｉｎｔａｉｎｉｎｇｌｏｗ ｄｅａｄｌｉｎｅ ｍｉｓｓｒａｔｅ．
X年无线产品和市场分析
DCN Wireless Solution Expert
Data Center Network
产品关键卖点
- 有线无线一体化控制器
- 6028、6222有线无线一体化，可以做核心交换的无线控制器
- 精细、优质入室覆盖
- 墙面AP：5分钟安装，信号完美入室，绿色无干扰，美观 - 智能动态室分（D分）：1分9智能动态室分，美化天线入室覆盖，双频覆盖，
无线频率-5GHz频段
频段范围：5.725~5.850GHz 125MHz带宽，划分为5个信道，每个信道带宽为20MHz，功率限制100mw
5725 5735
5755
5775
5795
5815
5835 5850
2.4GHz与5.8GHz均采用免费频段 ISM（（Industrial、Scientific、Medical）频段无需申请，无需缴费
1. 交换无线一体 2. 智能墙面无线 3. 安全易用接入 4. 动态智能室分
1. 无线控制云 2. 无线管理云 3. 无线认证云
八大 AIR 技术支撑
DCN Wireless Solution Expert
Data Center Network
彼此协同的实现稳定无线连接、安全的终 端控制、灵活的运营、全局管理
Data Center Network
第二篇 DCN无线产品销售指导
DCN Wireless Solution Expert
Data Center Network
1. 无线网络现状分析 2. 我们的客户在哪里 3. 我们准备了哪些 4. 为什么选择DCN 5. 在这个市场里都有谁在参与 6. 如何让无线项目从无到有
云计算时代互联网数据中心网络面临的挑战
亚太 & 中东 & 拉美
Thailand
Hong Kong
Thailand Customs APT Satellite
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Philippines
EW B
Turkey
ULAKBİM
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RNP
中国
7
Challenges Internet DCNs Face in the Cloud Computing Era
全局调优：
• Segment Routing：基于全局 网络资源和业务，智能计算路由， DCI链路利用率提升50%
某大型网络视频公司，全球遍布上百个DC，每年带宽租用费用 $300M+, 整网峰值利用率<30% SDN控制器广域链路调优后，链路利用率提升到80%
5
易运维：基于FabricInsight，实现分钟级故障定位
government
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• INFN • MPS bank • TI
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6
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• 中国区市场占有率NO.1 （2016 ） • 连续四年全球数据中心交换机增长率NO1.
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• 华为迈入2017 Gartner数据中心网络 魔力象限挑战者
什么是数据中心及数据中心的特点
什么是数据中心及数据中心的特点一、数据中心的概念数据中心(DataCenter)通常是指在一个物理空间内实现信息的集中处理、存储、传输、交换、管理，而计算机设备、服务器设备、网络设备、存储设备等通常认为是网络核心机房的关键设备。
关键设备运行所需要的环境因素，如供电系统、制冷系统、机柜系统、消防系统、监控系统等通常被认为是关键物理基础设施。
一、数据中心的概念数据中心(DataCenter)通常是指在一个物理空间内实现信息的集中处理、存储、传输、交换、管理，而计算机设备、服务器设备、网络设备、存储设备等通常认为是网络核心机房的关键设备。
关键设备运行所需要的环境因素，如供电系统、制冷系统、机柜系统、消防系统、监控系统等通常被认为是关键物理基础设施。
二、机房工程（数据中心）的类型及特点电子机房主要有计算机机房、电信机房、控制机房、屏蔽机房等。
这些机房既有电子机房的共性，也有各自的特点，其所涵盖的内容不同，功能也各异。
（一）屏蔽机房为了有效地防止电磁干扰式噪声、辐射对电子设备和测量仪器的影响，并严防电子信号泄漏从而威胁到机密信息的安全，国家机关、军队、公安、银行、铁路等单位需要建立屏蔽机房。
有保密要求的数据机房应建设屏蔽机房，确保数据在处理过程中，其信号不泄漏，从而满足数据保密的要求。
一些对抗电磁干扰要求较高的环境，如通信设备的测试试验室等场所，需要建设屏蔽机房，以防止外界电磁信号的干扰。
有强电磁干扰设备的机房应进行相应的电磁屏蔽处理，以避免干扰临近机房设备的正常还行。
（二）计算机机房计算机机房内放置重要的数据处理设备、存储设备、网络传输设备及机房保障设备。
计算机机房的建设应考虑以上设备的正常运行，确保信息数据的安全性以及工作人员身心健康的需要。
大型计算机机房一般由无人区机房、有人区机房组成。
无人区机房一般包括小型机机房、服务器机房、存储机房、网络机房、介质存储间、空调设备间、UPS设备间、配电间等;有人区机房一般包括总控中心机房、研发机房、测试机房、设备测试间、设备维修存储间、缓冲间、更衣室、休息室等。
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IEEE 802.1au March 13-15, 2007
Raj Jain
2
Datacenter Networks
Bounded delay-bandwidth product ! High-speed: 10 Gbps ! Short round-trip delays ! 1 Mb to 5 Mb delay-bandwidth product ! Storage Traffic ⇒ short access times ⇒ Low delay ! Packet loss ⇒ Long timeouts ⇒ Not desirable
Washington University in Saint Louis
IEEE 802.1au March 13-15, 2007
Raj Jain
1
Overview
! ! ! !
Top 10 Requirements for a Good Scheme FECN Overview Switch Algorithm and Enhancements Simulation Results ! FECN with TCP flows ! Symmetric Topology ! Large Topology ! Bursty Traffic
Washington University in Saint Louis
linear function Hyperbolic function
q Qeq
We analyzed many different functions and recommend the hyperbolic function because it gives smaller oscillations. [See reference]
! ! !
The switch use the same “Advertised Rate” in all RD tags All sources passing through the switch get the same feedback. The sources send at the rate received.
Forward Explicit Congestion Notification (FECN) for Datacenter Ethernet Networks
Jinjing Jiang, Raj Jain, Chakchai So-In Washington University In Saint Louis Saint Louis, MO 63131 Jain@ IEEE 802.1au Congestion Notification Group Meeting, Orlando, FL, March 12-15, 2007 These slides are also available on-line at /~jain/ieee/fecn703.htm
Washington University in Saint Louis
IEEE 802.1au March 13-15, 2007
time
Raj Jain
8
Enhancement 1: Queue-Control
1. Measurement: Let Ai be the measured arrival rate in bits/s then the load factor is z = Ai/C. We update this load factor based on the queue length so that the effective load factor is:
IEEE 802.1au March 13-15, 2007
Raj Jain
9
Queue Control Function: f(q)
Idea: Give less rate if queue length is large and more if queue length is small compared to desired queue length of Qeq and f(Qeq)=1 Reserves some capacity for draining the queue. f(q) b 1 c
Washington University in Saint Louis
IEEE 802.1au March 13-15, 2007
Raj Jain
7
The Basic Switch Algorithm
(i+1)T iT 0 T 2T C 0. Start with an Advertised Rate of r. r0 = N0 Here C is the link capacity. 1. Measure input rate every T interval 2. Compute overload factor z in the last T interval 3. Change the advertised rate to r/z 4. In every RD tag: set rate to min{rate in tag, advertised rate} 5. Go back to step 1 Although this simple algorithm will work but: ! It will oscillate even if the rate is close to optimal. ! Queues will not be constant ⇒ Need a Q Control Fn
!
Washington University in Saint Louis
IEEE 802.1au March 13-15, 2007
Raj Jain
3
Goals of FECN
1. Fast convergence to stability in rates Stable rates ⇒ TCP Friendly (IETF feedback) 2. Fast convergence to fairness 3. Good for bursty traffic ⇒ Fast convergence 4. Efficient operation: minimize unused capacity. Minimize chances of switch Q=0 when sources have traffic to send 5. Extremely low (or zero) loss 6. Predictable performance: No local minima 7. Easy to deploy ⇒ Small number of parameters 8. Easy to set parameters 9. Parameters applicable to a wide range of network configurations link speeds, traffic types, number of sources. 10. Applicable to a variety of switch architectures and queueing/scheduling disciplines
ρi =
Ai z = f (qi ) f (qi ) × C
2. Bandwidth Allocation:
ri + 1 =
ρi
ri
Note: We also tried additive queue control. It has similar performance.
Washington University in Saint Louis
Washington University in Saint Louis
IEEE 802.1au March 13-15, 2007
Raj Jain
5
FECN: Observations
! ! ! ! !
!
This is similar to what is done in TCP/IP, Frame Relay, ATM with 1 bit in every packet (n=1). ATM ABR had a similar explicit rate indication that was selected after 1 year of intense debate and scrutiny. Only the feedback format has to be standardized No need to standardize switch algorithm. Vendor differentiation: Different switch algorithms will “interoperate” although some algorithms will be more efficient, more fair, and achieve efficiency/fairness faster than others. We present a sample switch algorithm and show that it achieves excellent performance.
Washington University in Saint Louis
IEEE 802.1au March 13-15, 2007
Raj Jain
6
Switch Algorithm
Source Switch Source 5 Mbps 5 Mbps Destination Destination