计算机网络(INTERNET)

Click to edit Master title style,Click to edit Master text styles,Second Level,Third Level,Fourth Level,Fifth Level,*,*,*,计算机网络（,Internet,）,历史，现状与未来,舒炎泰,20,0,9,计算机网络,Transportation service: move objects,horse, train, truck, airplane .,Communication network: move information,bird, fire, telegraph, telephone,计算机网络,Internet ,Communication networks can be classified based on the way in which the nodes exchange information:,A Taxonomy of Communication Networks,Communication Network,SwitchedCommunication Network,BroadcastCommunication Network,广播，电视,Circuit-SwitchedCommunication Network,电话,Packet-SwitchedCommunication Network,Datagram Network,Virtual Circuit Network,Internet,The example,通话在,C,到,D (,只经过一个本地交换机,),的连接上进行,通话在,A,到,B (,经过四个交换机,),的连接上进行,思考：电话交换对于计算机是否适合？,效率,/,成本,应用实时,(,(,(,(,交换机,交换机,交换机,交换机,用户线,用户线,中继线,中继线,B,D,C,A,Circuit Switching （,电路交换-电话）,A node (switch) in a circuit switching network,incoming links,outgoing links,Node,Circuit Switching: Multiplexing/,Demultiplexing,Time divided in frames and frames divided in slots,Relative slot position inside a frame,determines,which conversation the data belongs to,Needs synchronization between sender and receiver,In case of non-permanent conversations,Needs to dynamic bind a slot to a conservation,How to do this?,Timing in Circuit Switching,propagation delay,between Host 1,and Node 1,propagation delay,between Host 2,and Node 1,DATA,Circuit Establishment,Data Transmission,Circuit Termination,Host 1,Host 2,Node 1,Node 2,processing delay at Node 1,报文,在发送端，先把较长的报文划分成较短的、固定长度的数据段。,1101000110101010110101011100010011010010,假定这个报文较长,不便于传输,Packet Switching,（,分组/包交换）,1961,Computer networks self-development-packet switching,分组交换网以“,分组,”(也称 包)作为数据传输单元,依次,把各分组发送到接收端（假定接收端在左边）。,数 据,首部,分组,1,数 据,首部,分组,2,数 据,首部,分组,3,Computer networks development-packet switching,最后，在接收端把收到的数据恢复成为原来的报文。,这里我们假定分组在传输过程中没有出现差错，在转发时也没有被丢弃。,数 据,数 据,数 据,报文,1101000110101010110101011100010011010010,Packet Switching,（,分组/包交换）,1961,Data are sent as formatted bit-sequences, so-called packets,Packets have the following structure:,Header and Trailer carry control information (e.g., destination address, check sum),Each packet is passed through the network from node to node along some path (,Routing,),At each node the entire packet is received, stored briefly, and then forwarded to the next node,(,Store-and-Forward,Networks),Typically no capacity is allocated for packets,Header,Data,Trailer,Router Congested,Router A,Router B,Router C,Router D,Router E,Packet Switching - Example,Router F,Timing of Datagram Packet Switching,Packet 3,Packet 3,Packet 1,Packet 2,Packet 1,Packet 2,Packet 1,Packet 2,Packet 3,processing delay of Packet 1 at Node 2,Host 1,Host 2,Node 1,Node 2,propagation,delay between,Host 1 and,Node 2,transmission,time of Packet 1,at Host 1,Packet Switching,（,分组/包交换）,1961,A node in a packet switching network,incoming links,outgoing links,Node,Memory,Packet Switching: Multiplexing/,Demultiplexing,Data from any conversation can be transmitted at any given time,How to tell them apart?,Use,meta-data (header),to describe data,Datagram Packet Switching,Each packet is independently switched,Each packet header contains destination address,No resources are pre-allocated (reserved) in advance,Example: IP networks,Use Queuing models to,Describe the behavior of queuing systems,Evaluate system performance,Model: Queuing System,Queuing System,Queue,Server,Customers,Response Time vs. Arrivals,Internet,历史(1),Sep69 1st IMP in UCLA, Oct69 2nd IMP in SRI Internet,之父-,L.,Kleinrock,1999 1969,History of the Internet (2),History of the Internet (3),Sep69 1st IMP in UCLA Oct69 2nd IMP in SRI,22:30 29Oct69,LOGIN from UCLA to SRI,CLA,We sent an “L” - did you get the “L”?,YEP!,We sent a “O” - did you get the “O”?,YEP!,We sent an “G” - did you get the “G”?,Crash!,History of the Internet (4),1961-1972: Early packet-switching principles,1961:,Kleinrock,queueing,theory shows effectiveness of packet-switching,1964:,Baran,- packet-switching in military nets,1967:,ARPAnet,conceived by Advanced Research Projects Agency (,Licklider, Roberts),1969:,first,ARPAnet,node operational,1972:,ARPAnet,has 15 nodes,ARPAnet,demonstrated publicly,NCP (Network Control Protocol) first host-host protocol,first e-mail program,History of the Internet (5),1972-1980:,Internetworking, research networks,1970:,ALOHAnet,satellite network in Hawaii (Abramson),1973:,Metcalfes PhD thesis proposes Ethernet,1974:,Cerf and Kahn - 2004 A.M. Turing Award,-define todays Internet architecture,minimalism, autonomy no internal changes required to interconnect networks,best effort service model,stateless routers,decentralized control,1979:,ARPAnet has 200 nodes,56 kbps,Late 70s:,proprietary architectures:,DECnet, SNA,Late 70s:,switching fixed length packets (- ATM),History of the Internet (6),1980s new protocols, a proliferation of net,1983:,deployment of TCP/IP. (Critical separation; Cohen),1982:,SMTP e-mail protocol defined,1983:,DNS defined for name-to-IP-address translation,mid-1980s:,IETF active,1985:,FTP protocol defined,1988:,TCP congestion control,new national networks:,Csnet,BITnet,Minitel,NSFnet,(1.5 Mbps,10,000 computers), NSI (NASA),ESNet(DOE,),DARTnet,TWBNet,(DARPA),100,000 hosts connected to confederation of networks,History of the Internet (7),1990s: commercialization, the WWW,Early 1990s:,ARPAnet,decommissioned,1991:,NSFnet,(,45 Mbps),- commercial use of NSF (decommissioned, 1995),Late 1990s:,multiple private backbones,50 million computers on Internet,100 million+ users,backbone links running at 1,Gbps,Early 1990s:,WWW,hypertext Bush 1945, Nelson 1960s,HTML, http: Berners-Lee,1994: Mosaic, later Netscape,late 1990s: commercialization of the WWW,Internet,提供的服务,Shared access to computing resources,telnet (1970s),Shared access to data / files,FTP, NFS, AFS (1980s),Communication medium over which people interact,email (1980s), on-line chat / messaging (1990s),audio, video (1990s),replacing telephone network?,A medium for information dissemination,USENET (1980s),WWW (1990s),replacing newspaper, magazine?,audio, video (1990s),replacing radio, CD, TV?,Internet Physical Infrastructure,Classification by Coverage,模型,协议,分层,Protocol Architecture,Dont Need All Layers Everywhere,Protocol Data Unit -,PDUs,Network Components (Examples),Fibers,Coaxial Cable,Links,Interfaces,Switches/routers,Ethernet card,Wireless card,Large router,Telephone,switch,Growth of the Internet,Today: backbones run at 2.4/10/100,Gbps,500 millions computers in 150 countries,中科院高能物理所,1993,年,3,月,64Kbps,1986.8.25 Email,TJU:1995,年,3,月,22,日,2009,年,7,月,网民,3.4,亿,WWW,站,306,万,CN,域名,1296,万,国际出口带宽,748,Gbps,连接美国、,俄罗斯、法国、英国、德国、日本、韩国、新加坡,等,宽带接入速度远远落后于发达国家,Internet,在中国,趋势: 网络时代,每一件事务都是数字的: 声音, 视频, 音乐, 画片,每一件事务都是在线的: 银行, 医疗, 航空, 天气情况, 公路交通,每个人之间都是相互联系的:医生,教师,经济人,母亲,儿子,朋友, 敌人,实现家庭,教育， 办公， 购物， 娱乐,/,网上娱乐,虚拟工作场所,2000年，美国有五千五百万人实现远程工作,网络制造,/,电子商务,趋势: 网络时代,计算机集成制造系统,/,先进制造,/,信息化,CIMS (Computer Integrated Manufacturing),1973,Dr. Joseph Harrington,目标：市场竞争 -,T, Q, C, S,时间,T,（,即开发新产品的时间或成熟产品的上市时间）、质量,Q,、,成本,C,和服务,S,核心思想,系统的观点 - 全局优化,企业的各个环节,，包括市场分析、产品设计、加工制造、经营管理及售后服务的全部经营活动，,是不可以分割的整体.,信息,的观点 -,信息,集成,企业的运行是,信息,采集，传递，加工,处理,的过程.,产品可以看作数据的物质表现.,目标-提高竞争力（,CIMS-Internet,）,70年代前,降低劳动成本,降低产品成本,70年代,提高企业整体效益,降低产品成本,提出,CIMS,80年代,TQCS,CIMS,推广应用,90年代,新产品开发，信息、知识,CIMS,发展,2000年代,核心：服务/用户,范围：全球企业间/供应链,资源：信息、知识（无时空）,网络制造,/,电子商务,网络制造,Internet,从单纯的信息工具变成”,E时代”的关键资源,.全球经济一体化成为制造业变革的最根本的推动力,基于,Internet,的虚拟制造与虚拟装配,在相互联结的网络上，建立24小时工作的协同工作组，大大加快了设计进度、及时获得所需要的零部件，减少库存、降低成本，提高质量,网络制造的本质特性就是产品的制造过程更加分散化，信息的传递网络化，信息的流动伴随着各项工作的并发进行而同时发生,电子商务,信息技术和,Internet,引发的商务过程的变化,利用以,Internet,为核心的信息技术，进行商务活动和企业资源管理,CIMS,是企业实施电子商务的基础,企业实施电子商务是,CIMS,发展的主要标志和主要内容,竞争环境改变,核心 产品竞争,电子商务产生背景,服务竞争,范围 单个企业,全球多企业,资源 人、财、物,信息、知识,管理重心迁移,生产管理,供应/营销链管理,集中内部资源,整合外部资源,离散管理,集约管理,商务模式转化,文秘型管理,关注后台（企业内部）,关注业务记录（报表）,地区性,推销产品为中心,（卖方市场）,自我服务型管理,关注前端（客户关系）,要求商业智能（分析）,全球化,客户为中心,（买方市场）,传统商务,电子商务,客户,供应商,合作伙伴,网络智能,市场营销,产品/服务,销售,产品制造,服务/支持,e,企业的业务体系结构,协同产品商务(,CPC),用户在互联网上参与产品的开发、设计及修订。,在虚拟市场空间中，顾客与生产者及供应商一起参与产品生命周期中的每一项技术及商业环节。,不受地域及时间的限制，信息可以快速地流动。,企业的发展趋势,部门之间的障碍,业务过 程重组,IDS Sheer,业务流程,2000年以后,电子商务工程,IDS Sheer,企业之间的障碍,网络制造,-,电子商务,网络发展趋势,趋势: 融合,趋势: 泛在（,Ubiquitous,）,趋势: 信息爆炸,更多的网络业务流量,数据流量 话声流量,更快的传输介质/骨干网（,Backbone）,更大的带宽（,Bandwidth）,宽带无线网,飞速增长,(WLAN) (,Wi-Fi,),Everything over IP,趋势: 融合,新闻/广告-媒体-信息提供者,数字媒体产品,有线电视,视频传输,电话,声音传输,计算机,数字媒体存储/处理,信息提供者和信息传输者的结合,电话公司, 有线公司, 娱乐事业, 和计算机公司的结合,Trend:,趋势: 更快的传输介质,局,域,网：,1,Gbps,over 4-pair UTP-5 up to 100 m, 10Gbps being discussed,Was 1 Mbps (1Base-5) in 1984,骨干网：光纤,DWDM,(,Dense Wavelength Division Multiplexing),OC-768 = 40,Gbps,over a to 65 km, 1600,Gbps,- 10,Tbps,Was 100 Mbps (FDDI) in 1993,无线网：,54 /500 Mbps(100-2km-50km) wireless networks, 2.5,Gbps,to 5km using light,Was 1 Mbps (IEEE 802.11) in 1998,Why Optical Networks?,DWDM,optoelectricl,metro network,Trend:,宽带无线网飞速增长,Trend:,宽带无线网,(,Wi-Fi,),飞速增长,Trend: Wireless / Mobile,Integration of 3G and WLAN-,offer possibility of achieving anywhere, anytime, high speed and low expense Internet access,3G,WLAN,Wide area,Local area,Low bit rate,(2M when stand still),High bit rate,(11M to 54M),Data/Voice service,(,QoS support,),Data service,High expense,Low expense,High mobility,Low mobility,Future Internet Research and Experimentation,Todays Internet,Millions of users,Web, email, low-quality audio & video,Interconnect personal computers and servers,Applications adapt to underlying technology,Todays Internet Doesnt,Provide,reliable,end-to-end performance,Encourage cooperation on new capabilities,Allow testing of,new technologies,Support development of revolutionary applications,Internet2 Project,Develop and deploy advanced network applications and technologies, accelerating the creation of tomorrows Internet.,Goals,Enable new generation of applications,Re-create leading edge R&E network capability,Transfer capability to the global production Internet,20,6,University Members,Jan,. 2005,Internet2 Focus Areas,Advanced Network Infrastructure - Abilene,Backbones operate at 10,Gbps,capacity - 100,Gbps,(2007),Middleware,A layer of software between the network and the applications,Authentication, Identification, Authorization, Directories, Security,Engineering,IPv6, Measurement, Multicast,QoS, Routing, Security, Topology,Advanced Applications,Distributed computation, Virtual laboratories, Digital libraries, Distributed learning, Digital video, Tele-immersion, All of the above in combination,Abilene Connections : Apr-2000,Abilene Connections:,July 2006,Abilene Connections : Apr-2000,Abilene International Peering 2006,Research and,Development,Commercialization,Partnerships,Privatization,Internet Development Spiral,Todays Internet,Internet2,Packet-Switching vs. Circuit-Switching,Most important advantage of packet-switching over circuit switching: ability to exploit statistical multiplexing:,Efficient,bandwidth usage; ratio between peek and average rate is,3:1 for audio, and,15:1 for data,traffic,However, packet-switching needs to deal with congestion:,More complex routers,Harder to provide good network services (e.g., delay and bandwidth,guarantees,),In practice they are combined:,IP over SONET, IP over Frame Relay,Virtual-Circuit Packet Switching,Hybrid of circuit switching and packet switching,Data is transmitted as packets,All packets from one packet stream are sent along a,pre-established path,( =,virtual circuit,),Guarantees in-sequence delivery of packets,However: Packets from different virtual circuits may be interleaved,Example: ATM networks,MPLS?,Virtual-Circuit Packet Switching,Host A,Host B,Host E,Host D,Host C,Node 1,Node 2,Node 3,Node 4,Node 5,Node 6,Node 7,Router A,Router B,Router C,Router D,Router E,1. Connection Establishment,2. Information Transfer,3. Circuit Disconnect,Virtual Circuit Packet Switching-Example,Router F,Packet 1,Packet 2,Packet 3,Packet 1,Packet 2,Packet 3,Timing of,Virtual-Circuit,Packet Switching,Packet 1,Packet 2,Packet 3,Host 1,Host 2,Node 1,Node 2,propagation delay,between Host 1,and Node 1,VC,establishment,VC,termination,Data,transfer,Asynchronous Transfer Mode: ATM,1990s/00 standard for high-speed (155Mbps to 622 Mbps and higher),Broadband Integrated Service Digital Network,architecture,Goal:,integrated, end-end transport of carry voice, video, data,meeting timing/QoS requirements of voice, video (versus Internet best-effort model),“next generation” telephony: technical roots in telephone world,packet-switching (fixed length packets, called “cells”) using,virtual circuits,ATM reference model,How far along are we?,Standardization bodies - ATM Forum, ITU-T,We may never see end-to-end ATM (1997),ATM - too complex - too expansive ,Backbone: - 1995,vBNS,(ATM) - 1998 Abilene (SONET) - 2000 IP over DWDM,Internet technology + ATM philosophy,but ATM ideas continue to powerfully influence design of next-generation Internet,ex:,MPLS, admission,ctl,., resource reservation, .,Best of Both Worlds,Multiprotocol,label switching (,MPLS,),MPLS + IP form a middle ground that combines the best of IP and the best of,virtual,circuit switching technologies,ATM and Frame Relay cannot easily come to the middle so IP has!,Label Encapsulation,MPLS Encapsulation is specified over various media types. Top labels may use existing format, lower label(s) use a new “shim” label format.,Label Substitution,Have a friend go to B ahead of you using one of the previous two techniques. At every road they reserve a lane just for you. At every intersection they post a big sign that says for a given lane which way to turn and what new lane to take.,We are at an Impasse,ISPs are unlikely candidates for architectural change,We cant test new architectures,- Despite sizable investments in,testbeds,We cant deploy new architectures,- And things are getting worse, not better,Yet there are pressing requirements for which the current architecture is not well suited,GENI (Global Environment for Network Innovations),-,NSF,2005 (1),What is GENI?,GENI is,a facility concept,being explored by the US computing community,back to an NSF workshop in 2005,focus on,architectural,research, and provide the,experimental,infrastructure needed to support that research,focus on the research agenda (and infrastructure needs) of the,optical,wireless,sensor,network, and,distributed,systems communities,GENI (Global Environment for Network Innovations),(2),The goal of GENI,Goal: a Future Internet that meets the demands of 21st century,to increase the,quality,and,quantity,of,experimental research,outcomes in networking and distributed systems,to accelerate the,transition,of these outcomes into products and services,enhance economic competitiveness and secure the Nations future,Ultimately, to lead to a,transition of the Internet,FIND (Future Internet Network Design), NSF 2006,FIND asks two broad questions:,What are the,requirements,for the global network,in 15 years,How,would we,re-conceive,tomorrows global network today, if we could design it from scratch?,FIND program solicits ,clean slate process, research proposals in the broad area of network architecture, principles, and design,FIRE (Future Internet Research and Experimentation), European 2007,FIRE is an,experimentally,-driven,long,-term research initiative on Future Internet,concepts,protocols,and,architectures,encompassing technological, industrial and socio-economic aspects,acting as proof-of-concept of the newly proposed technologies and services,FIRE RESEARCH,Long term multidisciplinary research on future internet paradigms,Open to,fresh bottom-up,ideas with,no backwards-compatibility,constraints,Building on the FET SAC initiative “Situated and Autonomic Communications”,Considering at the,same time,technological, economic and social/policy aspects,Build in from the outset and on all levels the right,balance,between security / accountability and privacy,