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计算机网络（ Internet ） 历史，现状与未来

计算机网络（ Internet ） 历史，现状与未来. 舒炎泰 20 0 8. 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 …. A Taxonomy of Communication Networks. Communication Network.

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计算机网络（ Internet ） 历史，现状与未来

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  1. 计算机网络（Internet）历史，现状与未来 舒炎泰 2008

  2. 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 …

  3. A Taxonomy of Communication Networks Communication Network • Communication networks can be classified based on the way in which the nodes exchange information: SwitchedCommunication Network BroadcastCommunication Network 广播，电视 Packet-SwitchedCommunication Network Circuit-SwitchedCommunication Network 电话 Datagram Network Virtual Circuit Network Internet

  4. Node incoming links outgoing links Circuit Switching （电路交换-电话） • A node (switch) in a circuit switching network

  5. Host 1 Host 2 Node 1 Node 2 DATA processing delay at Node 1 Circuit Establishment Data Transmission Circuit Termination Timing in Circuit Switching propagation delay between Host 1 and Node 1 propagation delay between Host 2 and Node 1

  6. 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?

  7. Node incoming links outgoing links Memory Packet Switching （分组/包交换） 1961 • A node in a packet switching network

  8. Header Data Trailer 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

  9. Timing of Datagram Packet Switching Host 1 Host 2 Node 1 Node 2 propagation delay between Host 1 and Node 2 Packet 1 Packet 2 transmission time of Packet 1 at Host 1 Packet 1 processing delay of Packet 1 at Node 2 Packet 3 Packet 2 Packet 1 Packet 2 Packet 3 Packet 3

  10. Host C Host D Host A Node 1 Node 2 Node 3 Node 5 Host B Host E Node 7 Node 6 Node 4 Datagram Packet Switching

  11. 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

  12. 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

  13. 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?

  14. Virtual-Circuit Packet Switching • Communication with virtual circuits takes place in three phases • VC establishment • data transfer • VC disconnect • Note: packet headers don’t need to contain the full destination address of the packet

  15. Packet 1 Packet 1 Packet 1 Packet 2 Packet 2 Packet 2 Packet 3 Packet 3 Packet 3 Timing of Virtual-Circuit Packet Switching Host 1 Host 2 Node 1 Node 2 propagation delay between Host 1 and Node 1 VC establishment Data transfer VC termination

  16. Host C Host D Host A Node 1 Node 2 Node 3 Node 5 Host B Host E Node 7 Node 6 Node 4 Virtual-Circuit Packet Switching

  17. Internet 历史(1)Sep69 1st IMP in UCLA, Oct69 2nd IMP in SRI Internet 之父-- L. Kleinrock1999 1969

  18. History of the Internet (2)

  19. 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!

  20. 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

  21. History of the Internet (5) • 1972-1980: Internetworking, research networks • 1970:ALOHAnet satellite network in Hawaii (Abramson) • 1973:Metcalfe’s PhD thesis proposes Ethernet • 1974:Cerf and Kahn - 2004 A.M. Turing Award -define today’s 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 70’s: proprietary architectures: DECnet, SNA • Late 70’s: switching fixed length packets (-> ATM)

  22. History of the Internet (6) • 1980’s 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-1980’s: 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

  23. History of the Internet (7) • 1990’s: commercialization, the WWW • Early 1990’s: ARPAnet decommissioned • 1991: NSFnet (45 Mbps) -> commercial use of NSF (decommissioned, 1995) • Late 1990’s: • multiple private backbones • 50 million computers on Internet • 100 million+ users • backbone links running at 1 Gbps • Early 1990s: WWW • hypertext [Bush 1945, Nelson 1960’s] • HTML, http: Berners-Lee • 1994: Mosaic, later Netscape • late 1990’s: commercialization of the WWW

  24. Growth of the Internet • Today: backbones run at 2.4/10 Gbps, 400 millions computers in 150 countries

  25. Internet 在中国 • 1993年3月 中科院高能物理所 64 Kbps • TJU:1995.3.22 • 2006年12月 • 计算机5940万 • 用户 1.4亿 • WWW站84万 • CN域名 180万 • 国际出口带宽 257 Gbps • 连接美国、俄罗斯、法国、英国、德国、日本、韩国、新加坡等

  26. Internet 提供的服务 • Shared access to computing resources • telnet (1970’s) • Shared access to data / files • FTP, NFS, AFS (1980’s) • Communication medium over which people interact • email (1980’s), on-line chat / messaging (1990’s) • audio, video (1990’s) • replacing telephone network? • A medium for information dissemination • USENET (1980’s) • WWW (1990’s) • replacing newspaper, magazine? • audio, video (1990’s) • replacing radio, CD, TV?

  27. Today’s Internet

  28. Internet Physical Infrastructure

  29. Classification by Coverage

  30. 模型, 协议, 分层

  31. Protocol Architecture

  32. Don’t Need All Layers Everywhere

  33. Protocol Data Unit - PDUs

  34. Network Components (Examples) Links Interfaces Switches/routers Ethernet card Large router Fibers Wireless card Coaxial Cable Telephone switch

  35. 趋势: 网络时代 • 每一件事务都是数字的: 声音, 视频, 音乐, 画片, 及生活日常事务 • 每一件事务都是在线的: 银行结算, 医疗记录, 各类书籍, 航空日程, 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

  36. 趋势: 网络时代 • 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 • 虚拟公司 • 虚拟制造与虚拟装配 (设计过程) • 制造过程更加分散化，并发进行 • 新型的价值链 • 虚拟兑现

  37. 趋势: 网络时代

  38. 趋势: 网络时代

  39. 网络制造 (1) • 随着基于Internet的全球化数字通信基础设施的建立，网络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。 • Internet向“资源功能”发展，基于Internet的网络化制造是适应时代的需要. • 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。

  40. 网络制造 (2) • 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

  41. 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

  42. 电子商务产生背景 竞争环境改变 核心 产品竞争 服务竞争 范围 单个企业 全球多企业 信息、知识 资源 人、财、物 生产管理 管理重心迁移 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

  43. 商务模式转化 电子商务 传统商务 • 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）

  44. e企业的业务体系结构 客户 产品/服务 销售 服务/支持 市场营销 产品制造 供应商 合作伙伴 网络智能

  45. 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

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