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Understanding Computer Networks: From Basics to Internet Services

This text offers a comprehensive overview of computer networks, highlighting their evolution from early communication methods like the telegraph and telephone to modern internet appliances and online services. Key topics include server-based and peer-to-peer architectures, internet service providers, and the functionality of various internet applications. Readers will gain insight into how data is transmitted through networks, the significance of different communication technologies, and the role of application service providers in delivering network-based solutions.

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Understanding Computer Networks: From Basics to Internet Services

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  1. Introduction toComputer Networks

  2. World’s smallest web server http://www-ccs.cs.umass.edu/~shri/iPic.html Internet Appliances (1/2) • Check email on your iPad • Browse web sites on ★ • Facebook, Twitter, the New Work Times • YouTube • KKBox, ezPeer+ • Skype and IM conversations • Watch movie on Netflix's streaming service Copy from Computer Networking: A Top Down Approach, 4th edition. Jim Kurose, Keith Ross. Addison-Wesley, July 2007

  3. Internet phones Internet Appliances (2/2) • Scroll through RSS feeds in a reader • Listen to podcast on your smartphone • Play on-line games Web-enabled toaster + weather forecaster IP picture frame http://www.ceiva.com/ Copy from Computer Networking: A Top Down Approach, 4th edition. Jim Kurose, Keith Ross. Addison-Wesley, July 2007

  4. Communications History (1/2) • Telegram in English (1839) • Alexander Graham Bell's telephone (1890s) • AM radio (1920) • FM radio (1939) • Microwave (1940) • ENIAC, the first general-purpose electronic computer (1946) • Transistors (1959) • Integrated Circuit (IC) (1967)

  5. Communications History (2/2) • Mainframes (1960s) • ARPANET (1969) • Ethernet (1969) • Email service (1972) • Apple II (1977), IBM PC (1981) • MILNET+Internet (1983) • NFSNET (1986) • Mosaic (1993), Netscape Navigator (1994) then, more and more events …

  6. Telecommunications • Telephone systems • Voice, symmetric, fixed rate • Circuit Switching Network • Form a dedicated connectionor circuit between two ends to deliver voice frame • Advantage：Guaranteed capacity • Disadvantage：Circuit costs are fixed oriented phone destination phone local switching office switching office trunk line

  7. Data Communications 1 2 3 • Data! Not voice only! • To share resources among computers • Files, pictures, video, audio… • Asymmetric, variable data rate, • Packet Switching Network • Data is divided into packets that are multiplexed onto high capacity inter-machine connections. • Advantage：Shared by all pairs of computers • Disadvantage：No QoS Guarantee 4 5

  8. Computer Networks • Internet ! • The most notable internet (internetwork) • A collaboration of hundreds of thousands of interconnected networks. • A computer network is a combination of systems (e.g., computers) connected through transmission media (e.g., wire, cable) to transmit data from one location to another. • Hardware: printers, disks, computers, routers, communication lines, … • Software: operating system, application programs

  9. Percentage of Net222work Traffic Sources: Cisco estimates based on CAIDA publications

  10. Server-based Architecture • Server-based or centralized control • Source is controlled by one or several computers • Authentication, Authorization, Accounting (AAA) • Client-server architecture • Client: request service • Server: provide service • Network: provide the environment of connections Request Response Server Client

  11. Peer to Peer Architecture • Data is not in a specific server but in many peer computers • To query and receive data from other peer • P2P applications and services • File sharing：Gnutella、eMule、WinMX、BitTorrent • VoIP：Skype、SIP、H.323 • Video streaming：PPStream、 PPLive、TVKoo、Tvants、QQ

  12. Internet Service Providers (1/2) • An Internet service provider (ISP) is a company that offers its customers access to the Internet. • The ISPs connect many types of networks and provide end users the services to connect to the other networks. End user Dial-up, ADSL, cable modem, wireless

  13. Internet Service Providers (2/2) From: Wikipedia

  14. Taiwan Gateway (TWGate)

  15. Connect to International

  16. Application Service Providers • An application service provider(ASP) is a business that provides computer-based services to customers over a network. • ASPs are a way to sell and distribute software and software services. • Ex: HiNet MOD, Apple Store, Google Apps Marketplace, Google Chrome Web Shop

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