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WWW and the Internet

WWW and the Internet Bus Different types of networks LAN (Local Area Network) Connects network devices over a relatively short distance Office Building / University / Home Possible topologies: Different types of networks MAN (Metropolitan Area Network) Connects an area larger than a LAN

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WWW and the Internet

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  1. WWW and the Internet

  2. Bus Different types of networks • LAN (Local Area Network) • Connects network devices over a relatively short distance • Office Building / University / Home • Possible topologies: Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  3. Different types of networks • MAN (Metropolitan Area Network) • Connects an area larger than a LAN • Connect Cities / States WAN (Wide Area Network) • Spans most of the world • Formed by connecting LANs and MANs (with routers) • E.g. Internet Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  4. Routers Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  5. WWW vs. Internet • Internet • A worldwide system of computer networks • Users at any one computer can, if they have permission, get information from any other computer • Web • Graphical user interface (GUI) on top of the Internet Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  6. History of internet • Who owns the internet? • Who operates the internet? • 1969: U.S. military established the initial computer network (ARPANet) • 1991: Tim Berners-Lee created a program for sharing of files • Mosaic  Netscape  IE • 130 Web sites in 1993, now > 25 million Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  7. Search engine • Search engine • Facility on the Web • 2 types • Directory search engine • Hierarchical organization • True search engine • Search the web for keywords Search for: Charles Babbage (father of computing) Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  8. Hardware for communication • Modem - a device that sends and receives data over telephone lines to and from computers • There are two types of modems – internal and external Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  9. External Modem Internal Modem (PCI) Two connectors, one connected to telephone, and the other to telephone socket (wall) Once you’re using modem, the telephone is not usable Hardware for communication Some modems have value-added functions: e.g. FAX, automatic answering machine Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  10. Hardware for communication • Modem – (Modulator / Demodulator) • Copper telephone line is analog in nature • Digital Signal would be distorted if it is directly sent via telephone line • Modem (sender side) encodes digital signal to analog form and convert it back to digital signal at receiver side • Modulation schemes: • Amplitude Modulation (AM) • Frequency Modulation (FM) • Phrase Modulation (PM) • Hybrid/Combination Schemes Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  11. Hardware for web surfing • Web computer • Scaled down version of computer system • Used for web access, email, maybe some simple task http://www.hitachi.co.jp/Prod/vims/wia/index.html http://www.mailbug.com/ Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  12. WebTV • Cable TV with web access through cable http://www.sky.com http://www1.sky.com/skyactive/whatisSkyActive/ • Web phones • Browse the web with microbrowser • Limitation • PDA Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  13. Software for web surfing • Web browser • Main objective is to communicate over the Internet with Web servers using HTTP • Interpret hypertext documents and formatted it on screen • Types of browser: • Text-based e.g. Lynx Point-And-Click Graphical User Interface e.g. Cello, Mosaic, Netscape, Internet Explorer Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  14. Internet connection Your home computer Destination computer Local ISP Local ISP Network Access Point (NAP) at another place Network Access Point (NAP) Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  15. Internet Service Provider (ISP) • A company that provides access to the Internet • How to choose a good ISP? • Features e.g. Speed, Web space, Email account • Technical support • Installation • Privacy • Price Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  16. Internet Service Provider (ISP) • More features with commercial ISPs • Personalized name for your site • More than 30 email accounts • Spam email filter • Larger storage space • Free ISPs www.netzero.net www.juno.com Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  17. Major ISPs in Hong Kong How to interpret the information ? Generally speaking, download speed is more Important than upload speed (e.g. when requesting a homepage/image) However, there are exceptions (e.g. using video conferencing / BT) Upload: Sending information from your machine to others Download: Receiving information from the others to your machine Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  18. ‘M’ means 220, which is roughly equals to 1,000,000 ‘k’ means 210 (=1024), which is roughly equals to 1,000 “bps”: bits per second The unit specifying transmission speed. (a bit is either a “0” or “1”) Note that “bps” is in lower case. If it is written as “Bps” (capital B), It means bytes per second 1 byte = 8 bits, which can be though of as a single character Major ISPs in Hong Kong Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  19. Also need to consider whether it is “10Mbps for each client”, or “10Mbps for the whole building” Major ISPs in Hong Kong Transmission speed of some ISP may be affected by geographical location Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  20. Roughly Hierarchical At center:“tier-1” ISPs For Example: UUNet, BBN/Genuity, Sprint, AT&T National/international coverage Treat each other as equals NAP Tier-1 providers also interconnect at public network access points (NAPs) Tier-1 providers interconnect (peer) privately Tier 1 ISP Tier 1 ISP Tier 1 ISP Internet structure: network of networks Ref: Computer Networking: A Top Down Approach Featuring the Internet, 3rd edition.Jim Kurose, Keith Ross Addison-Wesley, July 2004. Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  21. Tier-1 ISP: e.g., Sprint Sprint US backbone network Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  22. “Tier-2” ISPs: smaller (often regional) ISPs Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs NAP Tier-2 ISPs also peer privately with each other, interconnect at NAP • Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet • tier-2 ISP is customer of tier-1 provider Tier-2 ISP Tier-2 ISP Tier-2 ISP Tier-2 ISP Tier-2 ISP Internet structure: network of networks Tier 1 ISP Tier 1 ISP Tier 1 ISP Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  23. “Tier-3” ISPs and local ISPs last hop (“access”) network (closest to end systems) Tier 3 ISP local ISP local ISP local ISP local ISP local ISP local ISP local ISP local ISP NAP Local and tier- 3 ISPs are customers of higher tier ISPs connecting them to rest of Internet Tier-2 ISP Tier-2 ISP Tier-2 ISP Tier-2 ISP Tier-2 ISP Internet structure: network of networks Tier 1 ISP Tier 1 ISP Tier 1 ISP Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  24. a packet passes through many networks! Tier 3 ISP local ISP local ISP local ISP local ISP local ISP local ISP local ISP local ISP NAP Tier-2 ISP Tier-2 ISP Tier-2 ISP Tier-2 ISP Tier-2 ISP Internet structure: network of networks Tier 1 ISP Tier 1 ISP Tier 1 ISP Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  25. Voice over internet • Apart from data file, internet can also be used for transmitting voice information • PC-to-phone • Phone-to-internet-to-phone • Advantages: • Lower cost for long-distance telephone service • Other services such as Group-Communication, • Caller filtering • It’s possible to transmit video information also Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

  26. References • S. Haag, M. Cummings and A. Rea Jr., Computing Concepts, McGraw-Hill, 2002, Ch. 2 • Williams . Sawyer, “Using Information Technology”, 6th edition, McGraw-Hill, 2005, Ch. 2 • James F. Kurose, Keith W. Ross, “Computer Networking”, 3rd edition, Addison Wesley, 2004, Ch 1.5 Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

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