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GETTING CONNECTED

Explore the evolution of network connections from early computer-to-device connections to modern networks, including LANs, WANs, and the emerging network scenario. Learn about modems, data transmission, satellite communications, and the impact of the internet on communication.

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GETTING CONNECTED

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  1. GETTING CONNECTED Session III 11:15 - 12:15 Dr Deepak B Phatak, IIT Bombay

  2. MODERN INFORMATION DELIVERY MECHANISMS • Early Networks • Modern Network Components • Emerging Network Scenario Getting Connected

  3. EARLY NETWORKS • Computer to Devices • RS. 232, Parallel Centronics port • Computer to Intelligent Devices • Escape Sequences, Disk Read/Writes • Computers to Computers Getting Connected

  4. LOCAL AREA NETWORKS • Within A Building, Campus • Ethernet, Packet Switched Network • TCP/IP Protocol • IP Address 144.16.111.248 • Typical LAN 10/100 Mbps • Network Switches, Hubs • “Nodes” Connected Through RJ42 Getting Connected

  5. WIDE AREA NETWORKS • Same Principle, Stretched Across cities, countries and the globe • Variety of Media • Telephone lines (PSTN) • Microwave, Radio Links • VSATS Getting Connected

  6. MODEMS AND DATA COMMUNICATION • Modulation Standards (V.32, V.32bis, V.fast) • Interface Specifications (RS232, V.24, X.21) • Error Correction (MNP Class 4, V.42) • Data Compression (MNP Class 5, V.42bis) Getting Connected

  7. ASYNCHRONOUS DATA TRANSMISSION • High Overhead (20%) • Slower Speeds • Simpler Circuitry  Lower Cost • Dial-up Lines Getting Connected

  8. SYNCHRONOUS DATA TRANSMISSION • Low Overhead (Much Less Than 20%) • High Speeds • Complex Circuitry  Higher Cost • Leased Lines Getting Connected

  9. SATELLITE COMMUNICATIONS • History • Sputnik (1957), Explorer (1958), Intelsat, Comsat, .... INSAT • Geo-Stationary Orbit (35,680 km) • Footprint (30% of Earth’s Surface) • Low-Orbit (Iridium, Inmarsat) • Rotating Antenna, Out Of Range? Getting Connected

  10. SATELLITE COMMUNICATIONS • Frequency Bands (Transponders) • C Band Clashes With Terrestrial Radio • Ku Band Affected By Rain (Dampening) Getting Connected

  11. MODERN NETWORKS • Content Independent Delivery Mechanism • Like Postal Service • Addressing and Connectivity Issues Getting Connected

  12. MODERN NETWORKS • Bandwidth needs • CD audio 706 kbps, Digital Phone 64 kbps • Motion Video 96 Mbps • MPEG-2, 6 Mbps Getting Connected

  13. MODERN NETWORKS • More Bandwidth Issues • Bandwidth on Demand • Virtual Circuits • Isochronous Network Environment Needed (Low and Predictable Node to Node Delays) Getting Connected

  14. MODERN NETWORKS • The Glue That Holds Things Together • Software in Switches, Routers • Protocol Stacks (Software) Within a Computer Getting Connected

  15. EMERGING NETWORK SCENARIO • Indian: 64 Kbps, 2 Mbps • Global: T3, E3 • Address Bottleneck, IP-V6 • Frame Relay • ATM - the Ultimate Winner? Getting Connected

  16. LAN-WAN DIVIDE • Why? • Functionality Same • Move Bits From Point A To Point B • Obvious Differences • Distance, Ownership • Speeds (10 - 100 Mbps Vs Kbps) • Protocols Getting Connected

  17. LAN-WAN DIVIDE • LAN Is Shared Media • WAN Is Point-to-point Link • No Buffering Needed For LAN • Memory Needed In WAN Routers! Getting Connected

  18. EVOLUTION OF INTERNET • ARPANET of 60’s • TCP/IP included in BSD UNIX • Extensively Used for E-Mail and News Groups • Reducing Cost of Bandwidth • Address Bottleneck Getting Connected

  19. INTERNET GROWTH • Number of Host Machines • 1969 4 • 1971 23 • 1977 111 • 1984 1024 • 1987 28174 • 1989 130000 Getting Connected

  20. INTERNET GROWTH • Number of Host Machines • 10/1992 1,136,000 • 10/1993 2,056,000 • 01/95 4,852,000 • 01/96 9,472,000 • 01/97 16,146,000 Getting Connected

  21. ARRIVAL OF WWW • Traditional Network Utilisation • E-mail, FTP, Telnet / rlogin, Gopher, News Groups • HTTP and HTML Proposed • 1989 Tim Berners-Lee at Cern • Hyper Text Transfer Protocol • Hyper Text Mark-up Language Getting Connected

  22. ARRIVAL OF WWW • Hyper Links Within Documents • Browser as Front-End • NCSA Mosaic, 1993 • Marc Andreessen, Netscape, 1994 Getting Connected

  23. GROWTH OF WWW • Number of Web Sites • 06/1993 130 • 12/1993 623 • 06/1994 2,738 • 12/1994 10,022 • 06/1995 23,500 Getting Connected

  24. GROWTH OF WWW • Number of Web Sites • 01/1996 100,000 • 06/1996 252,000 • 01/1997 646,000 • 06/1997 1,117,000 Getting Connected

  25. DIMENSIONS OF WWW • Basic Characteristics • Hyperlinks - Distributed Documents • URL : Uniform Resource Locator • Multimedia data • Software Becomes Mobile • “Applets” in Java Language Getting Connected

  26. INTRANET • A WAY OF CARRYING OUT ALL INTERNAL CORPORATE ACTIVITIES USING INTERNET DERIVED TECHNOLOGIES WHILE INTERACTING WITH CUSTOMERS ON INTERNET Getting Connected

  27. CORPORATE ENTITIES NEED • Distributed Systems with Site Autonomy • Access to these distributed databases on-line for Business • Security against outsiders trying to access or change our corporate Data Getting Connected

  28. SOMETHING MORE • Apart from the above, INTRANET ALSO MEANS: • A Common Interface to All End-users of the Corporation, Typically Based on a Browser • Ability to Navigate Through Different Data Bases Getting Connected

  29. SECURITY IN INTRANET • IP Network Is Inherently “Unsafe”. • IP Addresses Can Be Faked • Access to Your INTRANET GATEWAY May Permit Access to Your Corporate Data! Getting Connected

  30. FIREWALLS • What is a Firewall: • System That Acts As a Security Buffer Between Your Intranet and The Outside Internet Getting Connected

  31. PROPERTIES OF FIREWALLS • Filtering and Screening Capabilities • Authentication Levels • Logging and Accounting • Transparency and Flexibility • Manageability Getting Connected

  32. CLIENT-SERVER APPLICATIONS ON INTERNET • What Is A Socket? • Analogy With Telephone • Instrument, Number, Line Getting Connected

  33. EXAMPLE APPLICATIONS • From/etc/services on Unix • Connection Oriented (TCP) • Mail, Telnet, FTP • WWW Browser • Connectionless (UDP) • SNMP • NFS Getting Connected

  34. WEB MODEL • Hyber-Text Transfer Protocol (HTTP) • Browser Decides How To Display Getting Connected

  35. WWW CONTENT • Static Content • Text, Data, Pictures, Sound • Viewer Has No Control • Dynamic Content • Interactive Games, Teaching Software, Drawings • User Interacts/Controls Content Getting Connected

  36. WWW DIMENSIONS • How To Get Non-static Information? • User Chooses Content He Desires To See • Gives Much More Power To WWW Getting Connected

  37. UNIFORM RESOURCE LOCATOR • Name Used For • http Hypertext (HTML) • (http://www.cse.iitb.ernet.in) • ftp FTP • (ftp://ftp.cc.iitb.ernet.in/pub/unix) • file Local File • (/usr/pg96/graj/prog.c) • news News Article news:EL8Gur.x4@bhishma.cse.iitb.ernet.in • gopher Gopher gopher://gopherr.tc.umn.edu/11/Libraries • mailto Sending Email mailto:grap@cse.iitb.ernet.in • telnet Remote Login telnet://www.w3.org:80 • Browser Hides Different Protocols • No Need To Learn Mail/ftp/telnet etc. Getting Connected

  38. WWW CLIENT SOFTWARE • Browsers • Netscape, IE, Lynx • Other • wget, WWW By Email! Getting Connected

  39. BROWSERS • Features Supported • Multimedia, Frames • Styles Sheets • Java Applets • Javascript • Secure Transactions Getting Connected

  40. BROWSERS • Performance • Availability • Cost • Open Source Model! • In The Future: Browser Is Everything! Getting Connected

  41. POPULAR BROWSERS • NCSA Mosaic • Arena/Amaya (W3C) • Red Baron (RedHat) • Lynx • Internet Explorer • Netscape Navigator/Communicator Getting Connected

  42. HTML TAGS • <HTML> ... </HTML> • Declares The Web Page To Be Written In HTML • <HEAD> ... </HEAD> • Delimits The Page’s Head • <B> ... </B>, <I> ... </I> • Set ... In Boldface, In Italics Getting Connected

  43. HTTP • Hyper Text Transfer Protocol • RFC 1945 By T. Berners-Lee, R. Fielding, H. Nielsen, “Hypertext Transfer Protocol - HTTP/1.0”, 05/17/1996 • Fielding, et. al., RFC 2068 HTTP/1.1 January 1997 Getting Connected

  44. HTTP REQUESTS • GET Fetches The Specified Document • POST Sends User-specified Data To A Script And Returns The Results • HEAD Requests Header Information About The Specified Document • PUT Places A Document On The Server • DELETE Deletes A Document On The Server Getting Connected

  45. HTTP REQUEST HEADERS • HTTP REQUEST HEADERSAccept Which MIME Types The Client Will Accept • Accept-Encoding, Accept-Language Compress, gzip • Authorization Username And Password Getting Connected

  46. HTTP REQUEST HEADERS • Content-length: Specify How Many Bytes It Is Sending via POST • Content-type: Application • From: User’s Email Address (Privacy!) Getting Connected

  47. HTTP REQUEST HEADERS • If-Modified-Since • Pragma: “no-cache” • User-Agent: Mozilla (Netscape), Lynx, ... Getting Connected

  48. HTTP RESPONSE HEADERS • Date: The Current Date • Last-Modified: The Last Time The Requested Document Was Modified • Expires: The Date Which The Requested Document Expires Getting Connected

  49. WEB SERVER SOFTWARE • Cern httpd [European Laboratory For Particle Physics (CERN)] • NCSA HTTPd • Microsoft IIS • Netscape Server Getting Connected

  50. WEB SERVER SOFTWARE • Apache • King Of All Web Server • 53% In Jan 1999 • Descended From NCSA httpd • www.apache.org • Open Source Model Getting Connected

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