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Chapitre 1.3

Chapitre 1.3. Réseaux. The question : Within a large organization, what is the optimal localization of Processing power Data storage The possibilities : In a global computer center In local computer centers With the user Any combination of the three previous solutions.

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Chapitre 1.3

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  1. Chapitre 1.3 Réseaux

  2. The question : Within a large organization, what is the optimal localization of Processing power Data storage The possibilities : In a global computer center In local computer centers With the user Any combination of the three previous solutions Client-Server systems

  3. The question : What is the optimal localization of Processing power Data storage The possibilities : In a global computer center In local computer centers With the user Any combination of the three previous solutions Client-Server systems

  4. Centralized Data Processing Mainframe Computer Star Network Dumb Terminals

  5. Benefits : Simple Access to Common Data Professional Data Management Enforceable Security Well Defined Cost Full control by EDP people

  6. Mainframe Computer But... Processing power limited by physics ! 1 GIPS : 10-9 s/instruction : d < 30 cm 1 TIPS : 10-12 s/instruction : d < 0.3 mm

  7. Technical arguments againstCentral Computers Processing Power of a single CPU can not grow indefinitely Transmission capacity needed between processor and terminal has become enormous

  8. Mainframe Computer But... Graphic User Interfaces put extreme stress on communications ! This screen = 2 359 296 bytes transmitting it at 2 Mb/s takes 10 s.

  9. Technical arguments againstCentral Computers Processing Power of a single CPU can not grow indefinitely Transmission capacity needed between processor and terminal has become enormous

  10. The question : What is the optimal localization of Processing power Data storage The possibilities : In a global computer center In local computer centers With the user Any combination of the three previous solutions Client-Server systems

  11. The Reaction : Independent Personal Computers

  12. Access to common data ??? Risk of loss of data ! Software Maintenance ! Cost of some peripheral equipment Limited processing power And many other hidden costs ! But ...

  13. The question : What is the optimal localization of Processing power Data storage The possibilities : In a global computer center In local computer centers With the user Any combination of the three previous solutions Client-Server systems

  14. Client - Server Systems Many computers with characteristics matching their specific usage interconnected by means of a network

  15. Client - Server Systems Interconnection Network

  16. Networked Computers Benefits Sharing of disk space (= access to common data & programs) (= centralized disk back-up facilities) Sharing of expensive peripherals (Spooling required) Sharing of processing power

  17. The users interface of all applications runs on the personal workstations. For some applications, the workstation requests help from specialized servers. The user remains unaware of such requests. Servers can be optimized for specific tasks Virtual Mainframes can be Very user friendly cost effective Virtual Mainframe= true Client-Server system

  18. Network Technology Local Area Networks In a room, a building, a campus High throughput, low delays, low cost RESULB: 10-100 Mb(it)/s in buildings Twisted pairs / coaxial cables 1 Gb(it)/s between buildings Optical Fibers

  19. From Brussels to New York Paris Antwerp 64 Kb/s 2.500 1.600 400 2 Mb/s 30.000 20.000 5 000 Network Technology Wide Area Networks All over the world Low throughput, high delays, high cost Leased lines: (Indicative prices in Euro per month)

  20. Network Technology Data Transmission over the Public Switched Telephone Network PSTN <= 30Kb/s

  21. Network Technology Data Transmission over the Integrated Services Digital Network ISDN = 64Kb/s

  22. Network Technology Internet Service Provider Access over an Hybrid Network ISP ISP ISDN = 64Kb/s 56Kb/s

  23. Public Access Network Technology Data Transmission over Data Networks Private Data Network (Banksys,...) PSTN Private Access

  24. The Early ARPANET (1976) London Hawaii 56 Kb/s terrestrial link Satellite link

  25. The INTERNET Cooperative interconnection of local area networks BELNET VUBNET RESULB RUGNET KULNET

  26. eunet Internet Cost Structure GIANT USA Surfnet NL Belnet BE Planet Planet Skynet Uunet Uunet - Backbone infrastructure and neutral interconnects paid by interconnected networks, proportional to their access bandwidth. - Cost of direct interconnects shared by partners. - Not ACTUAL but POTENTIAL traffic is charged.

  27. Via Internet Service Provider Main problem : local access line Via PSTN or ISDN Low throughput time based charges conflicting with phone and fax Via ADSL or Cable TV High throughput Volume based charges No Conflict with phone, fax or TV Via Wireless link GSM : slow & expensive GPRS : better UMTS : much better but not yet widely used WiMax : the wireless paradise ??? Private Internet Access

  28. ADSL ADSL ROUTER Co-located equipment SW A D S Lfor residential Internet access <=600 Kb/s <=6 Mb/s Subscriber's line Analog Voice

  29. ADSL ADSL Video Server Co-located equipment A D S Lfor Video On Demand A few Kb/s A few Mb/s Subscriber's line Analog Voice SW Local telephone exchange

  30. 7-8 MHz Return VTM RTBF VRT RTL Data frequency Co-located equipment Data over Cable TV TV Cablehead Cable modem Cable modem ROUTER SW

  31. Internet Usage Access to distributed multimedia databases (World Wide Web) Electronic Mail Internet Real-time Chat File transfers (FTP) Internet Telephony (Skype,…) Network File System

  32. Uniform hypertext based users friendly interface for distributed databases. Inexpensive, high quality, browsers available for almost all computers. Sophisticated and application specific users interactivity possible by downloading programs to be executed on client’s workstation (Java). Already well over 109 pages available worldwide, mainly for public relations, publicity and, to some extent, electronic commerce. Electronic commerce still restrained by security concerns. World Wide Web

  33. Hypertext Multimedia document Normal text Graphics and images (stored in separate files) Sound (stored in separate files) Executable programs (Java Applets) References of other hypertext documents (“Anchors”) “clickable” normal text or image (icon) address (URL) where the corresponding document can be found HTMLHyperText Markup Language

  34. Finding information becomes more and more difficult due to the amount of information. Automated indexing services, searching all available databases on the Internet and setting up keyword databases are very popular. Good ranking of keywords can be purchased from some indexing services. Many sites try to use tricks to be favorably presented by search engines Search Engines

  35. Root be edu com org ac vub info tiberghien Internet Domains(= internet distributed directory) uk ieee mtv vrt rtbf ulb lvhamme tiberghien@info.vub.ac.be

  36. email m4 is a “pop server”, with a mailbox for each registered user. Connection between pop server and users can be temporary m4 INTERNET d@m4 a@m1 b@m2 c@m4 d@m4

  37. IRC Internet

  38. Application X m4 m2 INTERNET User of X User of X Local terminal user Remote terminal user Telnet Telnet

  39. m4 File Transfer Protocol m2 Internet Direct FTP user Third party FTP user

  40. Internet Telephony Low cost POTS emulation Internet Telephone Gateways Local PSTN Local PSTN Internet • Access through local PSTN • Quality dependant from network load

  41. Network File System Shared file system Intranet

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