Optimal Localization of Processing Power and Data Storage in a Large Organization

1. Chapter 1.3 Computer Networks

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 = 892,800 bytes transmitting it at 56 Kb/s takes 124 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. Client Server Systems Minimal integration: “Terminal Emulation” Very User Unfriendly Full Integration: “Virtual Mainframe” The user has the feeling all resources of all networked computers are part of her/his personal computer

18. The personal workstations are used as stand alone computers as terminals connected to other computers The user has to mentally switch between widely different user interfaces and operating systems. Transferring data between local and remote applications is far from trivial Terminal emulation is very user unfriendly !!! Terminal Emulation= sub-minimal Client-server system

19. Client Server Systems Minimal integration: “Terminal Emulation” Very User Unfriendly Full Integration: “Virtual Mainframe” The user has the feeling all resources of all networked computers are part of her/his personal computer

20. 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

21. Network Technology Local Area Networks In a room, a building, a campus High throughput, low delays, low cost VUBNET: 10-100 Mbit/s in buildings Twisted pairs / coaxial cables 1 Gbit/s between buildings Optical Fibers

22. 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)

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

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

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

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

27. The Early ARPANET (1976) London Hawaii 56 Kbps terrestrial link Satellite link

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

29. eunet Internet Cost Structure RARE 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.

30. 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 : much better but not yet widely used UMTS : the wireless paradise ??? Private Internet Access

31. 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

32. 7-8 MHz ROUTER Return VTM RTBF BRTN RTL Data frequency SW Data over Cable TV TV Cablehead Co-located equipment Cable modem Cable modem

33. Internet Usage Access to distributed multimedia databases (World Wide Web) Electronic Mail Internet Real-time Chat Remote Login (TELNET) File transfers (FTP) Internet Telephony Network File System

34. 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 over 200,000,000 pages available worldwide, mainly for public relations, publicity and, to some extent, electronic commerce. Electronic commerce still restrained by security concerns. World Wide Web

35. 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

36. 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 indexing services. Many sites use tricks to be favorably presented by search engines Search Engines

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

38. 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

39. IRC Internet

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

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

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

43. Network File System Shared file system Intranet