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COMP1321 Digital Infrastructure

COMP1321 Digital Infrastructure. Richard Henson University of Worcester February 2013. Week 12: Network Operating Systems. Explain how client-server and peer-peer systems communicate and function Explain the dual role of any operating system

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COMP1321 Digital Infrastructure

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  1. COMP1321Digital Infrastructure Richard Henson University of Worcester February2013

  2. Week 12: Network Operating Systems • Explain how client-server and peer-peer systems communicate and function • Explain the dual role of any operating system • Explain the various essential roles of specialised software in a network operating system

  3. Functions of an Operating System • Coordinate hardware so it all works together cooperatively • Provide a means for human input into the system that can control the hardware components

  4. Early Operating Systems • Each of the early computers was unique • each had to have its own purpose-built operating system • IBM: world’s first mass produced “mainframe” • IBM 701 (1952) • purchasers expected to write their the operating system themselves! • first “mass produced” operating system written by General Motors: GM-NAA I/O in 1956 • adopted by IBM as IBSYS • IBM hugely successful; by 1980s, allegedly bigger than US government (?)

  5. First British Operating system • Leo 3 was the first mass produced British Computer • 94 units built 1961-1969 • full list of buyers http://www.leo-computers.org.uk/newleo3s.htm • each had a loudspeaker connected to the CPU… so operators could tell if it was “looping” • had a multi-tasking operating system called “master program” • Some continued in service until 1981

  6. First Minicomputer & Operating system • Produced by Digital Equipment Corporation (DEC) in 1963 • called the PDP-6 • “mini” in size compared to mainframes • huge by today's standards • operating system called “monitor” • evolved into the TOPS10 (1970) • ran on the legendary PDP-10 • still going until 1988 • can get it even now: • http://www.inwap.com/pdp10/96license.txt

  7. Unix • Spin-off (1969) from project MULTICS • First attempt at a multiuser operating system • Consortium including Bell Labs, AT&T, • US equivalent of BT at that time • FAILED! Too ambitious… • Bell Labs: cut down derivation called UNICS -> UNIX • written in assembly language by Ken Thompson • sharing of processes also being explored in The ARPAnet project • Commercial Challenge: • DEC PDP-7 minicomputer • needed a general purpose “time sharing” operating system for multiuser use… • their own os “monitor” had not yet matured into TOPS-10

  8. Thompson, Ritchie, “B”, NB, “C” & Unix • Thompson looking for a high-level language to develop a time sharing os • briefly toyed with Fortran • worked with colleague Dennis Ritchie to create their own higher level language – “B”, based on BCPL • http://cm.bell-labs.com/cm/cs/who/dmr/kbman.html • development of B = newB (NB) • development of NB -> C • Unix kernel was rewritten in “C” (1973)

  9. Development of Unix/C • “C” compiler completed by Ritchie in 1972 • Further commercial Unix versions (for Honeywell & IBM) released in 1973 • “C” further developed during 1973-7 • Full definition of language as Kernighan & Ritchie “C” (1978) • rapidly gained universal acclaim • Unix still written in “C” to present day! • 32-bit processing from the outset

  10. Open Sourceness of Unix • AT&T not allowed to be a commercial company • could not sell Unix • gave a copy away free to any developer who wanted to use it! • many universities contributed to its development • Result (in 1979): Unix version 7 • still recognisable today!

  11. Silicon Valley, TCP/IP and Unix • University of California created The ARPAnet (1969) • 1975 onwards: Berkeley, north of San Francisco • hub for its own unique brand of Unix developments • start of “Silicon Valley” (IT hot spot around SF) • ARPAnet team • developed TCP/IP • 1980, gained approval through RFC • operating system that would support TCP/IP arrived in 1983… • Berkeley Unix (v4.2) packaged with TCP/IP protocol stack • Sun Microsystems producing the hardware…

  12. Bell Labs Unix becomes Commercial… • US Dept of Justice broke up AT&T in 1984 • Bell Labs then allowed to sell their Unix source code… • Fortunately for SCO (Santa Cruz Operations) they had ported Bell Unix to Intel hardware the previous year (!) • SCO Unix for PC became a lucrative business market • operating system provided security on a PC where DOS couldn’t…

  13. Bad days for Unix… • Unix free by nature from outset • not so on an Intel PC, thanks to SCO!!! • Bell Labs jealously guarded the source code… • universities lost interest • Unix became expensive to buy… and was still not user-friendly or easy to use so even more expensive to own!

  14. Linux • From 1992 (Linus Torvalds, University of Helsinki) made free Unix possible again! • LINUX – based on his name… • Took… • Stallman’s GNU open source Unix • which Tanenbaum had developed into MINIX… • very stable • secure file system • very efficient, optimised code • earlier versions ran on an Intel 486! • Still Unix, still a server-end system • for client-server networking, need client-end software: • e.g. Banyan VINES

  15. Linux • Still freely available via Internet! • Huge range of software tools for managing UNIX networks available for download • Problems (compared to Windows): • not as easy to manage • limited on-screen help • limited range of good application software • not all hardware has UNIX/LINUX driver software

  16. Group exercise • Consider something that you’d like computer to do for you…. • What do you want to happen? • Which hardware must do what to make that a reality?

  17. Specialised Functions of a Network Operating System • Support for communication protocols and e.g. the TCP/IP stack • All of the centralised tasks needed to keep the network running normally • All achieved through software: • highly optimised • executes code as quickly as possible…

  18. Memory Management • Based on good use of addressing • All programs and their data stored within fixed memory location blocks • Need to ensure that there is no memory “creep”

  19. Virtual Memory Management • Extra space on hard disk • Data constantly being swapped between main memory and virtual memory to maximise performance

  20. Disk Management • Ensure data accessed from and directed to right addresses • Partitioning and formatting new disks and areas of disk • Using mirroring, duplexing and RAID as appropriate to maximise disk performance

  21. File Management • Choice of filing system when formatting • FAT? • FAT32? • NTFS • Others?

  22. IP address Management • Most networks now use IP addresses • System needed to manage IP addresses across the network… • Dynamic Host Configuration Protocol • Managed as client-server

  23. User and Group Management • New users have to be defined • Users have to be allocated to groups • Group have to be defined so as to allow appropriate access so people can do their jobs efficiently

  24. User Authentication • Usernames & passwords have to be matched against a database to ensure granting of access is justified

  25. Store of Network Information • Computer names and addresses • Device names • Group and User names • Service names…

  26. Transferring Data efficiently to another Device • Some will get corrupted en route… • Error(s) need to be detected • Request then follows to resend the data • Part of communication protocol

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