COMP1321 Digital Infrastructure Richard Henson University of Worcester February 2013.

COMP1321COMP1321Digital InfrastructureDigital Infrastructure

Richard HensonRichard Henson

University of WorcesterUniversity of Worcester

FebruaryFebruary 20132013

Week 12: Network Week 12: Network Operating SystemsOperating 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

Functions of an Functions of an Operating SystemOperating System

Coordinate hardware so it all works together cooperatively

Provide a means for human input into the system that can control the hardware components

Early Operating SystemsEarly Operating Systems Each of the early computers was uniqueEach of the early computers was unique

each had to have its own purpose-built each had to have its own purpose-built operating systemoperating system

IBM: world’s first mass produced IBM: world’s first mass produced “mainframe”“mainframe” IBM 701 (1952)IBM 701 (1952)

» purchasers expected to write their the operating purchasers expected to write their the operating system themselves!system themselves!

» first “mass produced” operating system written first “mass produced” operating system written by General Motors: GM-NAA I/O in 1956by General Motors: GM-NAA I/O in 1956

adopted by IBM as IBSYSadopted by IBM as IBSYS

IBM hugely successful; by 1980s, allegedly IBM hugely successful; by 1980s, allegedly bigger than US government (?)bigger than US government (?)

First British Operating systemFirst British Operating system Leo 3 was the first mass produced British Leo 3 was the first mass produced British

ComputerComputer 94 units built 1961-196994 units built 1961-1969

» full list of buyers full list of buyers http://www.leo-computers.org.uk/newleo3s.htm

each had a loudspeaker connected to the each had a loudspeaker connected to the CPU… so operators could tell if it was “looping”CPU… so operators could tell if it was “looping”

had a multi-tasking operating system called had a multi-tasking operating system called “master program”“master program”

Some continued in service until 1981Some continued in service until 1981

First Minicomputer First Minicomputer & Operating system& Operating system

Produced by Digital Equipment Corporation Produced by Digital Equipment Corporation (DEC) in 1963(DEC) in 1963 called the PDP-6called the PDP-6

» ““mini” in size compared to mainframesmini” in size compared to mainframes» huge by today's standardshuge by today's standards

operating system called “monitor”operating system called “monitor”» evolved into the TOPS10 (1970)evolved into the TOPS10 (1970)» ran on the legendary PDP-10ran on the legendary PDP-10» still going until 1988still going until 1988» can get it even now:can get it even now:» http://www.inwap.com/pdp10/96license.txt http://www.inwap.com/pdp10/96license.txt

Unix Unix Spin-off (1969) from project MULTICSSpin-off (1969) from project MULTICS

First attempt at a multiuser operating systemFirst attempt at a multiuser operating system» Consortium including Bell Labs, AT&T, Consortium including Bell Labs, AT&T,

US equivalent of BT at that timeUS equivalent of BT at that time

» FAILED! Too ambitious…FAILED! Too ambitious… Bell Labs: cut down derivation called UNICS -> UNIXBell Labs: cut down derivation called UNICS -> UNIX

» written in assembly language by written in assembly language by Ken ThompsonKen Thompson» sharing of processes also being explored in The ARPAnet sharing of processes also being explored in The ARPAnet

projectproject

Commercial Challenge: Commercial Challenge: • DEC PDP-7 minicomputerDEC PDP-7 minicomputer

» needed a general purpose “time sharing” operating system needed a general purpose “time sharing” operating system for multiuser use… for multiuser use…

» their own os “monitor” had not yet matured into TOPS-10their own os “monitor” had not yet matured into TOPS-10

Thompson, Ritchie, Thompson, Ritchie, “B”, NB, “C” & Unix“B”, NB, “C” & Unix

Thompson looking for a high-level language Thompson looking for a high-level language to develop a time sharing osto develop a time sharing os• briefly toyed with Fortranbriefly toyed with Fortran• worked with colleagueworked with colleague Dennis Ritchie Dennis Ritchie to create to create

their own higher level language – “B”, based on their own higher level language – “B”, based on BCPLBCPL

» http://cm.bell-labs.com/cm/cs/who/dmr/kbman.htmlhttp://cm.bell-labs.com/cm/cs/who/dmr/kbman.html

• development of B = newB (NB)development of B = newB (NB)• development of NB -> Cdevelopment of NB -> C• Unix kernel was rewritten in “C” (1973)Unix kernel was rewritten in “C” (1973)

Development of Unix/CDevelopment of Unix/C

““C” compiler completed by Ritchie in 1972C” compiler completed by Ritchie in 1972 Further commercial Unix versions (for Further commercial Unix versions (for

Honeywell & IBM) released in 1973Honeywell & IBM) released in 1973 ““C” further developed during 1973-7C” further developed during 1973-7 Full definition of language as Kernighan & Full definition of language as Kernighan &

Ritchie “C” (1978)Ritchie “C” (1978) rapidly gained universal acclaimrapidly gained universal acclaim

Unix still written in “C” to present day!Unix still written in “C” to present day! 32-bit processing from the outset32-bit processing from the outset

Open Sourceness of UnixOpen Sourceness of Unix

AT&T not allowed to be a commercial AT&T not allowed to be a commercial companycompany• could not sell Unixcould not sell Unix• gave a copy away free to any developer who gave a copy away free to any developer who

wanted to use it!wanted to use it!• many universities contributed to its developmentmany universities contributed to its development

Result (in 1979): Unix version 7Result (in 1979): Unix version 7• still recognisable today!still recognisable today!

Silicon Valley, TCP/IP and UnixSilicon Valley, TCP/IP and Unix University of California created The ARPAnet University of California created The ARPAnet

(1969)(1969) 1975 onwards: Berkeley, north of San 1975 onwards: Berkeley, north of San

FranciscoFrancisco• hub for its own unique brand of Unix developmentshub for its own unique brand of Unix developments• start of “Silicon Valley” (IT hot spot around SF) start of “Silicon Valley” (IT hot spot around SF)

ARPAnet teamARPAnet team• developed TCP/IPdeveloped TCP/IP• 1980, gained approval through RFC1980, gained approval through RFC• operating system that would support TCP/IP arrived operating system that would support TCP/IP arrived

in 1983…in 1983…» Berkeley Unix (v4.2) packaged with TCP/IP protocol stackBerkeley Unix (v4.2) packaged with TCP/IP protocol stack» Sun Microsystems producing the hardware…Sun Microsystems producing the hardware…

Bell Labs Unix becomes Bell Labs Unix becomes Commercial…Commercial…

US Dept of Justice broke up AT&T in 1984US Dept of Justice broke up AT&T in 1984• Bell Labs then allowed to sell their Unix source Bell Labs then allowed to sell their Unix source

code…code… Fortunately for SCO (Santa Cruz Operations) Fortunately for SCO (Santa Cruz Operations)

they had ported Bell Unix to Intel hardware they had ported Bell Unix to Intel hardware the previous year (!)the previous year (!)• SCO Unix for PC became a lucrative business SCO Unix for PC became a lucrative business

marketmarket• operating system provided security on a PC where operating system provided security on a PC where

DOS couldn’t…DOS couldn’t…

Bad days for Unix…Bad days for Unix…

Unix free by nature from outsetUnix free by nature from outsetnot so on an Intel PC, thanks to SCO!!!not so on an Intel PC, thanks to SCO!!!Bell Labs jealously guarded the source Bell Labs jealously guarded the source

code…code…universities lost interestuniversities lost interest

Unix became expensive to buy… and Unix became expensive to buy… and was still not user-friendly or easy to use was still not user-friendly or easy to use so even more expensive to own!so even more expensive to own!

LinuxLinux From 1992 (Linus Torvalds, University of From 1992 (Linus Torvalds, University of

Helsinki) made free Unix possible again!Helsinki) made free Unix possible again! LINUX – based on his name…LINUX – based on his name…

Took…Took… Stallman’s GNU open source Unix Stallman’s GNU open source Unix

» which Tanenbaum had developed into MINIX…which Tanenbaum had developed into MINIX… very stablevery stable secure file systemsecure file system very efficient, optimised codevery efficient, optimised code earlier versions ran on an Intel 486!earlier versions ran on an Intel 486!

Still Unix, still a server-end systemStill Unix, still a server-end system for client-server networking, need client-end for client-server networking, need client-end

software:software:» e.g. Banyan VINESe.g. Banyan VINES

LinuxLinux

Still freely available via Internet!Still freely available via Internet! Huge range of software tools for managing Huge range of software tools for managing

UNIX networks available for downloadUNIX networks available for download Problems (compared to Windows):Problems (compared to Windows):

not as easy to managenot as easy to manage limited on-screen helplimited on-screen help limited range of good application softwarelimited range of good application software not all hardware has UNIX/LINUX driver softwarenot all hardware has UNIX/LINUX driver software

Group exerciseGroup exercise

Consider something that you’d like Consider something that you’d like computer to do for you….computer to do for you….

What do you want to happen?What do you want to happen?

Which hardware must do what to make that Which hardware must do what to make that a reality?a reality?

Specialised Functions of a Specialised Functions of a Network Operating SystemNetwork Operating System

Support for communication protocols Support for communication protocols and e.g. the TCP/IP stackand 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…

Memory ManagementMemory Management

Based on good use of addressingBased on good use of addressing All programs and their data stored All programs and their data stored

within fixed memory location blockswithin fixed memory location blocks Need to ensure that there is no memory Need to ensure that there is no memory

“creep”“creep”

Virtual Memory ManagementVirtual Memory Management

Extra space on hard diskExtra space on hard disk

Data constantly being swapped Data constantly being swapped between main memory and virtual between main memory and virtual memory to maximise performancememory to maximise performance

Disk ManagementDisk Management

Ensure data accessed from and Ensure data accessed from and directed to right addressesdirected to right addresses

Partitioning and formatting new disks Partitioning and formatting new disks and areas of diskand areas of disk

Using mirroring, duplexing and RAID as Using mirroring, duplexing and RAID as appropriate to maximise disk appropriate to maximise disk performanceperformance

File ManagementFile Management

Choice of filing system when Choice of filing system when formattingformattingFAT?FAT?FAT32?FAT32?NTFSNTFSOthers?Others?

IP address ManagementIP address Management

Most networks now use IP addressesMost networks now use IP addresses System needed to manage IP System needed to manage IP

addresses across the network…addresses across the network… Dynamic Host Configuration ProtocolDynamic Host Configuration Protocol Managed as client-serverManaged as client-server

User and Group ManagementUser and Group Management

New users have to be definedNew users have to be defined Users have to be allocated to groupsUsers have to be allocated to groups Group have to be defined so as to allow Group have to be defined so as to allow

appropriate access so people can do appropriate access so people can do their jobs efficientlytheir jobs efficiently

User AuthenticationUser Authentication

Usernames & passwords have to be Usernames & passwords have to be matched against a database to ensure matched against a database to ensure granting of access is justifiedgranting of access is justified

Store of Network InformationStore of Network Information

Computer names and Computer names and addressesaddresses

Device namesDevice names Group and User namesGroup and User names Service names…Service names…

Transferring Data efficiently Transferring Data efficiently to another Deviceto another Device

Some will get corrupted en Some will get corrupted en route…route…

Error(s) need to be detectedError(s) need to be detected Request then follows to resend Request then follows to resend

the datathe data Part of communication protocolPart of communication protocol