Transcript Presentation6 - University of Worcester

COMP2122
Network Operating
Systems
Richard Henson
University of Worcester
November 2010
Week 6: Overview of
Important Network
Operating Systems
• Objective:
 Name significant network operating systems in
developments towards today’s local area networks
 Briefly explain features of proprietary products that
fulfil particular requirements of a network
operating system
 Link operating system architectures to the seven
layer model
Early Operating Systems
• Early computers were all unique and
•
had their own operating systems
IBM designed & built the world’s first
mass produced “mainframe”
 IBM 701 (1952)
• purchasers expected to write their own
operating systems!
• 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 (?)
First British Operating system
• Leo 3 was the first mass produced British
Computer
 94 units built 1961-1969
• full list of buyers http://www.leocomputers.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
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
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
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)
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
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!
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…
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…
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!
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
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
SCO v Linux (more Unix
lawsuits…)
• SCO sued Linux in 2003 for misappropriation
of Unix System V code
 subsequently sued:
• IBM
• Red Hat (Novell)
• Anyone else commercially involved with Linux

e.g DaimlerChrysler
• US Court finally shut them up in August 2007
by saying SCO had no rights to the code
Novell were using…
 Linux continues to be “free” to this day…
Unix Platforms in 2010…
• Typical hardware
 SUN SPARC
 not a PC!
• Excellent as an Internet platform
 very secure, if properly configured
• software bugs mostly sorted out a long time ago…
• always used TCP/IP for machine-machine
communications
• Server or standalone workstation mode
 Linux/Intel favourite for workstation mode
Operating Systems for PC
Ethernet Networks
• Original Topology (1980s, early 90s):
 bus, coaxial cable & BNC connectors (!)
• DOS not designed for server end, or
distributed communications…
 two popular client-server operating systems
emerged:
• Novell Netware


IPX/SPX protocol
not OSI compliant - proprietary & code secret
• DEC (Digital) PCSA


DECnet protocol
OSI compliant - code open source
Novell Netware (version 3)
• Netware - late 1980s
 Novell’s proprietary IPX/SPX network protocol
• networkID based on MAC address
• hardwired into network card during manufacture
• Server end…
 client-server networking only (no peer-peer)
 secure file system based on user, groups, rights &
inherited rights
 supported mirroring, duplexing, RAID
 TTS to reverse incomplete transactions
 network resource names, etc. stored as a
separate bindery on each server
Other Features of
• I/O optimisation:
disk caching
elevator seeking (disk accesses ordered
according to position on disk)
directory hashing
MHS protocol for message-handling and
email within the LAN
Strengths/Weaknesses
of Netware 3
• Strengths:
 fast and secure
• awarded Server Fault Tolerance (SFT) grade III, when
used with server duplexing
• Weaknesses
 proprietary protocol, not peer-peer
 inadequate accounting services
 only 16-bit processing
 250 user maximum
 each user needs to login to each server
Improvements (version 4)
• Scalable across servers
 Using Network Directory Service (NDS)
 network info stored in a managed naming system as
a bindery across the whole network
 security includes NDS attributes
• LANalyser tool for analysing packets &
•
identifying protocol problems
Easier to use than v3: GUI-based
 supported:
•
•
•
•
•
32-bit processing
long filenames - like Windows 95 on
SMP - symmetric multi-processing (2 processors)
Up to 1000 users
remote Network mgt
Enduring Problems
with Netware
• Only ran on Intel Platform
• Reliant on DOS/Windows at the client end
• NDS not not X500 compliant
• not directly compatible with Internet protocols
such as TCP/IP
 based on IPX/SPX protocol (OSI levels 3 and 4) for
interprocess communication
 used MAC addresses (fixed) as unique identifiers,
rather than IP addresses
• not suitable for peer-peer networking
• not pre-emptive in handling processes
What happened to Netware?
• V.successful in early 1990s
 better sales than DEC PCSA architecture, even
though the latter was OSI compliant (!!)
• SPX/IPX faster than TCP/IP…
 70% of the PC network market
• Didn’t see what was coming…
 DEC mini computers lost market share
• everyone wanted a PC network
• main rival DEC sold off and “asset stripped”
 BUT…
• by 1998, Novell Netware sales were sunk
• by 2000, even Oracle stopped supporting them
• only kept in business by merging with Red Hat Linux
What was DEC?
• World’s most innovative computer company for
many years…
 first minicomputer:
• PDP-1 (Programmable Data Processor)
 first UNIX/C implementation
• On PDP-5
 most successful minicomputer:
• VAX (Virtual Addresss eXtension)
 first virtual memory operating system
• VMS (virtual memory system) for VAX
 first commercially successful RISC chip
• alpha
 first commercial Internet domain & website
 first successful search engine: AltaVista
Where did DEC go?
• Second biggest computer company in the
world in 1990!
 over 100000 employees!
 With early 90s recession, went into decline…
• New MD in 1992, only accelerated the decline
 assets sold one by one…
• unkindest cut – alpha chip to Intel in 1997
 what was left (VMS) went to Compaq in 1998
• sold on to HP…
• still support VMS (as OpenVMS) to present day
• Why?
 as with the downfall of IBM and Novell…
• perhaps the name Microsoft might help…
What went wrong with DEC?
• Now long enough ago to be of historical
interest…
 Dave Cutler, brains behind DEC’s VMS went to
work at Microsoft in 1988 to develop “a new
operating system” (NT)
•
• DEC keen to get their alpha chip onto the original
Windows NT…
• signed away any rights to the code used in creating
windows NT
• so Microsoft effectively got the technologies behind VMS
for free!!!!
But thanks to HP, and enthusiastic users, VMS lives
 available for download at:
• http://www.openvms.compaq.com/openvms/freeware
Microsoft & Operating
Systems
• Original IBM PC operating system…
 whilst the US government was being defeated in the
courts by IBM…
 the deal that almost put them out of business was
pulled off by the young Bill Gates…
• story about IBM negotiations with Bill Gates (regarding his
mate Tim Paterson’s os):

http://inventors.about.com/library/weekly/aa033099.htm
• and the tragedy of Gary Kildall (creator of CP/M)…

http://www.businessweek.com/magazine/content/04_43/b390
5109_mz063.htm
DOS (Desktop Operating System)
• As was to be expected from a back-street
deal…
 DOS was an awful operating system…
 no way it could be satisfactorily used for even
multi-tasking, let alone networking…
 no way of
• logging in as an authenticated user…
• restricting access to resources…
 to the new (misguided?) computer generation…
• none of this mattered
 by the late 1980s Gates was the 4th richest person
in the world!
OS2, Windows,
and Windows NT
• By late 1980s, PCs being used for serious
business purposes
 IBM needed a serious operating system for the
PC…
 Microsoft worked them on OS2
 still didn’t see Gates as a rival!
• At about the same time…
 Cutler left DEC… joined Microsoft
 scope for a virtual memory operating system…
• (Windows)
Windows
• On the one hand
Microsoft were working with IBM on OS2
• One the other hand:
they were working on developing Windows
• and working with software developers to provide
applications for Windows…

users want apps, not operating systems!
• Guess which one won???
you’ve got it… Microsoft now bigger than IBM
Windows NT
• Windows was based on DOS
 virtual memory enabled multitasking
 but fundamentally flawed…
• Intermediate towards a new “serious”
operating system…
• using DEC technology…
• “New Technology” operating system quietly
released in 1993
 as a disguised front end enhancement to Windows
3.1
• i.e. Windows 3.11 (for workgroups)
NT Architecture
• Industry experts soon noticed that many
features were surprisingly similar to VMS…
 oddity… VMS + 1 = WNT (!!)
• But Microsoft’s customers were from a new
generation. The commercial product was still
basically DOS, but Gates now offered
 peer-peer networking and a simple network
protocol (
 user-friendly graphical interface
 sharing resources on apps
 even TCP/IP compatibility…
Flexibility of Windows NT
(followed the Unix pattern)
Applications
Operating system functions & interface
Operating system kernel
hardware
Windows NT v Unix v Netware
• By 1994, three possible network
platforms:
Novell: fast, proven, scalable, well
established, but proprietary (NDS &
IPX/SPX)
Unix: robust, scalable, open source &
Internet ready but complex, & limited apps
Windows NT: neither robust nor scalable
• but Gates by now a past master at exploiting
weakness…
Progressive Development of
Windows NT
Applications (Windows apps -> NT apps)
Operating system functions & interface (Windows)
os kernel (diff versions of NT available for diff CPUs)
range of CPUs, motherboards
NT version 4
• Major leap forward, released late 1996
 Windows 95 interface
 many www features, incl web server
• Server end:
 designed to support server applications
• no theoretical limit to number of users
 now a major challenge to Netware (not TCP/IP
compatible) & Unix (still not enough apps)
 main problem: not scalable
• Client end (Workstation/Professional version)
 designed for client machines or secure peer-peer
networks (upgrade of Windows for Workgroups)
 connectivity now uses TCP/IP as default
 max 10 concurrent sessions
The 32-bit Windows NT
architecture
• Secure kernel based on VMS
 available for multiple platforms
• Supports pre-emptive multitasking &
•
•
multithreading
Secure file system (NTFS)
Applications have separate address spaces
 up to 4 Gb of memory
 up to 16 Eb of disk space (1Eb = 260 bytes)
NT architecture (continued)
• Server products have scope for
huge additional functionality…
offered as services
• Problems:
much of the code in NT 4 was new,
and bugs had to be ironed out
each server had its own security
database which created considerable
problems for scalability
Windows 2000
• Further big jump
 Designed to merge:
• peer-peer networking capabilities of Windows
• client-server requirements of LANs
• Yet could still work with “DOS-based” i.e.
Windows 3.x/95/98 clients
 Microsoft’s own “history of Windows” (clientend/desktop versions):
 http://www.microsoft.com/windows/winhistorydeskt
op.mspx
Windows 2000
• Added functionality:
 Scalable
• active directory


X500 compliant directory service
enterprise-wide security & resource-sharing
• arguably better than NDS

finished off Novell Netware…
 Secure
•
•
•
•
secure remote authentication
Kerberos
PKI-ready
terminal services

remote log on with minimal computing resources
More Recent OS
Developments
• Novell survived by:
 merging with developers of Linux
 continuing to support “legacy” Netware systems
• HP kept VMS customer base…
 still developing as OpenVMS:
• http://h71000.www7.hp.com/openvms/30th/in
dex.html
 Once DEC alpha chip was history, developed
new Intel-based hardware platform (Integrity) to
interface with VMS kernel
• Linux slowly gaining popularity…
More recent OS developments
•
Microsoft has continued to improve NT:
 Server-end
• Windows 2003 Server, 64-bit!
• Windows 2008 Server
 Client end
• Vista
• Windows 7
 And although Bill Gates has now retired, Steve Cutler is still there…
VIDEO:
•
• http://www.amd.com/usen/assets/content_type/DownloadableAssets/Microsoft_Video_Stateme
nt.wmv
Desktop changes:
 ever smaller
 mobile devices also have CPUs & operating systems
 also have user interfaces & use apps…
So, which network operating
system would you use today?
• NT, VMS, or a variety of Unix
• Time to do some research…
