What a tangled mess tackling windows complexity
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What a tangled mess…. Tackling Windows Complexity. Rob Short Development Manager Windows NT Microsoft Corporation. What I’ll talk about. The problem Hardware detection/installation issues Application installation Managing large installations. Today’s Situation.

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What a tangled mess tackling windows complexity

What a tangled mess….Tackling Windows Complexity

Rob Short

Development Manager

Windows NT

Microsoft Corporation

What i ll talk about

What I’ll talk about

  • The problem

  • Hardware detection/installation issues

  • Application installation

  • Managing large installations

Today s situation

Today’s Situation

  • Computers are being used by everyone

  • >100 Million installed Windows systems

  • Feedback indicates severe problems

  • Changes are unpredictable

    • add/remove hardware

    • add/remove software

  • Windows is too hard to manage

    • both in single and large environments

Hardware configuration

Hardware configuration

  • Obvious: This should not be hard

    • most systems have less than two dozen devices

    • resource allocation is well defined problem

  • Reality

    • One out of ten attempts to change hardware has a problem of some sort

    • Out of 100 Million users that is 10 Million people with a problem!!!!!!

Hardware related issues

Hardware related issues

  • Incredible number and variety of devices

    • 4808 different system designs

    • 4000 + add in cards

    • 1200+ different printers

  • Few hardware standards,

    • many devices don’t implement the whole spec

    • newer devices are better, but people expect their old systems/devices to work

Windows nt 4 0 hcl

Windows NT 4.0 HCL

Hardware standards oxymoron

Hardware Standards(oxymoron)

  • No standard basic system structures

    • AT compatible core in most x86 systems

      • required to run DOS or WIN95

      • software can, sort of, assume its there

  • System buses, implementations are different

    • PCI, ISA, EISA, Microchannel,

  • Newer standards address SW problems

    • PCI, 1394, USB, ACPI, etc

Windows driver model

Windows Driver Model

  • Plug and Play and Power Management device driver interfaces for both flavors of Windows

  • Supports load/unload, start and stop

  • Support Plug and Play hardware standards

  • Built on existing Windows NT input/output (I/O) infrastructure

  • Separate class and port drivers

Wdm bus drivers

WDM Bus Drivers

  • Standard WDM driver that exposes a bus

  • “Bus” is any device (virtual or physical) on which other devices are connected

  • Includes enumeration routines

  • Responds to new Plug and Play and Power Management I/O request packets (IRPs)

  • Extensible via filter drivers

What a tangled mess tackling windows complexity

Windows NT 5.0Plug And Play Architecture






Plug and Play Manager



HW event








User mode

Kernel mode

Plug and Play




Plug and

Play Mgr


WDM Interface

Plug and Play bus drivers

WDM Device Drivers


PC Card



Wdm device tree









“Toaster” FDO


SCSI adapter FDO


“Toaster” PDO


SCSI adapter PDO





(Plug and Play Manager)

WDM Device Tree

Attachment (Functional Device Object, Physical Device Object)

Parent-child relationship

Logical device instance

Windows software issues

Windows Software Issues

  • “State” on systems has grown out of control

    • Poor separation of system, application, or user state (history of one pc, one user, few apps)

    • Applications put files in system directories

    • Shared libraries shipped with applications

      • versioning nightmare

    • End user has no idea what each file does

      • or what happens if it is deleted or replaced



  • Guidelines to separate the state

  • Better application guidelines

    • ideally an app can be dropped onto the system

  • Add an installation service to system

    • takes a “package” and installs it

    • tracks versions of shared components

    • puts application files in separate directories

    • tracks ownership of files

    • Tools needed to create packages

Managing large installations goals

Managing large InstallationsGoals

  • End user must not need to be administrator

  • Automatically install or update OS and apps

  • Keep SW consistent across the organization

  • Policies/apps assigned to groups of users

  • Support “roaming” users

  • Make system replacement possible

Technology to make this happen

Technology to make this happen

  • Coda-like file system features

    • client-side caching

    • single instance store

  • Directory service includes “Class Store”

  • Automatic application installation

  • Remote booting

  • Policy based management

  • Improved UI and tools

File document management client side caching

File/Document ManagementClient side caching

  • Master copy of files live on the server

  • Copy is cached on the local system

  • Caching is done by network re-director

  • Data is stored in file system with minimal meta-data

  • Improves performance and availability of network files and installed applications

Connected to a network

Connected to a Network

1: Open any file - redirected to network

2: Store copy in client

side cache

3: Read from local

client side cache

4: Write-through cache

5: “Pin” cached files

to prevent eviction

Working off line

Working Off-line

1: Request to open

network file

2: Redirect to local

cached copy

Reconnecting to the network

Reconnecting to the Network

1: Automatically copy

locally modified files

up to the server

2: Automatically copy

server modified

files to client

side cache

3: When file changes collide

Wizard walks user through

reconciliation process

File document management cont

File/Document management (cont)

  • Server provides single instance store

    • Asynchronous process on server

    • Detects duplicate files

    • Replaces with links to a master

    • Performs “copy-on-write”

  • Drive letters, system files, other clutter only available in “Advanced” explorer views

Directory service

Directory Service

  • Global, replicated, easily accessed place to store things

  • Class store resides in the directory

    • Populated automatically by administration tools

    • Takes a class ID and returns a path, or URL to an application or component

Centralized management

Centralized Management

  • Administrator creates groups of users, e.g. payroll, and assigns desktop properties and apps to groups and/or individuals

  • Profiles are stored in the directory

  • Easy to create “locked down” systems

  • End user performs no administration

    • OS installs and upgrades automatically

    • Application installation is automatic

    • Users can log on anywhere and see the exact same environment, including applications and documents

Application installation

Application Installation

  • Applications appear on desktop, start menu, and in class associations at log in

  • Application installation is transparent no matter how the App is invoked

  • Application invocation patterned on object instantiation for legacy apps

    • Verify if App is installed and if the version is correct

    • If version is incorrect, silent setup is performed

    • App is invoked after verification

  • System decides via policy if app should

    • be installed normally, Cached to local disk, or Run from the net

App deployment model assigned published applications

App Deployment ModelAssigned & Published Applications

  • Assigned Applications are automatically installed

    • User can’t delete app from machine

  • Published Applications are optional

    • Installed via “Add/Remove Programs”

    • Document invocation will auto-install too!

      e.g.: click on Visio doc in email

  • Apps deployed to users or machines

    • App pushed to machine; pulled by user

Deployment process

Office 98 CD

Network Server

“Sales Force” Group Policy


Deployment Process

1: Create a network install for app.

2: Customize installation options

3: Assign application in policy

4: User in OU “receives” policy

5: At User Logon, the machine receives portions of the app.

6: Upon user invocation, the app is installed on user’s machine

Remote boot

Remote Boot

  • Goals

    • Enable Remote Boot of Windows NT

    • Simplify management of server images

      • Most costly problem with remote boot today

    • Maintain ability to function offline

    • Automatic OS update & simple repair

  • Solution

    • Remote boot solution based on caching and single instance storage

Remote boot cont d

Remote Boot (cont’d)

  • NT maps client physical storage to “D:\”

  • “C:\” is a cache -- replica lives on net

    • Entirecontents of C:\ drive is placed on net

      • i.e.: Each client has their own disk image

    • Single instance storage (NTFS filter driver) eliminates storage of duplicate files

      • Enable flexible configuration without drive bloat.

        E.g.: older app, different driver

Remote boot1

Remote Boot

  • Client boots via new boot ROMs

  • DHCP server hosts extensions

    • Dialect between OS-less client & server

    • Fully defined in NetPC specification

  • Policy used to define client behavior

  • DS accounts used for state storage

  • Applet (OSChooser) sent as “bootstrap” code to offer initial choices

Scenario new machine

Directory Services



Remote Boot


Client A

Client B

Scenario: New Machine








Scenario existing machine

Directory Services



Remote Boot


Client A

Client B

Scenario: Existing Machine







Scenario machine failure

Directory Services



Remote Boot


Client A

Client B

Scenario: Machine Failure

Machine A


Machine B


Machine B



User Selects “Replace Machine”



  • Plug and play is non-trivial

    • requires significant hardware and software

  • Application installation problems

    • Architectural improvements,

    • engineering discipline

  • Large systems

    • use caching and single instance store to eliminate end user administration




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