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Windows NT A Distributed Architecture. Professor: Mohamed Khalil CSE 8343 GROUP-A5 Dhaval Sanghvi Amit Sharma Ali Abbas (Video-Tape). Agenda. Features

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windows nt a distributed architecture
Windows NT A Distributed Architecture

Professor: Mohamed Khalil

CSE 8343


Dhaval Sanghvi

Amit Sharma

Ali Abbas (Video-Tape)

  • Features
  • Design goals of Windows NT
  • Architecture
    • Three Layers
      • Upper Layer - Executive
      • Middle Layer - Kernel
      • Lower Layer - Hardware Abstraction Layer
  • Environment Subsystem
  • Summary
  • Biblography
  • Preemptive Multitasking
  • Support for Symmetric Multiprocessing
  • Integrated Networking services
  • Client/Server Architecture
  • Support for several file systems
  • Virtual Memory Management
  • Support for 2 GB linear space for application and also 2GB for OS
design goals of windows nt
Design goals of Windows NT
  • Extensibility
  • Portability
  • Reliability
  • Compatibility
  • Security
  • Performance
  • Scalability
  • Localization
windows nt architecture
Windows NT Architecture
  • Windows NT is a modular operating system

composed of simple modules : kernel mode and user mode.

  • Kernel Mode composed of mainly 3 layers:
    • Upper layer - Executive layer
    • Middle layer - The kernel
    • Lower layer - Hardware Abstraction Layer(HAL)
  • User Mode is composed of environment subsystems.
executive layer
Executive Layer
  • Each component of NT Executive provides a set of API’s
  • Some API’s are designed to be invoked by user-mode processes.
  • Some API’s are visible only in the kernel mode inside the Executive
  • NT’s API’s are flexible enough to implement a wide range of operating system environments.
  • NT’s Executive has six subsystems - Object Manager, Process Manager, Virtual Memory Manager, Security Reference Monitor, Local Procedure Call Facility, I/O subsystem
object manager
Object Manager
  • An object is a representation of a conceptual or physical entity in the system.
  • Examples of Objects:
    • Files
    • Directories
    • Processes
    • Threads
    • Synchronization Objects (semaphores, mutexes, events, timers)
    • Virtual Memory objects
  • Mostly everything passed around and processed within NT is represented as an object.
security reference monitor
Security Reference Monitor
  • Checks for proper authorization before granting access to objects
  • Object Manager is a customer of a SRM: it asks SRM if a process has the proper rights to execute a certain type of action on an object.
  • Implements auditing functions to keep track of attempts to access an object
  • Implements high level security:
    • Resource owners must be able to control who has access to it.
    • Unique user name and password identification
    • Audit trail of successful and unsuccessful attempts
    • Protection from unauthorized tampering of files
process manager
Process Manager
  • Creates,deletes and modifies processes and threads
  • Does not dispatch or schedules any work. This is done by the kernel
  • A process is represented within NT by a process object
  • Process Object = (process’ virtual address space, resources visible to the process, process threads)
  • NT does not maintain parent-child information between related processes.
virtual memory manager vmm
Virtual Memory Manager(VMM)
  • Implements a fetch policy(when the pager brings a page from disk to memory). Uses a demand paging algorithm with the locality of reference(“clustering”)
  • Implements shared memory segments(used by LPC to transfer large messages)
  • Certain parts of the VMM are processor dependent (e.g. page table entries,page size,virtual address translation)
  • Manages file system drivers,device drivers and network drivers
vmm cont d
VMM - cont’d
  • Drivers can be dynamically loaded, unloaded, started and stopped without rebooting the system
  • Multiple installable file systems including MS-DOS FAT ( File Allocation Table), High Performance File System(HPFS), the CD-ROM file system and the NT File System(NTFS)
i o manager
I/O Manager
  • Mapped file I/O capabilities for image activation, file caching and application use
  • Packet driven I/O system. Every I/O request is represented by an IRP (I/O Request Packet) that moves from one I/O system component to the other
  • Manages buffers for I/O requests
  • Provides time-out support for drivers
  • Records which installable components are loaded in the system
i o manager cont d
I/O Manager - cont’d
  • NTFS extends MS-DOS FAT with HPFS with:
    • Quick recovery of disk data after system failure
    • Ability to handle very large files (17 billion GB)
    • Security features (e.g. execute only files)
    • Support for POSIX OS environments
    • Features for future extensibility(e.g. transaction-based operations to enhance fault tolerance,user-controlled file version numbers, flexible options for file naming and file attributes)
kernel layer
Kernel Layer
  • Schedules threads to run.
  • Handles hardware interrupts and dispatches them to appropriate drivers and threads.
  • Handles software and hardware generated exceptions (e.g. writing to non-existing memory position, memory parity errors)
  • Graceful system shutdown and restoration after power failure
  • Provides an API to the executive to kernel-managed objects (e.g. events, mutexes, semaphores and timers)
hardware abstraction layer
Hardware Abstraction Layer
  • Isolates the kernel from hardware variations
  • Exports an API to upper layers to handle hardware dependent issues such as:
    • Processor initialization( support for SMP computers)
    • Instruction cache and data cache
    • Device driver support(e.g. bus addressing, interrupt control, DMA functions)
    • Timing and interrupt functions
    • Firmware interface functions
    • Low level error handling
environment subsystem
Environment subsystem
  • User mode process that provides services to applications
  • These services emulate the behavior of a specific OS
  • Converts requests made by an application to requests that NT’s kernel mode component understand
  • Implemented using Client/Server model:
    • Application Client
    • Environment subsystem Server
win32 subsystem
Win32 Subsystem
  • Implements the Win32 API
  • Each Win32 application runs on its own address space separate from Win32 subsystems’ address space
  • Manages all the keyboard and mouse input and all screen output for entire system

acts as a server to the other environment subsystems

os 2 subsystem
OS/2 Subsystem
  • Supports OS/2 up to 1.3 character-mode applications
  • Each OS/2 application runs on its own separate address space and separate from the OS/2 subsystem’s address space

POSIX Subsystem

  • Supports POSIX character-mode applications
  • Each POSIX application runs on its own separate address space and separate from POSIX subsystem’s address space
ms dos environment
MS-DOS Environment
  • Associates each DOS application with Virtual DOS Machines (VDM)
  • Each DOS applications runs on its own address space
  • A VDM provides the DOS application with:
    • Execution of Intel x86 instructions
    • Simulated DOS INT 21 services
    • Simulated DOS BIOS interrupt services
    • Simulated standard PC hardware devices
windows 16 bit environment
Windows 16-Bit Environment
  • All Win16 applications are supported by a single VDM called WOW (Win16 on Win32)
  • WOW is like a virtual windows machine
  • The WOW runs on an address space separate from all other user level processes
  • A WOW emulates a PC as a DOS VDM does
  • WOW converts Win16 API’s and messages to and from Win32
  • The Win32 subsystem is used to execute the translated calls
win 16 bit environment cont d
Win 16-Bit Environment – cont’d
  • Each Win16 application is assigned to a different thread within the WOW VDM process
  • Each such thread must yield control before another thread of the WOW is allowed to run
  • If Win16 application crashes it may take the whole WOW down but it does not affect the other Win 32 applications
  • Windows NT server 4.0 Administrator’s Bible, R.Cowart and K.Gregg, IDG Books
  • Inside Windows NT Workstation, George Eckel, New Riders, 1996.