Name License Source model

Target usage

Status Platforms

Abassi proprietary

closed embedded

active AVR, Coldfire, Cortex-M3, MSP430, PIC32, 8051

AMX RTOS  ?  ? embedded

 ? 680x0, 683xx, ARM, ColdFire, MIPS32, PowerPC

ARTOS (Locamation)

proprietary

 ? embedded

active x86

ARTOS (Robotu)

proprietary

 ? embedded

active ARM9+

Atomthreads BSD open source

embedded

active AVR, STM8

AVIX proprietary

closed embedded

active Atmel AT91SAM3(U/S), Energy Micro EFM32, NXP LPC13x/LPC17x, ST MicroSTM32, Texas Instruments LM3S, Toshiba TMPM330, Microchip PIC32MX, Microchip PIC24F, PIC24H, dsPIC30F & dsPIC33F

BeRTOS modifiedGNU GPL

open source

embedded

active DSP56K, I196, IA32, ARM, AVR

BRTOS MIT License

open source

embedded

active Freescale Coldfire V1, Freescale HCS08, Texas Instruments MSP430 and Atmel ATMEGA328/128 (Port for PIC18 in development

CapROS GNU GPL open source

embedded

active IA32, ARM9

ChibiOS/RT ModifiedGNU GPL orproprietary

open source

embedded, smallfootprint

active x86, ARM7, ARM9, Cortex-M0, Cortex-M3, Cortex-M4, PowerPC e200z, STM8,AVR, MSP430, Coldfire, H8S

ChorusOS  ?  ?  ?  ?  ?CMX RTOS proprieta

ry ? embedde

dactive IA32, ARM, AVR, H8, PIC, 8051

cocoOS BSD open source

embedded

active AVR, MSP430

Concurrent CP/M

proprietary

closed (meanwhile: open source)

general purpose

defunct

8080, Z80, 8086

Concurrent DOS

proprietary

closed general purpose

defunct

8086, 286, 386, 68000, (also 8080/Z80 in dual-processor variants)

Contiki BSD open source

embedded

active MSP430, AVR

COS proprieta closed process  defunc GEC 4000 series

ry control tDeos proprieta

ryclosed safety 

criticalactive x86, PowerPC, PowerQUICC

DioneOS proprietary

available for licensee

embedded

active Texas Instruments MSP430, MSP430x

DNIX proprietary

closed general purpose

defunct

68000

GEC DOS proprietary

closed process control

defunct

GEC 4000 series

DrRtos free? open?  ? active? ARM7DSPnano RTOS

Open Source and Commercial

Open Source

MCU, DSC, DSP SoC

active R8C, M16C, PIC24, dsPIC33

DSOS  ?  ?  ? defunct

TI-980A minicomputer

eCos modifiedGNU GPL

open source

general purpose

active ARM/XScale, CalmRISC, 68000/Coldfire, fr30, FR-V, H8, IA32, MIPS, MN10300, OpenRISC, PowerPC, SPARC, SuperH, V8xx

eCosPro modifiedGNU GPLand eCosPro license

open source with non-free portions

general purpose

active ARM/XScale, CalmRISC, 68000/Coldfire, fr30, FR-V, H8, IA32, MIPS, MN10300, NIOS2, OpenRISC, PowerPC, SPARC, SuperH, V8xx

embOS proprietary

closed embedded

active 8/16/32 bit processors

Embox BSD License

open source

embedded

active ARM, LEON, MicroBlaze, x86

ERIKA Enterprise

GPL+Linking exception

Open Source

embedded

active ARM7, H8 (Hitachi), Nios2 (Altera), PIC24/dsPIC/PIC32 (Microchip), ST10 (ST Microelectronics)/C167 (Infineon), PPC z7 Mamba, AVR, Tricore1, Mico32, S12XS, H8

EROS GPL open source

experimentalresearch use

dormant

IA32

Femto OS GPLv3 open source

embedded

active AVR

FlexOS proprietary

closed general purpose

defunct

186, 286, 386, V60, V70, 68000

FreeOSEK GPLv3 open source

embedded

active Posix, Windows, ARM7

FreeRTOS modifiedGNU 

open source

embedded

active ARM, AVR, AVR32, Freescale ColdFire, HCS12, IA32, MicroBlaze, MSP430, PIC, 

GPL Renesas H8/S, 8052, STM32FunkOS modified 

Sleepycat license

open source

embedded

active AVR, MSP430, Cortex-M3

Fusion RTOS free  ? semi-general purpose

active ARM, Blackfin, StarCore, DSP 56800E

HeartOS proprietary

closed safety critical

active x86, PowerPC, PowerQUICC

Helium free  ?  ?  ? Open-Source RTOS for HCS08 & AVR MCUsHP-1000/RTE  ?  ?  ?  ?  ?Hybridthreads

 ? open source

FPGA active Xilinx Virtex-II Pro ML310, Xilinx Virtex-II Pro XUP

IBM 4680 OS proprietary

closed general purpose

defunct

286

IBM 4690 OS proprietary

closed general purpose

active 286, 386

INTEGRITY proprietary

closed embedded

active ARM, XScale, Blackfin, Freescale ColdFire, MIPS, PowerPC, x86

IntervalZero RTX

proprietary

closed MS Windows extension

active x86

ITRON, uITRON, microITRON

varies varies embedded

active ARM, MIPS, x86, and others

ioRTOS proprietary

closed embedded, safety critical

active TI TMS320 Families (x2812, c6416)

iRTOS GNU LGPL

open source

embedded

active AVR, ARM7

LynxOS proprietary

source code available

embedded

active Motorola 68010, x86/IA-32, ARM, Freescale PowerPC, PowerPC 970, LEON3

MaRTE OS GNU GPL open source

embedded

active IA-32

MAX II,IV proprietary

 ?  ?  ? Modcomp II,IV,...

MenuetOS  ?  ?  ?  ?  ?Milos GNU GPL open 

sourceembedded

active Cortex-M3

MP/M proprietary

closed (meanwhile: open source)

general purpose

defunct

8080, Z80, 8086

MQX proprieta compli embedde active Freescale Power, ColdFire, Kinetis Cortex 

ry mentary source code available

d ARM, List of Freescale products,

MERT  ?  ?  ? inactive

PDP-11

Multiuser DOS

proprietary

closed general-purpose

defunct

386

Nano-RK mixed open source

embedded

active AVR, MSP430

Neutrino proprietary

some source code provided

microkernel

active ARM, MIPS, PPC, SH, x86, XScale

Nokia OS  ?  ? embedded GSM devices

 ? ARM

Nucleus OS proprietary

source code provided

embedded

active ARM (Cortex-M3, M4, R4, R4F, A8, A9, ARM7, ARM9, ARM11), PowerPC, MIPS32, MIPS16e, microMIPS, Coldfire, SuperH

NuttX RTOS BSD open source

embedded, small footprint

active Linux user mode, ARM7, ARM9, 8052, SH-1, Renesas MC16C/26, Zilog Z16F, Zilog eZ80 Acclaim!, Zilog Z8Encore!, Z80, partial ports for MIPS

On Time RTOS-32

proprietary

source code available

embedded

active 32/64-bit x86

OS4000 proprietary

closed process control

maintenance only

GEC 4000 series

OpenRTOS proprietary?

source code available

embedded

active see FreeRTOS

OSA BSD open source

embedded

active PIC10-PIC24, AVR 8bit, STM8

OSE proprietary

closed general purpose

active ARM, PowerPC, MIPS, IXP2400, TI OMAP, …

OS-9 proprietary

available to customers

embedded

active ARM/strongARM, MIPS, PowerPC, SuperH, x86/Pentium, XSCALE, Motorola 6809, Motorola 68000-series

OSEK n/a specific embedde active engine control units

ation dPhar Lap ETS  ?  ?  ?  ?  ?PaulOS GNU GPL open 

sourceembedded

 ?  ?

PICOS18 GNU GPL open source

embedded

 ? PIC18

picoOS Modified BSD License

open source

embedded

discontinued

6502, 80x86, ARM7, AVR, PowerPC

Phoenix-RTOS

GNU GPL open source

embedded

 ? ARM7, X86, PowerPC

PikeOS proprietary

available to customers

safety critical, virtualization

active PPC, x86, ARM, MIPS, SPARC/Leon, SuperH

Portos proprietary

source code provided

embedded, small footprint

active DSP/BIOS (ARM soon)

POK BSD open source

embedded

active x86, PowerPC, SPARC

PowerTV proprietary

 ?  ?  ?  ?

Prex BSD open source

microkernel

active ARM, IA32

pSOS proprietary

 ?  ? discontinued

Motorola 680x, Motorola 68000

QNX mixed  ? general purpose

active IA32, MIPS, PowerPC, SH-4, ARM, StrongARM, XScale

Q-Kernel proprietary

available to customers

embedded

active PIC-30, PIC-24, dsPIC, PIC32MX

QP Open Source and Commercial

Open Source

MCU, DSC, DSP SoC

active ARM7/9, ARM Cortex-M3/Cortex-M0, MSP430, TMS320C28x, AVR, AVRXmega, ColdFire, 68HC08, M16C/R8C, H8, 8051, 80251, PIC18, PIC24/dsPIC33, Nios II, PSoC1

RDOS proprietary

 ? general purpose

defunct

Data General Nova, Data General Eclipse

ReaGOS proprietary

closed, available with license

embedded

active x86, ATmega, ARM, portable

REAL/32 proprietary

closed general-purpose

active 386

Real-time  GPLv2 open  general  active same as Linux

Linux (CONFIG_RT_PREEMPT)

source purpose

RMX  ?  ?  ? active 8080, 8086, 80386 or higherRSX-11 proprieta

ry ?  ? histori

cPDP-11

RT-11 proprietary

 ? general purpose

defunct

PDP-11

RTAI GNU GPL open source

general purpose

active x86, ARM

RTEMS modifiedGNU GPL

open source

embedded

active ARM, Blackfin, ColdFire, TI C3x/C4x, H8/300, x86, 68k, MIPS, Nios II, PowerPC, SuperH, SPARC, ERC32, LEON, Mongoose-V

rt-kernel mixed available to customers

embedded

active ARM7, ARM9, Cortex-M3, Cortex-A8, Blackfin, PowerPC, Windows (simulation)

RTLinux GNU GPL open source

general purpose

active same as Linux

RT-Thread GPLv2 open source

embedded

active ARM, IA-32, AVR32,M16C, MIPS

RTXC Quadros

proprietary

source available

embedded

active ARM - Atmel/Freescale/NXP/ST/TI, Blackfin, Coldfire/68K, PowerPC, StarCore, TI/Luminary Stellaris, TI OMAP, XScale

Salvo proprietary

closed embedded

active 8051, ARM ARM7TDMI and Cortex-M3, Atmel AVR and Mega AVR, Epson S1C17, Motorola M68HC11, TI MSP430, PICmicro 12/14000/16/17/18, PIC24, dsPIC, PIC32, TMS320C2000

SCIOPTA proprietary

closed, source available

embedded, safety related

active ARM, Cortex-M3, Cortex-M0, XScale, PowerPC, ColdFire, HCS12, M16C,MSP430, Windows(simulation)

scmRTOS free open source

embedded

active ARM, Cortex-M3, Blackfin, MSP430, AVR

SDPOS GNU LGPL

open source

embedded

active ARM, Cortex-M3, Blackfin, PIC18, PIC24, i386 win32/linux synthetic targets

SHaRK GNU GPL open source

 ?  ?  ?

SimpleAVROS

GPLv3 open source

embedded

active, beta

AVR only

SINTRAN III  ?  ?  ?  ? Norsk Data computersSirius RTOS proprieta

ryavailable under license

embedded

active x86, i386+, ARM, 68k, 8051, ...

SMX RTOS proprietary

available under license

embedded

active ARM, Cortex, ColdFire, PowerPC, x86, ...

SOOS Project free open source

embedded

active, beta

H8/300

Symbian OS Eclipse Public License

open source

embedded

active ARM

Talon DSP RTOS

proprietary

 ? embedded DSP

active TMS320

TargetOS proprietary

available to customers

embedded

 ? ARM, Freescale ColdFire, Freescale PowerPC

T-Kernel free under T-License

source available

embedded RTOS

active ARM/MIPS/SH/others

THEOS  ?  ?  ?  ?  ?ThreadX proprieta

ryavailable to customers

 ? active ARC, ARM/Thumb, AVR32, BlackFin, ColdFire/68K, H8/300H, Luminary Micro Stellaris, M-CORE, MicroBlaze, PIC24/dsPIC, PIC32, MIPS, V8xx, Nios II, PowerPC, SH, SHARC, StarCore, STM32, StrongARM, TMS320C54x, TMS320C6x, x86/x386, XScale, Xtensa/Diamond, ZSP

Trampoline Operating System (OSEK and AUTOSAR)

GNU LGPL

open source

embedded

active AVR, H8/300H, POSIX, NEC V850e, ARM7, Infineon C166, HCS12 or PowerPC

TNKernel BSD open source

embedded

active ARM, PIC24/dsPIC, HCS08

Transaction Processing Facility

proprietary

 ? general purpose

active IBM System/360 derivatives

TRON Project

open? mixed mixed active any: not an implementation, but a specification

TUD:OS GNU GPL open source

 ?  ? IA-32

Unison RTOS Open Source and Commercial

Open Source

MCU, DSC, DSP SoC

active Pic32, ARM Cortex (TI Stellaris, ST STM32, NXP LPC1700), SH2A, SH2AFPU, R32C, MIPS4K, {SHARC, Coldfire, TMS320, Altera NIOS, Xilinx Microblaze, Proprietary}

µC/OS-II proprietary

Available under license

embedded

active ARM7/9/11/Cortex M1/3, AVR, HC11/12/S12, Coldfire, Blackfin, Microblaze, NIOS, 8051, x86, Win32, H8S, 

M16C, M32C, MIPS, 68000, PIC24/dsPIC33/PIC32, MSP430, PowerPC, SH, StarCore, STM32, …

µC/OS-III proprietary

Available under license

embedded

active ARM7/9/11/Cortex M1/3, AVR, HC11/12/S12, Coldfire, Blackfin, Microblaze, NIOS, 8051, x86, Win32, H8S, M16C, M32C, MIPS, 68000, PIC24/dsPIC33/PIC32, MSP430, PowerPC, SH, StarCore, STM32, …

UNIX-RTR  ?  ?  ?  ? PDP-11uSmartx  ? open 

sourceembedded

 ? ARM7TDMI, AVR, H8

µTasker proprietary

Open-code. Free for non-commercial or with support license

embedded

active Coldfire M522XX, AVR32, SAM7X, Luminary Micro, LPC2XXX, STR91X, NE64

u-velOSity  ?  ? microkernel

active  ?

velOSity  ?  ?  ? active Power Architecture, ARM/XScale, MIPS, x86/Pentium, ColdFire, Blackfin, OMAP, DaVinci

VRTX  ?  ?  ?  ? ARM, MIPS, PowerPC, RISCVxWorks proprieta

ry ? embedde

dactive ARM, IA32, MIPS, PowerPC, SH-4, 

StrongARM, xScaleWindows CE proprieta

ryMicrosoft Shared Source

embedded

active x86, MIPS, ARM, SuperH

Xenomai GPLv2 Open Source

general active x86, x86_64, PowerPC, ARM, Analog Devices Blackfin BF52x, BF53x, BF54x and BF56x

xPC Target proprietary

closed real-time testing/embedded

active x86

Y@SOS GNU LGPL

Open Source

embedded

active Cortex-M3, STM32

MontaVista Linux

 ?  ? embedded

active  ?

µnOS  ?  ?  ? historic

Motorola 68k

uOS GNU GPL Open Source

embedded

active AVR, ARM, MIPS32, MSP430, Intel i386, Linux386

An early example of a large-scale real-time operating system was the Transaction Processing

Facility developed by American Airlines and IBM for the Sabre Airline Reservations System.

Currently the best known, most widely deployed, real-time operating systems are[citation needed]

LynxOS

OSE

QNX

RTLinux

VxWorks

Windows CE

Authentication mechanisms

An authentication mechanism defines rules about security information, such as whether a credential is forwardable to another Java process, and the format of how security information is stored in both credentials and tokens.

Authentication is the process of establishing whether a client is who or what it claims to be in a particular context. A client can be either an end user, a machine, or an application. An authentication mechanism in WebSphere Application Server typically collaborates closely with a user registry. The user registry is the user and groups account repository that the authentication mechanism consults with when performing authentication. The authentication mechanism is responsible for creating a credential, which is an internal product representation of a successfully authenticated client user. Not all credentials are created equally. The abilities of the credential are determined by the configured authentication mechanism.

Although this product provides multiple authentication mechanisms, you can configure only a single active authentication mechanism at one time. The active authentication mechanism is selected when configuring WebSphere Application Server global security.

Authentication processThe figure demonstrates the authentication process. Authentication is required for enterprise bean clients and Web clients when they access protected resources. Enterprise bean clients, like a servlet or other enterprise beans or a pure client, send the authentication information to a Web application server using one of the following protocols:

Common Secure Interoperability Version 2 (CSIv2) Secure Authentication Service (SAS)

Note:

Web clients use the HTTP or HTTPS protocol to send the authentication information, as shown in the previous figure.

The authentication data can be from a basic authentication (user ID and password), a credential token (in the case of Lightweight Third Party Authentication (LTPA)), or a client certificate. The Web authentication is performed by the Web Authentication module.

The enterprise bean authentication is performed by the Enterprise JavaBean (EJB) authentication module, which resides in the CSIv2 and SAS layer.

The enterprise bean authentication is performed by the Enterprise JavaBean (EJB) authentication module

The authentication module is implemented using the Java Authentication and Authorization Service (JAAS) login module. The Web authenticator and the EJB authenticator pass the authentication data to the login module (2), which can use the following mechanisms to authenticate the data:

LTPA Simple WebSphere Authentication Mechanism (SWAM)

The authentication module uses the registry that is configured on the system to perform the authentication (4). Three types of registries are supported: local OS, Lightweight Directory Access Protocol (LDAP), and custom registry. External registry implementation following the registry interface that is specified by IBM can replace either the local OS or the LDAP user registry.

The login module creates a JAAS subject after authentication and stores the credential that is derived from the authentication data in the public credentials list of the subject. The credential is returned to the Web authenticator or to the enterprise beans authenticator (5).

The Web authenticator and the enterprise beans authenticator store the received credentials in the Object Request Broker (ORB) current for the authorization service to use in performing further access control checks. If the credentials are forwardable, they are sent to other application servers.

The first type authentication is accepting proof of identity given by a credible person which has evidence

on the said identity or on the originator and the object under assessment as his artifact respectively.

The second type authentication is comparing the attributes of the object itself to what is known about

objects of that origin. For example, an art expert might look for similarities in the style of painting, check

the location and form of a signature, or compare the object to an old photograph. An archaeologist might

use carbon dating to verify the age of an artifact, do a chemical analysis of the materials used, or

compare the style of construction or decoration to other artifacts of similar origin. The physics of sound

and light, and comparison with a known physical environment, can be used to examine the authenticity of

audio recordings, photographs, or videos.

Attribute comparison may be vulnerable to forgery. In general, it relies on the fact that creating a forgery

indistinguishable from a genuine artifact requires expert knowledge, that mistakes are easily made, or that

the amount of effort required to do so is considerably greater than the amount of money that can be

gained by selling the forgery.

In art and antiques certificates are of great importance, authenticating an object of interest and value.

Certificates can, however, also be forged and the authentication of these pose a problem. For instance,

the son of Han van Meegeren, the well-known art-forger, forged the work of his father and provided a

certificate for its provenance as well; see the article Jacques van Meegeren.

Criminal and civil penalties for fraud, forgery, and counterfeiting can reduce the incentive for falsification,

depending on the risk of getting caught.

The third type authentication relies on documentation or other external affirmations. For example,

the rules of evidence in criminal courts often require establishing the chain of custody of evidence

presented. This can be accomplished through a written evidence log, or by testimony from the police

detectives and forensics staff that handled it. Some antiques are accompanied by certificates attesting to

their authenticity. External records have their own problems of forgery and perjury, and are also

vulnerable to being separated from the artifact and lost.

Currency and other financial instruments commonly use the first type of authentication method. Bills,

coins, and cheques incorporate hard-to-duplicate physical features, such as fine printing or engraving,

distinctive feel, watermarks, and holographic imagery, which are easy for receivers to verify.

Consumer goods such as pharmaceuticals, perfume, fashion clothing can use either type of

authentication method to prevent counterfeit goods from taking advantage of a popular brand's reputation

(damaging the brand owner's sales and reputation). A trademark is a legally protected marking or other

identifying feature which aids consumers in the identification of genuine brand-name goods.

[edit]Authentication factors and identity

AUTHENTOCATION ALGO

Windows Vista and later operating systems support the following 802.11 authentication algorithms:

IEEE 802.11 Open System algorithm.

IEEE 802.11 Shared Key algorithm.

Wi-Fi Protected Access (WPA) algorithm. This algorithm is supported only for infrastructure basic

service set (BSS) networks.

WPA algorithm that uses preshared keys (PSK). This algorithm is supported only for

infrastructure BSS networks.

IEEE 802.11i Robust Security Network Association (RSNA) algorithm. This algorithm is supported

only for infrastructure BSS networks.

IEEE 802.11i RSNA algorithm that uses PSK. This algorithm is supported for infrastructure BSS

networks. This algorithm is also supported for independent BSS (IBSS) networks when used in

conjunction with the AES-CCMP cipher algorithm.

Data authentication

Common

functionsMD5 · SHA-1 · SHA-2

Functions FSB · SHA-3 · ECOH · GOST · HAS-160 · HAVAL · LM hash · MDC-2 · MD2 · MD4 · N-Hash · RadioGatún · RIPEMD

SHA-3 finalists BLAKE · Grøstl · JH · Keccak · Skein

MAC algorithms DAA · CBC-MAC · HMAC · OMAC/CMAC · PMAC · VMAC · UMAC · Poly1305-AES

Authenticated

encryption modesCCM · CWC · EAX · GCM · IAPM · OCB

Attacks Collision attack · Preimage attack · Birthday attack · Brute force attack · Rainbow table · Distinguishing attack · Side-channel attack

Misc. Avalanche effect · Hash collision · Merkle–Damgård construction · Salt

Standardization CRYPTREC · NESSIE · NIST hash function competition

Authorization Strategies

Authorization controls user access to resources. Using access control lists (ACLs), security groups, and NTFS file permissions, you can make sure that users have access only to needed resources, such as files, drives, network shares, printers, and applications.

Security Groups

Security groups, user rights, and permissions can be used to manage security for numerous resources while maintaining fine-grained control of files and folders and user rights. The four main security groups include:

Domain local groups Global groups Universal groups Computer local groups

Using security groups can streamline the process of managing access to resources. You can assign users to security groups, and then grant permissions to those groups. You can add and remove users in security groups according to their need for access to new resources. To create local users and place them within local security groups, use the Computer Management snap-in of MMC or the User Accounts option in Control Panel.

Within the domain local and computer local security groups there are preconfigured security groups to which you can assign users.

Administrators

Members of this group have total control of the local computer and have permissions to complete all tasks. A built-in account called Administrator is created and assigned to this group when Windows Vista is installed. When a computer is joined to a domain, the Domain Administrators group is added to the local Administrators group by default.

Power Users

Members of this group have read/write permissions to other parts of the system in addition to their own profile folders, can install applications, and can perform many administrative tasks. Members of this group have the same level of permissions as Users and Power Users in Windows XP Professional.

Users

Members of this group are authenticated users with read-only permissions for most parts of the system. They have read/write access only within their own profile folders. Users cannot read other users' data (unless it is in a shared folder), install applications that require modifying system directories or the registry, or perform administrative tasks.

Guests

Members of this group can log on using the built-in Guest account to perform limited tasks, including shutting down the computer. Users who do not have an account on the computer or whose account has been disabled (but not deleted) can log on using the Guest account. You can set rights and permissions for this account, which is a member of the built-in Guests group by default. The Guest account is enabled by default.

You can configure access control lists (ACLs) for resource groups or security groups and add or remove users or resources from these groups as needed. The ability to add and remove users makes user permissions easier to control and audit. It also reduces the need to change ACLs.

You can grant users permissions to access files and folders, and specify what tasks users can perform on them. You can also allow permissions to be inherited, so that permissions for a folder apply to all its subfolders and the files in them.

Group Policy

You can use Group Policy settings to assign permissions to resources and grant rights to users as follows:

To restrict which types of users can run certain applications. This reduces the risk of exposing the computer to unwanted applications, such as viruses.

To configure many rights and permissions for client computers. You can also configure rights and permissions on an individual computer to be used as the base image for desktop installations, to ensure standardized security management even if you do not use Active Directory.

Auditing features allow you to detect attempts to disable or circumvent protections on resources.

You can use preconfigured security templates that meet the security requirements for a given workstation or network. Security templates are files with preset security settings that can be applied to a local computer or to client computers in a domain by using Active Directory.