AWS Directory Service is a managed service that enables you to connect AWS resources with existing on-premises Microsoft Active Directory (AD) or set up a new standalone directory in the AWS Cloud. This service is crucial for workload migration and modernization as it simplifies identity management…AWS Directory Service is a managed service that enables you to connect AWS resources with existing on-premises Microsoft Active Directory (AD) or set up a new standalone directory in the AWS Cloud. This service is crucial for workload migration and modernization as it simplifies identity management during cloud transitions.
There are several directory types available:
1. **AWS Managed Microsoft AD**: A fully managed Microsoft Active Directory running on Windows Server. It supports trust relationships with on-premises AD, enabling seamless integration during hybrid migrations. Users can access both cloud and on-premises resources using existing credentials.
2. **AD Connector**: A proxy service that redirects directory requests to your on-premises AD. It allows AWS applications to use existing corporate credentials, making it ideal for organizations wanting to maintain their existing directory infrastructure while migrating workloads.
3. **Simple AD**: A standalone, cost-effective directory powered by Samba 4. Suitable for smaller organizations or workloads requiring basic AD features.
Key benefits for migration and modernization include:
- **Single Sign-On (SSO)**: Users authenticate once to access multiple AWS services and applications
- **Centralized Management**: Group policies, user management, and access controls from a single location
- **Seamless Integration**: Works with Amazon EC2, Amazon RDS, Amazon WorkSpaces, and other AWS services
- **High Availability**: Multi-AZ deployment options ensure resilience
During migration scenarios, AWS Directory Service enables organizations to extend their identity infrastructure to the cloud gradually. Applications can be modernized while maintaining consistent authentication mechanisms. The service supports both lift-and-shift migrations and application refactoring efforts by providing familiar AD capabilities.
For Solutions Architects, understanding directory service options helps design secure, scalable architectures that maintain compliance requirements while enabling smooth transitions from on-premises environments to AWS.
AWS Directory Service - Complete Guide
Why AWS Directory Service is Important
AWS Directory Service is critical for enterprises migrating to the cloud because it enables seamless integration of existing identity management systems with AWS resources. Organizations heavily invested in Microsoft Active Directory can extend their on-premises directories to the cloud or create new managed directories, maintaining consistent user authentication and authorization across hybrid environments.
What is AWS Directory Service?
AWS Directory Service provides multiple directory options to connect AWS resources with existing on-premises Microsoft Active Directory or to set up and operate new directories in the AWS Cloud. It offers managed directory services that handle the heavy lifting of deploying, operating, and scaling directory infrastructure.
Directory Types Available:
1. AWS Managed Microsoft AD - Fully managed Microsoft Active Directory running on Windows Server 2019 - Supports trust relationships with on-premises AD - Enables SSO for AWS applications and services - Supports Group Policy, LDAP, Kerberos, and NTLM authentication - Available in Standard (up to 30,000 objects) and Enterprise (up to 500,000 objects) editions
2. AD Connector - A proxy service that redirects directory requests to your on-premises AD - Does NOT cache or store any directory information in AWS - Requires VPN or Direct Connect to on-premises environment - Ideal when you want to use existing on-premises AD credentials - Available in Small (up to 500 users) and Large (up to 5,000 users) sizes
3. Simple AD - Samba 4-based, standalone managed directory - Provides basic AD features at lower cost - Does NOT support trust relationships with Microsoft AD - Best for small organizations with basic directory needs (up to 5,000 users) - Cannot be used with RDS SQL Server
4. Amazon Cognito User Pools - For web and mobile application user directories - Not part of Directory Service but serves similar identity purposes
How AWS Directory Service Works
AWS Managed Microsoft AD Architecture: - Deploys across two Availability Zones for high availability - Creates domain controllers in your VPC - AWS manages patching, monitoring, recovery, and snapshots - You manage users, groups, Group Policies, and trusts
Trust Relationships: - One-way trusts: Users from one domain access resources in another - Two-way trusts: Users from both domains can access resources in either - Forest trusts: Enable trust between entire AD forests - External trusts: Connect to specific external domains
1. Extending On-Premises AD to AWS: Use AWS Managed Microsoft AD with trust relationships
2. Lift-and-Shift Applications: Applications requiring AD authentication can use Managed AD
3. Using Existing Credentials: AD Connector proxies requests to on-premises AD
4. Simple Directory Needs: Simple AD for basic LDAP-compatible directory requirements
Exam Tips: Answering Questions on AWS Directory Service
Choosing the Right Directory Type: - AWS Managed Microsoft AD: Choose when you need trust relationships, full AD features, or RDS SQL Server authentication - AD Connector: Choose when you must use on-premises credentials and do not want to store credentials in AWS - Simple AD: Choose for cost-effective basic directory needs when trust relationships are not required
Key Decision Points: - If the question mentions trust relationships → AWS Managed Microsoft AD - If the question emphasizes no credentials stored in cloud → AD Connector - If the question mentions RDS SQL Server Windows Authentication → AWS Managed Microsoft AD (Simple AD does NOT support this) - If the question asks about lowest cost basic directory → Simple AD - If high availability is critical → AWS Managed Microsoft AD (multi-AZ by default)
Common Exam Scenarios:
1. Hybrid Authentication: Establish VPN/Direct Connect + either AD Connector or Managed AD with trust
2. WorkSpaces Deployment: Requires a directory service - any type works depending on requirements
3. Application Migration: AD-dependent applications typically need Managed Microsoft AD
4. Multi-Region Directories: AWS Managed Microsoft AD supports multi-region replication
Remember These Facts: - AD Connector requires persistent connectivity to on-premises; if connection fails, authentication fails - AWS Managed Microsoft AD runs actual Microsoft AD, not a simulation - Simple AD is based on Samba 4, not Microsoft technology - Directory Service directories are deployed inside your VPC - Shared directories can span multiple AWS accounts using AWS RAM - MFA is supported with AWS Managed Microsoft AD using RADIUS
Watch for Trick Questions: - AD Connector is NOT a directory - it is a proxy - Simple AD cannot join to an existing on-premises AD - Managed Microsoft AD Standard edition has object limits that may matter for large enterprises