#AzureAD : Azure Active Directory Domain Services Part I


Microsoft Azure cloud services are growing rapidly. Many organizations are using hybrid models and planning to move applications to the cloud as much as possible. One of the biggest hurdle in moving existing applications are identity and security. Most of the existing applications are controlled and managed by Windows server Active Directory, DNS and Group policies. At large, applications can be categorized under two umbrellas I.e. enterprise applications and line-of-business applications. Most of these enterprise applications and line-of-business applications leverage domain joined machines controlled by group policies and AD for identity needs. Now-a-days most of the enterprise applications are available in SAAS model and can leverage cloud identity for authentication and authorization, while line-of-business application can’t be rewritten overnight to support new technologies such as SAML, Open Id, OAuth etc. due to multiple reasons. Therefore, access to the domain controller from Microsoft Azure IaaS becomes a last option. Organizations achieve this goal in three ways:

  • By connecting Azure network with On-premises AD domain services.
  • By setting up a replica of existing AD domain/forest on Microsoft Azure IaaS using virtual machines.
  • By deploying a new AD domain/forest with trust between existing on-premises domain/forest and newly deployed domain/forest on MS Azure IaaS.

To resolve these issues, Microsoft has taken a leap into the directory services offerings. Microsoft Azure AD DS is managed active directory domain service provided by Microsoft Azure. It is an extension of on-premises active directory available in the cloud and managed by Microsoft. Azure AD DS doesn’t require any additional setup to sync with on-premises directory services.

It simply leverages your Azure Active Directory to connect with on-premises active directory. Once, you enable this service and link with your Azure VNet then your workloads/apps can connect to this domain services. As it is like your traditional domain controllers, deployed and managed by Microsoft therefore you can use all traditional authentication methods such as Windows Integrated authentication, NTLM, Kerberos etc. You can access these domain services by traditional AD management tools such as Active Directory Administrative Center but you don’t have to worry about the patching, management, replication, availability, backup etc. As, it is just a service therefore you will not be provided domain administrator and enterprise administrator privileges on this domain.

This service can be deployed/leveraged in two ways.

  • For hybrid organizations: In this scenario, Azure AD sync with on-premises directory services and Azure AD DS leverages user identities, their passwords and group memberships. Password sync is mandatory for hybrid organizations to leverage Azure AD DS. It is needed to authenticate users via NTLM and Kerberos authentication methods.

Courtesy: Microsoft

  • For Cloud-only organizations: In this scenario, organization doesn’t have any on-premises directory setup. AD DS leverage cloud native Azure AD tenant for all user identities, their password, and group memberships.

Courtesy: Microsoft

With the help of this service, on-premise applications can be lifted and shifted easily to the clouds. Azure AD DS deploy two domain controllers per tenant to maintain high availability of the services. It also provides automatic health detection and remediation. Azure AD DS offers LDAP bind, LDAP read and secure LDAP (including over internet). It maintains synced on-premises SIDHistory in your managed domains. Like your on-premises domain services, you can also manage your DNS and Group policies in a traditional way.

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