Amazon has launched an AWS Directory Service for Active Directory, a fully-managed implementation of Microsoft's authentication and user management service.

Using Active Directory in Amazon's cloud will enable companies to bring applications including SQL Server, SharePoint and custom applications built with .NET onto AWS. That's useful for businesses trying to move into the cloud from an on-premises deployment of Microsoft's software.

When companies start using the service, it creates a pair of domain controllers connected to a user's virtual private cloud running Windows Server 2012 R2. Each domain controller runs in a different availability zone of a user's choosing inside a single region, and Amazon will handle the nuts-and-bolts of managing things like host monitoring, data replication and snapshots.

Administrators will be able to configure a trust relationship between their on-premises Active Directory and the AD in Amazon's cloud, so that users can sign in to both systems using one login.

Companies can try the service for free for one month or 750 hours, whichever comes first. After that, the service costs US$0.40 per hour.

It's an interesting move for Amazon, since one of the key products Microsoft uses to push its cloud services into large enterprises is Azure Active Directory -- a fully-managed, cloud-based implementation of Microsoft's authentication and user management service with a whole bunch of other services and integrations baked in. It's an easy way to get one part of a business into Azure, which Microsoft can then use to try and up-sell companies on other cloud services.

It will be interesting to see if and how Amazon plans to expand this service to better compete against Azure AD in the future, especially as it continues to fight with Microsoft to pursue dominance in the public cloud market.