Active Directory Lightweight Directory Services (AD LDS) was originally a downloadable add-on to Windows Server called Active Directory Application Mode (ADAM). In Windows Server 2008 this became an additional role included in the operating system. AD LDS uses the same code as AD DS and thus provides some of the same functionality. As you will see, it provides a lot of the same functionality but is also flexible enough to offer additional options that are not possible using AD DS. You may want to see the following interesting articles: What happens when WDS and DNS are installed on the same Windows Server? DNS issues with WDS, What is Lightweight Directory Access Protocol, and Guide on federating ADFS with Azure Active Directory.
AD LDS Example: In this example, a user needs to access a web server. This web server has been placed on a perimeter network and separated from the internet and the internal network by a firewall. The web server needs to be able to authenticate users, however for security reasons the company does not want to place a Domain Controller on the perimeter network. Rather than install a Domain Controller on the perimeter network, another option is to install AD LDS on the web server.
Since it uses the same code base as a Domain Controller, it is able to authenticate users the same way a Domain Controller would. In order to achieve this, the user’s database is replicated from a Domain Controller on the commercial network to the perimeter network. AD LDS also allows you to choose which data you want to replicate, for example, you could choose to replicate the user data but not the group data. AD LDS also supports additional data to be added.
This means additional data can be added that the web server can be accessed through AD LDS which means this additional data does not need to be added to AD DS. This solution helps keep Active Directory secure and also helps prevents extra data from being added to the database.
I hope you found this blog post helpful. If you have any questions, please let me know in the comment session.