Nowadays, hosted applications, Software as a Service (SaaS), are a common business operation mode for lots of businesses. These services are normally deployed in the perimeter or in a public network. These applications also can have authentication requirements. But it is not recommended to install AD DS in the perimeter or public network. In such a situation, it is recommended to deploy AD FS to provide the federated access. But it still needs additional resources and skills to deploy and maintain. Instead of this, we can set up the AD LDS instance inside the perimeter/public network and provide the directory-enabled authentication service to applications. It doesn't have any connection with LAN or the other LDS instance in the perimeter network and provides a secured environment by design.