Wikipedia
DirectAccess, also known as Unified Remote Access, is a VPN-like technology that provides intranet connectivity to client computers when they are connected to the Internet. Unlike many traditional VPN connections , which must be initiated and terminated by explicit user action, DirectAccess connections are designed to connect automatically as soon as the computer connects to the Internet. DirectAccess was introduced in Windows Server 2008 R2, providing this service to Windows 7 and Windows 8 "Enterprise" edition clients. In 2010, Microsoft Forefront Unified Access Gateway (UAG) was released, which simplifies the deployment of DirectAccess for Windows 2008 R2, and includes additional components that make it easier to integrate without the need to deploy IPv6 on the network, and with a dedicated user interface for the configuration and monitoring. Some requirements and limitations that were part of the design of DirectAccess with Windows Server 2008 R2 and UAG have been changed (see requirements below). While DirectAccess is based on Microsoft technology, third-party solutions exist for accessing internal UNIX and Linux servers through DirectAccess. With Windows Server 2012, DirectAccess is fully integrated into the operating system, providing a user interface to configure and native IPv6 and IPv4 support.