The Application Layer Gateway Service (ALG) is a subcomponent of the Windows networking subsystem. It provides support for non-Microsoft plug-ins to allow network protocols to pass through the firewall and work behind Internet Connection Sharing. This service is installed by default and its startup type is Manual.

When the Application Layer Gateway Service is started in its default configuration, it logs on by using the Local Service account.

This service is not dependent on any other system service, nor is any service dependent on it.

The following table identifies the application protocol, network protocol, and ports that are used by the Application Layer Gateway Service: