Some tools, like Ivanti Application Manager, can take action depending on registry values. One example is to block access to a executable depending on the mac address. Or tweaking the Windows interface when the client is mobile. Or blocking access to some sites when client is connected to an external gateway. Other competing solutions write client information to the registry or set environment variables on the remote machine. As an example, they write a registry named Location external when the client is connected to an external gateway or Mac Adress with the client mac address. Parallels Ras could do the same.