We have shown how application-specific policies spanning multiple MCA domains can be introduced into the network. This allows applications to make use of application-specific knowledge that would otherwise be difficult if not impossible to exploit. To demonstrate the usefulness of these global policies, consider the case of mobile computing. A client may have very specific knowledge about the route followed by, or the communication pattern associated with a particular mobile system M (see Figure ). We assume that there are multiple MCA domains and that the mobile system roams among these domains. We are now able to install the client's application-specific knowledge across the entire administrative domain. It is even possible to have a DLA `follow' the mobile system as it travels from domain to domain (which means that it does not burden those parts of the network that M is not even close to). The DLA sets up connections for the mobile system, works out the routes for them and also collects data about the communication (e.g. for billing, etc.). This is an example of application-specific control using roaming policies of which a proof-of-concept implementation has been achieved.