1. A service gateway for connecting at least one local client to an external network, the service gateway being operable to hold at least one service module for providing a corresponding service, wherein the service gateway comprises a control mechanism that is operable in response to a request for a service provided by a service module not present at the service gateway, to send a message to an external source for resolving the absence of a service module at the gateway in one or more iterations until a response from the external service identifies information including a service module held by the gateway that enables resolution of the absent service module(s).