1. A method of operating a communications network including one or more service nodes providing resources for running communications services over the communications network, a registration server arranged to control access by client applications to the one or more service nodes, and a platform remote from the registration server running one or more communications client applications, the method including: (a) distributing data identifying service resources available on the or each service node connected to the communications network, the or each service node providing resources for running communications services over the communications network; (b) communicating to the registration server a request for access by at least one of the client applications running on the said platform to at least some of the service resources identified in step (a); (c) at the registration server, in response to the request of step (b), executing a digitally-signed access agreement permitting access by the client application to the one or more service nodes providing the said requested services resources, the digitally-signed access agreement being stored at the registration server with associated data including the identity of said client application and of the one or more said service nodes wherein; the digitally-signed access agreement is a single agreement specifying a specific fixed number of instances of the client application and a specific fixed number of services nodes; and the specific fixed number of instances of the client application is greater than one and/or the specific fixed number of service nodes is greater than one; and (d) thereafter, in response to execution of the digitally-signed access agreement in step (c), binding the specific fixed number of instances of the client application to the specific fixed number of service nodes.