A virtual network has a plurality of nodes. Each node has the capability to provide a service to another node. Each node maintains a list for storing entries each representing a link to another node; each entry contains the address of the other node and a label identifying a service that that other node may provide. Each node also has a store for storing messages received from other nodes, these messages serving to propose a link and containing the identity of the node originating the message, a label identifying a service that that other node may provide and a label identifying a service that that other node requires. When a node needs a service that it is not itself able to provide, it searches the link list for a link having a label that matches the service needed, and in the event that such a link is found it transmits to the node identified by the link a message requesting the service. If, however, no such link is found, it searches the message store for a message identifying another node where the label identifying a service that that other node may provide matches the service needed and the label identifying a service that that other node requires matches the service that the node needing the service has the capability to provide. In the event that such a message is found it initiates the creation of a corresponding entry in the link list. If no such message is found, the node needing the service generates a message serving to propose a link and containing its own identity, a label identifying a service that it has the capability to provide and a label identifying the service that it needs.