The invention relates to a data communications network and a method of operation thereof. A data communications network (14) is described which includes a call server (58, 60, 62, 64) for the purpose of signalling, and a routing server (66, 68) for the purpose of routing to permit communication between users of the network. The call server (58, 60, 62, 64) is operable to send a request to the routing server (66, 68) for the purpose of obtaining the identity of another call server (58, 60, 62, 64) to which it is required to communicate. The request is provided with a parameter which relates to the origin of the communication within the data network (14) to enable a desired routing of the communication through the network.