Data files are supplied to a plurality of requesting stations (102 to 106) by accessing serving devices (109 to 116). A plurality of requests are received for one or more data files at a traffic management system (101) from requesting stations via an external network (107). A specific server is selected at the traffic management system and a request is issued to the selected server over a local network for the requested file. The requested file is accepted at the traffic management system from the selected server over the local network and the requested file is sent from the traffic management system to the requesting station over external network. The response of selected servers is monitored (302) when responding to issued requests thereby generating monitored responses. The monitored responses are compared (303) against an operational criterion to identify sub-standard operations. Thereafter, where appropriate, measures are taken (305) to reduce the processing demand placed upon the selected server so as to improve the monitored operation of the selected server.