A data communications network comprises a plurality of terminals and a main server adapted to manage selective retrieval of data from a first server by at least one target terminal. Some or all of the terminals are adapted to act as relay servers for serving data retrieved from the first server to at least one target terminal. The network includes a network information database and the main server selects at least one target terminal to act as a relay server for serving data to other target terminals on the basis of terminal performance information stored in the network information database. Terminals acting as relay servers also select further downstream target terminals to act as further relay servers on the basis of the relative performances of the further target terminals. The load on the main server is thus distributed among all of the relay servers, providing improved network performance.