means for receiving a request for data from a client;

means for receiving client identification data from said client;

means for identifying a plurality of data providers having, or having access to, data in respect of which a request has been received from said client;

means for providing said client identification data to said data providers;

means for instructing said data providers to perform the following steps without requiring said client to install or execute additional software at said client:

(i) sending a test signal to said client;

(ii) receiving a return signal from said client;

(iii) obtaining a measure of the elapsed time between the sending of the test signal and the receipt of the return signal;

(iv) making a signal indicative of the elapsed time available to the system; and

v) making a signal indicative of their remaining capacity available to the system;

means for receiving elapsed time signals and remaining capacity signals from said data providers;

means for selecting a preferred data provider from said plurality of data providers on the basis of said signals; and

means for providing information relating to the identity of said preferred data provider to said client.