reference to fig2 the co ordination of tests between multiple agents 5 and 15 within the same network 2 includes the case in which all of the agents 5 and 15 within the network 2 are registered to the same proxy server 4 in response to the polling signal d 1 the proxy server 4 sends the test request d 2 to one agent 5 mentioned in the test request d 2 if the test involves another agent 15 the test request d 2 contains information about the identifier of the second agent 15 the first agent 5 then constructs the test request d 2 l for the second agent 15 and submits it to the proxy server 4 the proxy server 4 sends the test request d 22 to the second agent 15 the first agent 5 polls for test status d st of the second agent 15 via the proxy sever 4 the status message d st between the two agents 5 and 15 passed via the proxy server 4 is used to co ordinate the start and completion of tests between the two agents 5 and 15 the results f for both ends of the test will be collected by the first agent 5 and handed off to the proxy server 4 with reference to fig3 in the case in which there is a second network 22 with its own firewall 23 and second agent 25 therein it is possible that the two agents 5 and 25 are registered to two different proxy servers 4 and 24 in this case in response to the polling signal d 1 from the first agent 5 the test request d 2 is sent to the first agent.