Diagnostic testing in networks

A probe controller to obtain diagnostic test results in respect of network elements in a network, the test results being obtained from probes in a population of probes, each probe being associated with a network element, the probe controller comprising:

• an interface communicatively coupled to the probes and being adapted to receive a first-stage set of probe reports comprising, in respect of each of a plurality of probes in an initial subset of the population of probes, a test result and metadata, each test result indicating a state of or state in respect of the network element associated with the probe;
• and
• a processor adapted to identify, in dependence on test results received in respect of a plurality of probes in the initial subset, a specific subset of one or more probes in the initial subset wherein the test result or results from the one or more probes in the specific subset satisfy a predefined condition, and to determine a subsequent subset of a plurality of probes in the population of probes in dependence on the metadata of the at least one probe in the specific subset,
• wherein the interface is further adapted to communicate with the probes in the subsequent subset of probes to trigger the probes in the subsequent subset to provide a second-stage set of probe reports.