A method and protocol tester for decoding data for the performance of a measurement task, which data is encoded in accordance with a protocol description, includes modifying the protocol description with respect to the measurement task by compressing protocol elements that are of no relevance to the measurement task and decoding the encoded data according to the modified protocol description to provide only decoded data relevant to the measurement task. The decoded data may be filtered before further processing according to a filter condition determined by the measurement task. Alternatively the filter condition may be installed as part of the modified protocol description. Then additional filtering may be applied when there are further filter conditions determined by the measurement task. The result is a protocol tester that permanently stores the protocol description while allowing modification of the protocol description for each measurement task, reducing storage and calculation requirements.