Hello, I ran an example and when I read the ns trace file I get an 'r' in the operation field (the first one) Does this stand for the "receive opertaion" ? I thought there were only 4 characters for this field (from the ns doc) (d,h,+,-). Nesrine -- Nesrine Chaher Dea Networks and Distributed Systems MISTRAL - INRIA. 2004, Route des Lucioles FRANCE