the present invention faces the issue of racing conditions occurring during the establishment of an ip - can session in pcc architecture and a tdf session between a pcrf and a tdf of the pcc architecture . to overcome this issue , the present invention provides for cooperating apparatuses carrying out a method of establishing a traffic detection function “ tdf ” session in a policy and charging control “ pcc ” architecture with a policy and charging control rules function “ pcrf ”, a policy and charging enforcement function “ pcef ” and a tdf , the method comprising the steps of : signalling an ip - can session establishment from a pcef towards a pcrf ; selecting at the pcrf a tdf for detecting and reporting traffic through the ip - can session ; initiating from the pcrf establishment of a tdf session with the tdf ; submitting from the pcrf towards the tdf the adc rules to be installed for the ip - can session ; and submitting from the pcrf towards the pcef the pcc rules to be installed for the ip - can session . this method thus ensures that the tdf session has been established before having completed the establishment of the ip - can session .