In this paper we set up a family of conservative upper bounds for QoS measures applicable in QoS guaranteed packet-based communication networks. The bounds are distribution free that is they depend only on the number of traffic sources, the peak rates of the flows and the mean arrival intensity of the aggregated traffic stream. No other information on the traffic distribution is required. The bounds have been developed under the well known bufferless fluid flow multiplexing (bffm) modeling framework, nevertheless, an important property is also discussed in the paper, namely they can also be applicable to the buffered statistical multiplexer case when the input flows are regulated. The performances of the bounds are analyzed and comparative numerical investigations are also presented in both multiplexing models.