Dealing with the quality of the packet transport of multimedia services in overlay networks, we present the relation between the missing probability $P_m$ of transmitted packets of a variable bitrate video stream and distributions of the length of the overlay path, the upload capacity of nodes and the playback delay at a destination node. As active streams share the capacity of a transport channel, we select an equivalent bandwidth based on a bufferless fluid-flow model. A smallest equivalent capacity $u^*$ which provides the best trade-off between the mean delay between successfully delivered packets and the mean lossless time that is determined by the duration of consecutive successful packet transmissions is proposed as an optimal upload capacity. $u^*$ is less than the peak rate. The playback delay $b$ is selected as a quantile of a packet delay distribution. The normalized distribution of the length of the overlay path is derived to be geometric. The estimation of $u^*$ and $b$ requires inter-arrival times between packets, packet lengths of a peer-to-peer video flow and end-to-end packet delays. For SopCast IPTV data it is concluded that the signaling traffic does not impact on %the value of $u^*$ and increasing $b$ leads to the decrease of $P_m$.