On the impact of time scales on feedback based rate control

Since they are delay tolerable, the ABR applications can be allocated the remaining resources after CBR (constant bit rate) and VBR (variable bit rate) applications have been accommodated. To avoid excessive losses, the transmission rates of the ABR applications should be modulated by the amount of remaining resources. That is, the ABR rates should be controlled through a feedback based rate control mechanism. A network link shared by remote ABR and VBR applications is considered and the impact of various system time scales on the effectiveness of the feedback based flow control scheme is investigated. These time scales are expressed in terms of the network transmission speed, the minimum tolerable ABR rate and the rate of change of the VBR source rate. While the negative impact of a decreased network time scale on the effectiveness of this control scheme is well known, the impact of the ABR and VBR time scales has not been investigated in the past. It turns out that for a given network time scale, the induced cell losses can be significantly reduced for increased ABR and/or VBR time scales and thus, the latter time scales should be taken into consideration when evaluating the effectiveness of an adaptive feedback based rate control mechanism.