The Case Against Variable Bit Rate Service

additional advantages of RCBR are that it is easy to implement, since CBR service is well understood and we are merely adding a fast renegotiation component to it. By building on CBR service, we make the network design simple, since neither complex scheduling disciplines nor large network buuers are required for CBR traac. It has recently come to our notice that Chong et al 2] have independently arrived at conclusions similar to ours, that is, compressed VBR traac has sustained peaks, and thus is best carried by a renegotiated service. They have concentrated in their work on coming up with good predictors for rate changes. In contrast, our work has used large deviations analysis for insight into the nature of statistical multiplexing gain and is coupled with a systems perspective. dynamic bandwidth allocation for eecient transport of real-time VBR video over ATM. A novel variable bit rate service for integrated services networks. submitted to the ACM Sigcomm'95. Statistical multiplexing of multiple timescale Markov streams. Preprint. This article was processed using the L a T E X macro package with LLNCS style for lack of space, analysis shows that with careful coding and cleanly designed end-systems and switch controllers, renegotiation overheads are small. Due to the inherent uncertainty in the bandwidth requirements of calls over their lifetime, there is always a possibility that a renegotiation for a higher bandwidth can fail due to unavailable capacity. The probability of renegotiation failure is kept low by admission control, such that there is always excess capacity in the system. The amount of slack can be determined by estimating the renegotiation failure probability using large deviations techniques. For users who do not want to take any risk, they might reserve resources at or close to the peak rate. Note that even if the renegotiation fails, the source can keep whatever bandwidth it already has. For interactive applications, the signaling system can also ask the user or application to temporarily reduce its data rate, such as using an adaptive codec. Thus, we believe that there are a number of techniques we can call upon to deal with renegotiation failures. For more details of the analysis, refer to 4]. We have compared the statistical multiplexing gain (SMG) achievable through our scheme with two other scenarios. The rst scenario multiplexes n streams without any restriction on a server with rate c and buuer size nB. This is used …