A new approach for allocating buffers and bandwidth to heterogeneous, regulated traffic in an ATM node

Abstract

Abstract-A new approach to determining the admissibility of variable bit rate (VBR) traffic in buffered digital networks is developed. In this approach all traffic presented to the network is assumed to have been subjected to leaky-bucket regulation, and extremal, periodic, on-off regulated traffic is considered; the analysis is based on fluid models. Each regulated traffic stream is allocated bandwidth and buffer resources which are independent of other traffic. Bandwidth and buffer allocations are traded off in a manner optimal for an adversarial situation involving minimal knowledge of other traffic. This leads to a single-resource statistical-multiplexing problem which is solved using techniques previously used for unbuffered traffic. VBR traffic is found to be divisible into two classes, one for which statistical multiplexing is effective and one for which statistical multiplexing is ineffective in the sense that accepting small losses provides no advantage over requiring lossless performance. The boundary of the set of admissible traffic sources is examined, and is found to be sufficiently linear that an effective bandwidth can be meaningfully assigned to each VBR source, so long as only statistically-multiplexable sources are considered, or only nonstatistically-multiplexable sources are considered. If these two types of sources are intermixed, then nonlinear interactions occur and fewer sources can be admitted than a linear theory would predict. A qualitative characterization of the nonlinearities is presented. The complete analysis involves conservative approximations; however, admission decisions based on this work are expected to be less overly conservative than decisions based on alternative approaches.

Theories and models for Internet quality of service

“…With these weak assumptions, it is possible to find good probabilistic bounds. A first family of results is based on a heuristic which assumes that the worst case traffic is made of on-off sources [80], [81], [82], [83]. In contrast, in the rest of this section, we describe results that are exact bounds.…”

Tradeoffs in designing networks with end-to-end statistical QoS guarantees

“…The parameters are similar to those used in other studies on regulated adversarial traffic [12,25,31].…”

“…These or similar assumptions are used in many recent works on statistical QoS [3,10,12,17,18,20,25,26,31,32,33]. The assumptions are very general.…”

“…(7) and (8), an arrival will find a full buffer only if for some > 0, A Cmq (t ; t ) > G Cmq ( ") (11) whereà Cmq (s t) is the class-q traffic that arrives at node m in the interval s t). Thus, the probability that an arrival from class q at node m is dropped is P r 9 > 0 :à Cmq (t ; t ) > G Cmq ( ") : (12) Using L Cmq (s t) to denote the class-q traffic that would have arrived at node m but was dropped at upstream nodes, we haveà Cmq (t ; t ) = A Cmq (t ; t ) ; L Cmq (t ; t ) : (13) Thus, the probability that an arrival from class q at node m is dropped at time t is P r ; …”

“…Recent research on statistical QoS has attempted to exploit statistical multiplexing gain by taking advantage of knowledge about deterministic bounds on arrivals from individual flows, with limited knowledge about their statistical properties [3,10,12,17,18,20,25,26,31,32,33]. Under a very general set of traffic assumptions, which are sometimes referred to as 'regulated adversarial traffic,' one merely assumes that (1) traffic arrivals from a flow are constrained by a deterministic regulator, e.g., a leaky bucket, and (2) traffic arrivals from different flows are statistically independent.…”