Compressed digital video is one of the most important types of traffic in future integrated services networks. It is difficult to support this class of traffic since, on one hand, compressed video is bursty, while on the other hand, it requires performance guarantees from the network. The common belief is that we are unlikely to achieve a high network utilization while providing performance guarantees to such bursty sources. In this paper, we introduce a new Deterministic Bounding Interval-Dependent (D-BIND) traffic model, together with tight analysis techniques, to explore the possibility of providing deterministic performance guarantees to VBR traffic while still achieving a reasonable network utilization. The D-BIND model consists of a family of rate-interval pairs where the rate is a bounding rate over the interval length. The model captures the intuitive property that over longer interval lengths, a source may be bounded by a rate lower than its peak rate and closer to its long-te...

. This paper is motivated by the need to provide per session quality of service guarantees in fast packet-switched networks. We address the problem of characterizing and designing scheduling policies that are optimal in the sense of minimizing buffer and/or delay requirements under the assumption of commonly accepted traffic constraints. We investigate buffer requirements under three typical memory allocation mechanisms which represent trade-offs between efficiency and complexity. For traffic with delay constraints we provide policies that are optimal in the sense of satisfying the constraints if they are satisfiable by any policy. We also investigate the trade-off between delay and buffer optimality, and design policies that are "good" (optimal or close to) for both. Finally, we extend our results to the case of "soft" delay constraints and address the issue of designing policies that satisfy such constraints in a fair manner. Given our focus on packet switching, we mainly concern our...

One of the most important traffic types in future packet-switched networks is high-bandwidth, variable-bit-rate (VBR) video. Since video is a delay-sensitive media, the network must allocate resources to maintain quality-of-service (QoS) guarantees on throughput, delay, and delay jitter to video connections. A key component of resource al-location is the traffic characterization of video sources that determines the resources required to support video conne-tions. In this study, we propose a method for characterizing VBR vadeo traffic with a fixed number of leaky buckets in networks with a deterministic service. We explore tradeffs of network utilization in two directions: (I) the number of leaky buckets used for traffic characterization, and (2) the amount of information from a video sequence used to produce the characterization. We evaluate our method with a set of 30-minute long MPEG-compressed video traces.

Quality-of-Service #QoS# routing is indispensable to real-time applications on integrated services packet-switching networks. However, existing QoS-routing schemes based on either request #ooding or link-state dissemination are not e#cient in terms of their message overhead and#or operational cost. This paper proposes a QoS-routing algorithm with bounded #ooding which not only dramatically reduces message overhead and operational cost, but also provides good performance. This signi#cantoverhead reduction is achieved by limiting the search area within which connection-request messages are #ooded. Since our scheme is based on limited #ooding, it does not require on-demand path calculation nor link-state dissemination, which are often known to be very expensive. In order to limit the search area, we employ a distance table at each node storing hop counts of the shortest paths to all the nodes reachable via its outgoing links. Unlike link-state routing, the proposed scheme only needs netwo...

Abstract — In this paper we analyze feedforward tree networks of queues serving fixed length packets. Using sample path conservation properties and stochastic coupling techniques, we analyze these systems without making any assumptions about the nature of the underlying input processes. In the case when the server rate is the same for all queues, the exact packet occupancy distribution in any queue of a multi-stage network is obtained in terms of a reduced 2-stage equivalent model. Simple and exact expressions for occupancy mean and variance are derived from this result, and the network is shown to exhibit a natural traffic smoothing property, where preliminary stages act to smooth or improve traffic for downstream nodes. In the case of heterogeneous server rates, a similar type of smoothing is demonstrated, and upper bounds on the backlog distribution are derived. These bounds hold for general input streams and are tighter than currently known bounds for leaky bucket and stochastically bounded bursty traffic. Index Terms — stochastic coupling, network calculus I.

In this paper, we giveanoverview of the basic design principles and trade-o#s of output-bu#erATM switching. Outputbu #er switches give optimal performance in terms of o#ering bandwidth guarantees to individual #ows. Bandwidth scheduling and memory bandwidth requirements are also described. I.

This paper describes the design and implementation of the Dynamic Window-Constrained Scheduling (DWCS)[1][2][3] algorithm to schedule packets on network processors. The DWCS algorithm characterizes multimedia streams with diverse Quality of Service (QoS) requirements. Earlier implementations of DWCS on Linux and Solaris machines use a heap-based implementation, which requires O(n) time to find the next packet and send it out, and which frequently moves heap elements. For speed improvements and conservation of memory bandwidth, our design uses a Hierarchically Indexed Linear Queue (HILQ). The HILQ substantially reduces the number of memory accesses by scattering packets sparsely into the queue. Experimental results demonstrate improved scalability compared to a heap-based implementation in supporting thousands of streams with strict real-time constraints, while causing no loss in accuracy compared to the standard DWCS algorithm.