The proportional differentiation model provides the network operator with the `tuning knobs' for adjusting the per-hop quality-of-service (QoS) ratios between classes, independent of the class loads. This paper applies the proportional model in the differentiation of queueing delays, and investigates appropriate packet scheduling mechanisms. Starting from the proportional delay differentiation (PDD) model, we derive the average queueing delay in each class, show the dynamics of the class delays under the PDD constraints, and state the conditions in which the PDD model is feasible. The feasibility model of the model can be determined from the average delays that result with the strict priorities scheduler. We then focus on scheduling mechanisms that can implement the PDD model, when it is feasible to do so. The proportional average delay (PAD) scheduler meets the PDD constraints, when they are feasible, but it exhibits a pathological behavior in short timescales. The waiting time priority (WTP) scheduler, on the other hand, approximates the PDD model closely, even in the short timescales of a few packet departures, but only in heavy load conditions. PAD and WTP serve as motivation for the third scheduler, called hybrid proportional delay (HPD). HPD approximates the PDD model closely, when the model is feasible, independent of the class load distribution. Also, HPD provides predictable delay differentiation even in short timescales.

ABSTRACT Internet applications and users have very diverse quality-of-service expectations, making the same-service-to-all model of the current Internet inadequate and limiting. There is a widespread consensus today that the Internet architecture has to be extended with service differentiation mechanisms, so that certain users and applications can get a better service than others at a higher cost. One approach, referred to as absolute differentiated services, is based on sophisticated admission control and resource reservation mechanisms in order to provide guarantees or statistical assurances for absolute performance measures, such as a minimum service rate or a maximum end-to-end delay. Another approach, which is simpler in terms of implementation, deployment, and network manageability, is to offer relative differentiated services between a small number of classes of service. These classes are ordered based on their packet forwarding quality, in terms of per-hop metrics for the queueing delays and packet losses, giving the assurance that higher classes are better than lower classes. The applications and users, in this context, can dynamically select the class that best meets their quality and pricing constraints, without a priori guarantees for the actual performance level of each class. The relative differentiation approach can be further refined and quantified using the Proportional Differentiation Model. This model aims to provide the network operator with the `tuning knobs ' for adjusting the quality spacing between classes, independent of the class loads. When this spacing is feasible in short timescales, it can lead to predictable and controllable class differentiation, which are two important features for any relative differentiation model. The proportional differentiation model can be approximated in practice with simple forwarding mechanisms (packet scheduling and buffer management), that we briefly describe here.

In this paper we propose a Two-Tier resource management model for the global Internet. Our solution resembles the current two-tier routing hierarchy and allows individual administrative domains to independently make their own decisions on strategies and protocols to use for internal resource management and QoS support. The aggregate traffic crossing domain borders is served according to relatively stable, long-lived bilateral agreements. End-to-end QoS support is achieved through the concatenation of such bilateral agreements. We describe in detail a realization of this Two-Tier model, where a Bandwidth Broker (BB) acts as the resource manager for each administrative domain. Neighboring Bandwidth Brokers communicate with each other to establish Inter-domain resource agreements. As an illustrative example in this paper we used a simplified RSVP as an intradomain resource allocation protocol for the aggregate traffic between border routers. Our simulation results show that this Two-Tier...

This paper provides an initial look at how support for advance reservations affects the complexity of the path selection process in networks. Advance reservations are likely to become increasingly important as networks and distributed applications become functionally richer, and there have been a number of previous works and investigations that explored various related aspects. However, the impact of advance reservations on path selection is a topic that has been left largely untouched. This paper investigates several service models for advance reservations, which range from the traditional basic model of reserving a given amount of bandwidth for some time in the future, to more sophisticated models aimed at increasing the flexibility of services available through advance reservations. The focus is primarily on the issue of computational complexity when supporting advance reservations, and in that context, we derive a number of algorithms and/or intractability results fo...

The Differentiated Services architecture provides router mechanisms for aggregate traffic, and edge mechanisms for individual flows, that together can be used to build services with varying delay and loss behaviors. In this paper, we compare the loss and delay behaviors that can be provided using the services based on combinations of two router mechanisms, threshold dropping and priority scheduling and two packet marking mechanisms, edge-discarding and edge-marking. In the first part of our work, we compare the delay and loss behaviors of the two router mechanisms coupled with edge-discarding for a wide range of traffic arrivals. We observe that priority scheduling provides lower expected delays to preferred traffic than threshold dropping. In addition, we find that a considerable additional link bandwidth is needed with threshold dropping to provide same delay behavior as priority scheduling. We further observe little difference in the loss incurred by preferred traffic under both ro...

We survey recent advances in theories and models for Internet Quality of Service (QoS). We start with the theory of network calculus, which lays the foundation for support of deterministic performance guarantees in networks, and illustrate its applications to integrated services, differentiated services, and streaming media playback delays. We also present mechanisms and architecture for scalable support of guaranteed services in the Internet, based on the concept of a stateless core. Methods for scalable control operations are also briefly discussed. We then turn our attention to statistical performance guarantees, and describe several new probabilistic results that can be used for a statistical dimensioning of differentiated services. Lastly, we review recent proposals and results in supporting performance guarantees in a best effort context. These include models for elastic throughput guarantees based on TCP performance modeling, techniques for some quality of service differentiation without access control, and methods that allow an application to control the performance it receives, in the absence of network support.

We suggest that satisfactory statistical performance guarantees for streaming flows can be fulfilled when their packets receive expedited forwarding in non-preemptive priority queues. This relies on the conjecture that jitter remains negligible in the network such that performance measures can be bounded by assuming flows constitute Poisson arrival processes of MTU sized packets. We provide analytical and simulation evidence in support of this conjecture and show how it leads to simple engineering rules for both constant and variable rate streaming traffic. I.

Abstract—We study a dynamic, usage- and congestion-dependent pricing system in conjunction with price-sensitive user adaptation of network usage. We first present a resource negotiation and pricing (RNAP) protocol and architecture to enable users to select and dynamically renegotiate network services. We develop mechanisms within the RNAP architecture for the network to dynamically formulate prices and communicate pricing and charging information to the users. We then outline a general pricing strategy in this context. We discuss candidate algorithms by which applications (singly, or as part of a multiapplication system) can adapt their rate and QoS requests, based on the user-perceived value of a given combination of transmission parameters. Finally, we present experimental results to show that usage- and congestion-dependent pricing can effectively reduce the blocking probability, and allow bandwidth to be shared fairly among applications, depending on the elasticity of their respective bandwidth requirements. Index Terms—Adaptive systems, communication system economics, communication system signaling, communication system traffic, computer network management, multimedia communication, resource management. I.

This paper presents a decentralized auction-based approach to pricing of edge-allocated bandwidth in the differentiated services model of the Internet. The players in this architecture are users, one raw-capacity seller per network and one broker per service per network. With the Progressive Second Price auction mechanism as the basic building block, we conduct a game theoretic analysis, deriving optimal strategies for buyers and brokers, and the existence of network-wide equilibria. We investigate the system dynamics by simulating a scenario with three inter-connected networks, and two types of services built on the proposed standard expedited forwarding (EF) and assured forwarding (AF) per-hop behaviors.

Many per-flow scheduling algorithms have been proposed to provide rate and delay guarantees to flows. It is often argued that the need for maintaining per-flow state and performing per-packet classification seriously limits the scalability of routers that employ such per-flow scheduling algorithms. Consequently, design of algorithms that can provide per-flow rate and delay guarantees without requiring per-flow functionality in the network core routers has become an active area of research. In this paper, we propose a methodology to transform any Guaranteed Rate (GR) per-flow scheduling algorithm into a version that does not require per-flow state to be maintained in the core routers. We prove that a network of such core-stateless servers provides the same delay guarantee as a corresponding network of GR servers.