The Differentiated services (diffserv) architecture has been proposed as a scalable solution for providing service differentiation among flows without any per-flow buffer management inside the core of the network. It has been advocated that it is feasible to provide service differentiation among a set of flows by choosing an appropriate "markingprofile"for each flow. In this paper, we examine (i) whether it is possible to provide service differentiation among a set of TCP flows by choosing appropriate marking profiles for each flow, (ii) under what circumstances, the marking profiles are able to influencethe service that a TCP flow receives, and, (iii) how to choose a correct profileto achieve a given service level. We derive a simple, and yet accurate, analytical model for determining the achieved rate of a TCP flow when edge-routers use "token bucket"packet marking and core-routers use active queue management for preferential packet dropping. From our study, we observe three important results: (i) the achieved rate is not proportional to the assured rate, (ii) it is not always possible to achieve the assured rate and, (iii) there exist ranges of values of the achieved rate for which token bucket parameters have no influence. We findthat it is not easy to regulate the service level achieved by a TCP flow by solely setting the profileparameters. In addition, we derive conditions that determine when the bucket size influencesthe achieved rate, and rates that can be achieved and those that cannot. Our study provides insight for choosing appropriate token bucket parameters for the achievable rates.

The proportional differentiation model was proposed in [1] as a target for controllable and predictable relative differentiated services. [1] considered only the delay differentiation aspect of the model, and focused on packet scheduling mechanisms. In this paper, we extend the proportional differentiation model in the direction of loss rate differentiation. Severalprevious mechanisms for buffer management and packet dropping, such as complete buffer partitioning, partial buffer sharing, or multiclass RED, are not suitable for relative differentiated services. We proposeand evaluate two dropping mechanisms that closely approximate the proportional loss rate differentiation model. The two droppers, PLR(1) and PLR(M), differ in the time interval over which the loss rates are measured and proportionally adjusted. This difference results in several trade-offs, in terms of implementation complexity, accuracy, and ability to deal with nonstationary traffic loads. We also re-evaluate the dela...

We consider the setting of a network providing differentiated services. As is often the case in differentiated services, we assume that the packets are tagged as either being a high priority packet or a low priority packet. Outgoing links in the network are serviced by a single FIFO queue.

In this paper, we propose simple models of TCP behavior in a differentiated services network. Congestion avoidance technique in TCP makes it difficult for flows to achieve performance goal in differentiated services network. Our models are developed to estimate TCP throughput as functions in terms of the reservation rate, the probability of packet drop and the round-trip time. We present several simulations to validate our models, and the results clearly show that the models estimate TCP throughput quite accurately in various situations. Keywords : Differentiated service, TCP modeling, TCP throughput. 1 Introduction Differentiated services architecture is defined for providing different levels of services for different users or applications to meet their specific requirements (either or both throughput and delay guarantees) [1, 3, 5]. To support service differentiation for individual or aggregated flows, the architecture provides a meter and a marker at the edges of the network and...

We consider a network providing Differentiated Services (DiffServ) which allow network service providers to offer different levels of Quality of Service (QoS) to different traffic streams. We focus on loss and first show that only trivial bounds could be obtained by means of traditional competitive analysis. Then we introduce a new approach for estimating loss of an online policy called lossbounded analysis. In loss-bounded analysis the loss of an online policy is bounded by the loss of an optimal offline policy plus a constant fraction of the benefit of the online policy. We relate the lossbounded analysis to the throughput-competitive analysis. We derive tight upper and lower bounds for various settings of DiffServ parameters using the new loss-bounded model. We believe that lossbounded analysis is an important technique that can complement traditional competitive analysis providing new insight and interesting results.

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We study in this paper a TCP-like linear-increase multiplicative -decrease flow control mechanism. We consider congestion signals that arrive in batches according to a Poisson process. We focus on the case when the transmission rate cannot exceed a certain maximum value. We write the Kolmogorov equations and we use Laplace Transforms to calculate the distribution of the transmission rate in the steady state as well as its moments. Our model is particularly useful to study the behavior of TCP, the congestion control mechanism in the Internet. By a simple transformation, the problem can be reformulated in terms of an equivalent M/G/1 queue, where the transmission rate in the original model corresponds to the workload in the `dual' queue. The service times in the queueing model are not i.i.d., and they depend on the workload in the system.

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This paper introduces a new packet marking algorithm that can be used in the context of Assured Forwarding (AF) in the Differentiated Services (DiffServ) framework [1], [2]. The new marking algorithm is called Equation-Based Marking (EBM) and is based on the TCP model in [3]. EBM is to handle the problems found in other marking schemes regarding fairness among heterogeneous TCP flows through a tight feedback-loop operation and adaptation of the packet marking probability to network conditions. We design a packet marker that uses EBM as the marking algorithm, and evaluate its performance using in-depth simulation. We also prove analytically the correctness of the marking algorithm and compare it with other marking schemes for different network scenarios. Our evaluation results demonstrate the effectiveness of EBM in providing the required fairness among heterogeneous flows and ensuring protection against non-assured traffic. I.

In this paper, we consider a proportional delay model for Internet differentiated services. Under this model, an ISP can control the "spacing" of waiting times between different classes of traffic. Specifically, the ISP tries to ensure that the average waiting time of class i traffic relative to that of class i \Gamma 1 traffic is consistently a specifiable ratio. If the ratio is less than one, the ISP can legitimately charge users of class i traffic a higher tariff rate (compared to the rate for class i \Gamma 1 traffic), since class i users consistently enjoy better performance than class i \Gamma 1 users. We use time-dependent priority scheduling to realize the proportional delay model. We formally characterize the feasible regions in which given delay ratios can be achieved. Moreover, a set of scheduling parameters for obtaining the desired delay ratios can be determined by an efficient control algorithm. Experiments are carried out to illustrate the short-term, medium-term and long-term relative waiting time performances for different service classes.