Quality of Service over Specific Link Layers: state of the art report

The Integrated Services concept is proposed as an enhancement to the current Internet architecture, to provide a better Quality of Service (QoS) than that provided by the traditional Best-Effort service. The features of the Integrated Services are explained in this report. To support Integrated Services, certain requirements are posed on the underlying link layer. These requirements are studied by the Integrated Services over Specific Link Layers (ISSLL) IETF working group. The status of this ongoing research is reported in this document. To be more specific, the solutions to provide Integrated Services over ATM, IEEE 802 LAN technologies and low-bitrate links are evaluated in detail. The ISSLL working group has not yet studied the requirements, that are posed on the underlying link layer, when this link layer is wireless. Therefore, this state of the art report is extended with an identification of the requirements that are posed on the underlying wireless link, to provide differentiated Quality of Service

TCP throughput guarantee in the DiffServ Assured Forwarding service: what about the results?

Since the proposition of Quality of Service architectures by the IETF, the interaction between TCP and the QoS services has been intensively studied. This paper proposes to look forward to the results obtained in terms of TCP throughput guarantee in the DiffServ Assured Forwarding (DiffServ/AF) service and to present an overview of the different proposals to solve the problem. It has been demonstrated that the standardized IETF DiffServ conditioners such as the token bucket color marker and the time sliding window color maker were not good TCP traffic descriptors. Starting with this point, several propositions have been made and most of them presents new marking schemes in order to replace or improve the traditional token bucket color marker. The main problem is that TCP congestion control is not designed to work with the AF service. Indeed, both mechanisms are antagonists. TCP has the property to share in a fair manner the bottleneck bandwidth between flows while DiffServ network provides a level of service controllable and predictable. In this paper, we build a classification of all the propositions made during these last years and compare them. As a result, we will see that these conditioning schemes can be separated in three sets of action level and that the conditioning at the network edge level is the most accepted one. We conclude that the problem is still unsolved and that TCP, conditioned or not conditioned, remains inappropriate to the DiffServ/AF service

A new proposal for assuring services in internet

In this paper we present a new mechanism to provide an assured service in terms of target rate and fair excess bandwidth, like the Internet Assured Service. Research in Internet Assured Service faced up both questions in separate ways proposing different traffic conditioners to work with the RIO buffer management, and proposing different modifications to this buffer management, among others. In this work, we suggest using a buffer management scheme different from RIO that also treats in-of-profile and out-of-profile packets differently but avoiding interference between them. This scheme is used together with the Counters Based traffic conditioner because of its high accuracy in guaranteeing target rates. We evaluate and compare by simulation the performance of our proposal using TCP RENO sources. One important issue to be considered is that the proposal is a feasible alternative to the standard architecture for Differentiated Services in Internet.This work was supported by the Spanish Research Council under grant TIC2000-1734- C03-03

Counters-based modified traffic conditioner

Traffic conditioners play a key role in implementing the Assured Service in the framework of the DiffServ approach. Many research papers have focused on finding the best traffic conditioner able to assure contracted target rates and to fairly distribute the excess bandwidth among competing sources. Nevertheless, none of the proposals presented so far accomplishes simultaneously both features. We propose a traffic conditioner for the Internet Assured Service called Counters-Based Modified (CBM) that strictly guarantees target rates and performs a fair share of the excess bandwidth among TCP Reno sources. The ability of strictly providing the inbound bandwidth is inherited from its predecessor the Counters-Based algorithm, and the fairness in the outbound bandwidth distribution is met by probabilistically dropping OUT packets in the traffic conditioner. To determine the dropping probability of an OUT packet, the amount of excess bandwidth and the average RTT of all connections in the traffic conditioner have to be known. Although this fact implies using some sort of signaling, it results more feasible than other proposed intelligent traffic conditioners. The CBM traffic conditioner is evaluated under different conditions by simulation using TCP Reno sources. Simulation results presented in this paper lead us to suggest it as a feasible election for the traffic conditioner device implementation in DiffServ.This work was supported by the Spanish Research Council under grant FAR-IP TIC2000-1734-C03-03

GTFRC, a TCP friendly QoS-aware rate control for diffserv assured service

This study addresses the end-to-end congestion control support over the DiffServ Assured Forwarding (AF) class. The resulting Assured Service (AS) provides a minimum level of throughput guarantee. In this context, this article describes a new end-to-end mechanism for continuous transfer based on TCP-Friendly Rate Control (TFRC). The proposed approach modifies TFRC to take into account the QoS negotiated. This mechanism, named gTFRC, is able to reach the minimum throughput guarantee whatever the flow’s RTT and target rate. Simulation measurements and implementation over a real QoS testbed demonstrate the efficiency of this mechanism either in over-provisioned or exactly-provisioned network. In addition, we show that the gTFRC mechanism can be used in the same DiffServ/AF class with TCP or TFRC flows

Performance enhancement of large scale networks with heterogeneous traffic.

Finally, these findings are applied towards improving the performance of the Differentiated Services architecture by developing a new Refined Assured Forwarding framework where heterogeneous traffic flows share the same aggregate class. The new framework requires minimal modification to the existing Diffserv routers. The efficiency of the new architecture in enhancing the performance of Diffserv is demonstrated by simulation results under different traffic scenarios.This dissertation builds on the notion that segregating traffic with disparate characteristics into separate channels generally results in a better performance. Through a quantitative analysis, it precisely defines the number of classes and the allocation of traffic into these classes that will lead to optimal performance from a latency standpoint. Additionally, it weakens the most generally used assumption of exponential or geometric distribution of traffic service time in the integration versus segregation studies to date by including self-similarity in network traffic.The dissertation also develops a pricing model based on resource usage in a system with segregated channels. Based on analytical results, this dissertation proposes a scheme whereby a service provider can develop compensatory and fair prices for customers with varying QoS requirements under a wide variety of ambient traffic scenarios.This dissertation provides novel techniques for improving the Quality of Service by enhancing the performance of queue management in large scale packet switched networks with a high volume of traffic. Networks combine traffic from multiple sources which have disparate characteristics. Multiplexing such heterogeneous traffic usually results in adverse effects on the overall performance of the network

Performance evaluation of profiler mechanisms for the internet assured service

As Internet is rapidly growing and receiving traffic from multimedia applications that are sensitive to available bandwidth and delay experienced in the network, there is a strong need for quality of service (QoS) support. The Integrated and Differentiated Service models are two approaches for adding QoS to Internet. The Assured Service is an end-to-end service based on the Differentiated Service architecture. In this paper, we study and compare the performance of three profiler mechanisms to provide the guaranties of an Internet Assured Service. Two of them, TSW and Leaky Bucket are the most commonly used, and the third is a new Counter Based profiler, which is proposed in this paper. The study is done by simulation employing TCP RENO sources.This work was partly supported by the Spanish Research Council under grant TIC2000-1734-C03-03

Network level performance of differentiated services (diffserv) networks

The Differentiated Services (DiffServ) architecture is a promising means of providing Quality of Service (QoS) in Internet. In DiffServ networks, three service classes, or Per-hop Behaviors (PHBs), have been defined: Expedited Forwarding (EF), Assured Forwarding (AF) and Best Effort (BE). In this dissertation, the performance of DiffServ networks at the network level, such as end-to-end QoS, network stability, and fairness of bandwidth allocation over the entire network have been extensively investigated. It has been shown in literature that the end-to-end delay of EF traffic can go to infinity even in an over-provisioned network. In this dissertation, a simple scalable aggregate scheduling scheme, called Youngest Serve First (YSF) algorithm is proposed. YSF is not only able to guarantee finite end-to-end delay, but also to keep a low scheduling complexity. With respect to the Best Effort traffic, Random Exponential Marking (REM), an existing AQM scheme is studied under a new continuous time model, and its local stable condition is presented. Next, a novel virtual queue and rate based AQM scheme (VQR) is proposed, and its local stability condition has been presented. Then, a new AQM framework, Edge-based AQM (EAQM) is proposed. EAQM is easier to implement, and it achieves similar or better performance than traditional AQM schemes. With respect to the Assured Forwarding, a network-assist packet marking (NPM) scheme has been proposed. It has been demonstrated that NPM can fairly distribute bandwidth among AF aggregates based on their Committed Information Rates (CIRs) in both single and multiple bottleneck link networks