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

Abstract

International audienceSince the proposition of quality of service (QoS) architectures by the Internet Engineering Task Force (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 present 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 that is controllable and predictable. In this paper, we build a classification of all the propositions made during the past few years and compare them. As a result, we will see that these conditioning schemes can be separated into three sets of action levels 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 for the DiffServ/AF service

Improving RFC5865 Core Network Scheduling with a Burst Limiting Shaper

“…Basically, the BLS enforces the rate guarantee offered by the AF class whatever the traffic in the EF class. In particular, we have shown that the new service offered to the AF class is defined by the relation (7). Compared to the WRR, the AF output rate is less dependent on the EF traffic, which improves the quantification of the reserved capacity of AF, without impacting EF traffic.…”

“…The second service is called assured service and is built on top of the AF class where elastic traffic such as TCP traffic, is intended to achieve a minimum level of throughput [7]. Usually, the minimum assured throughput is given according to a negotiated profile with the client.…”

Comparative Analysis of Variants of Token Bucket Traffic Meter Algorithms for QoS Router using UDP as Traffic Agent

“…DiffServ is based on a simple model which attempts to move complexity of the network to the edge router and keep the functionality of the core network as simple as possible (Blake et al, 1998). Core devices perform only the forwarding operation (Lochin & Anelli, 2009). The admission control mechanism or conditioner is introduced at the boundary of the DiffServ network or domain to check whether a service request is to be granted or rejected (Georgoulas, 2007).…”

Analytical Model of TCP Relentless Congestion Control

“…RCC could perform efficiently over network architectures that enable Quality of Service (QoS) guarantees such as [3]. Indeed, a decade of research in QoS has shown that the standard TCP reaction to congestion events (which is to halve its congestion window) can be counterproductive over these QoS networks [4], [6]. The principle to decrease the current congestion window by the number of lost segments can also be implemented inside current congestion controls such as CUBIC, Newreno or Compound.…”