An end-to-end QoS framework with on-demand bandwidth reconfiguration

This paper proposes a new QoS framework, called the On-Demand QoS Path framework (ODP). It provides end-to-end QoS guarantees to individual flows with minimal overhead, while keeping the scalability characteristic of DiffServ. ODP exercises per-flow admission control and end-to-end bandwidth reservation at the edge of the network and only differentiates service types in the core of the network. In addition, to adapt to dynamically changing traffic load, ODP monitors the bandwidth utilization of the network and performs dynamic bandwidth reconfiguration in the network core based on the monitored bandwidth utilization. Through extensive simulations, the performance of ODP is investigated and compared with that of IntServ and DiffServ frameworks. The simulation results clearly showed that ODP provides end-to-end QoS guarantees to individual flows, which DiffServ can not provide, with much less overhead than IntServ.     

Edge-limited scalable QoS flow set-up

Although the Differentiated Services architecture supports scalable packet forwarding based on aggregate flows, the detailed procedure of Quality of Service (QoS) flow set-up within this architecture has not been well established. In this paper we explore the possibility of a scalable QoS flow set-up using a sink-tree paradigm. The paradigm initially constructs a sink tree at each egress edge router using network topology and bandwidth information provided by a QoS extended version of Open Shortest Path First (OSPF), which is a widely used link-state routing protocol. Our sink-tree paradigm dynamically reallocates network bandwidths online according to traffic demands. As a consequence, our paradigm easily supports QoS routing, resource allocation, and admission control at ingress edge routers without consulting core routers in a way that the QoS flow set-up time and overhead are minimized. Simulation results are very encouraging in that the proposed methodology requires significantly less communication overhead in setting up QoS flows compared to the traditional per-flow signaling-based methodology while still maintaining high resource utilization.     

A core stateless bandwidth broker architecture for scalable support of guaranteed services

We present a novel bandwidth broker architecture for scalable support of guaranteed services that decouples the QoS control plane from the packet forwarding plane. More specifically, under this architecture, core routers do not maintain any QoS reservation states, whether per-flow or aggregate. Instead, the QoS reservation states are stored at and managed by a bandwidth broker. There are several advantages of such a bandwidth broker architecture. Among others, it avoids the problem of inconsistent QoS states faced by the conventional hop-by-hop, distributed admission control approach. Furthermore, it allows us to design efficient admission control algorithms without incurring any overhead at core routers. The proposed bandwidth broker architecture is designed based on a core stateless virtual time reference system developed recently. This virtual time reference system provides a unifying framework to characterize, in terms of their abilities to support delay guarantees, both the per-hop behaviors of core routers and the end-to-end properties of their concatenation. We focus on the design of efficient admission control algorithms under the proposed bandwidth broker architecture. We consider both per-flow end-to-end guaranteed delay services and class-based guaranteed delay services with flow aggregation. Using our bandwidth broker architecture, we demonstrate how admission control can be done on a per domain basis instead of on a "hop-by-hop" basis. Such an approach may significantly reduce the complexity of the admission control algorithms. In designing class-based admission control algorithms, we investigate the problem of dynamic flow aggregation in providing guaranteed delay services and devise a new apparatus to effectively circumvent this problem. We conduct detailed analyses to provide theoretical underpinning for our schemes as well as to establish their correctness. Simulations are also performed to demonstrate the efficacy of our schemes.     

区分服务网络基于测量的接纳控制方案的设计与应用

提出了一种分布式可扩展的接纳控制方案，其目的是为区分服务网络提供端到端服务质量（Quality of Services,QoS)保证，该方案主要由以下部分构成：（1）连接接纳控制协议，主要负责主机和网络节点以及网络节点和带宽代理之间的信息传送，实现对连接请求的串行操作；（2）位于网络核心节点的可用带宽估计算法；（3）位于网络边缘节点的接纳控制算法；给出了该方案在视频传输方面的应用实例；利用多种网络拓扑结构和QoS指标评价该方案的性能，实验结果表明该方案能准确地控制可接纳区域和提高网络资源的利用率。     

Hybrid optimization for QoS control in IP Virtual Private Networks

A multiservice IP Virtual Private Network is considered, where Quality of Service is maintained by a DiffServ paradigm, in a domain that is supervised by a Bandwidth Broker (BB). The traffic in the network belongs to three basic categories: Expedited Forwarding (EF), Assured Forwarding (AF) and Best Effort (BE). Consistently with the DiffServ environment, the Service Provider’s Core Routers (CRs) only treat aggregate flows; on the other hand, the user’s Edge Routers (ERs) keep per-flow information and convey it to the BB. The latter knows at each time instant the number (and the bandwidth requirements) of flows in progress within the domain for both EF and AF traffic categories. A global strategy for admission control, bandwidth allocation and routing within the domain is introduced and discussed in the paper. The aim is to minimize blocking of the “guaranteed” flows (EF and AF), while at the same time providing some resources also to BE traffic. In order to apply such control actions on-line, a computational structure is sought, which allows a relatively fast implementation of the overall strategy. In particular, a mix of analytical and simulation tools is applied jointly, by alternating “local” decisions, based on analytical models, with flow-level simulation that determine the effect of the decisions on the whole system and provide feedback information. The convergence of the scheme (under a fixed traffic pattern) is investigated and the results of its application under different traffic loads are studied by simulation on three test networks.     

Managing QoS for Multimedia Applications in the Differentiated Services Environment

The overall quality of network connections has a significant impact on the performance of networked applications. As a result, Quality-of-Service (QoS) management for networked multimedia applications over IP is a significant and immediate challenge. While differentiated services (DiffServ) provide a sense of resource allocation and QoS, they do not guarantee QoS. This paper presents the design, implementation and evaluation of a content-aware bandwidth broker (CABB) that manages QoS for multimedia applications in a DiffServ environment. CABB allocates network resources to multimedia flows based on client requirements, the adaptability of the application, and its tolerance to network level parameters such as bandwidth, delay, and latency. It has been implemented and evaluated using the NS-2 simulator toolkit. Evaluations show that CABB improves network resource allocations and increases overall throughput. Furthermore multimedia application flows are better managed and controlled, improving perceived QoS and avoiding possible congestion at core routers.     

A new fast friendly window-based congestion control for real-time streaming media transmission

1 Introduction In the current Internet, not all applications use TCP and they do not follow the same concept of fairly sharing the available bandwidth. The rapid growing of real-time streaming media applications will bring much UDP traffic without integrating TCP compatible congestion control mechanism into Internet. It threats the quality of service (QoS) of real-time applications and the stability of the current Internet. For this reason, it is desirable to define appropriate rate rule…     

保证型QoS服务CSBP控制技术研究

提出了保证型QoS服务的CSBP控制技术，它能够保证每个数据流的预约速率，数据流分组经过网络后有确切的时延上界，核心路由器不需要维持有关每个数据流的状态信息。CSBP控制技术融合了集成服务和区分服务这两大类解决方案的优点，提供了具有高水平的服务质量保证，兼顾了网络资源利用率和扩展性。     

一种基于MPLS保证每流服务质量的方法*

分析了当前网络中保证服务质量的机制,针对目前MPLS本身的服务质量只支持区分服务的现状,提出将动态分组状态模型用于MPLS的方法,通过将状态信息封装在MPLS分组的二层标签中,使核心网络在不需保存每流状态的情况下提供基于每流的服务质量。详细阐述了该方案的总体结构、数据平面和控制平面等,并通过在NS中模拟分析对该方案进行了验证。     

基于差分服务的贪婪流问题解决算法

贪婪流问题是网络拥塞控制范畴的问题，泛指不遵从标准TCP拥塞控制机制的流。贪婪流给网络带来不公平性。提出了一种新的甄别算法，通过对目标流发送窗口随分组丢弃变化关系的分析，对不合规范的流进行检测。算法采用定长列表结构，具有实现简单、扩展性强的特点，提出了一种基于差分服务模式的体系结构，对传统Internet服务哲学进行了扩展，从根本上支持新型流式应用，实现了端到端的流量监管功能。     

An Effective Feedback Control Mechanism for DiffServ Architecture

As a scalable QoS(Quality of Service)architcture,DiffServ(Differentiated Service)mainly consists of two components:taffic conditioning at the edge of the DiffServ domain and simple packet forwarding inside the DiffServ domain.DiffServ has many advantages such as flexbility,scalability and simplicity.But when providing, AF (Assured Forwarding) services ,DiffServ has some problems such as unfairness among aggregated flows or among micro-flows belonging to an aggregated flow.In this paper,a feedback mechanism for AF aggregated flows is proposed to solve this problem.Simulation results show that this mechanism does improve the performance of DiffServ.Firt,it can improve the fairness among aggregated flows and make DiffServ more friendly toward TCP (Transmision Control Protocol)flows.Second,it can decrease the buffer requirements at the congested router and thus obtain lower delay and packet loss rate.Third,it also keeps almost the same link utility as in normal DiffServ,Einally,it is simple and easy to be implemented.     

Spanning tree elevation protocol: Enhancing metro Ethernet performance and QoS

The economics and familiarity of Ethernet technology is motivating the vision of wide-scale adoption of Metro Ethernet Networks (MEN). Despite the progress made by the community on additional Ethernet standardization and commercialization of the first generation of MEN, the fundamental technology does not meet the expectations that carriers have traditionally held in terms of network resiliency, load management, and Quality of Service (QoS). We propose a new concept of Spanning Tree Elevation Protocol (STEP) that increases MEN performance while supporting QoS including traffic policing and service differentiation. STEP manages multiple Spanning Trees as a means to control the traffic flow rates and to differentiate classes of traffic. Whenever a service level agreement is compromised, STEP redirects frames of affected flows to the next spanning tree in sequence utilizing the alternate paths. As a result, the capacity in terms of network throughput is greatly enhanced while almost avoiding any reconvergence time in the case of failures. The gain ranges from 1.7% to 7.3% of the total traffic in the face of failure; while load balancing increases an additional 12.8% to 37% of the total throughput. At the same time, STEP maintains the required bandwidth for high priority traffic class during the failure scenarios and the high congestion scenarios.     

A measurement-based approach for dynamic QoS adaptation in DiffServ networks

This paper presents a practical approach to managing multimedia traffic in DiffServ network, using network monitoring feedback and control. We exploit the flexibility of multimedia traffic and process network level parameters to adapt the traffic according to the current state of the network. The latter is determined based on reports sent by bandwidth monitors installed on each node of a DiffServ Domain. The bandwidth monitors interact with a policy server which, depending on the network state, decides the policy(ies) that should be enforced by the DiffServ network. The implementation of the selected policies typically leads to accepting, remarking, or dropping the multimedia traffic entering the network. Multimedia streams may be assigned different levels of QoS, as interpreted by the marker at the DiffServ edge router and marked according to network state. To achieve such dynamic QoS adaptation for multimedia applications, we have implemented and evaluated a policy-based management system. Performance evaluation shows that multimedia applications adapt better to network conditions using our approach.     

基于加权公平的DiffServ服务质量模型的研究

针对在核心节点实现的主动队列管理（AQM）以预见和防止拥塞，并且能够较公平地分配带宽，介绍了一种加权公平的主动队列管理算法，提出一个基于公平性的拥塞控制机制，即将这种AQM算法部署在可提供QoS服务的区分服务模型中，最后介绍仿真过程并分析该模型的性能．     

DiffServ和MPLS相结合的流量工程机制

MPLSTE对传统的流量工程进行扩展,实现端到端的QoS保证,但是以流量中继为服务粒度。对流量缺乏区分服务的能力。DifIServ模型提供了区分服务,但是缺乏端到端的QoS有效路由策略。通过将MPLSTE的有效路由策略和DiffServ的区分服务相结合,引入区分服务感知的流量工程．运用带宽约束模型,在网络中实现端到端区分服务的QoS保证。     

Conformance analysis in networks with service level agreements

To achieve some level of Quality of Service (QoS) assurance, a network usually has Service Level Agreements (SLAs) with its users and neighboring domains, which describe the QoS level that the service provider is committed to provide, and the specification of traffic that users or neighboring domains are allowed to send. An interesting and important question arises as to whether a flow is still conformant to its original traffic specification after crossing the network since it may interact with other flows within the network. In this paper, we study analytically the extent to which a flow and an aggregate of flows become non-conformant through an analysis of the stochastic burstiness increase of flows after crossing a per-flow scheduling network and an aggregate scheduling network . The stochastic behavior of a server in aggregate scheduling networks is also studied to determine the conformance deterioration of individual flows, which provides the theoretical conformance deterioration bound and provides useful results for conformance analysis in an aggregate scheduling network with general topology. Our theoretical results are verified by extensive simulations.     

Fairness of traffic controls for inelastic flows in the Internet

In best-effort networks, fairness has been used as a criterion to guide the design of traffic controls. The notion of fairness has evolved over time, from simple equality to a form of equality modulated by the user’s need (e.g. max–min and proportional fairness). However, fairness has always been defined on a per-user basis for a deterministic workload. In this paper, we argue that we must redefine the notion of fairness when we study traffic controls for the co-existence of elastic and inelastic traffics. Our results indicate that subjecting inelastic flows to fairness congestion control on a per-flow basis does not necessarily maximize the network’s utility. Instead, inelastic flows may follow their own form of traffic control, such as admission control (without congestion control). At the aggregate level, our results indicate that it still makes sense to maintain a balance between elastic and inelastic traffic. In order to support our arguments, we develop a methodology for comparing different traffic controls for given utility functions and different workloads, both deterministic and stochastic.     

Providing service differentiation in pure IP-based networks

The lack of an effective cooperation between the data, control and management plane of QoS routing solutions presented so far, prevents the implementation of service differentiation in the context of pure IP-based networks. Most of paths calculation proposals performed by the control plane are unaware of service characteristics of each flow. Scalable data plane QoS proposals ignore the issue about selecting the best paths to route the traffic. Proposed management plane schemes do not perform the network state maintenance and service level monitoring. Multi-service routing is a flow-based forwarding protocol that implements the service differentiation in pure IP-based networks, using a straight cooperation between data, control and management plane. This cooperation is accomplished by a data plane supporting the DiffServ model and performs route selection based on flows service class, which is exploited by the management plane to carry out the network state maintenance, and performance monitoring by using the RTCP protocol, to provide service metrics to control plane for route calculation. Simulation experiments show better performance results achieved by Multi-service routing compared to those obtained by traditional link state protocol with the DiffServ model and QoS routing in heavy loaded network scenarios of mixed traffic having different service requirements.     

数字家庭网关上网络QoS算法的研究

家庭网络中数字家电种类繁多,而且随着多媒体设备越来越多、功能越来越强,对服务质量（QoS）管理提出了更高的要求。现有的QoS架构中存在很多流量管理方面的问题,如低优先级流量饿死、拥塞、流量优先级指定等。通过分析比较各种QoS架构的优缺点,提出一种数字家庭网关上的网络QoS算法。采用带宽控制、准入控制、优先级验证等机制,从网络流量管理角度解决QoS问题,并通过模拟分析证实了该QoS算法的有效性。