QoS and multipoint support for multimedia applications over the ATMABR service

Multimedia applications with stringent delay requirements are usually supported by the constant bit rate (CBR) or real-time variable bit rate (rt-VBR) service categories of ATM. This article shows that the available bit rate (ABR) service, which was originally designed for data, can also support multimedia applications under certain circumstances. Issues related to the design of proper ABR traffic management algorithms for such support are presented     

Probabilistic delay budget assignment for synthesis of soft real-time applications

Unlike their hard real-time counterparts, soft real-time applications are only expected to guarantee their "expected delay" over input data space. This paradigm shift calls for customized statistical design techniques to replace the conventional pessimistic worst case analysis methodologies. We present a novel statistical time-budgeting algorithm to translate the application expected delay constraint into its components' local delay constraints. We utilize the mathematical properties of the problem to quickly calculate the system expected delay and incrementally estimate the component utility variation with its timing relaxation. Our algorithm determines the optimal maximum weighted timing relaxation of an application under expected delay constraint. Experimental results on core-based synthesis of several multimedia applications targeting field-programmable gate arrays show that our technique always improves the design area. Furthermore, it consistently outperforms optimal time budgeting under hard real-time constraint, which is the best existing competitor. Design area improvements were up to 26% and averaged about 17% on several MediaBench applications.     

QoS for applications

Neither the ISDN nor the subsequent broadband-ISDN (B-ISDN) delivered on the promise of being a network for all services. Now that mantle has been passed to IP networks born out of computer-to-computer communications. But their benefits, such as great flexibility of bit rate and resilience, are accompanied by other characteristics which are alien not only to traditional telephony but also to many of the multimedia services which telcos are now seeking to offer their customers. As part of the adaptation of IP networks to carry the widest range of services and applications, the concept of quality of service has been invoked. This paper looks at the performance characteristics which various applications require. It also describes techniques they can incorporate to reach a satisfactory overall result in combination with the network.     

互联网的服务质量控制和管理

文章介绍了互联网的业务管理模式、服务质量控制和管理体系结构,并对服务质量控制和管理的关键技术,如集成服务、区分服务、服务质量计费、服务质量测量等,进行了分析。     

QoS control by means of COPS to support SIP-based applications

The COPS protocol has been designed to enable communication on the interface between the policy decision administrator and the policy enforcement devices in a policy-based networking environment. It can be recognized that on the same interface there is the need to transfer information related to the request of resource by QoS clients and for the allocation of resources by resource allocation servers (e.g., bandwidth broker) in a DiffServ network. Hence, it is sensible to add this resource allocation functionality in the COPS framework. In particular, there are at least two cases where it is sensible to use COPS. The first case is on the interface between an edge node and a resource control node for handling resource allocation in a network provider domain. The second case is on the interface between a customer (client of a QoS enabled network) and the network provider: here COPS can be used as a protocol to signal dynamic admission control requests. In this article we present the definition of a new COPS client type to support the above-mentioned functionality, then describe an application scenario where SIP-based IP telephony applications can use Diffserv-based QoS networks. Simple backward-compatible enhancements to SIP are needed to interact with COPS/Diffserv QoS. A testbed implementation of the proposed solutions is finally described     

QoS differentiation and Internet neutrality

Internet neutrality is a debate controversial to a tiered, application-aware Internet. Bandwidth and end-to-end delay of connections across the Internet may vary by several orders of magnitude, therefore unequal data handling per node is commonly applied to achieve differentiated QoS. This practice contradicts Internet neutrality if it is not restricted to pure application awareness. A strict separation of network operation from service provisioning would perfectly fit to achieve Internet neutrality. But this may lack economic business models for network operators, especially in a flat-rate world. This paper provides a review on differentiated quality requirements, discusses the different viewpoints of network and content providers, and closes with a discussion on potential differentiated charging intended to achieve a fair, autonomous, and cost-related revenue distribution among stakeholders.     

QoS enabled voice support in the next generation Internet: issues,existing approaches and challenges

The Internet is under rapid growth and continuous evolution in order to accommodate an increasingly large number of applications with diverse service requirements. In particular, Internet telephony, or voice over IP is one of the most promising services currently being deployed. Besides the potentially significant cost reduction, Internet telephony can offer many new features and easier integration with widely adopted Web-based services. Despite these advantages, there still exist a number of barriers to the widespread deployment of Internet telephony. The most prominent one, however, is how to ensure the QoS needed for voice conversation. The purpose of this article is to survey the state-of-the-art technologies in enabling the QoS support for voice communications in the next-generation Internet. In this article, we first review the existing technologies in supporting voice over IP networks, including the basic mechanisms in the IETF Internet telephony architecture and ITU-T H.323-related Recommendations. We then discuss the IETF QoS framework, specifically the Intserv and Diffserv framework. Finally, we present two leading companies' (Cisco and Lucent) solutions to offering IP telephony services as examples to illustrate how real systems are implemented     

Internet QoS路由与业务工程

本文阐述了传统ＩＰ路由协议存在的问题,回顾了ＱｏＳ路由技术在电路交换网络,ＡＴＭ网络和ＩＰ网络中的演进与应用。论述了业务工程在Ｉｎｔｅｒｎｅｔ中的基本功能,以及与之相关的约束路由和ＭＰＬＳ技术。     

Internet QoS: Pieces of the puzzle

One of the biggest challenges faced when dealing with QoS over the Internet is how to deliver QoS over an unregulated, connectionless network that was designed, deployed, operated, managed, and commercialized without any QoS perspectives. This article gives a concise but comprehensive overview of the Internet QoS puzzle. We aim not only at identifying all the pieces of the puzzle, but also at discovering how to join them together. These include terminology, definitions and standards, architectures, traffic engineering, regulation, accounting, pricing, and marketing. We also explain throughout the article how network providers should envision their service offerings in the context of an SLA and QoS-centric Internet.     

Statistical multiplexing and QoS provisioning for real-time trafficon wireless downlinks

Quality of service (QoS) provisioning in wireless networks involves accounting for the statistical fluctuations in the wireless channel quality, in addition to the traffic variability of interest in a purely wireline setting. We consider providing QoS to packetized, delay-constrained (real-time) applications over a Rayleigh-faded wireless downlink. Since the wireless medium is prone to high error rates with typically correlated errors, it is essential to use some kind of link-layer error-recovery mechanism to provide the desired level of reliability. We call this procedure of converting a link with frequent and correlated errors into a near-lossless packet pipe “link shaping.” The link-shaping scheme considered in this paper exploits the natural interleaving provided by packet-by-packet transmissions to different mobiles to break up the error correlations due to Rayleigh fading and employs forward error correction (FEC) coding on the interleaved data. In addition to considering static (peak-rate) bandwidth sharing as in conventional wireless downlinks, we propose mechanisms for statistical multiplexing of traffic, which lead to substantial capacity gains. For example, for 13 kb/s voice sources over a 1-Mb/s link, we obtain a two-fold capacity gain over static (peak-rate) bandwidth allocation     

QoS support for integrated services over CATV

Cable TV has emerged as a promising access network infrastructure for the delivery of voice, video, and high-speed data traffic. A central issue in the design of protocols for CATV networks is to support different levels of QoS for diverse user applications. While CATV service providers and equipment have standardized, in the so-called MCNS protocol, the basic network architecture and interfaces, issues in the MAC layer for QoS support are likely to be left for differentiation in vendor products. This article first presents an overview of the basic CATV network architectural assumptions and the set of QoS requirements for supporting integrated services over CATV. It then discusses a MAC layer scheduling protocol that can efficiently multiplex constant bit rate traffic, such as voice over IP with guaranteed delay bound, and best-effort traffic, such as data services with minimum bit rate guarantee, while achieving fairness on any excess available bandwidth. The performance of this algorithm is illustrated by simulation results using Opnet. We also discuss a dynamic polling mechanism that enhances the link utilization while preserving delay bounds for latency-critical traffic     

QoS for multimedia applications in satellite systems

We present a policy for handling multimedia traffic over satellite air interfaces. It extends the advantages of ATM to satellite by the statistical multiplexing of variable-rate traffic sources. Effectiveness is assessed within a multimedia satellite platform called EuroSkyWay, based on Ka-band payload and on-board processing     

End-to-End QoS for Video Delivery Over Wireless Internet

Providing end-to-end quality of service (QoS) support is essential for video delivery over the next-generation wireless Internet. We address several key elements in the end-to-end QoS support, including scalable video representation, network-aware end system, and network QoS provisioning. There are generally two approaches in QoS support: the network-centric and the end-system centric solutions. The fundamental problem in a network-centric solution is how to map QoS criterion at different layers respectively, and optimize total quality across these layers. We first present the general framework of a cross-layer network-centric solution, and then describe the recent advances in network modeling, QoS mapping, and QoS adaptation. The key targets in end-system centric approach are network adaptation and media adaptation. We present a general framework of the end-system centric solution and investigate the recent developments. Specifically, for network adaptation, we review the available bandwidth estimation and efficient video transport protocol; for media adaptation , we describe the advances in error control, power control, and corresponding bit allocation. Finally, we highlight several advanced research directions.     

提高互联网QoS的设想

要提高互联网的服务质量，可以通过技术手段，例如可以改变IP的传输协议、在传输中加入流量控制等，或者增加带宽，但是技术手段增加了互联网的复杂性，而且全面改换传输协议等技术手段需要很大的成本，在经济上不一定可行；而用增加带宽来提高QoS的方法，即使不考虑成本因素，带宽也不可能无限制的提高。然而，在现有的技术条件和可利用的带宽下，由于不同的网络具有不同的流量特征，因此可以通过网络的融合来汇集流量，以达到提高互联网的QoS的目的。通过流量的汇集提高QoS用增加带宽的方法来解决网络拥挤问题虽然可以提高互联网的QoS…     

A practical approach for providing QoS in the Internet backbone

This article describes a practical approach for providing quality of service in the Internet backbone. The approach considers both technical and economic factors. We first present network service provider (NSP) billing models and how NSPs provision their networks. We then analyze causes of QoS-related problems, and describe a practical approach for providing QoS. This approach makes use of good network design, differentiated services, traffic protection, traffic engineering, and traffic management techniques. The relative importance of these techniques is pointed out. Although this approach largely focuses on issues within a single NSP domain, if multiple NSPs adopt such an approach (or a similar approach), interdomain QoS can also be provided.     

QoS of Internet Access with GPRS

In this paper we examine the effects of Internet traffic on the Quality of Service (QoS) in GPRS wireless networks. With a stochastic source traffic model describing the user behavior, we will derive subjective and objective Quality of Service measures in terms of WWW downloading time and the transmission bandwidths on TCP and TBF level. Comparing the obtained values with wireline network modems and ISDN yields a slowdown factor which indicates the subjective degradation that the wireless user experiences.     

Filters: QoS support mechanisms for multipeer communications

The nature of distributed multimedia applications is such that they require multipeer communication support mechanisms. The multimedia traffic needs to be delivered to end-systems, networks, and end-users in a form that they can handle while satisfying the constraints imposed by the multimedia application. Quality-of-service (QoS) mechanisms that can ensure full quality media playout at high-performance workstations, while at the same time providing appropriately filtered lower quality media for playout at other end-systems, are required. Existing multicast support mechanisms are deficient for this purpose, in a heterogeneous environment, because they work on a common denominator premise where the quality delivered depends on the least capable link or node involved in the multicast session. This paper begins by discussing video compression; it proposes and analyzes the use of filtering mechanisms as means of supporting disparate receiver capabilities and QoS requirements. The paper describes the implementation of a number of filtering mechanisms and highlights the communications architecture within which these mechanisms are built. This architecture constitutes a specific network topology and a new protocol family developed within a UNIX-like operating system     

Internet traffic, QoS, and pricing

Based on an analysis of the statistical nature of IP traffic and the way this impacts the performance of voice, video, and data services, we question the appropriateness of commonly proposed quality-of-service mechanisms. This paper presents the main points of this analysis. We also discuss pricing issues and argue that many proposed schemes are overly concerned with congestion control to the detriment of the primary pricing function of return on investment. Finally, we propose an alternative flow-aware networking architecture based on a novel router design called cross-protect. In this architecture, performance requirements are satisfied without explicit service differentiation, creating a particularly simple platform for the converged network.     

Internet protocol support for telephony

In this paper, we consider the evolution of telephone networks from time-division multiplexing circuit switching to packet switching and, in particular, to packet switching-based on Internet Protocol (IP-supported telephony). We analyze IP-supported telephony design solutions by proposing a layered reference model in which each layer is associated to a subset of the functions that support telephony. We use the reference model to establish a terminology and a framework for the comparison of the design solutions. We group the design solutions in scenarios and compare them in terms of the reference model proposed. We then focus on IP telephony, in which IP is used in telephone company networks, and on Internet telephony, in which the Internet is used to support telephony. We show that they both can be seen as implementations of the same architecture, which consists of a set of components, associated to functions, and of the interactions among these components. We then consider the issue of voice-data integration and analyze the variety of design solutions that can be adopted to integrate voice and data.     

Algebra and algorithms for QoS path computation and hop-by-hop routing in the Internet

Prompted by the advent of quality-of-service routing in the Internet, we investigate the properties that path weight functions must have so that hop-by-hop routing is possible and optimal paths can be computed with a generalization of E.W. Dijkstra's algorithm (see Numer. Math., vol.1, p.269-71, 1959). We define an algebra of weights which contains a binary operation, for the composition of link weights into path weights, and an order relation. Isotonicity is the key property of the algebra. It states that the order relation between the weights of any two paths is preserved if both of them are either prefixed or appended by a common, third, path. We show that isotonicity is both necessary and sufficient for a generalized Dijkstra's algorithm to yield optimal paths. Likewise, isotonicity is also both necessary and sufficient for hop-by-hop routing. However, without strict isotonicity, hop-by-hop routing based on optimal paths may produce routing loops. They are prevented if every node computes what we call lexicographic-optimal paths. These paths can be computed with an enhanced Dijkstra's algorithm that has the same complexity as the standard one. Our findings are extended to multipath routing as well. As special cases of the general approach, we conclude that shortest-widest paths can neither be computed with a generalized Dijkstra's algorithm nor can packets be routed hop-by-hop over those paths. In addition, loop-free hop-by-hop routing over widest and widest-shortest paths requires each node to compute lexicographic-optimal paths, in general.