IP QoS研究的现状与发展趋势

目前，随着电信业务的引入，IP网的服务质量（IP QoS）成为下一代Internet的重要研究课题。由于IP协议的无连接特性和IP网络松散的控制管理方式，使这项研究面临很大的挑战。IPQoS的研究范围十分广泛，不仅包含路由和业务流量控制，还涉及到网络管理、计费和网络测量。当前主要的IP QoS技术集成服务（IntServ）集成服务的基本思想是在传送数据之前，根据业务的QoS需求进行网络资源预留，从而为该数据流提供端到端的QoS保证。资源预留协议（RSVP）是集成服务的核心。这是一种信令协议，用来通知网络节点预留资源。如果资源预留失…     

基于ATM的实时多媒体技术

当前,传统的电信运营商、Internet业务提供商都面临着如何将他们的语音和数据网络合成单一的分组交换网络的问题。对于ISP来说,这意味着新的财源,而对电信公司来说则代表着设备、运营、管理等方面巨大的节约。语音和数据的融合在很大程度上依赖于分组语音能否保证质量和提供PSTN所支持的各种业务。分组交换网络上语音传输的QoSATM技术在Internet骨干网中的广泛应用表明,ATM支持QoS的特性能够保证VoIP业务的实时有效传输,可以通过ATM的CBR或VBR业务在ATM网络上发送经过打包的PSTN语音。ATM论坛的CES（电路竞争业务）…     

UMTS中的QoS

3G系统中,骨干和核心网全部采用IP或ATM标准,又有多业务种类的情况,再加上有庞大的前期开销和更高的传输速度,都要求必须提供强大的QoS管理,使业务QoS管理和系统资源QoS的管理都达到较高要求。UMTS与Internet QoS映射目前研究的一个热点是3G中的UMTS（Universal Mobile Telecom-munication System）与Internet QoS的映射,但还没有完全的结论。因为3G系统预计将来的传输都是基于IP/ATM的,这样充分利用了有线系统的优势,并能实现顺利地平滑过渡,同时提供一定的QoS。Internet只提供尽力而为的业务标准,没有时间限制…     

IP网络的服务质量讲座 第3讲 InterServ模型与DiffServ模型

1前言目前的因特网只提供了一种非常简单的业务：尽力而为（besteffort）的点到点服务。随着业务的发展，尤其是支持需要严格服务质量（QoS）保证的实时业务的需要，必须改变因特网原来的体系结构，增加对QoS、多播（multicast）等业务的支持。本文介绍IETF标准化的IP网上的两种QoS业务模型：InterServ（IntegratedService）模型和DiffServ（DifferentiatedService）模型。最早出现的InterServ模型使用了面向连接的方式提供QoS保证，使用资源预留协议（RSVP）作为请求带宽和其他网络资源的信令协议（RFC2205、RFC2210）。Diff…     

解决QoS问题的一个新思路

目前，解决Internet服务质量（QoS）问题的方法主要有：Intserv、RSVP、Diffserv、MPLS等。它们的共同之处在于：都是建立在有限带宽的基础上。本文结合当前波分复用（WDM）技术的发展，提出了一种新的基于无限带宽理论的Internet QoS解决办法，并利用排队论简要分析其原理。     

ATM上的实时多媒体业务

随着Internet的迅速发展,人们不仅要求在分组网络上传输数据,还要求分组网络能够传输实时多媒体业务,即将语音等实时业务和数据传输融合到一个单一的分组网络中。目前,在语音通过分组网络传输方面,出现了VoATM、VoIP。VoATM在利用ATM技术服务质量（QoS）保障的同时,为语音在ATM网络上的传输提供了特殊网关,将PSTN语音业务进行抽样编码,使其能够在ATM上传输,这使VoATM有可能在长途电话服务上获得成功应用。而VoIP因为缺乏普遍认可或广泛应用的信令标准和资源预留,而面临着更大的挑战。然而,对于能够在其内部网内提…     

IP与ATM结合技术发展的必然趋势——MPLS

多协议标记交换（MPLS）是实现宽带Internet的一种IP与ATM相结合的新兴网络技术。本文讲述了MPLS的发展背景,并对MPLS的网络构成、基本术语、工作过程、技术特点进行了简明的阐述,并通过将其与IntServ、Diff-Serv比较,描述了MPLS对于QoS的支持,最后提出了MPLS技术未来发展的方向。     

局域网仿真技术

采用ATM技术互连传统局域网，其中最重要的原因就是解决带宽问题。但随着新应用的不断出现，需要引入其他ATM业务特性，比如QoS。ATM论坛于1997年7月推出的局域网仿真（LANE）2．O规范，可以满足这方面的需求。LANEZO规范的一个重要部分--LANE网络间接口（LNN）解决了服务器之间的通信接D问题，从而使各份问题得到解决。然而，LANE仍留有一些难题没有解决，如，在某些情况下，它与其他业务间的中继没有定义。ILANE概述为了理解LANEZO的优势，有必要回顾一下LANE推出之前ATM的状况。设想一个典型的网络结构，它是由以太…     

ATM网络互联技术

由于ATM网络能够实现综合业务（语音、数据、图像等）的交换和传输，所以它已经成为当前电信业界的热点技术。由于它特有的优势，如高带宽、业务综合和丰富的业务质量能力，使得它将成为下一代网络，即宽带网络的基础技术。尽管ATM技术得到了大力发展，ATM网络的硬件和软件越来越丰富，ATM网络的规模也在不断地扩大，但是它仍然是一种有待于进一步完善的新技术。同时，传统网络用户也不会轻易放弃在现有网络上的硬件和软件的投资。所以ATM网络完全替代传统网络不是短时期能够实现的目标，在很长一段时间内它不可避免地与传统网络并存…     

我国发展MPLS技术的策略

多协议标签交换（MPLS）是一种在开放的通信网上利用标签引导数据高速、高效传输的新技术。MPLS组网技术是实现IPoverATM的技术方案。采用带有MPLS功能的IP路由器和带有MPLS功能的ATM交换机组建未来宽带综合业务通信网，是业界迫切需要解决的问题。它的价值在于能够在一个无连接的网络中引入连接模式的特性。多协议标签交换技术的主要优点是减少了网络复杂性，兼容现有的各种主流网络技术，使网络的总体成本降低50%，在提供IP业务时能确保QoS和安全性，具有流量工程能力。MPLS的实用价值在于它能够在像IP这样的无连接型网络…     

RSVP Extensions for Real-Time Services in Hierarchical Mobile IPv6

The Mobile IPv6 (MIPv6) provides many great features, such as sufficient addressing space, mobility, and security; MIPv6 is one of the most important protocols for next generation mobile Internet. Simultaneously, with the rapid improvement of wireless technologies, the real-time multi-media IP services such as video on demand, videoconference, interactive games, IP telephony and video IP phone will be delivered in the near future. Thus, to furnish accurate QoS for real-time services is one of the most important thing in the next generation mobile Internet. Although RSVP, which is a resource reservation protocol, processes signaling messages to establish QoS paths between senders and receivers, RSVP was originally designed for stationary networks and not aware of the mobility of MNs. Therefore, this paper proposes a novel RSVP extension to support real-time services in Hierarchical Mobile IPv6 (HMIPv6) environments. For intra-site mobility, the concept of QoS Agent (QA) is proposed to handle the RSVP QoS update messages and provide the advanced reservation models for real-time services. For inter-site mobility, IP multicast can help to invite inter-site QAs to make pre-reservation and minimize the service disruption caused by re-routing the data path during handover. Simulation results show that the proposed scheme over HMIPv6 is more suitable for real-time services than the famous RSVP tunnel-based solution.     

ATM in MPLS-based converged core data networks

Services supported by asynchronous transfer mode account for the majority of data and Internet service revenues generated by carrier networks today. This is based on ATM's ability to support high availability services with quality of service. However, the influences of the Internet and a highly dynamic telecommunications market have raised demands for increased flexibility while controlling costs. Therefore, future carrier networks are likely to continue to be based on established technologies, such as ATM, as well as IP. In many cases, this is achieved through maintaining separate ATM and IP core networks, with the IP network supporting Internet services, while the ATM network continues to support guaranteed services such as private lines, broadband access, and video. In some cases, however, it can be advantageous for a carrier to transport segments of their ATM network over their IP network core; for example, to transport ATM traffic currently carried on leased facilities onto an IP network where the service provider owns the facilities. Developments in IP and MPLS-based traffic engineering and QoS may increase the ability of IP-based networks to support ATM services using MPLS. This article provides an overview of approaches enabling a network based on MPLS that naturally supports IP services to also support ATM services. The drivers and requirements for convergence on an IP/MPLS core network are presented, followed by an overview of the different approaches and associated challenges currently being debated in the standards bodies.     

Design and implementation of an RSVP-based quality of servicearchitecture for an integrated services Internet

The Internet Engineering Task Force (IETF) is currently in the process of overhauling the architecture of the Internet to meet new challenges and support new applications. One of the most important components of that venture is the enhancement of the Internet service model from a classless best effort service architecture to an integrated services architecture supporting a multitude of classes and types of services. This paper presents the design, implementation, and experiences with a protocol architecture for the integrated services Internet. It is based on the emerging standards for resource reservation in the Internet, namely, the RSVP protocol and the associated service specifications defined by the IETF. Our architecture represents a major functional enhancement to the traditional TCP/IP protocol stack. It is scalable in terms of performance and number of network sessions, and supports a wide variety of network interfaces ranging from legacy LAN interfaces, such as Token Ring and Ethernet, to high-speed ATM interfaces. The paper also describes the implementation of this architecture on the IBM AIX platform and our experiences with the system. We then present a performance analysis of the system which quantifies the overheads imposed by all components of the QoS support, such as traffic policing, traffic shaping, and buffer management     

Internet integrated service over ATM: a solution for shortcut QoSvirtual channels

In principle, the interaction of the resource reservation protocol (RSVP) and ATM should allow the IP level to benefit from some features of the ATM layer. The most interesting one is the native support of end-to-end quality of service provided by ATM. On the other hand, there are issues that must be clarified to define correct interworking: for example, the possible overlapping between the mechanisms used in the IP and ATM levels to support QoS, or the needed IP/ATM address resolution mechanism. This article proposes a solution to exploit ATM shortcut VCs supporting QoS in the Internet integrated services model. A straightforward enrichment to the RSVP protocol is defined, which only impacts the devices (hosts and routers) involved in the shortcut procedure. A mechanism for IP/ATM address resolution is provided, avoiding the use of other mechanisms such as NHRP. Special care has been taken to maintain compatibility with “traditional” RSVP hosts and routers     

Internet protocols for multimedia communications. II. Resourcereservation, transport, and application protocols

Part I (ibid., July-Oct. 1997) surveyed the evolution of Internet protocols and applications and described the Internet protocol IPv6 in detail. This part discusses new developments at the upper layers that support real-time Internet multimedia, such as audio and video conferencing and shared whiteboard applications. Application-level framing (ALF), proposed in 1990 for protocol and application design, now forms the basis for many new Internet protocols and applications, including Real-time Transport Protocol (RTP) and Mbone multimedia applications. RTP supports real-time applications that adapt to changing network situations to maintain the quality of service (QoS). The Resource Reservation Protocol (RSVP) provides new Internet services with higher quality than best-effort by means of resource reservations     

Internet QoS: a big picture

We present a framework for the emerging Internet quality of service (QoS). All the important components of this framework-integrated services, RSVP, differentiated services, multiprotocol label switching (MPLS), and constraint-based routing-are covered. We describe what integrated services and differentiated services are, how they can be implemented, and the problems they have. We then describe why MPLS and constraint-based routing have been introduced into this framework, how they differ from and relate to each other, and where they fit into the differentiated services architecture. Two likely service architectures are presented, and the end-to-end service deliveries in these two architectures are illustrated. We also compare ATM networks to router networks with differentiated services and MPLS. Putting all these together, we give the readers a grasp of the big picture of the emerging Internet QoS     

The complementary roles of RSVP and differentiated services in thefull-service QoS network

With the growth of the Internet and intranets, QoS technology that has been developed over a span of several years is quickly becoming more relevant. This article first defines QoS and introduces a taxonomy for QoS mechanisms. The evolution of several major QoS mechanisms is described with a special focus on RSVP and differentiated services. Special attention is paid to the role of the IETF in developing QoS mechanisms. We describe a QoS network that combines RSVP and differentiated services in a manner that realizes the benefits of each. We show that, in general, the adoption of increasingly sophisticated QoS mechanisms can enhance the ability of a network to offer high-quality service guarantees while simultaneously making efficient use of raw network resources. These mechanisms carry a cost in the form of increased overhead, which must be weighed against the benefits of the mechanism     

Evolution of the Internet QoS and support for soft real-time applications

The past few years have witnessed the emergence of many real-time networked applications on the Internet. These types of applications require special support from the underlying network such as reliability, timeliness, and guaranteed delivery, as well as different levels of service quality. Unfortunately, this support is not available within the current "best-effort" Internet architecture. In this paper, we review several mechanisms and frameworks proposed to provide network- and application-level quality of service (QoS) in the next-generation Internet. We first discuss the QoS requirements of many of the above-mentioned real-time applications, and then we categorize them according to the required service levels. We also describe the various building blocks often used in QoS approaches. We briefly present asynchronous transfer mode (ATM) and Internet Protocol precedence. Then, we present and compare two service architectures recently adopted by the Internet Engineering Task Force, called integrated services (IntServ) and differentiated services (DiffServ), for providing per-flow and aggregated-flow service guarantees, respectively. We focus on DiffServ because it is a candidate QoS framework to be used in next-generation Internet along with multiprotocol label switching and traffic engineering. We also examine several operational and research issues that need to be resolved before such frameworks can be put in practice.     

Implementing integrated and differentiated services for theInternet with ATM networks: a practical approach

This article reports on design, implementation, and preliminary experimentation of a network architecture that supports quality of service for Internet applications. It gives an overview of the various approaches toward communication networks that support application-specific degrees of QoS. Special emphasis is put on the integrated and differentiated services approaches and on combinations of them. A new architecture is described which aims to bring these concepts closer to practical realization in wide-area networks. The new architecture supports the integrated as well as differentiated services approaches in a smoothly integrated way, and uses the capabilities of an underlying ATM network to realize QoS. The enhancements to the existing network infrastructure are deliberately limited to the integration of a single new type of network element called an edge device. The potential benefits of such an architecture for various stakeholders are explained, and how the new architecture could be introduced smoothly in existing networks by small migration steps, also covering networks based on technologies other than ATM. It is shown that the approach can be scaled up to a very large QoS-aware overlay network for the Internet     

A New Transport Protocol for Broadcasting/Multicasting MPEG-2 Video Over Wireless ATM Access Networks

Because of the telecommunications de-regulation act and progress in wireless technologies, we will see the co-existence of heterogeneous broadband access infrastructures in the broadband video service industry in the near future. In this paper, we addressed the error control issue when transmitting MPEG-2 video streams over wireless access networks for broadband video broadcast or multicast services. An end-to-end transport protocol based on ATM and wireless ATM technologies is proposed. For video services, the underlying transport network should be transparent and quality should be maintained uniformly over all the segments whether wireline or wireless links. For network resources to be used efficiently, error control should be applied locally on the wireless segments so as to avoid the excessive overhead over the reliable wireline portions. Because a broadband video broadcast or multicast service is a one-to-multiple point service, FEC is the most prevalent error control mechanism. Due to the important role of MPEG-2 control information in the decoding process, priority MPEG-2 control information has to be differentiated from MPEG-2 data information, and excess error protection has to be allocated to it in order to achieve satisfactory QoS. Therefore, a header redundancy FEC (HRFEC) scheme for error control is applied at the local distribution centers before the MPEG-2 encoded video streams are transmitted over the wireless channels. HRFEC is an FEC-based selective protection scheme, which allocates extra error protection to important control information. Simulation results show that the quality of the reconstructed video sequence is vastly improved by using HRFEC, when the channel condition is poor.