基于IntServ/RSVP的CORBA A/V Stream QoS实现策略研究

首先简要介绍基于资源预留的集成服务模型(IntServ/RSVP)、以及CORBA A/V Stream规范中的QoS相关概念。在此基础上给出一个集成QoS模型,论述CORBA A/V Stream QoS与IntServ/RSVP之间的映射模型及绑定策略。     

充满活力的下一代网络技术--RSVP

近年来，随着经济的发展和计算机的普及，Internet业务出现了爆炸性的增长，并且出现了许多新兴的业务，如IP电、话、视频点播、视频会议等，现有Internet只提供传统单一尽力传送（best—effort）业务，因而急需新的网络协议以支持未来分类业务所需的不同带宽和服务质量（QoS）保障，现有网络虽然可以通过ATM（Asynchronous Transfer Mode）来解决QoS问题。但由于ATM信元的开销在整个帧中占了30％，严重降低了网络的传输效率，故未来网络不可能使用它。新出现的RSVP（资源预留协议）根据其自身的特点，必然会替代ATM，成为下一代网络保证QoS的关键网络技术。下面详细介绍RSVP的特点以及它如何有效的与未来的IPv6相结合。     

CORBA过滤机制在网管系统中的应用研究

CORBA事件服务提供了一种在事件提供者和事件使用者之间的异步通信机制。但该机制在实际应用中存在着诸如不支持事件过滤、不能永久存放事件提供者和事件使用者的连接或者没有发送的事件数据以及不支持QoS等不足之处。阐述了CORBA通告服务的结构化事件、过滤机制和服务质量等新特点,提出了将推模式的CORBA通告服务应用于网络管理系统以实现事件上报的过滤机制。该过滤机制的应用,可以有效区分不同用户和不同事件,使事件的传送更有效率,避免了处理上的浪费。     

RSVP and integrated services in the Internet: a tutorial

The growing use of multimedia communication applications, with specific bandwidth and real-time delivery requirements has created the need for an integrated services Internet in which traditional best-effort datagram delivery can coexist with additional enhanced quality of service (QoS) delivery classes. Such classes provide data flows with QoS commitments with regard to bandwidth, packet loss, and delay through the reservation of network resources along the data path, which can be done using the Resource Reservation Protocol (RSVP). This article is a tutorial on how RSVP can be used by end applications to ensure that they receive the end-to-end QoS that they require     

Architecture and experimental results for quality of service in mobile networks using RSVP and CBQ

Efforts are underway to enhance the Internet with Quality of Service (QoS) capabilities for transporting real‐time data. The issue of wireless networks and mobile hosts being able to support applications that require QoS has become very significant. The ReSerVation Protocol (RSVP) provides a signaling mechanism for end‐to‐end QoS negotiation. RSVP has been designed to work with wired networks. To make RSVP suitable for wireless networks, changes need to be made by: (i) changing the way control messages are sent, and (ii) introducing wireless/mobile specific QoS parameters that take into account the major features of wireless networks, namely, high losses, low bandwidth, power constraints and mobility. In this paper, an architecture with a modified RSVP protocol that helps to provide QoS support for mobile hosts is presented. The modified RSVP protocol has been implemented in an experimental wireless and mobile testbed to study the feasibility and performance of our approach. Class Based Queueing (CBQ) which is used as the underlying bandwidth enforcing mechanism is also modified to fit our approach. The experimental results show that the modified RSVP and CBQ help in satisfying resource requests for mobile hosts, after handoff occurs. The experiments also show how different power and loss profile mechanisms can be used with our framework. The system performance using the modified RSVP control mechanism is also studied. This revised version was published online in July 2006 with corrections to the Cover Date.     

基于MPLS的话音传输

因特网的快速发展,促使各种应用及服务不断涌现.多协议标签交换(MPLS)作为一种非常灵活的载体,不仅可以传输数据,而且可以利用其在资源预留协议(RSVP)、服务质量(QoS)方面的优势提供语音及多媒体等方面的服务.文章首先介绍MPLS两种主流语音传输技术,进而与VoIP的传输性能进行了比较分析,最后探讨了VoMPLS存在的技术问题和VoMPLS将来的应用前景.     

RSVP extensions for real-time services in wireless mobile networks

Currently, the RSVP model, which is efficient resource reservation in the fixed endpoints, becomes invalid under host mobility. We investigate the problems of standard RSVP in providing real-time services in wireless mobile networks. We also observe carefully how to interoperate IntServ services over DiffServ networks, and how to map IntServ QoS parameters into a wireless link. We then identify the advantages and drawbacks of the existing RSVP proposals to support QoS under both micromobility and macromobility. We finally propose a dynamic resource allocation scheme for reducing service disruption of real-time applications due to frequent mobility of a host     

应用RSVP提高视频会议系统业务传输质量

传统的IP网络基于尽力而为的设计思想,不对上层承载业务提供任何服务质量保障。而视频会议应用对服务质量要求相对严格,延迟及延迟抖动会降低用户的应用体验。针对基于IP网络的视频会议系统中缺少服务质量保障的问题,提出了在视频会议系统中部署资源预留协议以提供服务质量保障的方案,并且在Vxworks系统中完成资源预留协议的开发。为了验证方案效果,分别在中度负载和重度负载的情况下对业务性能进行测试。测试结果表明,该方案能够为视频会议系统提供有效的服务质量保障。     

移动IP环境下的RSVP研究

资源预留协议RSVP能够为用户提供端到端的传输带宽。为保证在移动IP下的服务质量,针对RSVP协议提出很多改进方案,如隧道RSVP,MRSVP和HMRSVP等。对宏移动和微移动下的RSVP扩展方案进行了讨论,最后提出进一步的研究方向。     

Fast RSVP: Efficient RSVP Mobility Support for Mobile IPv6

In recent years, with the development of mobile communication technologies and the increase of available wireless transmission bandwidth, deploying multimedia services in next generation mobile IPv6 networks has become an inevitable trend. RSVP (resource reservation protocol) proposed by the IETF is designed for hardwired and fixed networks and can not be used in mobile environments. This paper proposes a protocol, called Fast RSVP, to reserve resources for mobile IPv6. The protocol adopts a cross-layer design approach where two modules (RSVP module and Mobile IPv6 module) at different layers cooperate with each other. Fast RSVP divides a handover process with QoS guarantees into two stages: (1) setup of the resource reservation neighbor tunnel and (2) resource reservation on the optimized route. It can help a mobile node realize fast handover with QoS guarantees as well as avoid resource wasting by triangular routes, advanced reservations and duplicate reservations. In addition, fast RSVP reserves “guard channels” for handover sessions, thus greatly reducing the handover session forced termination rate while maintaining high performance of the network. Based on extensive performance analysis and simulations, Fast RSVP, compared with existing methods of resource reservation in mobile environments, performs better in terms of packet delay and throughput during handover, QoS recovery time after handover, resource reservation cost, handover session forced termination rate and overall session completion rate.     

Reliable RSVP path reservation for multimedia communications under an IP micromobility scenario

We focus on how quality of service (QoS) guarantees can be provided for RSVP flows during handoff events in an IP micromobility network. For this purpose, RSVP message delays and signaling overheads should be minimized, and handoff service disruption should also be minimized. By rerouting the RSVP branch path at a crossover router at every handoff event, and establishing the new RSVP path between the CR and new BS in advance while the existing reservation path is maintained, ongoing RSVP flows can be kept with the guaranteed QoS. We propose the seamless switching of an RSVP branch path for soft handoff, and also show that this scheme could provide QoS guarantee with simulation and examples.     

Quality-of-service mechanisms in all-IP wireless access networks

In this paper, we focus on resource reservation protocol (RSVP)-based quality-of-service (QoS) provisioning schemes under Internet protocol (IP) micromobility. We consider QoS provisioning mechanisms for on-going RSVP flows during handoff. First, the rerouting of RSVP branch path at a crossover router (CR) at every handoff event can minimize resource reservation delays and signaling overheads, and in turn the handoff service degradation can be minimized. We show that RSVP branch path rerouting scheme could give a good tradeoff between the resource reservation cost and the link usage. Second, the new RSVP reservation can be made along the branch path toward the CR via a new base station in advance, while the existing reservation path is maintained, and in turn the on-going flow can be kept with the guaranteed QoS. We also show that seamless switching of RSVP branch path could provide the QoS guarantee by adaptively adjusting the pilot signal threshold values. Third, during RSVP resource reservation over wireless link, dynamic resource allocation scheme is used to give a statistical guarantee on the handoff success of on-going flows. We finally obtain the forced termination probability of guaranteed service flows, the average system time of best effort flows by using a transition rate matrix approach.     

Dynamic bandwidth management and adaptive applications for avariable bandwidth wireless environment

This article describes an approach for providing dynamic quality of service (QoS) support in a variable bandwidth network, which may include wireless links and mobile nodes. The dynamic QoS approach centers on the notion of providing QoS support at some point within a range requested by applications. To utilize dynamic QoS, applications must be capable of adapting to the level of QoS provided by the network, which may vary during the course of a connection. To demonstrate and evaluate the dynamic QoS concept, we have implemented a new protocol called dynamic resource reservation protocol (dRSVP) and a new QoS application program interface (API). The paper describes this new protocol and API and also discusses our experience with adaptive streaming video and audio applications that work with the new protocol in a testbed network, including wireless local area network connectivity and wireless link connectivity emulated over the wired Ethernet. Qualitative and quantitative assessments of the dynamic RSVP protocol are provided     

基于CORBA的自适应负载均衡服务的研究

随着越来越多的企业级分布式应用采用CORBA作为其构造平台和通过分布式对象集为猝发式客户请求提供高QoS的服务，基于CORBA的负载均衡服务具有重要的研究价值。本文分析了传统的基于CORBA的负载均衡设计模式，提出了一种基于CORBA自适应的负载均衡服务设计模式。本模式诉效率、吞吐量和负载均衡服务的有效性、小粒度、可移植性和动态性之间进行适当的平衡。     

Supporting mobile multimedia applications through adaptivemiddleware

The traditional approach to developing middleware platforms is to adopt a “black box” philosophy whereby the platform offers a fixed programming model to applications together with fixed per-platform implementations. In this paper, we describe research which is exploring an open approach to the implementation of middleware platforms. Our motivation is to accommodate the demanding requirements for quality-of-service (QoS) adaptation as imposed by mobile multimedia applications. We use an extended CORBA computational model featuring the concept of explicit open bindings. This provides an architectural framework for openness and QoS adaptation. The paper concludes by considering the more general application of an open systems philosophy; in particular, we introduce the concept of reflective middleware     

Collected experience from implementing RSVP

Internet quality of service (QoS) is still a highly debated topic for more than fifteen years. Even with the large variety of QoS proposals and the impressive research advances, there is little deployment yet of network layer QoS technology. One specific problem domain is QoS signalling, which has recently attracted increasing attention to bring forward new standardization approaches. In this paper, an extensive study of RSVP is presented, covering protocol design, software design, and performance aspects of the basic version of RSVP and of certain standardized and experimental extensions. This work is based on and presents the experience from implementing RSVP for UNIX systems and the ns-2 simulation environment. The implementation includes a variety of protocol extensions and incorporates several internal improvements. It has been subject to extensive functional and performance evaluations, the results of which are reported here.     

一种改进的支持无线IP网络的资源预留协议

移动IP技术能够支持基于IP的无线网络,资源预留协议(RSVP)用来保证多媒体传输的服务质量。然而把现有的RSVP应用于移动IP网络就会存在许多问题。提出了一种改进的RSVP支持方案(ERSVP)来实现无线IP网络的服务质量保证。ERSVP在分层网络中结合了MRSVP和RSVP隧道技术。根据性能分析,ERSVP方案能够获得比MRSVP较少的信令延迟、信令负载和资源耗费。     

支持IPv6／RSVP的网络中基于数字视频的教育服务

为了保证基于数字视频的教育服务的网络的服务质量,更好地提升Internet的网络性能,使综合数据的传输更加流畅,将IPv6相对于IPv4的优势和RSVP对的QoS支持两方面结合起来,提出了支持IPv6／RSVP的网络中基于数字视频的教育服务的基本设计思想、系统总体框架结构与技术实现,并给出了视频教育服务体系结构、通信协议栈和资源预留的实现方式。该方法在拟定的实验环境下能实现预期目标,并被证明了有为基于教育服务的视频提供端对端服务质量的可能性。     

Mobility protocols and RSVP performance in wireless IPv6 networks: shortcomings and solutions

Resource reservation protocol (RSVP) is a network‐control protocol used to guarantee Quality‐of‐Service (QoS) requirements for real‐time applications such as Voice‐over‐IP (VoIP) or Video‐over‐IP (VIP). However, RSVP was designed for end‐systems whose IP addresses do not change. Once mobility of an end‐system is allowed, the dynamically changing mobile IP address inevitably impacts on RSVP performance. Our study aims to first quantify the significance of this impact, and then propose a modified RSVP mechanism that provides improved performance during handoffs. Our simulations reveal that the deployment of standard RSVP over Mobile IPv6 (MIPv6) does not yield a satisfactory result, particularly in the case of VIP traffic. Fast Handovers for Mobile IPv6 (FMIPv6) was found to be providing the best performance in all tested scenarios, followed by Hierarchical Mobile IPv6 (HMIPv6) with a single exception: during low handoff rates with VoIP traffic, MIPv6 outperformed HMIPv6. We then designed a new RSVP mechanism, and tested it against standard RSVP. We found that the proposed approach provides a significant improvement of 54.1% in the Total Interruption in QoS (TI_QoS) when deployed over a MIPv6 wireless network. For HMIPv6, performance depended primarily on the number of hierarchical levels in the network, with no improvement in TI_QoS for single‐level hierarchy and up to 37% for a 5‐level hierarchy. FMIPv6 on the other hand, provided no room for improvement due to pre‐handoff signaling and the tunneling mechanism used to ensure a mobile node (MN)'s connectivity during a handoff, regardless of the RSVP mechanism used. Copyright © 2007 John Wiley & Sons, Ltd.     

A CORBA-based quality of service management framework fordistributed multimedia services and applications

For distributed multimedia services, it is essential that quality of service be guaranteed system-wide, including end systems, communication systems, and networks. Although many researchers have addressed issues of QoS management, little attention has so far been paid to the QoS management services in distributed multimedia services and applications. To address this deficiency, we have designed a layered model for end-to-end QoS management called the QoS management framework. Our framework, which is CORBA-based, includes a generic QoS MIB for the QoS parameterization of various multimedia services and the services needed to perform various QoS functions. A key component of this framework is the QoS management service object (QMSO), which orchestrates resources at endpoints, coordinating resource management across layer boundaries. Services such as translation, monitoring, admission, and negotiation are provided by the QMSO. To validate this concept, we have developed a QoS management system for managing and controlling the QoS of a distributed multimedia system called MAESTRO. The QoS management system has been implemented through CORBA objects and provides an interface to multimedia applications, which can be dynamic negotiation and renegotiation of QoS by users. Some performance results in QoS negotiation and renegotiation are also presented