基于CORBA和集成服务网络的分布式多媒体应用构架

描述的分布式多媒体构架提供了一种如何从高一层次来解决开放系统中连续媒体的处理方法,该结构以CORBA和它的系统服务作为控制信息和媒体数据传输的基础,在应用层,该结构能定义端到端QoS需求释译成相关的网络层配置参数。     

适用于多媒体消息服务的一种网络机制

多媒体消息服务(MMS)可以提供丰富的数据信息通信,现有的MMS网络机制是由WAP论坛和3GPP定义的以MMSProxy-Relay(MPR)为核心的网络机制,针对这种机制可能引起网络服务效率的下降和负载平衡的问题,介绍了一种可行的MMS网络机制,即使用缓存代理(CachingProxy)的方法,可以更好地平衡负载,降低网络拥塞的可能性,同时可以将服务的延迟尽量减少。     

A Rate Allocation Framework for Multi-Class Services in Software-Defined Networks

Software defined networking (SDN) is a network architecture with a programmable control plane (e.g., controllers) and simple data plane (e.g., forwarders). One of the popular SDN protocols/standards is OpenFlow, for which researchers have recently proposed some quality-of-service (QoS) supports. However, the proposals for rate allocation have some limitations in network scalability and multi-class services’ supports. In the literature, rate allocation formulations are commonly based on the framework of network utility maximization (NUM). Nevertheless, multi-class services are rarely considered in that framework since they make the formulated NUM become nonconvex and prevent its subgradient-based algorithm from converging. In this paper, we propose a scalable QoS rate allocation framework for OpenFlow in which multi-class services are considered. The convergence issue in the algorithm of our NUM-based framework is resolved by an admission control scheme. The network scalability is improved by our decentralized algorithms that can run on multiple parallel controllers. Extensive simulation and emulation results are provided to evaluate the performance of our method.     

面向大规模网络的基于政策的访问控制框架

研究防火墙(或过滤路由器)应用于传输网络中的管理问题与吞吐量问题.一方面,手工配置分布在各个接入点的大量防火墙,无法满足开放的、动态的网络环境的安全管理需求;另一方面,大量过滤规则的顺序查找导致了防火墙吞吐量下降.针对一个典型的传输网络和它的安全政策需求,提出了一种基于政策的访问控制框架(PACF),该框架基于3个层次的访问控制政策的抽象:组织访问控制政策(OACP)、全局访问控制政策(GACP)和本地访问控制政策(LACP).根据OACP,GACP从入侵监测系统和搜索引擎产生,作为LACP自动地、动态地分配到各防火墙中,由防火墙实施LACP.描述了GACP的分配算法和LACP的实施算法,提出了一种基于散列表的过滤规则查找算法.PACF能够大量减轻管理员的安全管理工作,在描述的安全政策需求下,基于散列表的规则查找算法能够将传统顺序查找算法的时间复杂度从O(N)降低到O(1),从而提高了防火墙的吞吐量.     

End-to-End Resource Management for Federated Delivery of Multimedia Services

Recently, the Internet has become a popular platform for the delivery of multimedia content. Currently, multimedia services are either offered by Over-the-top (OTT) providers or by access ISPs over a managed IP network. As OTT providers offer their content across the best-effort Internet, they cannot offer any Quality of Service (QoS) guarantees to their users. On the other hand, users of managed multimedia services are limited to the relatively small selection of content offered by their own ISP. This article presents a framework that combines the advantages of both existing approaches, by dynamically setting up federations between the stakeholders involved in the content delivery process. Specifically, the framework provides an automated mechanism to set up end-to-end federations for QoS-aware delivery of multimedia content across the Internet. QoS contracts are automatically negotiated between the content provider, its customers, and the intermediary network domains. Additionally, a federated resource reservation algorithm is presented, which allows the framework to identify the optimal set of stakeholders and resources to include within a federation. Its goal is to minimize delivery costs for the content provider, while satisfying customer QoS requirements. Moreover, the presented framework allows intermediary storage sites to be included in these federations, supporting on-the-fly deployment of content caches along the delivery paths. The algorithm was thoroughly evaluated in order to validate our approach and assess the merits of including intermediary storage sites. The results clearly show the benefits of our method, with delivery cost reductions of up to 80 % in the evaluated scenario.     

A Framework for Internet Media Services Delivery to the Home Environment

In this paper, we propose a framework that enables Internet service providers (ISPs) to provide multimedia content to generic devices located inside the domestic networks of their customers (such as PCs and generic media players) in a seamless manner. In order to achieve this transparent integration between ISP-provided multimedia content and generic consumer media players, the domestic gateway becomes a managed UPnP AV/DLNA (Universal Plug and Play/Digital Living Network Alliance) media server, which can be dynamically updated by the broadband operator using Broadband Forum’s CPE (Customer Premises Equipment) WAN Management Protocol (CWMP) extensions specifically designed for this purpose. This framework enables the domestic gateway to become a mediator for both operator-provided and Internet media content, provided through UPnP services visible inside the domestic LAN. The adoption of a neutral UPnP/DLNA architecture that uses plugins to abstract each service allows it to become independent of the domestic gateway platform, allowing ISPs to easily add support for new media services while better coping with protocol updates. The proposed framework has been developed and validated in the scope of the project S3P, in cooperation between the University of Coimbra and Portugal Telecom’s PT Inovação innovation and R&D unit.     

云服务传递网络研究进展

云服务传递网络(Cloud Services Delivery Networks,CSDN)在Internet之上构建了一层分布式服务器网络,以就近和按需的方式向用户提供云传递服务。互联网流量的非线性快速增长及其表现出的视频化、移动化和交互化等特点,使得以提供高效、可信云传递服务为目标的CSDN面临诸多新挑战。首先在介绍和分析CSDN背景与新挑战的基础上,从基础设施层、平台层和服务层等3个维度提出了一个现有相关技术的分类模型。然后全面综述了CS-DN相关技术的最新研究现状,包括节点内组网、服务器部署、内容命名、内容管理、请求解析和系统管理等。最后指出了CSDN的未来研究趋势,即CSDN亟需突破的新技术问题,包括协同、移动管理和交互支持等。     

一种非完全组播网络中的算法可选组播框架

提出了一种新型实用的算法可选组播框架-FMPN（Flexible Multicasting on Partial-multicast Networks），该框架能够在非完全组播网络中实现组播功能，并且可以根据不同的业务和数据类型采用算法可选的组播机制，以达到系统整体最优的组播传输性能．FMPN有三个主要的特点：（1）算法可选组播机制，根据不同的应用需求来灵活地选择组播算法．并且通过IP隧道使得在路由器不支持的情况下也可以使用组播．（2）数据分类，通过对应用类型与数据的分析来调用合适的组播算法．（3）分层传输为可伸缩性码流提供各自独立的组播信道．实验表明，FMPN多媒体传输的系统整体性能高于当前常用的反向路径组播（RPM）、生成树（SpT）等组播算法，特别适合于实时多媒体应用．     

IP媒体流业务在3G移动网络中的应用

主要从理论上研究了3G网络中使用的一种流媒体的端到端QOS框架,探讨了运用PLMN中的多媒体流业务避免通过外部的IP-PDN访问流业务的可能性。在这个框架的基础上分析了流会话的UMTS和IETF下的协议之间的相互作用。这两组协议可以合作提供无缝的端到端的实时业务。特别是,本文提出P多媒体子系统可以利用实时流协议,将其控制范围从基于SP的业务延伸到基于R御的业务,如多媒体流媒体业务。在提出上述框架的基础上,本文还概括了3C移动网络中的音频流业务的提供。     

A Normalization Framework for Multimedia Databases

We present a normalization framework for the design of multimedia database schemas with reduced manipulation anomalies. To this end, we introduce new extended dependencies. Such dependencies are based on distance functions that are used for detecting semantic relationships between complex data types. Based upon these new dependencies, we have defined five multimedia normal forms. Finally, we have performed a simulation on a large image data set to analyze the impact of the proposed framework in the context of content-based retrieval applications and in e-learning applications.     

Using RTT Variability for Adaptive Cross-Layer Approach to Multimedia Delivery in Heterogeneous Networks

A holistic approach should be made for a wider adoption of a cross-layer approach. A cross-layer design on a wireless network assumed with a certain network condition, for instance, can have a limited usage in heterogeneous environments with diverse access network technologies and time varying network performance. The first step toward a cross-layer approach is an automatic detection of the underlying access network type, so that appropriate schemes can be applied without manual configurations. To address the issue, we investigate the characteristics of round-trip time (RTT) on wireless and wired networks. We conduct extensive experiments from diverse network environments and perform quantitative analyses on RTT variability. We show that RTT variability on a wireless network exhibits greatly larger mean, standard deviation, and min-to-high percentiles at least 10 ms bigger than those of wired networks due to the MAC layer retransmissions. We also find that the impact of packet size on wireless channel is particularly significant. Thus through a simple set of testing, one can accurately classify whether or not there has been a wireless network involved. We then propose effective adaptive cross-layer schemes for multimedia delivery over error-prone links. They include limiting the MAC layer retransmissions, controlling the application layer forward error correction (FEC) level, and selecting an optimal packet size. We conduct an analysis on the interplay of those adaptive parameters given a network condition. It enables us to find optimal cross-layer adaptive parameters when they are used concurrently.     

移动视频业务QoE自适应测量工具

针对不同无线环境（3G、WiFi）下获取用户体验质量（Quality of Experience,QoE）数据困难和不精确的问题,提出一种基于安卓（Android）移动终端视频业务QoE的自适应测量方法.通过实时测量并评估用户在线视频业务体验质量,提高用户体验质量评价的准确性和实用性.为此开发了能自动测量视频QoE的工具,测量服务质量（Quality of Service,QoS）客观参数,通过效用函数映射到主观QoE（MOS值）.通过对理论QoE评价模型（取自文献）与用户实际反馈相关性研究改进理论模型.结果表明,无线环境下改进的模型测量结果更接近用户实际反馈,可以更好地评价QoE.     

Efficient Movie Retrieval Strategies for Movie-on-Demand Multimedia Services on Distributed Networks

In this paper, for a network-based multimedia Video/Movie-on-demand(VoD/MoD) service, we design and analyze efficient retrieval strategies to minimize both the access times of the movies and the block rates. We consider a heterogeneous set of servers and a generic network topology in which clients can request for movies from any site. We design and analyze a multiple servers retrieval strategy (MSRS) to retrieve the movies requested by the clients and present a rigorous analysis on its performance with respect to access times of the requested movies and the block rates. A generalized approach of MSRS is designed in a judicious manner using a two-step approach. In the first step, we partition the available bandwidth among the requested movies and in the second step, we derive optimal portions of the movies to be retrieved from each of the servers for each movie, based on allocated bandwidths in the first step. Thus, with the optimal playback portions of the movies using aggregate retrieval bandwidth from several servers, the access times of the movies are minimized. In the first step, in addition to the access times, we minimize the block rates by balancing the total accesses/requests among the servers. In generating the retrieval schedule, our scheme utilizes the available bandwidth (resource) among the servers and guarantees to use less buffer space than a single server retrieval strategy (SSRS). With this two-step approach, a complete flexibility is provided in tuning the access times of the movies and also shown to be robust to any variations in the user access rates of the movies, in reality. Rigorous simulation experiments are presented to observe the performance of MSRS with respect to some important system dependent parameters. Comparing with SSRS, MSRS shows better performance in the simulation.     

接入以太网上的IP组播与多媒体服务

论文首次深入分析了接入以太网的组播问题,提出了一个基于网管和动态虚拟局域网(VLAN)的接入以太网组播方案。该方案充分考虑了业务质量需求、管理、安全和计费等问题,具有安全性好、可扩展性强和成本低等特点,可以在公共接入以太网中提供商业化的宽带多媒体组播业务。     

A Binding Architecture for Multimedia Networks

An open architecture that achieves seamless binding between networking and multimedia devices is proposed. The building blocks of the binding architecture consist of a set of interfaces, methods and primitives. The former abstract the functionalities of multimedia networking devices and are realized as objects organized into a binding interface base. The methods and primitives are invoked for implementing binding applications. The binding architecture is embedded into a reference model for multimedia networking architectures that supports a clean separation between binding interfaces and binding algorithms. Communication between the objects realizing the binding interfaces is supported by CORBA. Public interfaces in the binding interface base are specified using CORBA IDL. The architecture is illustrated with a simple connection management algorithm and an example of computational binding.     

无线多媒体传感器网络视频流区分服务多径Qos路由算法

无线多媒体传感器网络视频流传输需要提供多样性QoS保障,传统的无线传感器网络路由协议不能很好地保证多媒体视频流数据传输, 改进多径路由算法TPGF下一跳节点选择方法,提出一种适合视频流传输的区分服务多路径Qos路由算法DSMQRA。综合考虑各路径跳数与节点剩余能量情况,在源节点与汇聚节点间找到多条优化的节点不相交路径;采用区分服务机制,重点保护视频流关键帧,提高视频流传输质量。在NS2环境下与AODV、GPSR、TPGF等算法进行仿真对比分析,实验结果表明DSMQRA算法能够有效延长网络生存时间、降低丢包率、减小帧延时、图像峰值信噪比较高,更加适合无线多媒体传感器网络视频流数据传输。     

云服务传递网络资源动态分配模型

云服务传递网络(Cloud Services Delivery Networks,CSDN)在Internet之上构建了一层分布式服务器网络,以就近和按需的方式向用户提供云传递服务.面对互联网规模化和多样化云服务的资源需求特点,CSDN形成了针对不同类型云服务传递的逻辑子服务器网络.CSDN的很大一部分服务器和带宽资源...     

多媒体网络:从内容分发网络到未来互联网

近年来,随着网络技术的飞速发展,互联网流量视频化的趋势日益明显,视频应用使互联网的可扩展性、可演进性、服务质量和网络安全面临诸多挑战.内容分发网络通过在应用与网络间构建覆盖网,为解决网络视频应用面临的分发难题提供了有力的支持,也成为当前网络视频产业中的关键技术.但是随着视频应用在移动性、交互性、异构性以及可扩展性方面需求的不断增长,现有内容分发网络技术面临重大挑战,学术界与工业界都试图从互联网体系架构入手解决网络视频应用中的问题.文中系统总结了内容分发技术面临的挑战以及现有互联网体系结构研究的思路与核心技术,提出了面向未来网络的多媒体网络设计思路.