SIP终端中拓扑感知的P2P中继查找机制实现①

由于Internet采用尽力而为的服务,VoIP系统存在QoS问题。为改善QoS,多数系统采用“应用层路由”方案,该方案关键是如何查找拓扑最优中继节点。结合P2P技术,提出一种拓扑感知的P2P中继查找机制。首先构建一个Cluster Overlay网络来模拟真实的Internet拓扑;在Cluster Overlay网络上设计一种拓扑感知的中继查找算法;最后在SIP终端中实现这种方案。在NS2平台上对Cluster Overlay网络和中继查找机制进行了仿真实验。结果表明：Cluster Overlay网络和真实的Internet拓扑相似度很高,中继查找算法能查找到最优中继结点,从而改进了路径质量。     

An efficient relay node selection scheme to improve the performance of P2P-based VoIP applications in Chinese internet

Peer-to-peer (P2P) systems have been widely deployed and used to provide voice-over-IP (VoIP) service in the Internet. However, the current best-effort Internet cannot readily provide the service guarantees that meet the quality standards achieved in the public switched telephone network (PSTN). To address this problem, many studies have demonstrated that exploiting path diversity is a promising approach, such as multi-homing and overlay routing. In this paper, we focus on the overlay scenario and bring forward a previously unexplored approach that exploits the properties of delay space of Internet to select relay node to enhance the performance of P2P-based VoIP applications in Chinese Internet. By conducting intensive Internet measurements, we analyze the properties of delay space of Chinese Internet and show these properties can be readily exploited to select relay node with as small a cost as possible. Exploiting these properties we bring forward an efficient relay node selection scheme to improve the performance of P2P-based VoIP applications in Chinese Internet. Our intensive evaluation by trace-driven simulation shows our scheme is highly efficient and easy to be implemented.     

A novel forwarding and routing mechanism design in SDN-based NDN architecture

Combining named data networking (NDN) and software-defined networking (SDN) has been considered as an important trend and attracted a lot of attention in recent years. Although much work has been carried out on the integration of NDN and SDN, the forwarding mechanism to solve the inherent problems caused by the flooding scheme and discard of interest packets in traditional NDN is not well considered. To fill this gap, by taking advantage of SDN, we design a novel forwarding mechanism in NDN architecture with distributed controllers, where routing decisions are made globally. Then we show how the forwarding mechanism is operated for interest and data packets. In addition, we propose a novel routing algorithm considering quality of service (QoS) applied in the proposed forwarding mechanism and carried out in controllers. We take both resource consumption and network load balancing into consideration and introduce a genetic algorithm (GA) to solve the QoS constrained routing problem using global network information. Simulation results are presented to demonstrate the performance of the proposed routing scheme.     

QoS-aware path switching for VoIP traffic using SCTP

Voice over Internet protocol (VoIP) has been a prevalent multimedia service nowadays. It allows us to transmit voice data over IP networks. However, quality of service (QoS) is a major challenge to VoIP services. It must provide similar quality to traditional public switched telephone network or cellular phone services. Therefore, QoS related protocols have become important for real-time applications. Multi-protocol label switch (MPLS) is one of the important techniques to improve the network performance from QoS point of view. It employs label swapping to speed up packet forwarding. However, when a large number of users utilize VoIP services, the network congestion issue still exists. It causes delay, jitter and packet loss that affect VoIP QoS. In this paper, we propose a QoS-aware path switching strategy by using stream control transmission protocol (SCTP) in MPLS network to improve the VoIP traffic. This was done by employing SCTP selective acknowledgment mechanism to report the transmission parameters of primary path and to determine the criteria to switch to backup path. Simulation results show significant improvement in VoIP QoS.     

P2P网具有QoS保障的语义Web服务匹配方法

在P2P网络中,有大量的web服务,如何准确高效的发现零散分布于世界各地的语义Web服务呢？文章从P2P网络的特点出发,分析了现有的一些研究和方法,在扩展UDDI的基础上,结合目前语义Web服务匹配的多层匹配思想,提出了P2P网络中支持QoS的语义Web服务匹配和发现的有效方法。该方法采用一个四层次的匹配筛选算法,对QoS各层的匹配算法进行了深入讨论,并以相似函数来度量服务提供方与服务请求方的Web服务相似程度。     

无线Mesh网络中VOIP的QoS性能分析

针对VoIP(Voice over IP)业务在无线Mesh网上进行传输时存在服务质量(QoS)需求难以保证、带宽利用率低的问题,介绍了VoIP的QoS影响因素,分析了端到端时延、时延抖动和丢包率等几个重要参数,并对VoIP在无线Mesh网中的传输性能进行了论述。提出了基于无线Mesh网络的QoS保证机制,可以为端到端的数据传输公平的分配带宽,并能在保证QoS下实现大规模的实时任务的多跳转发。仿真试验表明能有效降低端到端时延,有着更好的QoS性能。     

一种基于种族分类进化的QoS异构组播路由机制

随着新型网络应用的大量涌现,传统的网络技术已无法满足当前应用在带宽、延迟及出错率等方面的需求,IP over DWDM光互联网以其独特性能优势成为研究热点。基于种族分类进化算法,提出了一种IP over DWDM光互联网服务质量QoS异构组播路由机制。具体地,利用概率论方法处理网络状态参数信息的不确定性;引入模糊数学方法,确定用户对QoS的需求并提供柔性QoS支持;综合考虑网络提供方和用户方的利益,设计公平的带宽定价方法。仿真结果表明,该路由机制获得了良好的综合性能指标,可以有效地解决IP over DWDM光互联网中的柔性QoS异构组播路由选择问题。     

基于推拉结合机制的P2P流媒体分发算法

随着流媒体直播应用的日益扩大,传统C/S（Client/Server）模式网络构架的服务器负载过重,导致QoS（Quality of Service）得不到保证,而P2P（Peer-to-Peer）网络具有负载均衡、可扩展性、容错性强等优点。目前P2P技术开始逐步走向成熟。大多数P2P流媒体数据分发采用Pull模式或Push模式,本文提出基于推拉结合机制的P2P流媒体分发算法,通过仿真实验,从系统开销、端到端延迟等方面对两者进行了性能对比。实验结果表明,该推拉结合机制有效的降低了数据块传输时延,并且在很大程度上避免了数据块的重复推送,降低了数据冗余。     

基于最差2跳查找的P2P VoIP性能分析

在各种P2P应用系统中,节点之间的业务量往往随着实际距离的增加而减少。根据上述特点,提出一种最差2跳查找的P2P系统,保证节点最差在2跳内即可找到目标,同时具有较低的系统维护流量和较小的路由表尺寸。针对IP网上的语音覆盖网络系统进行最差 2跳查找的特性分析,结果证明,系统中正在通话的用户平均约有80％享受1跳查找服务,只有约20％的用户享受2跳查找服务。     

Design and implementation of QoS-provisioning system for voice over IP

In this paper, we address issues in implementing voice over IP (VoIP) services in packet switching networks. VoIP has been identified as a critical real-time application in the network QoS research community and has been implemented in commercial products. To provide competent quality of service for VoIP systems comparable to traditional PSTN systems, a call admission control (CAC) mechanism has to be introduced to prevent packet loss and over-queuing. Several well-designed CAC mechanisms, such as the site-utilization-based CAC-and the link-utilization-based CAC mechanisms have been in place. However, the existing commercial VoIP systems have not been able to adequately apply and support these CAC mechanisms and, hence, have been unable to provide QoS guarantees to voice over IP networks. We have designed and implemented a QoS-provisioning system that can be seamlessly integrated with the existing VoIP systems to overcome their weakness in offering QoS guarantees. A practical implementation of our QoS-provisioning system has been realized.     

Admission control by implicit signaling in support of voice over IP over ADSL

Voice over DSL (VoDSL) is a technology that enables the transport of data and multiple voice calls over a single copper-pair. Voice over ATM (VoATM) and Voice over IP (VoIP) are the two main alternatives for carrying voice over DSL. ATM is currently the preferred technology, since it offers the advantage of ATM’s built-in Quality of Service (QoS) mechanisms. IP QoS mechanisms have been maturing only in recent years. However, if VoIP can achieve comparable performance to that of VoATM in the access networks, it would facilitate end-to-end IP telephony and could result in major cost savings. In this paper, we propose a VoIP-based VoDSL architecture that provides QoS guarantees comparable to those offered by ATM in the DSL access network. Our QoS architecture supports Premium and Regular service categories for voice traffic and the Best-Effort service category for data traffic. The Weighted Fair Queuing algorithm is used to schedule voice and data packets for transmission over the bottleneck link. Fragmentation of large data packets reduces the waiting time for voice packets in the link. We also propose a new admission control mechanism called Admission Control by Implicit Signaling. This mechanism takes advantage of application layer signaling by mapping it to the IP header. We evaluate the performance of our QoS architecture by means of a simulation study. Our results show that our VoIP architecture can provide QoS comparable to that provided by the VoATM architecture.     

基于P2P的语言IP穿越网络地址转换和防火墙的统一模型

从P2P网络出发,提出了一种新的语言IP（Voice over IP,VoIP）穿越网络地址转换（Network Address Translation,NAT）和防火墙的统一模型。该模型利用分布式P2P网络的二层拓扑结构,通过最优路径建立算法（Optimal Path Establishment Algorithm,OPEA）以一种更有效的方式组织会话建立过程,使之能在各种情况下对NAT和防火墙的穿透问题提供最优解。与STUN等单一模型相比,具有更高的效率和健壮性。通过建立原型系统,在校园网环境中进行了模拟测试,证实了该模型的可行性以及提高服务质量的有效性。     

Hotspot Avoidance for P2P Streaming Distribution Application: A Game Theoretic Approach

Today's peer-to-peer (P2P) streaming application periodically suffers from routing hotspots, which are also known as flash crowds. A routing hotspot is typically created by an unanticipated new event that triggers an unanticipated surge of users to request streaming service from some particular peers, temporarily overwhelming the peer's delivery capabilities. In this paper, we propose novel methods that avoid routing hotspots proactively, that is, prior to a congestion event. More specifically, we define an incentive-compatible pricing vector explicitly and show that the hotspot can be avoided if all nodes in the network follow the incentive-compatible pricing policy. In order to apply this mechanism to the P2P streaming distribution applications, we propose an adaptive algorithm for distributed computation of the incentive-compatible pricing vector. The simulation results show that the incentive-compatible pricing mechanism can avoid the routing hotspot effectively.     

基于P2P的自适应多媒体服务发布平台

研究一种基于P2P的多媒体服务发布平台,用于提供多媒体数据的传输和处理服务。平台将多媒体服务分割成小的服务元,并将它们按预先定义的规则离散到一个P2P网络中去,对服务元可以是:对多媒体数据进行的编码转换,对音频/视频数据进行的有损压缩,或者提供具有QoS保证的数据传输与路由等。平台根据用户终端特性和具体的服务定制生成服务需求,在P2P网络中动态的查找并连接服务元,以构建一个可以提供对应服务的服务链路,因此平台具有自适应的特性。平台基于内容可索引网络(Content Addressable Network),目标系统通过理论分析和局域网内的仿真进行验证。     

基于蚁群算法的对等网络自适应寻径协议

针对现有的蚁群算法在对等网络寻径中,不能根据访问的对等体状况去自适应克隆转发相应数目的蚂蚁,自适应设置克隆蚂蚁的TTL的问题,给出一种面向对等网络的自适应寻径模型,提出一种基于蚁群算法的对等网络自适应寻径协议AARP,描述蚁群在对等网络中自适应的克隆、寻径过程。分析和仿真实验结果表明,AARP能够以较低的寻径开销、较短的寻径时延,实现较高的寻径效率。     

P2PSIP网络与PSTN的一种互通机制

P2PSIP用P2P算法实现SIP的位置管理功能,解决了单点失效问题,有良好的可扩展性,将成为VoIP的关键技术。现有相关研究缺乏对不同网络互通的深入探讨。提出P2PSIP网络与PSTN的一种新颖的互通机制,并且基于该机制设计了一个易于实现的P2PSIP终端与PSTN电话互通的原型系统。互通的关键设计是一个具有双重身份的网关,在P2PSIP网络中作为对等端,在PSTN中负责连接电话机。经测试分析,该互通机制可以应用于实际网络,实现P2PSIP网络和PSTN之间的会话建立。     

SmartPeerCast: a Smart QoS driven P2P live streaming framework

The P2P swarm technologies have been shown to be very efficient for medium scale content distribution systems in the last few years, such as the file sharing and video-on-demand (VOD) applications. However it is still an open topic about how to deploy the P2P paradigm for the real time video broadcasting (RTVB) applications. The P2P RTVB application is different from the cache based P2P system because it has more stringent restrictions for startup time and packet loss ratio. In this paper, an adaptive media broadcasting P2P framework named SmartPeerCast which employs the media transrating service to control the quality of service (QoS), is proposed. SmartPeerCast achieves a network awareness, codec awareness, and high performance RTVB service with four key designs: (1) It groups the newly joined peers into different quality clusters by their uploading capability. This clustering mechanism avoids the bandwidth bottleneck between the heterogeneous peers of the overall P2P overlay by only forwarding the same quality stream over the peers in the same cluster. (2) The streaming quality is adjusted adaptively between the sending and the receiving peers by a Smart QoS algorithm to compensate for the network jitters to reduce the receiving peer’s playback jitter. (3) The receiving peer monitors the data forwarding QoS of the sending peer to select the best suitable parent node dynamically. The SmartPeerCast uses this Smart QoS framework to implement an incentive mechanism to award the peers with high uploading contributions by migrating them to a higher quality cluster. (4) A transrating engine is used at the leaf nodes of the high quality cluster to forward the stream with suitable bits rate to the nodes of the low quality cluster; this transrating service not only can fully utilize the uploading bandwidth of the peers in the higher quality cluster but also avoids the bandwidth bottleneck of stream forwarding between the heterogeneous peers. Our experiment results and the real deployment show that SmartPeerCast can eliminate the bandwidth bottleneck and content bottleneck between the heterogeneous peers with a smaller startup time and packet loss and it is a high performance and medium scale P2P RTVB framework.     

多播路由在无线网络中的OPNET建模与性能测试

多播路由技术凭借其有效节省网络带宽的优势,已成为研究无线多媒体网络服务质量(QoS)的热点内容。其中协议独立多播稀疏模式(PIM-SM)是域内多播路由协议中常见的协议。使用OPNET平台进行基于IEEE802.11无线局域网的仿真实验,首先对单播路由和PIM-SM多播路由在吞吐量上进行比较,实验结果表明多播路由在带宽的利用率上具有明显的优势。然后对文件传输、数据库访问、网络电话和视频会议等多媒体业务,进行单播路由和PIM-SM多播路由对比仿真实验,并且从延迟、延迟抖动和丢包率等方面给出结论,为真实无线多媒体网络环境的搭建提供一个很好的参考。     

基于P2P的匿名通信技术研究

随着P2P网络的发展和广泛使用,用户隐私安全的重视程度不断提高。现有的加密技术虽然可以保护通信中的数据内容,却不能很好地保护用户身份,因此在利用匿名技术的同时也要防止不法分子趁机散布非法信息。为了在P2P系统中实现匿名通信,提出了一种基于无环分组路由选择机制,即通过将网络地址切割、成员分组保护、组管理员统一管理来实现通信隐私和涉密通信。仿真实验表明,采用此机制的路由策略得到明显改善,且在保证通信效率的同时提高了用户的匿名性,从而使P2P网络得到更有效的实时保护。     

P2P网络应用动态规划算法控制搭便车行为的研究

针对P2P网络中节点共享存储资源时存在的“搭便车”问题,在节点存储资源分配时引入控制机制,节点根据请求者的贡献值分配其存储资源,以使贡献值小的节点获取资源少,从而抑制搭便车行为。仿真实验表明,该控制机制的动态规划算法能有效地实现P2P网络中存储资源分配的公平性,达到控制节点搭便车行为的目的。