电视与广播

TN93 02021600基千ACK和NAK的可靠组播传输协议的性能分析和比较/王斌,刘增基,李红滨,张冰(西安电子科大综合业务网国家重点实验室)11电子学报一2001,29(10)一1314一1318在目前各种可靠组播传轴协议的基础上,归纳构建了两类基本的可靠组播传输协议一基于确认(ACI勺的和基于否定确认(NAK)的可靠组播传输协议.在典型的组播网络系统模型基础上,对这两类协议以及一种主要的改进协议在占用网络带宽和可扩展性方面的性能恃点进行了定性的分析和比较.性能分析结果表明,基于否定确认且采用否定确认压缩策略(NAK Compression)的可靠组播传翰…     

可靠多播传输协议研究

战术通信网需要多播技术以支持多种组播应用,如情形感知、任务协作等。无线通信可为战术通信网组播通信提供支持,但其可靠性不高,不能直接应用,必须加以控制。为此,研究了一种利用IP多播路由和转发服务提供端到端可靠数据传输协议,即面向否定确认的可靠多播协议(NORM)。深入分析了NORM协议的反馈确认、拥塞控制、包级FEC等关键技术。在结论与展望中,提出了这一领域的难点和对今后工作的展望。     

一种实时可靠多播协议延迟性能分析

现有的可靠多播协议种类繁多,但尚不能满足有些应用中的特殊实时性要求,即在新数据不断以固定时间步长到达之前,必须完成旧就数据的修复,否则旧数据将会失效.实时可靠多播协议正是针对这种特殊需求提出的,该协议采用了混合FEC、分层网络局部修复技术和一种主动NAK机制,可有效控制并降低修复时间,同时还采取了NAK抑制机制使协议具有较好的扩展性能.为了评价协议的性能,论文在建立协议传输模型的基础上,基于泊松理论,精确地量化了节点和端系统的处理延迟以及修复过程延迟,导出了其传输延迟的计算公式.仿真计算结果表明,该实时可靠多播协议的传输延迟性能稳健,且表现出较好的可扩展性,能够满足应用的要求.     

一种卫星网络中基于Agent的可靠组播传输协议

IP 组播技术是一种可以把单个数据信息同时分发到不同的用户去的网络技术。卫星网络固有的广播信道特性使得它很适合组播应用。然而目前针对卫星网络的可靠组播服务研究很少,虽然已经有一些关于地面Internet组播协议建议,但他们并不适合于卫星网络。在卫星网络组播传输中的一个关键技术是传输协议设计。该文提出一种基于Agent的宽带卫星网络可靠组播传输协议(ASMTP)。该协议利用接收端Agent来实现卫星组播,采用分组级FEC和本地差错恢复纠正传播中的非相关错误和相关错误。在ASMTP中,还实现了流量控制和拥塞控制机制。仿真结果表明,在卫星网络环境中,ASMTP性能优于MFTP(Multicast File Transport Protocol),同时具有较好的网络可扩展性。     

全双工自适应选择式ARQ通信协议的设计

文章针对远距离点对点无线通信的特点 ,在标准全双工选择式ARQ滑动窗口协议的基础上 ,引进了多种自适应措施 ,包括可变的回传确认定时、重发计次措施以及自适应多次确认。对协议性能的理论分析和实验测试表明 ,协议在长RTT延时和强干扰的通信条件下能够实现高效可靠的数据传输     

基于UDP的可靠传输协议的研究与实现

在高速数据传输网络中,用户数据报协议(UDP)有着其他数据传输协议无法比拟的优势,但同时也存在着传输可靠性差的问题.文章作者在详细分析UDP特点的基础上,对其关键技术进行了改进,设计了一种可靠的传输机制.文章最后给出了在VxWorks操作系统下实现UDP可靠传输的方法和流程.     

基于RTP协议的网络流媒体组播传输技术

在简述RTP协议、组播技术及DirectShow技术的基础上,介绍了一个基于RTP协议的网络流媒体组播传输系统,重点对本系统的过滤器图的整体思路进行描述和演示.     

基于RTP协议的网络流媒体组播传输技术

在简述RTP协议、组播技术及DirectShow技术的基础上,介绍了一个基于RTP协议的网络流媒体组播传输系统,重点对本系统的过滤器图的整体思路进行描述和演示.     

Ad hoc网络基于协同的可靠组播丢失恢复算法设计

在Ad hoc网络中保证组播通信的可靠性要面对Ad hoc网络高误码率、带宽受限、节点能量有限和拓扑结构频繁变化等技术挑战。该文将协同的思想引入到组播丢失恢复设计中,设计了新的基于协同的可靠组播丢失恢复算法(CoreRM)。根据各个节点经历的不同丢失情况,通过自适应选择本地恢复、全局恢复或发送端恢复,分布式地处理整个网络的丢失恢复。CoreRM还设计了恢复路径缓存、NAK抑制机制,以及源路由数据包(SPM)发送机制来应对Ad hoc网络中的拓扑变化。性能分析和NS2的仿真实验表明相对于UDP和PGM可靠组播通信,CoreRM算法可以在网络吞吐量和丢失恢复延时方面有显著性能改善。     

基于ASON光组播的建模和算法研究

文章在对互联网工程任务组(简称IETF)相关草案研究的基础上,提出了基于自动交换光网络(ASON)的光组播模型,对组播算法和结构模型进行了分析,提出了光组播路由算法的基本思路、性能分析和比较,并建立了基于集中方式的组播模型,该模型可满足ASON对多播业务应用的需求.     

The PGM reliable multicast protocol

Pragmatic general multicast (PGM) is a reliable multicast transport protocol that runs over a best effort datagram service, such as IP multicast. PGM obtains scalability via hierarchy, forward error correction, NAK elimination, and NAK suppression. It employs a novel polling scheme for NAK delay tuning to facilitate scaling up and down. This article describes the architecture of PGM, and discusses performance and security issues. We show that PGM supports asymmetric networks, achieves high network utilization, and is capable of high-speed (> 100 Mb/s) operation. PGM is currently an IETF experimental RFC that has been implemented in both commercial and academic settings.     

Scalable feedback for large groups

We investigate the scalability of feedback in multicast communication and propose a new method of probabilistic feedback based on exponentially distributed timers. By analysis and simulation for up to 10⁶ receivers, we show that feedback implosion is avoided while feedback latency is low. The mechanism is robust against the loss of feedback messages and works well in case of homogeneous and heterogeneous delays. We apply the feedback mechanism to reliable multicast and compare it to existing timer-based feedback schemes. Our mechanism achieves lower negative acknowledgment character (NAK) latency for the same performance in terms of NAK suppression. No topological information of the network is used, and data delivery is the only support required from the network. The mechanism adapts to a dynamic number of receivers and leads to a stable performance for implosion avoidance and feedback latency     

TCP-Peachtree: a multicast transport protocol for satellite IP networks

In this paper, a reliable multicast transport protocol TCP-Peachtree is proposed for satellite Internet protocol (IP) networks. In addition to the acknowledgment implosion and scalability problems in terrestrial wirelined networks, satellite multicasting has additional problems, i.e., different multicast topology, different type of congestion control problems, and low bandwidth feedback link. In TCP-Peachtree, the modified B+ tree logical hierarchical structure is used to form dynamic multicast groups. Local error recovery and acknowledgment (ACK) aggregations are performed within each subgroup and also via logical subgroups. In order to avoid the overall performance degradation caused by some worst receivers, a local relay scheme is designed. Two new algorithms, jump start and quick recovery, which are based on the usage of a type of low-priority segments called NIL segments, are proposed for congestion control. NIL segments are used to probe the availability of network resources and also for error recovery. The delayed selective acknowledgment (SACK) scheme is adopted to address the bandwidth asymmetry problems and a hold state is developed to address persistent fades. The simulation results show that the congestion control algorithms of TCP-Peachtree outperform the TCP-NewReno when combined with our hierarchical groups and improve the throughput performance during rain fades. It is also shown that TCP-Peachtree achieves fairness and is very highly scalability.     

Power aware scalable multicast routing protocol for MANETs

Multicasting is an effective way to provide group communication. In mobile ad hoc networks (MANETs), multicasting can support a wide variety of applications that are characterized by a close degree of collaboration. Since MANETs exhibit severe resource constraints such as battery power, limited bandwidth, dynamic network topology and lack of centralized administration, multicasting in MANETs become complex. The existing multicast routing protocols concentrate more on quality of service parameters like end‐to‐end delay, jitter, bandwidth and power. They do not stress on the scalability factor of the multicast. In this paper, we address the problem of multicast scalability and propose an efficient scalable multicast routing protocol called ‘Power Aware Scalable Multicast Routing Protocol (PASMRP)’ for MANETs. PASMRP uses the concept of class of service with three priority levels and local re‐routing to provide scalability. The protocol also ensures fair utilization of the resources among the nodes through re‐routing and hence the lifetime of the network is increased. The protocol has been simulated and the results show that PASMRP has better scalability and enhanced lifetime than the existing multicast routing protocols. Copyright © 2005 John Wiley & Sons, Ltd.     

Scalable location guide overlay multicast in mobile ad hoc networks using tree partition scheme

Nodes mobility brings flinty challenges to multicast in Mobile ad hoc Networks (MANETs). To track nodes mobility, flooding messages are widely used for data delivery structure construction and maintenance in many multicast protocols. These periodic flooding messages significantly consume network resources, such as energy and bandwidth, and result in network collisions. To release data delivery structure maintenance onus, profited from GPS location service, a number of stateless location based multicast protocol were proposed, where a destination list is encapsulated into each data packet for data packet orientation. However, due to data packet capability limitation, the way of encapsulating a destination list in each data packet header restricts the protocol scalability. To solve the scalability issue of multicast protocols, we propose a Scalable Location Guide Overlay Multicast (SLGOM) for MANETs. Analysis and simulation results show that SLGOM achieves high performance in large multicast group and significantly improves the scalability of stateless multicast with respect to group size. Copyright © 2010 John Wiley & Sons, Ltd.     

一种适用于动态/移动环境的新的组播协议

组播协议由于能够有效的利用网络带宽并降低服务器的负担因而受到广泛的关注.其中的共享树组播协议由于具有良好的扩展性而得到更多的支持,然而目前的共享树组播协议在动态移动环境中的性能很差,一些改进协议(单核移动协议)虽然可以很好的提高原有协议的性能但是所需要的额外开销很大.针对这种情况,本文提出了一种新的共享树组播协议-动态多核协议,该协议能够根据组播成员的分布动态的渐进的调整组播树的形状,从而能够在低开销的情况下为移动用户提供良好的性能.计算机仿真和数学分析都表明动态多核协议要明显优于共享树组播协议和单核移动协议.     

Error counter-based negative acknowledgement mode in CCSDS file delivery protocol

Deep space communication has its own features such as long propagation delays,heavy noise,asymmetric link rates,and intermittent connectivity in space,therefore TCP/IP protocol cannot perform as well as it does in terrestrial communications.Accordingly,the Consultative Committee for Space Data Systems (CCSDS) developed CCSDS File Delivery Protocol (CFDP),which sets standards of efficient file delivery service capable of transferring files to and from mass memory located in the space segment.In CFDP,four optional acknowledge modes are supported to make the communication more reliable.In this paper,we gave a general introduction of typical communication process in CFDP and analysis of its four Negative Acknowledgement (NAK) modes on the respect of file delivery delay and times of retransmission.We found out that despite the shortest file delivery delay,immediate NAK mode suffers from the problem that frequent retransmission may probably lead to network congestion.Thus,we proposed a new mode,the error counter-based NAK mode.By simulation of the case focused on the link between a deep space probe on Mars and a terrestrial station on Earth,we concluded that error counter-based NAK mode has successfully reduced the retransmission times at negligible cost of certain amount of file delivery delay.     

SLM-一种安全分层组播协议

流媒体分发的一种典型实现方法是采用具有接收方驱动拥塞控制机制的分层组播.由于目前分层组播拥塞控制协议缺乏对用户行为的限制,接收方可违规订阅上层组播组发起自利型攻击,导致非公平的带宽利用.本文提出了一种较通用的安全分层组播协议SLM(Secure Layered Multicast).在路由器辅助拥塞控制条件下,在边界路由器采用基于Shamir秘密共享体制的拥塞状态相关访问控制(CR-AC,Congestion state Related Access Control)算法,管理用户组订阅行为,避免了用户自利型攻击,并使服务提供商可根据其与用户的协约限定不同用户的最高订阅级别.分析和仿真实验表明,该协议可实时保证网络流量安全共享带宽并具有较好的可扩展性.     

Scalable reliable multicast using multiple multicast channels

We examine an approach for providing reliable, scalable multicast communication, involving the use of multiple multicast channels for reducing receiver processing costs and reducing network bandwidth consumption in a multicast session. In this approach a single multicast channel is used for the original transmission of packets. Retransmissions of packets are done on separate multicast channels, which receivers dynamically join and leave. We first show that protocols using an infinite number of multicast channels incur much less processing overhead at the receivers compared to protocols that use only a single multicast channel. This is due to the fact that receivers do not receive retransmissions of packets they have already received correctly. Next, we derive the number of unwanted redundant packets at a receiver due to using only a finite number of multicast channels, for a specific negative acknowledgment (NAK)-based protocol. We then explore the minimum number of multicast channels required to keep the cost of processing unwanted packets to a sufficiently low value. For an application consisting of a single sender transmitting reliably to many receivers we find that only a small number of multicast channels are required for a wide range of system parameters. In the case of an application where all participants simultaneously act as both senders and receivers a moderate number of multicast channels is needed. Finally, we present two mechanisms for implementing multiple multicast channels, one using multiple IP multicast groups and the other using additional router support for selective packet forwarding. We discuss the impact of both mechanisms on performance in terms of end-host and network resources