基于多跳间时延协作的最久分组优先算法

提出了一种基于多跳间时延协作的Crossbar调度算法。该算法以分组头中记录的时延为权重对分组进行调度，通过控制分组在各跳上的时延来达到调节端到端时延的目的。算法还使路由器避免了维护每个流的状态信息以及对单个流进行的复杂的队列管理和调度。计算机仿真表明，算法具有较高的资源利用率、较低的端到端时延抖动和较低的分组丢弃率等特点。     

一种前向共享信道下多业务的分层混合调度策略

前向采用共享信道方式的系统在承载多种业务时,单一的调度算法很难满足所有业务的QoS需求。在介绍了前向共享信道分组调度的模型后;论文依据不同类别业务的传输需求,提出一种两层的混合调度策略,该策略按业务类别对分组进行分类缓存,并按比例将传输时隙分配到各个数据类,而各数据类采用先到先服务、保证带宽的或是比例公平的调度来实现按用户的分组发送;最后,通过仿真实验对该策略的有效性进行了验证。     

Quantum-Based Earliest Deadline First Scheduling for Multiservices

Latency-rate (LR) schedulers have shown their ability in providing fair and weighted sharing of bandwidth with an upper bound on delivery latency of packets while earliest departure first (EDF) schedulers have shown their ability in providing LR-decoupled service whereby the delivery latency of packets is not bounded by the reserved rate. However, EDF schedulers require traffic shapers to ensure flow protection. We propose quantum-based earliest deadline first scheduling (QEDF), a quantum-based scheduler that provides flow protection, throughput guarantee and delay bound guarantee for flows that require LR-coupled and LR-decoupled types of reservations. It classifies flows into time-critical (TC), jitter-sensitive (JS), and rate-based (RB) classes and uses a quality-of-service forwarding rule to determine the next packet to be serviced by the scheduler. It provides nonpreemptive priority service to TC queues. This allows LR-decoupled reservation for flows that have a low rate and intolerable delay. Packets from JS queues can be delayed by other packets if forwarding the latter will not result in the former missing its deadline. As a quantum-based scheduler, the QEDF scheduler provides throughput guarantees for RB queues. We present both analytical and simulation results of QEDF, whereby we evaluated QEDF in its deployment as a single-class as well as a multiservice scheduler     

Providing QoS with the Deficit Table Scheduler

A key component for networks with Quality of Service (QoS) support is the egress link scheduling algorithm. An ideal scheduling algorithm implemented in a high-performance network with QoS support should satisfy two main properties: good end-to-end delay and implementation simplicity. Table-based schedulers try to offer a simple implementation and good latency bounds. Some of the latest proposals of network technologies, like Advanced Switching and InfiniBand, include in their specifications one of these schedulers. However, these table-based schedulers do not work properly with variable packet sizes, as is usually the case in current network technologies. We have proposed a new table-based scheduler, which we have called Deficit Table (DTable) scheduler, that works properly with variable packet sizes. Moreover, we have proposed a methodology to configure this table-based scheduler in such a way that it permits us to decouple the bounding between the bandwidth and latency assignments. In this paper, we thoroughly review the provision of QoS with the DTable scheduler and our configuration methodology, and evaluate the performance of our proposals in a multimedia scenario. Simulation results show that our proposals are able to provide a similar latency performance than more complex scheduling algorithms. Moreover, we show the advantages of our decoupling configuration methodology over the usual ways of configuring this kind of table-based schedulers.     

Estimation of the available bandwidth ratio of a remote link or path segments

Available bandwidth is usually sensitive to network anomalies such as physical link failure, congestion, and DDoS attack. Thus, real-time available bandwidth information can be used to detect network anomalies. Many schemes have been proposed to estimate the end-to-end available bandwidth or end-to-end capacity. However, the problem of estimating the available bandwidth for a specific remote link has not been investigated in detail yet. We propose a new scheme to estimate the available bandwidth ratio of a remote link or remote path segments, a group of consecutive links, without deploying our tool at the remote nodes. The scheme would be helpful in accurately pinpointing anomalous links. Two streams of ICMP timestamp packets are sent to both end nodes of a target link according to a Poisson process, and the available bandwidth ratio for the target link is estimated based on the measured packet delay. Since the proposed scheme needs not incur a short-term congestion, unlike conventional end-to-end available bandwidth estimation mechanisms, the intrusiveness is low and the proposed scheme overcomes the limitation of conventional approaches, inability to probe the links beyond the tight link with the minimum available bandwidth. The performance of the proposed scheme is evaluated by ns-2 simulation.     

Incorporating packet semantics in scheduling of real-time multimedia streaming

In this work, we develop a novel packet scheduling algorithm that properly incorporates the semantics of a packet. We find that improvement in overall packet loss does not necessarily coincide with improvement in user perceivable QoS. The objective of this work is to develop a packet scheduling mechanism which can improve the user perceivable QoS. We do not focus on improving packet loss, delay, or burstiness. We develop a metric called, “Packet Significance,” that effectively quantifies the importance of a packet that properly incorporates the semantics of a packet from the perspective of compression. Packet significance elaborately incorporates inter-frame, intra-frame information dependency, and the transitive information dependency characteristics of modern compression schemes. We apply packet significance in scheduling the packet. In our context, packet scheduling consists of two technical ingredients: packet selection and interval selection. Under limited network bandwidth availability, it is desirable to transmit the subset of the packets rather than transmitting the entire set of packets. We use a greedy approach in selecting packets for transmission and use packet significance as the selection criteria. In determining the transmission interval of a packet, we incorporate the packet significance. Simulation based experiments with eight video clips were performed. We embed the decoding engine in our simulation software and examine the user perceivable QoS (PSNR). We compare the performance of the proposed algorithm with best effort scheduling scheme and one with simple QoS metric based scheduling scheme. Our Significance-Aware Scheduling scheme (SAPS) effectively incorporates the semantics of a packet and delivers best user perceivable QoS. SAPS can result in more packet loss or burstier traffic. Despite these limitations, SAPS successfully improves the overall user perceivable QoS.     

MANET典型路由协议的性能分析与仿真

移动Ad Hoc网络(MANET)是由一组无线移动主机组成的一个没有任何事先建立好的基础设施或集中管理设备的临时网络,其特点是网络拓扑易变,带宽、能源有限及容易受到攻击等。该文对AODV, DSR, DSDV这几种典型的路由协议进行分析比较,指出它们的优缺点及适用场合。通过2个场景的配置,从路由开销、分组投递率、端到端的平均时延3个方面进行实验。仿真结果表明,按需路由协议在3个方面都表现出较好的性能。     

A Novel Framework for IP DiffServ over Optical Burst Switching Networks

This paper presents a novel framework for IP Differentiated Services (DiffServ) over optical bursts witching (OBS), namely, DS-OBS. The network architecture, functional model of edge nodes and core nodes,the control packet format, a novel burst assembly scheme at ingress nodes and scheduling algorithm of core nodes are presented. The basic idea is to apply DiffServ capable burst assembly at ingress nodes and perform different per hop behavior (PHB) electronic treatments for control packets of different QoS class services at core nodes. Simulation results show that the proposed schemes can provide the best differentiated service for expedited forwarding (EF), assured forwarding (AF) and best effort (BE) services in terms of end-to-end delay, throughput and IP packet loss probability.     

An efficient homomorphic MAC-based scheme against data and tag pollution attacks in network coding-enabled wireless networks

Recent research efforts have shown that wireless networks can benefit from network coding (NC) technology in terms of bandwidth, robustness to packet losses, delay and energy consumption. However, NC-enabled wireless networks are susceptible to a severe security threat, known as data pollution attack, where a malicious node injects into the network polluted packets that prevent the destination nodes from decoding correctly. Due to recoding, occurred at the intermediate nodes, according to the core principle of NC, the polluted packets propagate quickly into other packets and corrupt bunches of legitimate packets leading to network resource waste. Hence, a lot of research effort has been devoted to schemes against data pollution attacks. Homomorphic MAC-based schemes are a promising solution against data pollution attacks. However, most of them are susceptible to a new type of pollution attack, called tag pollution attack, where an adversary node randomly modifies tags appended to the end of the transmitted packets. Therefore, in this paper, we propose an efficient homomorphic message authentication code-based scheme, called HMAC, providing resistance against data pollution attacks and tag pollution attacks in NC-enabled wireless networks. Our proposed scheme makes use of three types of homomorphic tags (i.e., MACs, D-MACs and one signature) which are appended to the end of the coded packet. Our results show that the proposed HMAC scheme is more efficient compared to other competitive tag pollution immune schemes in terms of complexity, communication overhead and key storage overhead.     

联合车速–队列感知的路边单元分组调度随机优化

路边单元(RSU)是车联网中为其无线覆盖范围内过往车辆提供信息服务的基础设施,路边单元间的分组传输可通过移动车辆"存储–载带–转发"的方式进行,其传输过程中分组的端到端时延由源RSU缓存中的排队时延与车辆载带过程的传播时延两部分组成.为使RSU间分组传输过程中平均端到端时延最小化,本文提出一种联合车速–队列感知的路边单元分组调度随机优化方法,该方法根据源RSU缓存队列长度和经过源RSU覆盖范围的车辆速度状态作分组调度决策.通过马尔科夫决策(MDP)框架对分组传输过程中的平均排队时延和平均传播时延进行分析,建立一个非线性平均端到端时延最小化问题并求解.仿真结果表明,所提出的RSU分组调度随机优化方法可以显著降低RSU间分组传输过程中的平均端到端时延,并提高系统中分组传输的吞吐量.     

无线传感器网络中基于能量效率的多路径路由算法

针对无线传感器网络节点能量受限的特点,本文提出了一种能量有效、负载均衡的多路径路由算法(EMR)。该算法在按需路由协议AODV基础上,不单纯以最小跳数或者最小时延作为路由选择依据,充分考虑到了路由的能量消耗最小化,避开剩余能量过低的节点,数据沿着最小跳数或路径关键能量比较高的路径传输,降低了网络的能量消耗,也避免关键节点的过量负载。分析与仿真结果表明,与AODV协议相比较,EMR具有更好的分组投递率、端到端时延,推迟了网络中出现死亡节点的时间,从而延长了网络生命周期。     

带内信令系统实现Ad Hoc网络的邻居预留

提出使用带内信令系统实现跨层的邻居预留机制(NR INSIGNIA),该机制在进行带宽预留时考虑MAC层的信道竞争。节点为某个QoS流预留一定带宽之后,在所有的邻居节点上同时预留等量的带宽,以此来消除信道竞争对带宽预留产生的不利影响。仿真试验对比了没有邻居预留机制的原始INSIGNIA(In band signaling system)系统与NR INSIGNIA系统的性能,结果表明NR INSIGNIA系统可以显著提高QoS流的平均预留包比率、投递率,减少端－端延迟。     

Hardware design and implementation of packet fair queuing algorithms for the quality of service support in the high-speed internet

The increasing amount of real-time traffic carried over the Internet requires end-to-end quality of service (QoS) support. To this end, the QoS Schedulers, that are implemented in routers, assign the available bandwidth resources to packet flows according to their respective allocated rates. Packet Fair Queuing (PFQ) schedulers can provide fair service and low end-to-end delay bound to the traffic flows. However, they have higher implementation complexity compared to other algorithms, because of the requirements of tracking the system state, and searching for the packet to get service among all flows, that are queued at the outgoing interface. QoS scheduling is a data plane functionality, which requires hardware implementation for high speed router interfaces. The previous works on hardware implementation of PFQ schedulers are specific to certain algorithms, and they do not provide any results on real hardware platforms. In this paper, we present a general hardware design framework for PFQ schedulers, and apply this framework to the WF²Q+ PFQ algorithm to demonstrate its properties. We carry out the entire implementation of the WF²Q+ algorithm on an FPGA, and evaluate its performance with real traffic flows. In addition, we implement WFQ as a second PFQ algorithm to demonstrate the generality of the framework.     

多通道并行传输中接收缓存阻塞的缓解方法

针对多通道并行传输中的接收缓存阻塞问题,分析了引起接收缓存阻塞的原因,提出一种改进的缓解接收缓存阻塞的数据包调度方法,综合考虑通道的带宽、时延和丢包率,引入通道质量的评价函数,优化多通道之间的数据包调度,选择质量最好的通道进行传输,减少由于通道特性不同造成的接收端数据包乱序;提出一种改进的数据包重传策略,基于时延和丢包率选择能使数据包最快到达接收端的通道进行重传;提出一种根据通道的带宽-延迟积估算所需接收缓存大小的方法。仿真实验表明,所提出的调度方法和重传策略能够有效地减轻接收缓存阻塞,与CMT-SCTP相比具有更优的性能,所提出的缓存大小的估算方法也能够准确估算所需接收缓存的大小。     

网络QoS的分组调度算法仿真研究

随着Internet的不断发展,实时数据的应用对网络提出了更高的服务质量控制要求,分组调度是实现网络服务质量控制的核心技术之一.分组调度按照一定的规则决定队列中分组的发送次序并分配共享链路带宽.文中介绍了一种先进的分组调度和资源管理模型:链路共享模型, 以及两种不同的实现算法:CBQ和HPFQ,分析了它们用于传输实时流的可行性.HPFQ算法为实时数据提供了严格的时延保证和完全意义上的等级链路共享服务.文中使用网络仿真工具NS2,对链路共享模型下实时流传输的服务质量性能进行了仿真分析.     

Hardware implementation study of several new egress link scheduling algorithms

The provision of Quality of Service (QoS) in interconnection networks is required for new multimedia and time-sensitive applications, which are very important for recent utility computing data centers (UCDCs) using high performance networks. These interconnection networks support switch-based principles and establish high demands in terms of bandwidth, time-delay, and delivery over short distances. A key component for networks with QoS support is the egress link scheduling algorithm. Apart from providing a good performance in terms of, for example, good end-to-end delay (also called latency) and fair bandwidth allocation, an ideal scheduling algorithm implemented in a high-performance network with QoS support should satisfy another important property which is to have a low computational and implementation complexity. In this paper, we propose specific implementations (taking into account the characteristics of current high performance networks) of several fair-queuing scheduling algorithms and compare their complexity in terms of silicon area and computation delay. In order to carry out this comparison, we have devised our own hardware comparison methodology. Following this methodology, we have performed our own hardware implementation for the different schedulers. We have modeled the schedulers using the Handel-C language and employed the DK design suite tool from Celoxica in order to obtain hardware estimates on silicon area and arbitration time.     

一种适用于IPv6的高效瓶颈带宽测量方法

提出了一种下一代网络的瓶颈带宽测量方法——IPv6-pckt-pr。该方法在OPNET仿真环境下，以自相似业务流为背景流量，给探测报文赋予相同的流标签，同时将其业务类别设置为最高级，通过发送不等长的探测包对测量端到端瓶颈带宽。分析与实验表明，该方法的测量结果准确度较好，分布比较集中，测量时间较短，并能有效减少测量带宽。     

Universal Timestamp-Scheduling for real-time networks

Consider a network of computers interconnected by point-to-point communication channels. For each flow of packets through the network, the network reserves a fraction of the packet rate of each channel along the path of the flow. We define a family of scheduling protocols, called Universal Timestamp-Scheduling, to forward packets in this network, such that all members of the protocol family provide the same upper bound on packet delay as the well-known packet delay of Virtual Clock scheduling. The protocol family is called universal because it encompasses a wide variety of protocols. To show this, we prove that many scheduling protocols in the literature are members of the protocol family, and thus provide the above guarantee. In addition, we show that the protocols in the literature have only considered one side of the spectrum of possible scheduling protocols, and that there is another side of the spectrum that deserves attention and remains to be investigated.     

高效自适应的抗污染攻击网络编码传输方案

本文主要研究网络编码在抗污染攻击中的应用,针对中间节点对收到的所有编码包进行验证浪费网络资源和目的节点解码速率慢等问题,提出一种高效自适应的抗污染攻击网络编码传输方案-EANC(Efficient and Adaptive Network Coding transmission scheme against pollution attack)。EANC方案在数据分组编码阶段,利用按照网络编码的时间和空间特性构造的线性子空间签名方案准确地验证数据分组是否被污染从而有效控制污染数据分组的传播,并且能使中间节点调节验证步骤使之自适应于当前网络的污染程度,从而提高验证效率;在目的节点解码阶段,EANC方案利用目的节点重传恢复机制降低解码恢复时延。仿真结果表明,EANC方案能够减少子空间的签名长度并且降低目的节点解码恢复的平均时延。     

基于SASR的多路径协议SAMSR研究

比较和分析了自组网络中单路径与多路径的反应式路由协议,在SASR的基础上提出了一个新的多路径路由协议SAMSR。它通过记录重复的RREQ报文以获得更多网络拓扑信息,从而发现更多的可达路径,以及在收到重复的RREP报文后,发回重选报文RSEL保证路径间的节点不相干性。最后通过在NS-2平台上模拟考查其性能,表明SAMSR协议虽然增加了网络开销,但提高了分组抵达率,减少了端到端的路由时延。