FCA-ItswTCM:区分服务中一种公平的拥塞自适应标记算法

 本文提出了一种新的滑动窗口标记算法——公平的拥塞自适应标记算法(FCA-ItswTCM).算法近似识别TCP流和UDP流,适度区分标记,规避拥塞控制机制对公平性的影响;细粒度描述拥塞,预测拥塞,以此自适应调节各流注入黄包比例,兼顾网络拥塞状态对公平性的影响.仿真实验表明,与其他几种滑动窗口标记算法相比,FCA-ItswTCM对确保TCP流和UDP流带宽共享的公平性、提高资源利用率及系统稳定性有较好的效果.     

区分服务中一种拥塞感知的单速三色标记算法

确保服务的实现依赖于在边界路由器执行的数据包标记策略和在核心路由器执行的队列管理策略.TCP流由于其拥塞自适应的特点对丢包很敏感,网络拥塞对其吞吐量影响很大.为此,我们设计了一种拥塞感知的单速三色标记算法CASR3CM.仿真实验表明,该算法不仅提高了AS TCP流的平均吞吐量,而且增强了吞吐量的稳定性.另外该算法也提高了AS TCP流之间占用带宽的公平性.     

区分服务的改进主动队列管理算法

在区分服务模型中，具有不同微流数量、分组长度和目标速率的流聚集在资源共享时往往无法获得公平带宽。本文在自适应RIO算法基础上提出了一种区分RIO算法（Differentiated RIO，DRIO），DRIO对具有不同目标速率的流区别对待，使得无论在何种情况下都可以很好地保证各流聚集在共享带宽资源上的公平性，而且算法实现简单。仿真结果表明，DRIO对提高流聚集之间的公平性有很明显的效果。     

区分服务中一种TCP友好的公平数据包标记算法

在DiffServ网络中,存在一些对带宽利用的不公平性。为了解决这些不公平性,该文提出了一种基于TSW的标记算法,称之为TCP友好的公平数据包标记算法,它能以一种近似按比例的方式在各个汇聚流之间公平地分配网络中的剩余带宽,同时还能在汇聚流内部对TCP流和UDP流进行公平的带宽分配。通过仿真试验对算法进行了验证,并与其它几种标记算法进行比较,结果证实本算法比其它几种算法具有更好的公平性。     

区分服务网络中直接拥塞反馈机制与动态流量调节

IP服务质量是目前国际上的一个研究热点,IETF为此而定义了区分服务体系结构.然而,该体系中存在不公平问题.本文提出了一种直接拥塞反馈机制(DCCS),配合网络边缘的动态流量调节(DTC)算法,能够为该体系提供很好的公平性.该机制不仅能保证响应流与非响应流之间的公平性,而且能解决响应流(如TCP)自身由于分组长度,微流数目及环回时延(RTT)等因素而产生的差异.     

一种自适应的FRED缓存管理算法

如何保证业务流的公平性,特别是在存在UDP业务流的情况下,有效地保护TCP流一直是一个热点研究课题.本文提出了一种自适应的FRED缓存管理算法AFRED,通过动态的调节分组丢弃的门限,保护了TCP流,提高了系统的公平性,同时保证了带宽利用的有效性.算法的复杂度与FRED相近,但是能获得更好地性能.     

基于聚集算法的DDoS数据流检测和处理

提出了一种应用于路由器的嵌入式DDoS（分布式拒绝服务攻击）防御算法.针对DDoS攻击的本质特征,对IP数据流进行轻量级协议分析,把IP数据流分为TCP、UDP和ICMP（网间控制报文协议）数据流,分别建立相应的聚集模式,根据该模式来检测DDoS聚集所占资源,采取相应的抑制措施过滤攻击数据包,从而保证合法数据流的正常转发.仿真试验证明该方法能准确地检测到DDoS攻击,处理效果很好.     

确保最小发送速率的TCP友好拥塞控制算法

提出一种确保最小发送速率的TCP友好拥塞控制算法CQTCCA(certified quality TCP-friendly congestion control algorithm)。该算法通过将网络结点和端点相结合，在端点对UDP数据流采用基于公式的发送速率调整，使之体现对TCP数据流的友好性；在结点对RED进行改造，得到提供带优先级包标记的MRED算法，保证对实时多媒体数据流的最小带宽要求。仿真实验验证了本算法有效性。     

一种改进的双速率三色标记器

提出了一种改进的双速率三色标记算法。该算法用两个上三角矩阵表示标记器之间的令牌借用关系，在某一个标记器对应的流(或者聚合流)空闲时，把它多余的令牌能够按照一定的概率借用给需要令牌的数据流。在某个数据流繁忙时，若发现自己目前的令牌不足，就向原来借用自己令牌的数据流索还一定的令牌。该算法能用来在区分服务环境下对确保传输的分组进行丢弃优先级标记。仿真结果表明，相对于原来的双速率三色标记算法，该算法能够提供较高的吞吐量。     

基于2-D稳定条件的混合流网络参数设置

由于网络容量的限制,任何一个网络都不可能避免拥塞问题。传统的RED算法只考虑了少量TCP用户,没有涉及UDP用户的情况,同时随着网络应用的多样化,如越来越多的UDP用户接入网络,传统的RED机制无法控制它们,保证不了TCP用户的服务质量(QoS)。针对TCP/UDP混合流多用户的情况,本文提出TCP/UDP混合流的区分控制,这里TCP和UDP流使用不同的带宽,及TCP/UDP混合流单瓶颈网络的2-D稳定条件。基于该稳定条件可以选择一个合适的RED控制参数Pmax,获得满意的网络拥塞控制性能。本文建立了一个TCP和UDP流单瓶颈网络的线性时滞系统模型,利用2-D拉普拉斯-Z变换,推导出基于稳定条件的混合流网络参数配置。利用NS2仿真验证所提出的混合流网络参数配置能够有效获得关于路由器队列长度和TCP窗口的稳定性。     

A low-state packet marking framework for approximate fair bandwidth allocation

Misbehaving, non-congestion-reactive traffic is on the rise in the Internet. One way to control misbehaving traffic is to enforce local fairness among flows. Locally fair policies, such as fair-queueing and other fair AQM schemes, are inadequate to simultaneously control misbehaving traffic and provide high network utilization. We thus need to enforce globally fair bandwidth allocations. However, such schemes have typically been stateful and complex to implement and deploy. In this letter, we present a low state, lightweight scheme based on stateless fair packet marking at network edges followed by RIO queueing at core nodes, to control misbehaving flows with more efficient utilization of network bandwidth. Additionally, with low-state feedback from bottleneck routers, we show that, in practice, we can approximate global max-min fairness within an island of routers. We show, using simulations, that we can indeed control misbehaving flows and provide more globally fair bandwidth allocation.     

一种提高802.11无线Ad Hoc网络公平性的新机制-FFMA

实现多个数据流对无线信道的公平共享是802.11无线Ad Hoc网络中的一个重要议题,但802.11DCF机制在无线Ad Hoc网络中存在严重的公平性问题,甚至有可能出现单个节点或数据流独占信道而其他节点和数据流处于"饥饿"状态的情况.论文提出了一种新颖的保证数据流间公平性的MAC层接入机制FFMA(Flow rate-based Fair Medium Access),通过公平调度和公平竞争的方式,FFMA能够在数据流间公平地分配信道带宽资源.仿真结果表明,在无线Ad Hoc网络中,FFMA可以在保证信道吞吐量的前提下取得远优于802.11 DCF的数据流间的公平性.     

A weighted fairness guarantee scheme based on node cooperation for multimedia WLAN mesh networks

In this paper, we focus on weighted fairness in multimedia WLAN mesh networks. Based on the analysis of the fairness problem of IEEE 802.11e Enhanced Distributed Channel Access (EDCA) scheme in WLAN mesh networks, we propose a weighted fairness guarantee scheme (WFGS), which provides weighted fairness for multimedia flows with different QoS requirements through node cooperation. WFGS piggybacks extra field in RTS/CTS frames to declare the channel occupation ratio of each flow. Accordingly, the transmitters can get the neighboring flows’ channel occupation ratio via overhearing the RTS/CTS frames from its neighbors, and cooperatively adjust the contention window size to achieve weighted fairness among the flows. Also, to reliably reserve transmissions, an adaptive power control based RTS/CTS handshake mechanism is introduced. Simulation results show that compared with EDCA scheme, WFGS can effectively resolve the collisions induced by the carrier interference and thereby guarantee both the short-term and long-term weighted fairness among multimedia flows.     

A topology-independent wireless fair queueing model in ad hoc networks

Fair queueing of rate and delay-sensitive packet flows in a shared-medium, multihop wireless network is challenging due to the unique design issues. These issues include: 1) spatial contention among transmitting flows in a spatial locality, as well as spatial reuse of bandwidth through concurrent flow transmissions in different network locations; 2) conflicts between ensuring fairness and maximizing spatial channel reuse; and 3) the distributed nature of ad hoc fair queueing. In this paper, we propose a new topology-independent fair queueing model for a shared-medium ad hoc network. Our fairness model ensures coordinated fair channel access among spatially contending flows, while seeking to maximize spatial reuse of bandwidth. We describe packetized algorithms that realize the fluid fairness model with analytical performance bounds. We further design a distributed implementation which approximates the ideal centralized algorithm. We present simulations and analysis on the performance of our proposed algorithms.     

Dual-Resource TCP/AQM for Processing-Constrained Networks

This paper examines congestion control issues for TCP flows that require in-network processing on the fly in network elements such as gateways, proxies, firewalls and even routers. Applications of these flows are increasingly abundant in the future as the Internet evolves. Since these flows require use of CPUs in network elements, both bandwidth and CPU resources can be a bottleneck and thus congestion control must deal with ldquocongestionrdquo on both of these resources. In this paper, we show that conventional TCP/AQM schemes can significantly lose throughput and suffer harmful unfairness in this environment, particularly when CPU cycles become more scarce (which is likely the trend given the recent explosive growth rate of bandwidth). As a solution to this problem, we establish a notion of dual-resource proportional fairness and propose an AQM scheme, called Dual-Resource Queue (DRQ), that can closely approximate proportional fairness for TCP Reno sources with in-network processing requirements. DRQ is scalable because it does not maintain per-flow states while minimizing communication among different resource queues, and is also incrementally deployable because of no required change in TCP stacks. The simulation study shows that DRQ approximates proportional fairness without much implementation cost and even an incremental deployment of DRQ at the edge of the Internet improves the fairness and throughput of these TCP flows. Our work is at its early stage and might lead to an interesting development in congestion control research.     

Flow rank based probabilistic fair scheduling for wireless ad hoc networks

Fair scheduling is an ideal candidate for fair bandwidth sharing and thereby achieving fairness among the contending flows in a network. It is particularly challenging for ad hoc networks due to infrastructure free operation and location dependent contentions. As there is no entity to serve coordination among nodes, we need a mechanism to overcome inherent unreliability of the network to provide reduced collision and thereby higher throughput and adequate fair allocation of the shared medium among different contending flows. This paper proposes a flow rank based probabilistic fair scheduling technique. The main focus is to reduce the collision probability among the contending flows while maintaining the prioritized medium access for those flows, which ensures a weighted medium access control mechanism based on probabilistic round robin scheduling. Each flow maintains a flow-table upon which the rank is calculated and backoff value is assigned according to the rank of the flow, i.e., lower backoff interval to lower ranked flow. However, flow-table instability due to joining of a new flow, partially backlogged flow, hidden terminal and partially overlapped region exhibits a challenging problem that needs to be mitigated for our mechanism to work properly. We take appropriate measures to make the flow-table stabilized under such scenarios. Results show that our mechanism achieves better throughput and fairness compared to IEEE 802.11 MAC and existing ones.     

PASA: power adaptation for starvation avoidance to deliver wireless multimedia

In recent years, there has been an increasing interest to deliver multimedia services over wireless ad hoc networks. Due to the existence of hidden terminal and absence of central control, the medium access control protocol as used in the ad hoc networks may lead to channel capture, where some flows monopolize the channel while others suffer from starvation. As a consequence, the system throughput and fairness are greatly degraded. After showing that static power control leads to channel capture, we propose and study a distributed dynamic power control scheme termed "power adaptation for starvation avoidance" (PASA), which dynamically adjusts the transmission power of a node so as to avoid starvation. PASA is shown to be effective in breaking channel captures, hence improving short-term fairness among contending flows. It is simple, fully autonomous and requires no communication overhead. Via extensive simulations, we show that our power control algorithm achieves much better fairness without compromising system throughput through better spatial reuse. Our experiments with video sequences transmitting over different network topologies show that PASA achieves much better video quality with lower start-up delay and buffer requirement.     

Congestion control for fair resource allocation in networks with multicast flows

We consider the problem of congestion control in networks which support both multirate multicast sessions and unicast sessions. We present a decentralized algorithm which enables the different rate-adaptive receivers in different multicast sessions to adjust their rates to satisfy some fairness criterion. A one-bit ECN marking strategy to be used at the nodes is also proposed. The congestion-control mechanism does not require any per-flow state information for unicast flows at the nodes. At junctions nodes of each multicast tree, some state information about the rates along the branches at the node may be required. The congestion-control mechanism takes into account the diverse user requirements when different receivers within a multicast session have different utility functions, but does not require the network to have any knowledge about the receiver utility functions.