一种区分服务网络边缘路由器动态阈值的公平性标记算法

针对区分服务分组标记算法没有考虑到流特性,从而导致不同的流在带宽竞争中出现公平性较差的问题,提出了应用在网络边缘路由器上的一种基于动态阈值的三色标记算法DTTCM。该算法通过调整流速阈值minth和maxth,按照一定的策略对数据包进行标记,从而保证数据流在带宽不足时能公平地享受带宽。理论分析和仿真结果表明,DTTCM在UDP流与TCP流的带宽分配上,以及目标速率对于聚流间剩余带宽分配的影响上,均有着较好的公平性。     

基于速率预测的三色标记算法

提出了一种适用于比例区分服务的数据包标记算法——基于速率预测的三色标记算法(Rate Prediction Marker, RPM)。RPM算法基于在线流量预测算法,对DiffServ网络中经过分类器划分的网络流或者进入标记器的网络流进行提前1期流量预测,根据预测结果以及历史流量的均值进行加权后的结果对数据包进行标记。当源端可能进入TCP的拥塞恢复阶段时,按比例将网络中的可用带宽分配给服务聚集流,从而提高网络带宽的利用率。仿真和实验结果表明,RPM算法与现有的算法相比在目标速率影响和带宽吞吐量上具有更好的性能,从而获得了很好的公平性和带宽利用率。     

保证无线上行链路TCP公平的调度算法

针对无线局域网中上行链路TCP流之间存在严重的无线信道资源分配不公平问题,提出一种上行链路TCP流的调度算法UFWFQ。该算法在接入节点上对上行TCP流采用与WFQ算法相同的轮询机制,根据流的传送速率动态计算其服务概率,分配给高速发送流较大的权重,使各上行TCP流占用的信道时间相等,以保证各流的加权公平性,提高网络的总吞吐率。仿真实验结果验证了该算法的有效性。     

路由器队列调度算法仿真研究

该文指出互联网技术的发展,带来了网络大流量业务的不断增加,特别是UDP业务数据急剧增加.由于UDP协议不具有拥塞控制能力,TCP协议具有拥塞控制能力,UDP数据极易阻塞网络链路,产生了严重的不公平性,影响了其他业务的进行.该文分析了路由器队列调度算法的原理,通过Opnet仿真,模拟了不同队列调度算法的拥塞状况,分析出采...     

基于pmax和p的RED算法改进及分析

对RED的最大丢弃概率pmax和丢弃概率p进行了优化,NS2仿真实验结果表明,改进后的算法PO_RED,在网络轻载时,能同时提高TCP流和UDP流的性能;在网络重载时,能够抑制UDP流、增强TCP流,使网络资源分配更加公平。     

一种边界到边界的拥塞感知的三色标记器*

通过对基本的流量标记,特别是在CATC、CASR3CM和ITSW3CM研究的基础上提出了拥塞感知的流量标记器CATSW3CM。理论分析和仿真实验表明,CATSW3CM与CATC相比,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,提高了AS TCP流之间占用带宽的公平性,并且更为简单,具有很好的扩展性。     

区分服务中一种公平的汇聚流标记算法

区分服务是提供QoS的重要机制之一,但在区分服务中存在着汇聚流之间剩余带宽分配的不公平性问题。为解决该问题,提出了动态数据包标记算法（DPMA）,该算法通过监测汇聚流的流速变化,能动态地调整标记策略,它能以一种近似按比例的方式在各汇聚流之间公平地分配网络中的剩余带宽。仿真结果表明该算法是有效的。     

区分服务网络中带宽利用的公平性

为了解决DiffServ网络中带宽利用的不公平性 ,该文提出了一种自适应的数据包标记算法AFM(AdaptiveFairMarker) .与现有的标记算法相比 ,它有两个显著的不同 :( 1)增加了一种带宽估计机制 ,对网络中可使用的带宽进行动态估计 ,并将所估计的带宽以按比例的方式公平地分配给各个汇聚流 ;( 2 )对TCP协议作了一个微小而又非常有效的改进 ,在控制TCP拥塞窗口的同时尽量避免TCP协议的AIMD机制 .该文通过仿真试验对算法进行了验证 ,结果证实AFM算法比其它几种算法具有更好的公平性     

区分服务中基于彩票算法的公平带宽分配

区分服务是提供QoS的重要机制之一,但在区分服务中存在着汇聚流之间剩余带宽分配的不公平性问题。为解决该问题,本文提出了基于彩票算法的区分服务标记算法,该算法基于彩票算法,能够根据区分服务的优先级,调整标记各汇聚流的标记策略。它能以一种近似按比例的方式在各汇聚流之间公平地分配网络中的剩余带宽。仿真结果表明该算法是有效的。     

高速TCP算法的最新进展及MIMD算法的公平性分析

随着网络应用的增长和性能的提高，传统TCP协议开始显现对高速网络的不适应性，因此急需对其进行改进。作者首先简单介绍了高速TCP算法产生的背景和几种有代表性的算法，然后具体分析其中MIMD算法与传统TCP之间的影响。分析结果表明，在按比例丢包的链路中，MIMD流和传统TCP流占有的带宽将会保持一定比例，并且能各自维持平衡。但是当链路出现大量同时丢包时，MIMD流将显现极强的资源掠夺性。     

A provision aware proportional fair sharing three colour marker

Traffic conditioners enforce agreements between domains to allow service profiles to conform to subscribers Service Level Agreements. To ensure fairness in the network, these traffic conditioners should allocate bandwidth to subscribers according to their agreed contracted rate and share excess bandwidth in proportion to this agreed rate when the network is over or well provisioned. In instances where the network is under provisioned, the allocation of bandwidth to a subscriber should degrade in proportion to its agreed rate. In this paper a provision aware proportional fair sharing three colour marker is proposed to ensure that these fairness criteria are fulfilled for aggregated flows. Its main contributions are in achieving fairness in under provisioned networks and in the presence of UDP traffic whilst being insensitive to the number of flows in an aggregate. This is demonstrated through a quantitative simulation analysis and also exhibits improved performance over other aggregated approaches, including a recent proposal to provide fairness in under provisioned networks. These results infer that fairness can be achieved by considering the provision of the network in the design of the algorithm, by using separate marking algorithms for TCP and UDP traffic and by using an adaptive factor that mitigates sensitivity to the number of flows in an aggregate.     

Evaluating TCP-friendliness in light of Concurrent Multipath Transfer

In prior work, a CMT protocol using SCTP multihoming (termed SCTP-based CMT) was proposed and investigated for improving application throughput. SCTP-based CMT was studied in (bottleneck-independent) wired networking scenarios with ns-2 simulations. This paper studies the TCP-friendliness of CMT in the Internet. In this paper, we surveyed historical developments of the TCP-friendliness concept and argued that the original TCP-friendliness doctrine should be extended to incorporate multihoming and SCTP-based CMT.Since CMT is based on (single-homed) SCTP, we first investigated TCP-friendliness of single-homed SCTP. We discovered that although SCTP’s congestion control mechanisms were intended to be “similar” to TCP’s, being a newer protocol, SCTP specification has some of the proposed TCP enhancements already incorporated which results in SCTP performing better than TCP. Therefore, SCTP obtains larger share of the bandwidth when competing with a TCP flavor that does not have similar enhancements. We concluded that SCTP is TCP-friendly, but achieves higher throughput than TCP, due to SCTP’s better loss recovery mechanisms just as TCP-SACK and TCP-Reno perform better than TCP-Tahoe.We then investigated the TCP-friendliness of CMT. Via QualNet simulations, we found out that one two-homed CMT association has similar or worse performance (for smaller number of competing TCP flows) than the aggregated performance of two independent, single-homed SCTP associations while sharing the link with other TCP connections, for the reason that a CMT flow creates a burstier data traffic than independent SCTP flows. When compared to the aggregated performance of two-independent TCP connections, one two-homed CMT obtains a higher share of the tight link bandwidth because of better loss recovery mechanisms in CMT. In addition, sharing of ACK information makes CMT more resilient to losses. Although CMT obtains higher throughput than two independent TCP flows, CMT’s AIMD-based congestion control mechanism allows other TCP flows to co-exist in the network. Therefore, we concluded that CMT is TCP-friendly, similar to two TCP-Reno flows are TCP-friendly when compared to two TCP-Tahoe flows.     

Assured forwarding fairness using equation-based packet marking and packet separation

Fairness is one of the important problems in assured forwarding (AF) performance in the differentiated services (DiffServ) framework [An architecture for differentiated services, RFC 2475, IETF, December 1998; A two-bit differentiated services architecture for the Internet, Internet-draft, draft-nichols-diff-svc-arch-02.pdf, IETF, April 1999]. In this paper we present a two-part solution for the fairness problem in AF. The first part is a new packet marking algorithm called equation-based marking (EBM) and is based on the TCP model given by Padhye et al. [Modeling TCP throughput: A simple model and its empirical validation, in: Proceedings of ACM SIGCOMM ’98, October 1998]. EBM is to handle the problems found in other marking schemes regarding fairness among heterogeneous TCP flows through a tight feedback-loop operation and adaptation of the packet marking probability to network conditions. The second part is called packet separation used at routers to handle the fairness between responsive and non-responsive traffic. We evaluate the performance of a packet marker that uses EBM as the marking algorithm using in-depth simulation. We prove, analytically and using simulation, the correctness of the marking algorithm and compare it with other marking schemes for different network scenarios. We also use simulation to show the effectiveness of the packet separation mechanism in solving the fairness problem between responsive and non-responsive traffic. Our evaluation results demonstrate the effectiveness of EBM along with packet separation in providing the required fairness among heterogeneous flows and ensuring protection against non-assured traffic.     

确保服务中一种基于动态阈值的数据包标记算法

确保转发过程中带宽享用的公平性问题一直是区分服务网络研究的热点，影响这种公平性的因素包括回路响应时间RTT、数据包大小、目标速率及聚流中包含的单流数量等．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，基于动态阈值的数据包标记策略DTBM的目的就是处理异质的TCP流之间带宽享用的公平性问题。DTBM通过测量局部吞吐量来调整标记算法中的阈值，以改变不同颜色的标记概率从而达到公平带宽享用的目的。DTBM的主要优点在于其实现简单、对参数不是很敏感并且对端结点主机是“透明”的，仿真实验表明，和其他几种标记算法相比，DTBM能有效地消除上述因素的影响，具有更好的公平性。     

Understanding Performance for Two 802.11 Competing Flows

It is well known that 802.11 suffers from both inefficiency and unfairness in the face of competition and interference.This paper provides a detailed analysis of the impact of topology and traffic type on network performance when two flows compete with each other for airspace.We consider both TCP and UDP flows and a comprehensive set of node topologies.We vary these topologies to consider all combinations of the following four node-to-node interactions:(1) nodes unable to read or sense each other,(2)nodes able to sense each other but not able to read each other's packets and nodes able to communicate with(3)weak and with(4)strong signal.We evaluate all possible cases through simulation and show that the cases can be reduced to 9 UDP and 10 TCP 802.11g models with similar efficiency/fairness characteristics. We also validate our simulation results with extensive experiments conducted in a laboratory testbed.These more detailed models improve on previous work such as hidden-/exposed-terminal categorization and are thus better suited as a basis for adaptive techniques to improve performance in 802.11 multi-hop WLAN or Mesh Networks.     

基于ECN阶跃标记的TFRC改进协议

针对无线网络中TCP友好速率控制(TFRC)协议无法准确判断分组丢弃原因而导致的效率低下问题,提出一种基于显式拥塞反馈的阶跃标记方法,设计新的无线流媒体传输协议。仿真实验表明,新协议能在无线信道下准确区分丢包原因,并提供准确的拥塞通告信息,在保证TCP友好性的同时提高吞吐率。     

Privacy-preserving smart metering with multiple data Consumers

The increasing diffusion of Automatic Meter Reading (AMR) and the possibility to open the system to third party services has raised many concerns about the protection of personal data related to energy, water or gas consumption, from which details about the habits of the users can be inferred.This paper proposes an infrastructure and a communication protocol for allowing utilities and third parties (data Consumers) to collect measurement data with different levels of spatial and temporal aggregation from smart meters without revealing the individual measurements to any single node of the architecture.The proposed infrastructure introduces a set of functional nodes in the smart grid, namely the Privacy Preserving Nodes (PPNs), which collect customer data encrypted by means of Shamir’s Secret Sharing Scheme, and are supposed to be controlled by independent parties. By exploiting the homomorphic properties of the sharing scheme, the measurements can be aggregated directly in the encrypted domain. Therefore, an honest-but-curious attacker can obtain neither disaggregated nor aggregated data. The PPNs perform different spatial and temporal aggregation for each Consumer according to its needs and access rights. The information Consumers recover the aggregated data by collecting multiple shares from the PPNs.The paper also discusses the problem of deploying the information flows from the customers to the PPNs and, then, to the information Consumers in a resource constrained environment. We prove that minimizing the number of PPNs is a NP-hard problem and propose a fast greedy algorithm. The scalability of the infrastructure is first analyzed under the assumption that the communication network is reliable and timely, then in presence of communication errors and node failures. The paper also evaluates the anonymity of external attackers.     

基于强度控制的并行TCP拥塞控制策略研究

随着网络带宽的不断提升,基于并行TCP的应用方式得到广泛使用。当节点为同一个应用打开多个TCP连接时,对于使用单一TCP连接的网络用户存在严重的不公平。提出一种基于强度控制的并行TCP拥塞控制方案TCP C,使这些TCP流共享拥塞信息,同时限制并行TCP流的有效连接数量,以控制并行流的侵略性。实验结果显示该方案能够较好地保证公平性,同时有效地利用网络带宽。     

Evaluating transport protocol performance over a wireless mesh backbone

IEEE 802.11n wireless physical layer technology increases the deployment of high throughput wireless indoor mesh backbones for ubiquitous Internet connectivity at the urban and metropolitan areas. Most of the network traffic flows in today’s Internet use ‘Transmission Control Protocol’ (TCP) as the transport layer protocol. There has been extensive works that deal with TCP issues over wireless mesh networks as well as noisy wireless channels. Further, IEEE 802.11n is well known for its susceptibility to increased channel losses during high data rate communication. This paper investigates the dynamics of an end-to-end transport layer protocol like TCP in the presence of burst and correlated losses during IEEE 802.11n high data rate communication, while maintaining fairness among all the end-to-end flows. For this purpose, we evaluate four TCP variants-Loss Tolerant TCP (LT-TCP), Network Coded TCP (TCP/NC), TCP-Horizon and Wireless Control Protocol (WCP), where the first two protocols are known to perform very well in extreme lossy networks, and the last two are specifically designed for mesh networks. Our evaluation shows that WCP performs better in a IEEE 802.11n supported mesh networks compared to other three variants. However, WCP also results in negative impact at high data rates, where end-to-end goodput drops with the increase in physical data rate. The analysis of the results reveals that explicit loss notifications and flow balancing are not sufficient to improve transport protocol performance in an IEEE 802.11n supported mesh backbone, rather a specific mechanism is required to synchronize the transport queue management with lower layer scheduling that depends on IEEE 802.11n features, like channel bonding and frame aggregation. The findings of this paper give the direction to design a new transport protocol that can utilize the full capacity of IEEE 802.11n mesh backbone.