An Effective Feedback Control Mechanism for DiffServ Architecture

As a scalable QoS(Quality of Service)architcture,DiffServ(Differentiated Service)mainly consists of two components:taffic conditioning at the edge of the DiffServ domain and simple packet forwarding inside the DiffServ domain.DiffServ has many advantages such as flexbility,scalability and simplicity.But when providing, AF (Assured Forwarding) services ,DiffServ has some problems such as unfairness among aggregated flows or among micro-flows belonging to an aggregated flow.In this paper,a feedback mechanism for AF aggregated flows is proposed to solve this problem.Simulation results show that this mechanism does improve the performance of DiffServ.Firt,it can improve the fairness among aggregated flows and make DiffServ more friendly toward TCP (Transmision Control Protocol)flows.Second,it can decrease the buffer requirements at the congested router and thus obtain lower delay and packet loss rate.Third,it also keeps almost the same link utility as in normal DiffServ,Einally,it is simple and easy to be implemented.     

Fast,Fair and Frugal Bandwidth Allocation in ATM Networks

Abstract. ATM networks are used to carry a variety of types of traffic. For some types of traffic, in particular Available Bit Rate (ABR) traffic, the bandwidth of a network is typically insufficient to satisfy the requests of all the sessions, and so some fair allocation scheme must be devised. The ATM Forum, the standards setting body for ATM networks, has specified that the fairness criterion for ABR traffic should be Max-Min Fairness , which intuitively means that raising the bandwidth of any session comes at the expense of some other session of no greater bandwidth. Protocols to allocate bandwidth to sessions in a max-min fair manner are an important part of a network design. For a protocol to be realistic, it must conform to the Resource Management (RM) cell mechanism specified by the ATM Forum. Such RM cells get sent as a constant fraction of all cells sent by the source; however, they have only a few fields. RM cells are the only means of communication allowed from link to link so any reasonable protocol is totally distributed and asynchronous, since the RM cell mechanism does not easily lend itself to synchronization. Finally, RM Cells must be handled very quickly at each link. We call a protocol frugal if at each link it performs O(1) computation per RM cell and uses O(1) space per session. Recently, several frugal RM cell protocols have been proposed for ABR traffic, but none have been shown to converge to the max-min fair state. Protocols that are known to converge in a linear number of maximum round-trip times require RM cell processing that is linear in the number of sessions that go through a link. In this paper we give a frugal RM cell protocol for ABR that matches the convergence time of the fastest known non-frugal protocol. A second type of ABR traffic is the Minimum Cell Rate (MCR) type, where every session can specify a minimum amount of bandwidth. The max-min fair allocation should then respect these MCR requests. We extend our results to give the first frugal RM cell protocol for MCR and achieve a quadratic convergence rate.     

PRED:一种配合队列调度的RED算法

论文讨论了队列管理和队列调度的关系,提出了一种新的基于势的RED机制:PRED,以增强SPFQ调度机制的公平性,来达到整个报文处理系统的性能改善。通过严格的仿真验证,同其他的队列管理机制相比,PRED同SPFQ的结合能够最大限度地利用系统资源,提高服务的公平性。     

无需中央机构的电子投票协议分析

针对无需中央机构的电子投票协议——Su-协议,分析指出投票者在给出其解密选票结果的参数时,协议无法确保投票人给出的参数是正确的,攻击者可以在投票的第5步给出经过设计的参数从而可以左右系统的计票结果。据此给出针对Su-协议的3种可行的攻击：公平性攻击,选票篡改攻击和秘密性攻击。     

一种自适应的无线传感器网络拥塞缓解机制

提出一种自适应的拥塞缓解机制。当无线传感器网络发生拥塞时,尝试在拥塞节点附近建立新路径,路径建立失败时引入公平汇聚机制,按汇聚数据流权重大小比例限制上游节点速率以减少源节点数据发送率。仿真实验表明,该机制减少了能耗,降低了丢包率,使重要的数据能实时、公平地传送到目的节点。     

一种基于HSTCP改进的公平性算法

在高速网络中现有的标准TCP不能充分的利用网络带宽,HSTCP(HighSpeed TCP)作为解决这一问题的可行方法被提出.试验表明HSTCP比标准TCP能够更充分的利用带宽,但存在着严重的RTT不公平性.首先通过仿真试验和数学分析对HSTCP的RTT不公平性进行研究,然后在原有算法的基础上添加一个公平性因子来降低由于RTT不同造成的窗口增长差异.试验表明改进算法有效保证了HSTCP流的带宽公平性、降低了丢包率.     

无线Ad Hoc网络MAC层关键技术研究

无线Ad Hoc网络是一种无中心、自组织的多跳网络,其MAC层的研究是近年来的研究热点。在MAC层的研究中,有一些关键的技术问题有待解决,包括隐藏终端和暴露终端问题,公平性问题,QoS保证,速率自适应等。文章详细论述了每一个问题,并提供了一些解决的思路。     

Control and data abstraction: the cornerstones of practical formal verification

In spite of the impressive progress in the development of the two main methods for formal verification of reactive systems – Symbolic Model Checking and Deductive Verification, they are still limited in their ability to handle large systems. It is generally recognized that the only way these methods can ever scale up is by the extensive use of abstraction and modularization, which break the task of verifying a large system into several smaller tasks of verifying simpler systems. In this paper, we review the two main tools of compositionality and abstraction in the framework of linear temporal logic. We illustrate the application of these two methods for the reduction of an infinite-state system into a finite-state system that can then be verified using model checking. The technical contributions contained in this paper are a full formulation of abstraction when applied to a system with both weak and strong fairness requirements and to a general temporal formula, and a presentation of a compositional framework for shared variables and its application for forming network invariants.     

多用户 MIMO 无线通信系统中基于 QoS 的比例公平调度算法研究简

未来的无线通信系统是一个多业务系统,不同的业务有不同的QoS要求,如最大时延和最小误码率等,这就要求调度算法在提高系统吞吐量和保证用户公平性的同时,还要提供对不同业务QoS的区分保障机制.针对这一趋势,在比例公平调度算法的基础上,通过引入表征QoS的参数,提出了一种改进的可以保证QoS的比例公平调度算法,并对改进算法的各项性能进行计算机仿真,验证了它的性能.     

基于并发签名的网络易货协议

针对目前易货网站无法保证用户交易公平性的现状,提出了一种网络易货协议.协议双方用户基于完美并发签名在网上进行双方签名的公平交换,在签名交换完成并且双方签名生效后,每个用户将自己欲交换的物品交给邮递人员,由邮递人员将物品送至对方.协议引入了“保密柜”的概念,收货方公开其保密柜地址而不是其真实通信地址,快递人员与之交流的是收货方的保密柜,而不是收货方本人,从而保护收货方的隐私.研究分析表明,协议无需可信第三方的参与即可让双方用户公平地交易实物,并且能够为用户提供有效的隐私保护.协议只需用户与用户之间发送3条消息,用户与快递人员交互1次,简洁高效.