一种改进的光纤通道存储扩展流量控制方法

 存储扩展是容灾的基础,为克服光纤通道与扩展网络流量控制不同步对存储扩展性能的影响,提出了一种改进的光纤通道存储扩展流量控制方法,根据扩展网关中缓存队列长度与设定的队列高、低门限值间的关系调整Credit更新频率.建立了基于OPNET的仿真模型,仿真结果表明:改进的流量控制方法能降低数据的排队时延,提高存储扩展的性能.     

支持优先级与公平策略的队列规程

首先介绍了队列调度算法在流量控制中的关键地位,然后讨论了现有队列调度算法,如基于优先级的调度算法、轮询调度算法与公平队列调度算法,最后提出了一种新的队列规程,该队列规程融合了优先级调度算法与DRR调度算法。在网络正常情况下,不同业务流公平地共享网络带宽,在网络出现拥塞的情况下,高优先级业务流能够抢占带宽,保证其较低的丢包率,并能够实现两种调度算法的快速切换。     

The throughput time delay function of anM/M/1queue (Corresp.)

A study of the design requirements of the data link control protocol leads us to consider a throughput time delay criterion as a performance measure for optimal flow control of computer communication networks. A closed network model consisting of acdot /M/1queuing system (the receiver node) controlled by an exponential queuing system with variable rate (the source node) is considered. The flow control maximizing the throughput of the M/M/1 queuing system in equilibrium under a bounded average time delay criterion is shown to be a window flow control mechanism. The window sizeLcan be easily derived from the maximum tolerated average time delayTand the maximum offered loadc. The dependence of the maximum throughput on the average time delay is also analyzed.     

一种基于预测PI控制器的自相似网络主动队列管理算法

近年研究发现网络中的业务量呈自相似特征,这种自相似特征显著影响网络的流量控制与排队性能,本文在自相似网络流量可预测的基础上,利用线性回归分析理论进行流量预测,并应用控制理论中的预测PI控制器原理设计了动态矩阵PI控制主动队列管理(Dynamic Matrix PI Control-Active Queue Management,简称DMPIC-AQM)算法,以克服队列的剧烈振荡,保持队列稳定在期望的长度.仿真实验结果表明,DMPIC-AQM算法在网络流量剧烈变化和小期望队列长度的情形下,DMPIC-AQM算法明显优于RED与PI算法.     

Optimizing routing based on congestion control for wireless sensor networks

Along with the increasing demands for the applications running on the wireless sensor network (WSN), energy consumption and congestion become two main problems to be resolved urgently. However, in most scenes, these two problems aren’t considered simultaneously. To address this issue, in this paper a solution that sufficiently maintains energy efficiency and congestion control for energy-harvesting WSNs is presented. We first construct a queuing network model to detect the congestion degree of nodes. Then with the help of the principle of flow rate in hydraulics, an optimizing routing algorithm based on congestion control (CCOR) is proposed. The CCOR algorithm is designed by constructing two functions named link gradient and traffic radius based on node locations and service rate of packets. Finally, the route selection probabilities for each path are allocated according to the link flow rates. The simulation results show that the proposed solution significantly decreases the packet loss rate and maintains high energy efficiency under different traffic load.     

Flow assignment method with traffic characteristics over multiple paths for reducing queuing delay

In traffic engineering (TE), it is vital to take traffic characteristics of the flows into account in appropriately assigning the flows to multiple network paths to achieve better delay performance as a whole in order to effectively distribute traffic flows over the paths. This paper presents a novel traffic characteristic-aware flow assignment method to reduce the queuing delay in a fundamental case where two types of flows with distinct traffic characteristics (e.g., burstiness) are distributed into two paths. First, we extensively analyze the queuing delays in assigning flows in the manner of various combinations of flows in terms of minimizing the worst queuing delay among two paths and show that it is not easy to find the optimal flow assignment when the paths have different bandwidths. Second, we propose an on-line flow assignment method for the different-bandwidth paths and show that the numerical simulation with the method finds a nearly optimal flow assignment and outperforms up to 40% compared with the conventional path-bandwidth-based flow assignment. Our evaluation suggests that considering the traffic characteristics in the flow distribution over multiple paths significantly improves the delay performance when the flows have distinct characteristics.     

Traffic characterization for integrated services networks

A discrete-time queuing analysis is presented for integration of multiple traffic types in a packet-switched TDM (time-division multiplexing) system. The correlation of each traffic type is represented in terms of the power spectral density. The general expression obtained for the aggregate mean queue size indicates that slowly varying traffic types exert the largest effect on the queuing process. Also, a lengthy-steady traffic is highly predictable. An adaptive flow control and routing scheme, based on signal prediction, which successively adjusts the short-burst traffic arrival rate at each TDM node, is introduced and analyzed. The analytical results indicate a substantial reduction in the correlation effect on the system queuing behavior     

基于排队时延和丢包率的拥塞控制

作为拥塞度量,排队时延具有很多优点,但仅利用排队时延并不能完全避免丢包,而在链路缓存不足出现丢包时,排队时延已不能有效反应网络拥塞情况。该文提出了一种基于排队时延和丢包率的拥塞控制模型,该模型采用双模控制的方法。在瓶颈链路上有足够缓存时,模型利用排队时延作为拥塞度量,使各流获得稳定的动态性和成比例公平性。当瓶颈路由器上没有足够缓存不可避免要丢包时,模型利用丢包率作为拥塞度量,使各流仍能获得与不丢包情况下相近的流特性。模型在两种模式的切换中保持稳定,实现平滑过渡。     

基于VoIP的校园网络管理系统的设计

文章在分析和比较其他VoIP网络管理系统设计方案的基础上,重点论述了VoIP校园网络管理系统的设计方案,阐述了校园网络管理系统主要的实施过程.并提出了采用约定访问速度对流量进行控制,采用排队的技术对拥塞进行处理,并根据校园网络的实际情况给出网络路由的总体设计方案.     

Efficient fair queuing using deficit round-robin

Fair queuing is a technique that allows each flow passing through a network device to have a fair share of network resources. Previous schemes for fair queuing that achieved nearly perfect fairness were expensive to implement; specifically, the work required to process a packet in these schemes was O(log(n)), where n is the number of active flows. This is expensive at high speeds. On the other hand, cheaper approximations of fair queuing reported in the literature exhibit unfair behavior. In this paper, we describe a new approximation of fair queuing, that we call deficit round-robin. Our scheme achieves nearly perfect fairness in terms of throughput, requires only O(1) work to process a packet, and is simple enough to implement in hardware. Deficit round-robin is also applicable to other scheduling problems where servicing cannot be broken up into smaller units (such as load balancing) and to distributed queues     

Hardware implementation of fair queuing algorithms for asynchronoustransfer mode networks

Providing quality-of-service guarantees in both cell- and packet-based networks requires the use of a scheduling algorithm in the switches and network interfaces. These algorithms need to be implemented in hardware in a high-speed switch. The authors present a number of approaches to implement scheduling algorithms in hardware. They begin by presenting a general methodology for the design of timestamp-based fair queuing algorithms that provide the same bounds on end-to-end delay and fairness as those of weighted fair queuing, yet have efficient hardware implementations. Based on this general methodology, the authors describe two specific algorithms, frame-based fair queuing and starting potential-based fair queuing, and discuss illustrative implementations in hardware. These algorithms may be used in both cell switches and packet switches with variable-size packets. A methodology for combining a traffic shaper with this class of fair queuing schedulers is also presented for use in network interface devices, such as an ATM segmentation and reassembly device     

Intelligent Network Analysis by Closed Queuing Models

With the wide deployment of intelligent network (IN) services, there is an urgent need to understand and solve teletraffic performance issues of the evolving network intelligence platform. This paper discusses a queuing system model for the performance analysis of IN call processing. The intelligent network is presented as a network of queues where the total number of customers (e.g., SSPs) is fixed, thus forming a closed queuing network. The IN distributed architecture is modeled as a finite source queuing model – M/G/1/K/K. The expected response time for that model is analyzed and computed. The numerical results and the corresponding curves are provided and, related to open questions, future work is summarized.     

串联排队RED、ERED网络分析模型

基于串联排队网络理论,建立了包括多个网络节点的串联排队RED和ERED分析模型。推导了具有指数分布分组丢失函数的RED算法(ERED)。在概率生成函数域,推导了节点的离去过程,并将其拟合为后续节点的到达过程,从而,刻画了多节点级联拥塞控制的通信场景。通过求解串联排队系统,得出串联排队RED、ERED以及DT 3种AQM机制的网络性能指标,分析了AQM参数设置对其性能的影响。针对不同突发度的业务源,给出每个节点和系统端到端性能指标。     

A novel Hα control strategy for design of a robust dynamic routing algorithm in traffic networks

In this paper novel centralized and decentralized routing control strategies based on minimization of the worst-case queuing length are proposed. The centralized routing problem is formulated as an H_infin optimal control problem to achieve a robust routing performance in presence of multiple and unknown fast time-varying network delays. Unlike similar previous work in the literature the delays in the queuing model are assumed to be unknown and time-varying. A Linear Matrix Inequality (LMI) constraint is obtained to design a delay-dependent H_infin controller. The physical constraints that are present in the network are then expressed as LMI feasibility conditions. Our proposed centralized routing scheme is then reformulated in a decentralized frame work. This modification yields an algorithm that obtains the "fastest route", increases the robustness against multiple unknown time-varying delays, and enhances the scalability of the algorithm to large scale traffic networks. Simulation results are presented to illustrate and demonstrate the effectiveness and capabilities of our proposed novel dynamic routing strategies.     

Numerical methods for modeling computer networks undernonstationary conditions

Numerical techniques for modeling computer networks under nonstationary conditions are discussed, and two distinct approaches are presented. The first approach uses a queuing theory formulation to develop differential equation models which describe the behavior of the network by time-varying probability distributions. In the second approach, a nonlinear differential equation model is developed for representing the dynamics of the network in terms of time-varying mean quantities. This approach allows multiple classes of traffic to be modeled and establishes a framework for the use of optimal control techniques in the design of network control strategies. Numerical techniques for determining the queue behavior as a function of time for both approaches are discussed and their computational advantages are contrasted with simulation     

Novel Radio Link Buffer Management Schemes for End-User Multi-class Traffic in High Speed Packet Access Networks

The requirement to provide multimedia services with QoS support in mobile networks has led to standardization and deployment of high speed data access technologies such as the High Speed Downlink Packet Access (HSDPA) system. HSDPA improves downlink packet data and multimedia services support in WCDMA-based cellular networks. As is the trend in emerging wireless access technologies, HSDPA supports end-user multi-class sessions comprising parallel flows with diverse Quality of Service (QoS) requirements, such as real-time (RT) voice or video streaming concurrent with non real-time (NRT) data service being transmitted to the same user, with differentiated queuing at the radio link interface. Hence, in this paper we present and evaluate novel radio link buffer management schemes for QoS control of multimedia traffic comprising concurrent RT and NRT flows in the same HSDPA end-user session. The new buffer management schemes—Enhanced Time Space Priority (E-TSP) and Dynamic Time Space Priority (D-TSP)—are designed to improve radio link and network resource utilization as well as optimize end-to-end QoS performance of both RT and NRT flows in the end-user session. Both schemes are based on a Time-Space Priority (TSP) queuing system, which provides joint delay and loss differentiation between the flows by queuing (partially) loss tolerant RT flow packets for higher transmission priority but with restricted access to the buffer space, whilst allowing unlimited access to the buffer space for delay-tolerant NRT flow but with queuing for lower transmission priority. Experiments by means of extensive system-level HSDPA simulations demonstrates that with the proposed TSP-based radio link buffer management schemes, significant end-to-end QoS performance gains accrue to end-user traffic with simultaneous RT and NRT flows, in addition to improved resource utilization in the radio access network.     

物元分析方法在通信网可靠性评价中的应用

本文主要研究物元分析方法在通信网可靠性评价中的应用，首先应用物元变换方法对通信网可靠性评价的研究思路进行了转换，提出了分析可靠性增长与通信网发展的相关适应性的物元评价方法。这种方法的应用在实际中显示出较好的效果。     

分组交换网络调度算法概述

为了合理利用网络资源,提高网络吞吐率,降低通信时延,需要采取有效的调度算法实现输入端和输出端的匹配.基于VOQ的输入排队交换结构是当前分组交换网络最常用的结构.本文介绍了几种基于VOQ的调度算法:用于单级crossbar的PIM、iRRM和iSLIP算法,以及适用于三级Clos网络的RD和CDDR算法.对每种算法,介绍其基本原理和性能,以及与其他算法的区别.     

Experimental evaluation of SunOS IPC and TCP/IP protocolimplementation

Results of a study that characterizes the performance of SunOS Inter-Process Communication (IPC) and TCP/IP protocol implementation for distributed high-bandwidth applications are presented. Components studied include queuing in different layers, protocol control mechanisms (such as flow and error control), per-packet processing, buffer requirements, and interaction with the operating system. The Unix kernel and two public-domain tools for IPC measurement are reviewed     

基于非合作博弈的无线自组织网络流量控制模型

该文根据无线自组织网络中流量控制和无线信道的特性,利用非合作博弈理论构造了基于网络流量速率和时延为参数的流量效用函数,建立了非合作博弈的无线自组织网络流量控制模型,证明了流量控制模型的Nash均衡解存在性,给出了模型的Nash均衡解的具体形式。数值仿真结果表明该模型存在Nash均衡解,能有效对网络中流量进行控制,满足不同业务的用户流量QoS需求。