高速路由器中一种有效的组播交换排队机制

许多Internet新业务产生的网络流量都属于组播类型．高速路由器中组播交换队列设计是解决组播数据在复杂网络中有效传输的关键问题之一．理想情况下,为保证服务的公平性及有效性,不应该在排队和调度时对组播和单播人为地进行区分．在二者共存的情况下,如何进行公平地排队、交换是亟待解决的问题．基于共享存储交换结构,提出了一种有效的组播交换队列设计方案,同时提供了相应的与组播比例和平均扇出相关的缓存管理机制和队列调度算法．仿真结果表明,与在Cisco高端路由器中广泛应用的ESLIP设计方案相比,在输入负载大于80％的重负载环境中,该系统能够获得更低的平均时延和更小的系统丢包率．     

一种新的流媒体拥塞控制算法

提出一种新的拥塞控制算法(TCP MS).该算法更适用于流媒体应用,有更高的带宽利用率、公平性,传输速率也更平滑.不同于传统的利用丢包率和排队延迟来探测拥塞的TCP拥塞控制算法,该算法通过确认数据包的速率来探测拥塞,并在每一轮往返时间内及时调整窗口.该算法提供的拥塞窗口变化更准确,传输速率抖动更小.因此,提高了网络带宽的利用率以及传输速率的平滑性.最后,文章将TCP MS与典型的基于丢包率的TCP Reno算法和基于排队延迟的TCP Vegas算法在带宽利用率、速率抖动以及公平性等方面分别做了比较,仿真结果表明TCP MS是一种理想的流媒体拥塞控制算法.     

An output queueing analysis of multipath ATM switches

The performance of output buffers in multipath ATM switches is closely related to the output traffic distribution, which characterizes the packet arrival rate at each output link connected to the output buffer of a given output port. Many multipath switches produce nonuniform output traffic distributions even if the input traffic patterns are uniform. Focusing on the nonuniform output traffic distribution, we analyze the output buffer performances of several multipath switches under both uniform and nonuniform input traffic patterns. It is shown that the output traffic distributions are different for the various multipath switches and the output buffer performance measured in terms of packet loss probability and mean waiting time improves as the nonuniformity of the output traffic distribution becomes higher.     

Controlling mean queuing delay under multi-class bursty and correlated traffic

This paper presents an adaptive queue management scheme to maintain queuing delay in a router at a required level based on a comprehensive analytical model under aggregated Internet traffic flows from various traffic classes. The proposed scheme uses a closed-loop feedback control mechanism to constrain the average queuing delay by regulating traffic arrival rate implicitly through a movable queuing threshold. A discrete-time queuing model is developed to derive the relationship between average queuing delays and queuing thresholds based on a traffic model that models aggregated Internet traffic through superposition of N MMBP-2 arrival processes. The queuing threshold is adjusted dynamically with reference to the relationship derived in the analytical model and also feedback of average queuing delay measurement. Packets are dropped dynamically with respect to the changes of queuing threshold and the packet loss events serve as implicit congestion indicators. Matlab is used to perform queuing analysis and simulation. Statistical evaluation is performed to show the efficiency and accuracy of the analytical and simulation results.     

Investigation of the M2/G2/1/∞,N queue with restricted admission of priority customers and its application to HSDPA mobile systems

This paper investigates a queuing system for QoS optimization of multimedia traffic consisting of aggregated streams with diverse QoS requirements transmitted to a mobile terminal over a common downlink shared channel. The queuing system, proposed for buffer management of aggregated single-user traffic in the base station of High-Speed Downlink Packet Access (HSDPA), allows for optimum loss/delay/jitter performance for end-user multimedia traffic with delay-tolerant non-real-time streams and partially loss tolerant real-time streams. In the queuing system, the real-time stream has non-preemptive priority in service but the number of the packets in the system is restricted by a constant. The non-real-time stream has no service priority but is allowed unlimited access to the system. Both types of packets arrive in the stationary Poisson flow. Service times follow general distribution depending on the packet type. Stability condition for the model is derived. Queue length distribution for both types of customers is calculated at arbitrary epochs and service completion epochs. Loss probability for priority packets is computed. Waiting time distribution in terms of Laplace–Stieltjes transform is obtained for both types of packets. Mean waiting time and jitter are computed. Numerical examples presented demonstrate the effectiveness of the queuing system for QoS optimization of buffered end-user multimedia traffic with aggregated real-time and non-real-time streams.     

Port partitioning and dynamic queueing for IP forwarding

With the increase of internet protocol (IP) packets the performance of routers became an important issue in internet/working. In this paper we examine the matching algorithm in gigabit router which has input queue with virtual output queueing. Dynamic queue scheduling is also proposed to reduce the packet delay and packet loss probability. Port partitioning is employed to reduce the computational burden of the scheduler in a switch which matches the input and output ports for fast packet switching. Each port is divided into two groups such that the matching algorithm is implemented within each pair of groups in parallel. The matching is performed by exchanging the pair of groups at every time slot. Two algorithms, maximal weight matching by port partitioning (MPP) and modified maximal weight matching by port partitioning (MMPP) are presented. In dynamic queue scheduling, a popup decision rule for each delay critical packet is made to reduce both the delay of the delay critical packet and the loss probability of loss critical packet. Computational results show that MMPP has the lowest delay and requires the least buffer size. The throughput is illustrated to be linear to the packet arrival rate, which can be achieved under highly efficient matching algorithm. The dynamic queue scheduling is illustrated to be highly effective when the occupancy of the input buffer is relatively high.Scope and purposeTo cope with the increasing internet traffic, it is necessary to improve the performance of routers. To accelerate the switching from input ports to output in the router partitioning of ports and dynamic queueing are proposed. Input and output ports are partitioned into two groups A/B and a/b, respectively. The matching for the packet switching is performed between group pairs (A, a) and (B, b) in parallel at one time slot and (A, b) and (B, a) at the next time slot. Dynamic queueing is proposed at each input port to reduce the packet delay and packet loss probability by employing the popup decision rule and applying it to each delay critical packet.The partitioning of ports is illustrated to be highly effective in view of delay, required buffer size and throughput. The dynamic queueing also demonstrates good performance when the traffic volume is high.     

Multi-indicator Active Queue Management Method

A considerable number of applications are running over IP networks. This increased the contention on the network resource, which ultimately results in congestion. Active queue management (AQM) aims to reduce the serious consequences of network congestion in the router buffer and its negative effects on network performance. AQM methods implement different techniques in accordance with congestion indicators, such as queue length and average queue length. The performance of the network is evaluated using delay, loss, and throughput. The gap between congestion indicators and network performance measurements leads to the decline in network performance. In this study, delay and loss predictions are used as congestion indicators in a novel stochastic approach for AQM. The proposed method estimates the congestion in the router buffer and then uses the indicators to calculate the dropping probability, which is responsible for managing the router buffer. The experimental results, based on two sets of experiments, have shown that the proposed method outperformed the existing benchmark algorithms including RED, ERED and BLUE algorithms. For instance, in the first experiment, the proposed method resides in the third-place in terms of delay when compared to the benchmark algorithms. In addition, the proposed method outperformed the benchmark algorithms in terms of packet loss, packet dropping, and packet retransmission. Overall, the proposed method outperformed the benchmark algorithms because it preserves packet loss while maintaining reasonable queuing delay.     

A case for exploiting self-similarity of network traffic in TCP congestion control

Analytical and empirical studies have shown that self-similar traffic can have detrimental impact on network performance including amplified queuing delay and packet loss ratio. On the flip side, the ubiquity of scale-invariant burstiness observed across diverse networking contexts can be exploited to better design resource control algorithms. In this paper, we explore the issue of exploiting the self-similar characteristics of network traffic in TCP congestion control. We show that the correlation structure present in long-range dependent traffic can be detected on-line and used to predict the future traffic. We then devise a novel scheme, called TCP with traffic prediction (TCP-TP), that exploits the prediction result to infer, in the context of AIMD steady-state dynamics, the optimal operational point at which a TCP connection should operate. Through analytical reasoning, we show that the impact of prediction errors on fairness is minimal. We also conduct ns-2 simulation and FreeBSD 4.1-based implementation studies to validate the design and to demonstrate the performance improvement in terms of packet loss ratio and throughput attained by connections.     

高吞吐量的核心无状态公平队列算法

提出了一种优化的核心无状态公平队列凋度算法(xCSFQ),在CSFQ的基础上,根据缓冲区占用率和数据流到达速率决定丢包概率,缓存管理上采用基于CHOKC原理的机制进行缓存管理,解决了CSFQ链路利用率低的问题,提高了带宽在UDP流和TCP流之间分配的公平性,最后对算法进行了仿真分析。     

Achieving destination differentiation in ingress aggregated fairness for resilient packet rings by weighted destination based fair dropping

The IEEE 802.17 is a standardized ring topology network architecture, called the Resilient Packet Ring (RPR), to be used mainly in metropolitan and wide area networks. This paper introduces destination differentiation in ingress aggregated fairness for RPR and focuses on the RPR MAC client implementation of the IEEE 802.17 RPR MAC in the aggressive mode of operation. It also introduces an enhanced active queue management scheme for ring networks that achieves destination differentiation as well as higher overall utilization of the ring bandwidth with simpler and less expensive implementation than the generic implementation provided in the standard. The enhanced scheme introduced in this paper provides performance comparable to the per destination queuing implementation, which is the best achievable performance, while providing weighted destination based fairness as well as weighted ingress aggregated fairness. In addition, the proposed scheme has been demonstrated via extensive simulations to provide improved stability and fairness with respect to different packet arrival rates as compared to earlier algorithms.     

Hybrid fluid modeling approach for performance analysis of P2P live video streaming systems

In this paper a hybrid modeling approach with different modeling formalisms and solution methods is employed in order to analyze the performance of peer to peer live video streaming systems. We conjointly use queuing networks and Fluid Stochastic Petri Nets, developing several performance models to analyze the behavior of rather complex systems. The models account for: network topology, peer churn, scalability, peer average group size, peer upload bandwidth heterogeneity and video buffering, while introducing several features unconsidered in previous performance models, such as: admission control for lower contributing peers, control traffic overhead and internet traffic packet loss. Our analytical and simulation results disclose the optimum number of peers in a neighborhood, the minimum required server upload bandwidth, the optimal buffer size and the influence of control traffic overhead. The analysis reveals the existence of a performance switch-point (i.e. threshold) up to which system scaling is beneficial, whereas performance steeply decreases thereafter. Several degrees of degraded service are introduced to explore performance with arbitrary percentage of lost video frames and provide support for protocols that use scalable video coding techniques. We also find that implementation of admission control does not improve performance and may discourage new peers if waiting times for joining the system increase.     

Modeling and performance analysis for IPv6 traffic with multiple QoS classes

This paper focuses on the modeling and performance analysis for IPv6 traffic with multi-class QoS in virtual private networks (VPN). The multi-class QoS is implemented on differentiated service basis using priority scheme of 4 bits defined in the packet header of IPv6. A VPN-enabled IP router is modeled as a tandem queuing system in which each output link consists of two parallel priority output queues. The high-priority queue is used to carry the delay sensitive traffic while the low-priority queue is used to carry the delay insensitive traffic. On the other hand, multiple thresholds are implemented in each queue, respectively, for packet loss priority control. The performance analysis is done using fluid flow techniques. The numerical results obtained from the analysis show that the differentiated service based on the priority schemes defined in IPv6 is able to effectively satisfy the multi-class QoS requirement for supporting multimedia services in VPN. The performance trade-off between the delay sensitive traffic and delay insensitive traffic in terms of traffic throughput, packet loss probability and end-to-end delay in VPN networks is presented.     

多媒体传感器网络中服务感知的公平调度算法

针对多媒体传感器网络中基于异常事件驱动的服务模式和基于用户查询驱动的服务模式,分析不同服务的流量模式,提出一种服务感知的公平调度策略,采用基于流量预测的动态公平缓冲共享机制和速率分配算法实现2类数据QoS的公平保障。仿真实验表明,该算法在传输延迟和成功到达率方面实现了公平性目标。     

基于自相似排队模型的星上交换输入缓存分配算法

针对空间信息网络的自相似分组业务流、星上交换节点的有限缓存资源,提出一种基于自相似排队模型的星上交换输入缓存分配算法。构建了基于VOQ的空间信息网络星上Crossbar交换节点模型,依据空间信息网络业务流的自相似性,通过建立虚通道自相似排队模型,估算出各个虚通道的缓存溢出概率,再根据其溢出概率采用贪婪算法来实现缓存资源的优化分配。仿真分析了在自相似分组业务流下优化分配算法和均匀分配算法的性能。结果表明,在相同缓存开销下,优化分配算法可以有效降低分组的平均时延;在同等分组平均时延下,分组业务流自相似程度为0.8和0.6时,可分别节省缓存开销约25%和17.4%。     

Per-stream loss behavior of ∑MAP/M/1/K queuing system with a random early detection mechanism

In this paper, the matrix-analytic approach is applied to explore the per-stream loss behavior of the multimedia traffic under RED scheme. We constructed a ∑MAP/M/1/K queuing model for the RED mechanism with multimedia traffic which follows a continuous-time Markovian arrival process (MAP). In addition to evaluating the long-term per-stream packet drop probabilities, we examine the bursty nature of per-stream packet drops by means of conditional statistics with respect to dropped periods and the probability that the queuing system stays in the dropped period. The dropped period corresponds to having more than a certain number of packets in router buffer; non-dropped period corresponds to the opposite. These performance measures describe the quality of service provided by the router to particular multimedia traffic streams in the presence of background multimedia traffic.     

基于车辆载带中继的路边单元突发业务分组调度最优策略

高速公路车联网场景中,路边单元(Roadside units,RSUs)可作为多种周边监测数据的汇入网关,其业务具有突发特性,且可通过移动车辆以"存储—载带—转发"方式传输到与骨干网络互联的RSU.针对RSU间业务传输问题,源RSU可根据实时业务到达率按需匹配资源,以应对业务突发性对分组端到端时延的影响.本文首先针对R...     

TPDCM:一种新型的分布式拥塞管理方案

提出一种新型的面向区分服务网络的分布式拥塞管理方案,基本思想是利用拥塞状态反馈信息在边缘节点或主机上实施拥塞管理。该方案主要包括三个组成部分:流量控制信息协议、早期拥塞检测和流量控制算法。该方案具有以下特点:(1)在核心网络中,拥塞控制机制独立于特定的传输层协议;(2)对将要发生的拥塞做出快速响应;(3)降低网络的分组丢失率;(4)不需要在网络核心节点中保存每个传输流的状态信息。实验结果表明,与标准的区分服务网络相比,该方案能在TCP和UDP聚集之间公平地分配带宽并能显著地降低分组丢失率。     

A proportional fairness scheduling for wireless sensor networks

This paper describes a packet scheduling algorithm for wireless sensor networks (WSNs) that meets the proportional fairness principle. Based on the weighted round-robin strategy, the proposed scheduling algorithm allocates a different service quota to different traffic according to the average packet arrival rate. This guarantees proportional fairness in terms of the average packet delivery delay and the average packet loss ratio. Since the scheduling algorithm does not perform high-load operations such as time stamping and sorting, it can be implemented easily and is suitable for resource-limited WSNs. The proposed scheduling algorithm is tested in a WSN and is found to guarantee the proportional fairness of the average packet delivery delay when this is used as the performance metric, and to realize proportional fairness in the average packet loss ratio when all the queues are overflowing and the average packet loss ratio is used as the performance metric.     

一种改进的RED算法

本文就目前路上器中如何实现数据流隔离和公平分配带宽进行了探讨，首先研究了Sally等人提出的RED算法，指出其缺陷，并根据TCP的有效吞吐率公式，提出了一种改进的RED算法，它可以实现更好的公平性，仿真结果验证了算法的有效性。     

Performance analysis of adaptive buffer management mechanism using autoregressive based MPEG-4 encoded video traffic model

The burstiness of video traffic in future wired and wireless networks makes dynamic management of network resources more critical. This helps to meet stringent delay and loss requirements of video traffic and improves its Quality of Service (QoS). Since buffer management in queueing system plays an important role towards effective control of QoS for various types of applications, we have focused on its dynamic management. In this paper, we have proposed ADPBS scheme for priority queueing system. The performance of this scheme is analyzed with MPEG-4 encoded video sequence as input to the ADPBS queue. The simulation is carried out in MATLAB for various combinations of threshold control parameters, different traffic load and input traffic mix variations. The results of simulations indicate that dynamically controlled threshold in ADPBS contributes to significant reduction of packet loss of different priority classes as compared with static partial buffer sharing queue and first in first out queue based on threshold control parameters and the traffic type.