A Utility-Based Buffer Management Policy for Improving Data Dissemination in Opportunistic Networks

In opportunistic networks, most existing buffer management policies including scheduling and passive dropping policies are mainly for routing protocols. In this paper, we proposed a Utility-based Buffer Management strategy(UBM) for data dissemination in opportunistic networks. In UBM, we first design a method of computing the utility values of caching messages according to the interest of nodes and the delivery probability of messages, and then propose an overall buffer management policy based on the utility. UBM driven by receivers completely implements not only caching policies, passive and proactive dropping policies, but also scheduling policies of senders. Simulation results show that, compared with some classical dropping strategies, UBM can obtain higher delivery ratio and lower delay latency by using smaller network cost.

Traffic dynamics considering packet loss in finite buffer networks

In real complex systems, the limited storage capacity of physical devices often results in the loss of data. We study the effect of buffer size on packet loss threshold in scale-free networks. A new order parameter is proposed to characterize the packet loss threshold. Our results show that the packet loss threshold can be optimized with a relative small buffer size. Meanwhile, a large buffer size will increase the travel time. Furthermore, we propose a Buffered-Shortest-Path-First(BSPF) queuing strategy. Compared to the traditional First-In-First-Out(FIFO) strategy, BSPF can not only increase the packet loss threshold but can also significantly decrease the travel length and travel time in both identical and heterogeneous node capacity cases. Our study will help to improve the traffic performance in finite buffer networks.

HAS Dynamic Buffer-Driven Resource Management to Enhance QoE in Mobile Network

Hypertext transfer protocol(HTTP) adaptive streaming(HAS) plays a key role in mobile video transmission. Considering the multi-segment and multi-rate features of HAS, this paper proposes a buffer-driven resource management(BDRM) method to enhance HAS quality of experience(QoE) in mobile network. Different from the traditional methods only focusing on base station side without considering the buffer, the proposed method takes both station and client sides into account and end user's buffer plays as the drive of whole schedule process. The proposed HAS QoE influencing factors are composed of initial delay, rebuffering and quality level. The BDRM method decomposes the HAS QoE maximization problem into client and base station sides separately to solve it in multicell and multi-user video playing scene in mobile network. In client side, the decision is made based on buffer probe and rate request algorithm by each user separately. It guarantees the less rebuffering events and decides which HAS segment rate to fetch. While, in the base station side, the schedule of wireless resource is made to maximize the quality level of all access clients and decides the final rate pulled from HAS server. The drive of buffer and twice rate request schemes make BDRMtake full advantage of HAS's multi-segment and multi-rate features. As to the simulation results, compared with proportional fair(PF), Max C/I and traditional HAS schedule(THS) methods, the proposed BDRM method decreases rebuffering percent to 1.96% from 11.1% with PF and from 7.01% with THS and increases the mean MOS of all users to 3.94 from 3.42 with PF method and from 2.15 with Max C/I method. It also guarantees a high fairness with 0.98 from the view of objective and subjective assessment metrics.

Major impact of queue-rule choice on the performance of dynamic networks with limited buffer size

We investigate the similarities and differences among three queue rules,the first-in-first-out(FIFO)rule,last-in-firstout(LIFO)rule and random-in-random-out(RIRO)rule,on dynamical networks with limited buffer size.In our network model,nodes move at each time step.Packets are transmitted by an adaptive routing strategy,combining Euclidean distance and node load by a tunable parameter.Because of this routing strategy,at the initial stage of increasing buffer size,the network density will increase,and the packet loss rate will decrease.Packet loss and traffic congestion occur by these three rules,but nodes keep unblocked and lose no packet in a larger buffer size range on the RIRO rule networks.If packets are lost and traffic congestion occurs,different dynamic characteristics are shown by these three queue rules.Moreover,a phenomenon similar to Braess’paradox is also found by the LIFO rule and the RIRO rule.

Contract theory based incentive mechanism design for buffer resource in wireless caching networks

Evidences indicate that,due to the limited caching capacity or inaccurate estimation on users’preferences,the requested files may not be fully cached in the network edge.The transmissions of the un-cached files will also lead to duplicated transmissions on backhaul channels.Buffer-aided relay has been proposed to improve the transmission performance of the un-cached files.Because of the limited buffer capacity and the information asymmetric environment,how to allocate the limited buffer capacity and how to incentivize users in participating buffer-aided relay have become critical issues.In this work,an incentive scheme based on the contract theory is proposed.Specifically,the backlog violation probability,i.e.,the buffer overflow probability,is provided based on the martingale theory.Next,based on the backlog violation probability,the utility functions of the relay node and users are constructed.With the purpose to maximize the utility of the relay node,the optimal contract problem is formulated.Then,the feasibility of the contract is also demonstrated,and the optimal solution can be obtained by the interior point method.Finally,numerical results are presented to demonstrate effectiveness of the proposed contract theory scheme.

Design of an unbuffered switch for network on-chip

In the complex multicore chip system,network on-chip(NoC)is viewed as a kind of system interconnection that can substitute the traditional interconnect networks,which will improve the system performance and communication efficiency.With regard to the complex and large scale NoC,simple and efficient routing nodes are the critical factors to achieve low-cost and low-congestion communication performance.This paper proposes an unbuffered switch architecture and makes detailed analysis of the mechanism of buffer in the switch architecture.According to the simulation results,the S-mesh using the unbuffered switch architecture is better in terms of the optimal performance in message latency than some typical NoC architectures,such as 2D-mesh,Fat-tree,Butterfly,Octagon and so on.The synthesis results of design compiler indicate that the unbuffered switch has obvious advantages of achieving cost and operating speed for the chips.

A Shared Multi-buffer Banyan Network

A Shared Multi-buffer Banyan Network is presented in this letter. Its control algorithm and switching fabric are simple, and it fits the high speed ATM network well. The simulation results show that the throughput of the proposed model is high.

Calculation and Analysis of Destination Buffer for Multimedia Service in Mobile Ad Hoc Network

Jitter is one of the most important issues for multimedia real time services in future mobile ad hoc networks（MANET）. A thorough theoretical analysis of the destination buffer for smoothing the jitter of the real time service in MANET is given. The theoretical results are applied in moderate populated ad hoc networks in our simulation, the simulation results show that by predicting and adjusting destination buffer in our way, Jitter will be alleviated in large part and this will contribute much to the quality of service （QOS） in MANET.

PiBuffer:面向数据中心的OpenFlow流缓存管理模型

基于OpenFlow的SDN(Software Defined Networking)技术在数据中心中得到广泛研究和应用,如何缓解集中的控制平面成为网络性能的瓶颈是其中的研究热点.OpenFlow规范提出,当数据平面有缓存能力时,未命中的报文仅需发送少量摘要信息至控制器触发规则下发,从而减少控制平面与数据平面的通信负载.然而,现有的缓存模型采用报文粒度的缓存方式,使得同一条流的多个未命中报文会被送至控制器造成额外的通信负载,而且交换机处理报文的顺序会导致流内报文乱序,从而降低通信的性能.针对上述问题,该文提出了一种支持流内报文保序的OpenFlow交换机流缓存管理模型.通过基于流粒度的未命中报文缓存方式,进一步减少控制平面与数据平面的通信开销.通过设计流动作预处理机制,实现同一条流内报文传输保序.该文分别基于软件交换机OFSoftSwitch与硬件网络实验平台NetMagic对该流缓存管理模型进行了原型系统验证.

一种环形Buffer自适应NoC路由器设计

在片上网络(Network-on-Chip,NoC)系统中,对路由器缓存进行有效的设计及管理,能够有效提高系统多方面的性能.设计了一种环形缓冲结构的自适应路由器,该路由器中所有通道的缓冲资源相互连接形成一个封闭的环,繁忙的输入通道能够共享其他通道的空闲缓冲资源.2D Mesh网络中的实验结果表明,环形缓冲结构的路由器与传统路由器相比,能量消耗得到了降低,缓冲使用缩小了5倍.此外,大量的仿真研究表明,该路由器结构提高了网络性能,减少了平均信息延时.

Optimization of Global Signal Networks for Island-Style FPGAs

We present a staggered buffer connection method that provides flexibility for buffer insertion while designing global signal networks using the tile-based FPGA design methodology. An exhaustive algorithm is used to analyze the trade-off between area and speed of the global signal networks for this staggered buffer insertion scheme, and the criterion for determining the design parameters is presented. The comparative analytic result shows that the methods in this paper are proven to be more efficient for FPGAs with a large array size.

基于Protocol Buffers的配置下发接口适配与应用

简述了网管接口技术的发展现状,对现有网管接口技术使用的编码方式做出了比较;介绍了一种简单快速的序列化机制Protocol Buffers的基本功能与特点;提出了一种采用Protocol Buffers作为编码方式的网管配置下发模型,设计了一个Protocol Buffers与现有命令行(CLI)接口进行适配的适配层,给出了其工作原理与部署方法。

Queuing Management in Wireless Sensor Networks for QoS Measurement

Data transmission in multimedia WSNs are required high bandwidth and reliable transfer because of large amount of data size. However, some applications of WSNs are required high quality. In this context, main factor in quality of services (QoS) metrics in WSNs becomes longevity of the network and high quality. In sensor nodes, choosing relevant transceiver and microcontroller components plays important role in assembling sensor devices, in which data controls should be designed so that packet loss is minimized. Available QoS metrics based on queuing/buffer management in wired and other wireless networks don’t applicable in WSNs because of its unique characteristics. In this paper the simplest model of QoS model-bufferless system were proposed. In the proposed model, measurement of the probability of blocking of the arrival packets was suggested by using queuing theory in order to increase QoS. Given probability of blocking (PB) illustrates clear picture how system specification should be chosen so that blocking state would be minimized.

基于ProtocolBuffer协议的服务端-客户端通信

利用Python和Socket编程,实现基于ProtocolBuffer的服务端-客户端通信和接口的平滑升级。

Effect of Transmission Control Protocol on Limited Buffer Cognitive Radio Relay Node

Transmission Control Protocol (TCP) is the most important transport layer protocol being used nowadays. It suffers from many problems over mobile networks especially over Cognitive Radio (CR). CR is one of the latest mobile technologies that brings its own share of problems for TCP. The buffer overflow for CR secondary network relay node can affect the performance of TCP. The contribution of this paper is the novel cross-layer model being used to evaluate the effect of the TCP congestion control on the secondary relay node buffer size in Cognitive Radio Network (CRN). The performance has been assessed by buffer overflow probability.

Design and implementation of near-memory computing array architecture based on shared buffer

Deep learning algorithms have been widely used in computer vision,natural language processing and other fields.However,due to the ever-increasing scale of the deep learning model,the requirements for storage and computing performance are getting higher and higher,and the processors based on the von Neumann architecture have gradually exposed significant shortcomings such as consumption and long latency.In order to alleviate this problem,large-scale processing systems are shifting from a traditional computing-centric model to a data-centric model.A near-memory computing array architecture based on the shared buffer is proposed in this paper to improve system performance,which supports instructions with the characteristics of store-calculation integration,reducing the data movement between the processor and main memory.Through data reuse,the processing speed of the algorithm is further improved.The proposed architecture is verified and tested through the parallel realization of the convolutional neural network(CNN)algorithm.The experimental results show that at the frequency of 110 MHz,the calculation speed of a single convolution operation is increased by 66.64%on average compared with the CNN architecture that performs parallel calculations on field programmable gate array(FPGA).The processing speed of the whole convolution layer is improved by 8.81%compared with the reconfigurable array processor that does not support near-memory computing.

Coping with handover effects in video streaming over cellular networks

The 3rd generation partnership project (3GPP) has defined the protocols and codecs for implementing media streaming services over packet-switched 3G mobile networks. The specification is based on IETF RFCs on audio/video transport.It also adds new features to achieve better adaptation to the mobile network environment. In this paper, we propose an algorithm for handover detection and fast buffer refill that is based on the existing feedback and signaling mechanisms. The proposed algorithm refills the receiver buffer at a faster pace during a limited time frame after a hard handover is detected in order to achieve higher video quality.

Method of Preventing Buffer Overflow Attacks by Intercepting DLL Functions

The way of intercepting Windows DLL functions against buffer overflow attacks is evaluated. It＇s produced at the expense of hooking vulnerable DLL functions by addition of check code. If the return address in the stack belongs to a heap or stack page, the call is from illicit code and the program is terminated. The signature of malicious code is recorded, so it is possible for the next attack to be filtered out. The return-into-libc attacks are detected by comparing the entry address of DLL functions with the overwritten return address in the stack. The presented method interrupts the execution of malicious code and prevents the system from being hijacked when these intercepted DLL functions are invoked in the context of buffer overflow.

QoE-driven voice quality evaluation model of VoIP based on network simulation

The quality of experience（ QoE） evaluation model for voice over IP（ VoI P） service is studied to analyze the impact of network parameters on voice quality and monitor voice quality in real-time for operators.Firstly,the influence of some network parameters on the voice quality of VoI P is investigated. Then,a simulation platform for VoI P transmission is built to collect voice data under different network enviornments. According to the simulation results,a new mapping model between these arguments and VoI P voice quality is deduced. Finally,the accuracy of this voice quality evaluation model is examined and the results demanstrate that it has high reliability and feasibility.

A Dynamic Resource-Aware Routing Protocol in Resource-Constrained Opportunistic Networks

Recently,Opportunistic Networks(OppNets)are considered to be one of the most attractive developments of Mobile Ad Hoc Networks that have arisen thanks to the development of intelligent devices.OppNets are characterized by a rough and dynamic topology as well as unpredictable contacts and contact times.Data is forwarded and stored in intermediate nodes until the next opportunity occurs.Therefore,achieving a high delivery ratio in OppNets is a challenging issue.It is imperative that any routing protocol use network resources,as far as they are available,in order to achieve higher network performance.In this article,we introduce the Resource-Aware Routing(ReAR)protocol which dynamically controls the buffer usage with the aim of balancing the load in resource-constrained,stateless and non-social OppNets.The ReAR protocol invokes our recently introduced mutual informationbased weighting approach to estimate the impact of the buffer size on the network performance and ultimately to regulate the buffer consumption in real time.The proposed routing protocol is proofed conceptually and simulated using the Opportunistic Network Environment simulator.Experiments show that the ReAR protocol outperforms a set of well-known routing protocols such as EBR,Epidemic MaxProp,energy-aware Spray and Wait and energy-aware PRoPHETin terms of message delivery ratio and overhead ratio.