Performance analysis of BusNet protocol for backplane bus-based interprocessor communication

Nowadays, backplane bus-based multiprocessor systems often utilize the standard network protocol such as TCP/IP for communication between processors on the backplane bus. In such systems, it is common for the backplane bus to emulate the standard MAC protocols such as CSMA/CD. This paper aims to analyze the delay performance of the MAC emulation-based backplane network by constructing queueing models based on detailed bus operations. For this purpose, we choose BusNet as a target protocol. BusNet is an ANSI standard network protocol and its specification contains basic operations commonly used in most backplane buses. We investigate the throughput-delay characteristics in terms of packet size, block transfer scale, and arbitration scheme. We also compare the packet delay in BusNet with the IEEE 802.3 CSMA/CD network which BusNet is expected to be compatible with. The simulation result shows how an optimal block transfer scale can be determined in respect of the performance trade-off between BusNet and other real-time traffics.     

一种WLAN的新安全标准CCMP协议

新一代WLAN安全标准IEEE 802.11 i定义了三种协议来保护数据的传输,这三种协议增强了WLAN中数据的加密和鉴别性能,取代了IEEE 802.11 WEP方案。CCMP协议是数据保密协议之一。CCMP协议使用基于AES的加密算法和CCM加密鉴别模式,在软件和硬件实现上都提供了很好的安全性能。     

即插即用的智能传感器IEEE P1451.4标准研究

IEEE P1451.4是关于即插即用的模拟传感器的新标准,该标准在传统传感器的基础上定义了一种自我识别和描述的机制,这种机制大大减少了系统的配置和诊断时间;对1451.4传感器的模型和结构进行了研究,具体分析了用于存放传感器信息的数据表单TEDS的结构及用于传输模拟和数字信号的混合模式接口,并简要介绍了数字接口的通信协议,最后指出了IEEE1451.4与IEEE1451的其他标准一起将成为智能传感器的发展方向.     

一种具有自适应传输门限的变速率MAC协议研究

IEEE802.11a是已得到广泛应用的无线局域网标准,可支持多种传输模式。然而,标准中并未给出如何在多种传输模式之间自适应切换的方法。基于IEEE802.11a,提出了一种Ad Hoc网络应用中具有自适应传输门限的变速率MAC,即AV-MAC(Variable rate Media Access Control protocol with Adaptive transmission-threshold)。该算法通过计算发送端所发送的RTS控制帧的接收信噪比,感知信道状态,并依据计算所得的自适应传输门限来判断是否可以发送其后的数据分组。如可以发送该数据分组,发送端将进一步根据接收信噪比选择最佳传输模式,从而优化网络的通过率。利用仿真工具OMNET++4.0对算法进行性能仿真分析,结果表明所提出的AV-MAC可显著提升网络的通过率。     

基于Wi-Fi的无线控制网络TDMA协议的设计

为解决多种网络协议共存的混合无线网络环境中,控制信息高速、实时、可靠传输的问题,在IEEE802.11协议MAC层基础上开发了TDMA协议。该协议在充分利用Wi-Fi高传输速率的同时,解决了Wi-Fi退避重传机制导致传输时延不确定的问题,增强系统的实时性。实验结果表明,协议在保证95%以上的传输可靠性的同时,传输速率可达5 Mb/s,相较于典型的基于IEEE 802.15.4协议的工业控制网络有大幅提高。TDMA系统中的短帧中有95.4%、长帧中有89.87%可以在2 ms以内的发送完成,传输时延远低于原有的Wi-Fi标准。此外,系统不改变上层协议栈,保持接口的兼容性,便于控制应用程序的开发。     

增强安全性的IEEE802.15.4协议研究

IEEE 802．15．4标准因其低速率、低成本、低功耗、高质量，被认为是无线传感器网络和无线个人域网络的理想实现技术。简要介绍了无线传感器网络及其主要特点和问题，及无线传感器网络的安全需求。提出了增强安全性的IEEE802．15．4协议SE-IEEE802．15．4研究，其中使用公钥加密算法ECC来实现IEEE802．15．4协议的数字签名。最后采用NS-2平台对其进行仿真，并进行了性能和安全性的分析。     

增强安全性的IEEE802.15.4协议研究

IEEE 802.15.4标准因其低速率、低成本、低功耗、高质量,被认为是无线传感器网络和无线个人域网络的理想实现技术。简要介绍了无线传感器网络及其主要特点和问题,及无线传感器网络的安全需求。提出了增强安全性的IEEE802.15.4协议SE-IEEE802.15.4研究,其中使用公钥加密算法ECC来实现IEEE802.15.4协议的数字签名。最后采用NS-2平台对其进行仿真,并进行了性能和安全性的分析。     

一种无线局域网漫游接入认证

在无线mesh网络中,用户对快速漫游切换需求愈发突出,但现有的IEEE802.1s WLan Mesh认证协议并未对此进行定义,且初始接入认证过程中,信息交换次数较多,时延较高。在现有协议基础上提出了采用基于签名的身份认证方式,将认证转移到用户和路由节点之间,并且将用户向服务器注册与用户对路由节点认证过程并发执行,减少了认证的时延。分析结果表明,接入认证方式总体性能优于现有网络标准。     

IEEE802.15.4无线传感器网络仿真与性能评估

IEEE802.15.4标准是为满足低速率、低能耗、低成本需求而制定的无线个人区域网（LR_WPAN）规范。通过用网络仿真软件NS2对基于IEEE802.15.4的无线传感器网络的主要性能指标进行分析,较为详实地论述了IEEE802.15.4MAC层基于时槽的CSMA/CA机制,最后给出仿真环境及其结果,并进行度量分析和阐述各指标间的依赖关系。     

IEEE 802.11p车载自组网络协议的EDCA自适应退避算法研究

IEEE 802.11p是IEEE针对车辆网络颁布的物理层与MAC层标准,网络中车辆密度是动态变化的,而IEEE 802.11p协议没有提出根据网络情况动态调整EDCA参数来优化网络性能。为了解决网络中节点密度变化带来的吞吐量低、碰撞率高的问题,提出一种EDCA自适应退避优化算法。仿真实验结果表明,该算法相对于传统EDCA算法,性能大幅度提高。     

PLC协处理器板的VME总线接口系统

总线接口系统是ＰＬＣ协处理器与宿主机之间交互的硬件通道。它的设计需要满足ＰＬＣ协处理器在交互作用方面的功能要求，同时要满足宿主机总线及操作系统在硬件和软件方面的各种协议。本文讨论了在ＳＵＮ－ＯＳ环境下，基于ＶＭＥ总线的数据传输，作为总线主设备的ＤＭＡ传输和从设备传输的优缺点。对传输速度进行了实验比较，确定了简洁可靠的方案。采用优化设计以及ＦＰＧＡ技术，实现了Ｐｒｏｌｏｇ／Ｌｉｓｐ协处理器板与Ｓｕｎ     

一种基于SCI的高效输入队列分配协议

ＳＣＩ是ＩＥＥＥ于１９９２年通过的高速互联标准,它为机群系统的互联提供了一个高效,经济,可扩展的解决方案。为了更有效地利用ＳＣＩ标准提供的高带宽,文中对标准中的输入队列分配协议－Ａ／Ｂ年龄协议进行了深入分析,并提出了一种改进方案：智能Ａ／Ｂ年龄协议。文中还讨论了改进方案的实现及性能。     

Performance of IEEE 802.15.4 Clusters with Power Management and Key Exchange

The IEEE 802.15.4 specification is a recent low data rate wireless personal area network standard.While basic security services are provided for,there is a lack of more advanced techniques which are indispensable in modern personal area network applications.In addition,performance implications of those services are not known.In this paper,we describe a secure data exchange protocol based on the ZigBee specification and built on top of IEEE 802.15.4 link layer.This protocol includes a key exchange mechanism.We assume that all nodes are applying power management technique based on the constant event sensing reliability required by the coordinator.Power management generates random sleep times by every node which in average fairly distributes the sensing load among the nodes.Key exchange is initiated by a cluster coordinator after some given number of sensing packets have been received by the coordinator.We develop and integrate simulation model of the key exchange and power management technique into the cluster's reliable sensing function.We evaluate the impact of security function and its periodicity on cluster performance.     

A Timed Verification of the IEEE 1394 Leader Election Protocol

The IEEE 1394 architecture standard defines a high performance serial multimedia bus that allows several components in a network to communicate with each other at high speed. In the physical layer of the architecture, a leader election protocol is used to find a spanning tree with a unique root in the network topology. If there is a cycle in the network, the protocol treats this as an error situation. This paper presents a formal model of the leader election protocol in the language IOA and a correctness proof. Hereby, it is shown that under certain timing restrictions the protocol behaves correctly. The timing parameters in the IEEE 1394 standard documentation obey the restrictions found in this proof.     

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.     

IEEE 802.15.4 MAC协议退避机制的改进

考虑节点移动且数据传输率不断变化对网络性能的影响,针对IEEE802.15.4提出了一种网络负荷概率判断和指数加权滑动平均(PJNL_EWMA) 的退避策略,在每次载波监听多路访问/冲突避免（CSMA/CA）算法开始时采用网络负荷概率判断思想判定当前网络状况,然后通过指数加权滑动平均方法动态地调整退避指数。通过NS2的仿真结果表明：与IEEE802.15.4标准协议算法及MBS+EWMA算法相比,PJNL_EWMA算法不仅提高了网络吞吐量,同时还减小了数据包的丢包率和碰撞概率,提高了网络性能。     

DotDFS: A Grid-based high-throughput file transfer system

DotGrid platform is a Grid infrastructure integrated with a set of open and standard protocols recently implemented on the top of Microsoft .NET in Windows and MONO .NET in UNIX/Linux. DotGrid infrastructure along with its proposed protocols provides a right and solid approach to targeting other platforms, e.g., the native C/C++ runtime. In this paper, we propose a new concurrent file transfer protocol called DotDFS as a high-throughput distributed file transfer component for DotGrid. DotDFS introduces some open binary protocols for efficient file transfers on current Grid infrastructures. DotDFS protocol also provides mechanisms for multiple file streams to gain high-throughput file transfer similar to GridFTP protocol, but by proposing and implementing a new parallel TCP connection-oriented paradigm. Almost no research work has been conducted to suggest a concurrent file transfer protocol that simultaneously employs threaded and event-driven models in the protocol level. Due to our knowledge, DotDFS is the first concurrent file transfer protocol that, from this viewpoint, presents a new computing paradigm in the field of data transmission protocols. In our LAN tests, we have achieved better results than Globus GridFTP implementation particularly in multiple TCP streams and directory tree transfers. Our LAN experiences in memory-to-memory tests show that DotDFS accesses to the 94% bottleneck bandwidth while GridFTP is accessing 91%. In LAN disk-to-disk tests, comparing DotDFS protocol with GridFTP protocol unveils a set of interesting and technical problems in GridFTP for both the nature of the protocol and its implementation by Globus. In the WAN experimental studies, we propose a new idea for analytical modeling of file transfer protocols like DotDFS inspired by sampling, experimentation and mathematical interpolation approaches. The cross-platform and open standard-based features of DotDFS provide a substantial framework for unifying data access and resource sharing in real heterogeneous Grid environments.     

应用于IEEE802.1x的可扩展认证协议的安全分析

IEEE802．1x协议是对现行lEEE802．11协议的安全补充，lEEE委员会为IEEE802．11推出了一个安全架构，称之为RSN(Robust Security Network)。RSN利用IEEE802.lx标准来实现访问控制、认证以及密钥的管理。可扩展认证协议(EAP)是IEEE802．1x中引入的一个重要协议，该标准为基于802标准的局域网提供了一个认证的框架。文章对EAP在应用中所遇到的问题和安全隐患进行分析，并对这些问题提出了可能的解决方案。     

Performance Analysis and Throughput Enhancement of the STET Technique for WLAN IEEE 802.11ad

The IEEE 802.11ad innovation has enabled the impact of remote devices in unauthorized 60 GHz unlicensed frequency band at Giga bits per second information transfer rate in speed concentrated 5G applications. We have presented an innovative work that deals with the upgradation of the ability of IEEE 802.11ad wireless LAN to make it suitable for wireless applications. An exact examination on the IEEE 802.11ad analysis has been carried out in this work to achieve the greatest throughput. This has pulled attraction in broad consideration for accomplishing the pinnacle transmission rate of 8 Gbit/s. IEEE 802.11ad is a convention utilized for extremely high information rates (around 8 Gbit/s) and for short range remote correspondence of around 1 to 10 meters. The Multi-layer with Multi-User Multiple Input Multiple-Output (MLMU-MIMO) innovation has enabled transmission of multiple information packets all the while from the WLAN IEEE 802.11 ad Access Point (AP) to various receivers by means of different wireless applications. To help the MLMU-MIMO innovation at Medium Access Control (MAC), a new method called Simultaneous Transmission for Enhanced Throughput (STET) has been presented for enhancement of the transmission rate of the wireless standard. A mathematical model has been used for the evaluation of the performance of an IEEE 802.11ad AP empowering the STET allocation technique. This STET model can help determination of the throughput improvement of a STET technique, for example, audio information, images, good quality and foundation impact. The main goal of this work is to analyze the improvement of the STET allocation technique in regard to the usage of rare frequency band, when obtaining spectrum access between the various access points. The theoretical and simulation outcomes are also confirmed by Riverbed modeler 17.5 simulation tool.