移动自组网多层分布式认证技术研究

移动自组网是一种新型的移动网络,它的无中心、无基础设施等特性决定了在这种网络中提供证书服务必须采用分布式的体系结构。现有的分布式认证技术是基于(n,t)门限方案的单层结构,当一个节点的单跳邻居节点数目小于系统门限值时就无法正常工作。该文结合Feldman可验证秘密共享策略提出了一种多层分布式认证技术,一方面可以解决单层分布式认证技术中邻居节点数目不足问题,另一方面可以在证书签名合成中验证私钥分量正确性,保护系统私钥不泄漏。     

多层交换提高企业网的性能：提高性能和加强应用程序控制的关键

网络是为应用程序服务的,其最终目的是提高企业工作效率和效益,但在多种因素的共同作用下,如服务器的集中管理、多媒体应用及需要高带宽的应用程序等等,经常会出现应用程序需要的带宽大于可用带宽的情况。在这种情况下,网络就如同一个漏斗,应用程序或者争抢带宽,或者在网络中全部受阻,而系统管理人员无法确保重要应用程序的顺利运行,他们必须尽全力来应付来自企业内各个不同部门对应用程序带宽的竞争性需求。     

无线传感网多信道的MAC层协议

无线传感网(Wireless Sensor Networks,WSNs)作为计算机、通信和传感器三项技术相结合的产物,已成为计算机与通信领域一个活跃的研究分支。信道接入协议是无线传感网协议的重要组成部分,基于多信道的信道接入协议具有一些特殊的优点。分析了无线传感网多信道的MAC(Media Access Control)协议:DCA-PC(Dynamic Channel Assignment withPower Control),并与其他的多信道协议作了比较。     

无线传感网多信道的MAC层协议

无线传感网（Wireless Sensor Nelworks，WSNs）作为计算机、通信和传感器三项技术相结合的产物，已成为计算机与通信领域一个活跃的研究分支。信道接入协议是无线传感网协议的重要组成部分，基于多信道的信遭接入协议具有一些特殊的优点。分析了无线传感网多信道的MAC（Media Access Control）协议：DCA—PC（Dynamic Channel Assignment with Power Control），并与其他的多信道协议作了比较。     

超级计算机的多层架构抽象及描述

超级计算机系统发展迅猛,不仅速度上日新月异,而且其结构也日益复杂化、多样化。为了能够准确有效地描述超级计算机的结构,给出统一的描述方法,提出超级计算机的多层架构思想。为超级计算机的进一步逻辑抽象或编写其模拟器提供了基础,并对超级计算机系统的设计具有一定的指导作用。     

提高分布式多层系统执行效率方法的研究

分布式多层系统由客户端应用程序、应用服务器层、数据库服务器层构成.由于分布式多层应用系统均在网络环境下运行,所以,它的执行效率成为设计时不可忽视的重点.以提高分布式多层应用系统的执行效率为目的,文中总结了如何使用Delphi所提供的相关技术来提高分布式多层MIS系统执行效率的几种方法.并得出结论:合理地运用Delphi所提供的相关技术可以大幅度提高分布式多层应用系统的执行效率.     

Delphi中分布式多层MIS系统执行效率的研究

分布式多层系统由客户端应用程序、应用服务器层、数据库服务器层构成.由于分布式多层应用系统其自身的结构特征及其运行环境,决定了它的执行效率将成为其设计中不可忽视的重点.本文总结了如何使用Delphi所提供的相关技术来提高分布式多层系统执行效率的几种方法.     

无线mesh网TCP性能改进研究

无线mesh网(WMN)是一种近年来快速发展起来的新型网络技术,支持宽带高速多媒体业务服务,是一种有效的无线宽带接人手段.为了提高无线mesh网络的性能,使TCP协议在可靠性低、突发错误时间长以及切换时延高的无线移动环境更为有效地工作,人们提出了种种改进传输层TCP技术的方案.文中结合无线mesh网络的自组织、自修复和多跳的特点,将目前的TCP改进方案进行了归类和比较,并分析了其性能特点,同时指出了今后可能的研究方向.     

多层交换技术

本文从交换技术和路由技术谈起，简单地介绍了第三层交换技术的原理和目前主要使用的第三层交换技术；随后介绍了第四层交换技术的基本原理和作用，还介绍了第四层交换技术和服务器集群技术的联系。     

多层分布式的Intranet应用

Ｉｎｔｒａｎｅｔ作为企业内部的信息交互和信息共享平台,大大提高了企业的竞争力。叙述了构建Ｉｎｔｒａｎｅｔ应用的多层分布式模型,介绍了ＤＣＯＭ和ＡＳＰ对开发多层分布Ｉｎｔｒａｎｅｔ应用的技术支持,并给出了利用ＤＣＯＭ和ＡＳＰ技术建立多层分布式应用的主要步骤和一个Ｉｎｔｒａｎｅｔ多层分布式应用实例。     

Cycles embedding in hypercubes with node failures

The hypercube has been widely used as the interconnection network in parallel computers. The n-dimensional hypercube Qn is a graph having n² vertices each labeled with a distinct n-bit binary strings. Two vertices are linked by an edge if and only if their addresses differ exactly in the one bit position. Let fv denote the number of faulty vertices in Qn. For n?3, in this paper, we prove that every fault-free edge and fault-free vertex of Qn lies on a fault-free cycle of every even length from 4 to n²−2fv inclusive even if fv?n−2. Our results are optimal.     

Edge-fault-tolerant vertex-pancyclicity of augmented cubes

The n-dimensional augmented cube, denoted as AQn, a variation of the hypercube, possesses some properties superior to those of the hypercube. In this paper, we show that every vertex in AQn lies on a fault-free cycle of every length from 3 to n², even if there are up to n−1 edge faults. We also show that our result is optimal.     

Fault-tolerant routing based on approximate directed routable probabilities for hypercubes

Recently, parallel processing systems have been studied very actively, and many topologies have been proposed. A hypercube is one of the most popular topologies for interconnection networks. In this paper, we propose two new fault-tolerant routing algorithms for hypercubes based on approximate directed routable probabilities. Probabilities represent the ability of routing toward any node located at a specific distance and are calculated by considering from which direction the message has been received. Each node chooses one of its neighbor nodes to forward the message by comparing the approximate directed routable probabilities. We also conducted a computer experiment to verify the effectiveness of our algorithms.     

Proof that pyramid networks are 1-Hamiltonian-connected with high probability

Wu revealed in 2001 that pyramid networks are Hamiltonian-connected. This investigation demonstrates that a pyramid network with one faulty node or one faulty edge is Hamiltonian-connected, excluding some special faulty cases by building a Hamiltonian path between any two distinct nodes in it. Although a pyramid network with one fault is not Hamiltonian-connected, this study indicates that a pyramid network is 1-Hamiltonian-connected with a very high probability.     

SINOMP:并行机互联网络通信性能模拟系统

研究并设计实现了并行机互联网络通信性能模拟系统——SINOMP。在单机系统上实现了互联网络的网络特征和通信过程的描述,提供路由选择和交换策略。通过指定目标系统的环境参数,获得目标系统互联网络在存储转发和虫蚀方式下的平均距离、吞吐率和以时钟周期为单位的通信时延,为并行机系统的研究和设计提供了直观、有效的工具。     

Performance modeling of Cartesian product networks

This paper presents a comprehensive performance model for fully adaptive routing in wormhole-switched Cartesian product networks. Besides the generality of the model which makes it suitable to be used for any product graph, experimental (simulation) results show that the proposed model exhibits high accuracy even in heavy traffic and saturation region, where other models have severe problems to predict the performance of the network. Most popular interconnection network can be defined as a Cartesian product of two or more networks including the mesh, hypercube, and torus networks. Torus and mesh networks are the most popular topologies used in recent supercomputing parallel machines. They have been widely used for realizing on-chip network in recent on-chip multicore and multiprocessors system.     

紧耦合网络接口的并行性研究

高效的网络接口已成为多机系统中的重要技术之一。文中通过对当前各种接口类型的分析认为，紧耦合应是网络接口的方向；同时，不同类型信息的串行处理是网络接口进一步提高性能的瓶颈。为此，对不同信息间的并行性进行分析后，提出了并行网络接口的概念结构，并对其性能进行了评价。     

Edge-bipancyclicity of star graphs with faulty elements

In this paper, we investigate the fault-tolerant edge-bipancyclicity of an n-dimensional star graph S_n. Given a set F comprised of faulty vertices and/or edges in S_n with |F|≤n−3 and any fault-free edge e in S_n−F, we show that there exist cycles of every even length from 6 to n!−2|F_v| in S_n−F containing e, where n≥3. Our result is optimal because the star graph is both bipartite and regular with the common degree n−1. The length of the longest fault-free cycle in the bipartite S_n is n!−2|F_v| in the worst case, where all faulty vertices are in the same partite set. We also provide some sufficient conditions from which longer cycles with length from n!−2|F_v|+2 to n!−2|F_v| can be embedded.     

Edge-fault-tolerant pancyclicity and bipancyclicity of Cartesian product graphs with faulty edges

Let r≥ 4 be an even integer. Graph G is r-bipancyclic if it contains a cycle of every even length from r to $2\lfloor \frac{n(G)}{2}\rfloor$, where $n(G)$ is the number of vertices in G. A graph G is r-pancyclic if it contains a cycle of every length from r to $n(G)$, where $r\ge 3$. A graph is k-edge-fault Hamiltonian if, after deleting arbitrary k edges from the graph, the resulting graph remains Hamiltonian. The terms k-edge-fault r-bipancyclic and k-edge-fault r-pancyclic can be defined similarly. Given two graphs G and H, where $n(G)$, $n(H)\ge$ 9, let $k_1$, $k_2\ge 5$ be the minimum degrees of G and H, respectively. This study determined the edge-fault r-bipancyclic and edge-fault r-pancyclic of Cartesian product graph $G\times H$ with some conditions. These results were then used to evaluate the edge-fault pancyclicity (bipancyclicity) of ${\mathit{NQ}}_{m_r,\dots ,m_1}$ and ${\mathit{GQ}}_{m_r,\dots ,m_1}$.     

Performance analysis of cut-through buffered banyan networks with finite buffer size

In this paper, we present an analytic model to estimate the performance of cut-through buffered banyan networks with finite buffer size. Two conflict resolution policies are considered in order to resolve conflicts when two packets are destined to the same output link, and their performances are compared. Our analytic model enables analysis of the networks in which buffers are unevenly distributed, i.e., each stage has a different buffer size. It is shown that if buffers are properly distributed in the network, higher throughput and lower delay are possible, although the improvement is considered small. Finally, in order to validate our model, some analytic results are compared to simulation.