Automated network management and configuration using Probabilistic Trans-Algorithmic Search

Online configuration of large-scale systems such as networks requires parameter optimization within a limited amount of time, especially when configuration is needed as a response to recover from a failure in the system. To quickly configure such systems in an online manner, we propose a Probabilistic Trans-Algorithmic Search (PTAS) framework which leverages multiple optimization search algorithms in an iterative manner. PTAS applies a search algorithm to determine how to best distribute available experiment budget among multiple optimization search algorithms. It allocates an experiment budget to each available search algorithm and observes its performance on the system-at-hand. PTAS then probabilistically reallocates the experiment budget for the next round proportional to each algorithm’s performance relative to the rest of the algorithms. This “roulette wheel” approach probabilistically favors the more successful algorithm in the next round. Following each round, the PTAS framework “transfers” the best result(s) among the individual algorithms, making our framework a trans-algorithmic one. PTAS thus aims to systematize how to “search for the best search” and hybridize a set of search algorithms to attain a better search. We use three individual search algorithms, i.e., Recursive Random Search (RRS) (Ye and Kalyanaraman, 2004), Simulated Annealing (SA) (Laarhoven and Aarts, 1987), and Genetic Algorithm (GA) (Goldberg, 1989), and compare PTAS against the performance of RRS, GA, and SA. We show the performance of PTAS on well-known benchmark objective functions including scenarios where the objective function changes in the middle of the optimization process. To illustrate applicability of our framework to automated network management, we apply PTAS on the problem of optimizing link weights of an intra-domain routing protocol on three different topologies obtained from the Rocketfuel dataset. We also apply PTAS on the problem of optimizing aggregate throughput of a wireless ad hoc network by tuning datarates of traffic sources. Our experiments show that PTAS successfully picks the best performing algorithm, RRS or GA, and allocates the time wisely. Further, our results show that PTAS’ performance is not transient and steadily improves as more time is available for search.     

铁通扩容工程中网络迁移的研究

本文介绍了铁通全国扩容工程中,铁通全国网络由OSPF协议迁移到IS-IS协议的过程。在扩容工程实施以前,铁通全国网络中运行的是OSPF协议。网络运行得基本稳定,鉴于网络扩客后用户敷量剧增。容量扩大的情况。本工程决定将网络由OSPF迁移到IS-IS协议上来,本文详细介绍了两种协议。并做出了比较。在论证了方案可行性后,本文给出了迁移的详细步骤。供读者参考。     

Crystallization and structure solution at 4 A resolution of the recombinant synthase domain of N(5'-phosphoribosyl)anthranilate isomerase:indole-3-glycerol-phosphate synthase from Escherichia coli complexed to a substrate analogue

The recombinant synthase domain of the bifunctional enzyme N-(5'-phosphoribosyl)anthranilateisomerase:indole-3-glycerol-phosphate synthase from Escherichiacoli has been crystallized, and the structure has been solvedat 4 Å resolution. Two closely related crystal forms grownfrom ammonium sulphate diffract to 2 Å resolution. Oneform (space group R32, a = 163 Å, = 29.5°) containsthe unliganded synthase domain; the second crystal form (spacegroup P6₃22, a = 144 Å, c = 158 Å) is co-crystallizedwith the substrate analogue N-(5'-phosphoribit-1-yl)anthranilate.The structure of the synthase–inhibitor complex has beensolved by the molecular replacement method. This achievementrepresents the first successful use of a (ß)_g-barrelmonomer as a trial model. The recombinant synthase domain associatesas a trimer in the crystal, the molecules being related by apseudo-crystallographic triad. The interface contacts betweenthe three domains are mediated by those residues that are alsoinvolved in the domain interface of the bifunctional enzyme.This system provides a model for an interface which is usedin both intermolecular and intramolecular domain contacts.     

Study on the fracture reason and fatigue life for guide pillar of injection machine

Some injector guide pillars (IGP) used in injection machine were fractured only after 1.5-year service. In order to determine the cause of the fractures, the numerical simulation technology was applied to analyze the mechanical properties of the IGP. To model the contact between the mating surfaces of the clamping mechanism, nonlinear multi-region contacts of surface-surface were applied to establish the contact model of FEA. The constraint of tie was used for modeling thread joint. The simulated results indicated that the smaller area of contact surface yielded higher value of stress in the neck of IGP. The value of maximum stress concentration factor (SCF) was obtained by FEA. The stresses at outer wall of the IGP were measured by strain gages, in order to check the results of FEA and examine the load balance between each IGP. The experimental data agree with the simulated results very well because the relative error of them is no more than 3.7%. The experimental results also proved that the load of the IGP was equal with each other, which means there was no partial load between each IGP. Based on the numerical analysis and experimental study, the structure of the IGP was improved by adopting a smoother double-round neck. The fatigue life of the improved structure is longer than that of the original machine.     

MPLS流量工程的内部网关协议

围绕MPLS流量工程的内部网关协议问题进行讨论,文章首先介绍传统的Internet流量工程内部网关协议,再介绍目前流量工程的约束路由,约束路由的特征,分析了现有增强内部网关协议（EIGP）对MPLS流量工程的支持,最后作者根据EIGP的一些问题,提出了一套改进方案。     

GMPLS网络中基于约束的最短路径优先算法

对多种基于约束的最短路径优先算法设计思想进行了分析对比,选择了一种适用于GMPLS网络的路由算法,而且阐述了满足我们需求的设计方案。     

用MPLS在骨干网上实施流量工程

实施流量工程可以优化网络资源的使用，提高网络性能。MPLS具有很强的流量工程能力，可以在IP网上有效地实现流量工程。约束路由和增强链路状态IGP在实施流量工程的过程中起到重要作用。流量工程的实施是一个连续和反复的过程。     

IGP路由收敛分析及优化

本文介绍了常用IGP路由协议ISIS,对ISIS的收敛过程进行了深入地分析,提出ISIS收敛的计算公式,并在实验中得到较好地验证.最后在收敛过程分析的基础上,给出加快收敛速度的优化建议.     

计算机支持的基于IGP的创新设计

表述了创新设计的出现背景及其研究现状。分析了IGP的基本思想、遗传操作及其主要特点。根据创新设计与IGP存在的共同点,将IGP引入产品创新设计的实现上,利用GP的操作,对遗传程序树进行处理,以产生创新性的设计造型。最后展现了该思想在建筑设计上的应用,显现了它的发展潜力。