共查询到20条相似文献，搜索用时 125 毫秒
1.
主动式队列管理（Active Queue Management,AQM）技术是IETF（The Intemet Engineering Task Force）为了解决Intemet拥塞控制问题而提出的一种路由器缓存管理技术。本文详细分析了RED算法、BLUE算法以及基于RED改进策略的SRED算法三种算法的优缺点,并在NS2中对它们的性能进行了仿真和比较。仿真结果表明RED和SRED性能都要优于BLUE算法。 相似文献
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网络仿真是网络技术研究的一种基本手段。NS-3是目前广泛使用的离散事件驱动的网络模拟器NS-2的后续版本。目前NS-3版本中的实现的队列管理模块只有默认的使用DropTail方式的队列管理模块。以实现主动队列管理算法RED算法为例,阐述了如何在NS-3中实现一个新的队列管理模块并进行仿真的方法。 相似文献
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随着Internet的快速发展网络拥塞问题随之产生,拥塞控制行之有效的手段是在网络层实现队列管理。队列管理算法可以分为主动队列管理和被动队列管理两种。通过NS2仿真实验,对主动队列管理算法RED、被动队列管理算法DropTail的平均队列长度、吞吐量、丢包率、时延四个主要性能指标进行了比较。将得到的仿真数据进行分析,在队列长度、时延、丢包率方面,RED算法比起DropTail算法有着绝对的优势;在吞吐量方面,两种算法相差不大。因此,得出在队列管理算法中采用RED比采用DropTail更有效,为进一步研究拥塞控制算法提供了依据。 相似文献
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为实现基于路由器的拥塞控制算法性能提升,分析了RED与ARED拥塞控制算法,并提出一种改进算法QARED。与传统DropTail算法对比,RED算法具有较高链路利用率、吞吐量及较低网络延迟、丢包率等优点,但存在参数配置无法适应网络动态改变的缺点。ARED算法增加了自适应功能,根据平均队列长度变化动态调整最大丢包概率,稳定平均队列长度在最小阈值与最大阈值之间,但存在瞬时队列长度振荡等稳定性问题。改进算法QARED,通过优化最大丢包概率计算函数,以提高平均队列长度稳定性、降低丢包率、提高吞吐量。通过NS2仿真网络环境对比,改进算法QARED相对ARED算法在控制平均队列长度上更具稳定性,能够实现更低网络延迟与丢包率,提高了动态网络环境下拥塞控制稳定性。 相似文献
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推导了基于流体流理论的网络简化模型,并基于该模型将遗传算法应用于PID控制器参数优化,定义了一个综合调节时间、上升时间、超调量、系统误差等动静态性能指标函数,在给定的参数空间进行组合优化搜索,迅速求得使性能指标优化函数极小化的一组PID控制器参数,而将PID控制器应用于网络主动队列管理系统中。仿真结果表明,在大时滞和突发业务流的冲击两种情况下,该方法设计的控制器的动静态性能优于RED、PI算法。 相似文献
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欧瑜枫 《南宁职业技术学院学报》2012,(1):91-93
随机早期检测RED(Random Early Detection)算法是一种有效的基于中间节点的拥塞控制策略。结合平均队列长度和瞬时队列长度,通过一种简单而有效的机制调节RED的丢包率,得出一种改进算法—SERED。NS2仿真实验结果表明,新算法的性能优于RED算法。 相似文献
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队列管理机制是网络拥塞控制和网络服务质量的基础,采用NS2仿真工具基=JaQOS性能评价指标对主、被动队列的代表算法RED、DropTail进行仿真分析,得出两种算法性能差异及各自的特点,为进一步研究提供依据． 相似文献
9.
王军祥 《广东职业技术师范学院学报》2014,(11):41-44
针对网络最大流问题,基于丢包概率提出了一种新的计算方法（Network Maximum Flow based on Dropping rate,NMFD）.该方法首先利用实际队列长度和到达速率定义了丢包策略,并在以前的研究基础上对最大流的计算方法进行了改进.同时,通过仿真实验对比分析了该算法与DINIC算法、FORD算法的性能,结果表明NMFD具有较好的适应性. 相似文献
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影响网络服务质量的因素很多,但最基本、最核心的是拥塞控制机制,主动队列管理是端到端拥塞控制研究中的热点。通过分析端到端拥塞控制存在的局限性,说明基于路由器技术的队列管理算法在改善端到端拥塞控制、提高QoS中所发挥的重要作用,对当前拥塞控制中基于路由器技术的RED和WRED进行分析与总结。 相似文献
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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 相似文献
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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献
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Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F. 相似文献
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邱崇丙 《唐山师范学院学报》2014,(1):21-23
汉字的六书,《说文》对“转注”一类,语焉不详。后世学者提及转注,也仅限于许慎所举出的例字。《汉字例说》一文,作者从转注的角度综合考虑,对部分现代常用字作了分析,跟传统的解释有所不同。希望能抛砖引玉,互相切磋,以推进学术研究。 相似文献
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陈美曦 《山东教育学院学报》2008,23(2):103-107
Different nations have different social cultures, and the social culture of every nation is developing with the development of the nation, language is greatly influenced by social culture, which enables language to possess national and historical characteristics. Word is the smallest, independent, meaningful linguistic unit of language. It can well reflect the national and historical characteristics. From synchronic aspect, the social and cultural influence on word meaning is mainly embodied in conceptual and associative meanings of word. The incorrespondence of word meaning is a phenomenon that exists in both conceptual and associative meanings of word among different languages. From diachronic aspect, the development of social culture causes some changes of word meaning to some extent. Therefore, social culture plays a key role in vocabulary learning and mastery of a language. 相似文献
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Rachel Zupek 《海外英语》2007,(11):40-41
我们绝大部分人都同意一件事情——我们喜欢金钱。但是你对金钱的喜欢之情足够到让你创立一份事业么?.财富通常被人忽视,主要在于人们不能真正了 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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YANGShiguo 《重庆大学学报(英文版)》2004,3(1):86-88
The problem on the geometrc inequalities involving an n-dimensional simplex and its inscribed simplex is studied. Aninequality is established, which reveals that the difference between the squared circumradius of the n-dimensional simplex andthe squared distance between its circumcenter and barycenter times the squared circumradius of its inscribed simplex is not lessthan the 2(n-1)th power of n times its squared inradius, and is equal to when the simplex is regular and its inscribed siplex is atangent point one. Deduction from this inequality reaches a generalization of n-dimensional Euler inequality indicating that thecircumradius of the simplex is not less than the n-fold inradius. Another inequality is derived to present the relationship betweenthe circumradius of the n-dimensional simplex and the circumradius and inradius of its pedal simplex. 相似文献
20.
Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献