Rate And Queue Controlled Random Drop (RQRD) A Buffer Management Scheme for Internet Router

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运筹学英汉词汇ABC

运筹学英汉词汇(0,1) normalized ――0-1规范化Aactivity ――工序additivity――可加性adjacency matrix――邻接矩阵adjacent――邻接aligned game――结盟对策analytic functional equation――分析函数方程approximation method――近似法arc ――弧artificial constraint technique ――人工约束法artificial variable――人工变量augmenting path――增广路avoid cycle method ――避圈法Bbackward algorithm――后向算法balanced transportation problem――产销平衡运输问题basic feasible solution ――基本可行解basic matrix――基阵basic solution ――基本解basic variable ――基变量basic ――基basis iteration ――换基迭代Bayes decision――贝叶斯决策big M method ――大M 法binary integer programming ――0-1整数规划binary operation――二元运算binary relation――二元关系binary tree――二元树binomial distribution――二项分布bipartite graph――二部图birth and death process――生灭过程Bland rule ――布兰德法则branch node――分支点branch――树枝bridge――桥busy period――忙期Ccapacity of system――系统容量capacity――容量Cartesian product――笛卡儿积chain――链characteristic function――特征函数chord――弦circuit――回路coalition structure――联盟结构coalition――联盟combination me――组合法complement of a graph――补图complement of a set――补集complementary of characteristic function――特征函数的互补性complementary slackness condition ――互补松弛条件complementary slackness property――互补松弛性complete bipartite graph――完全二部图complete graph――完全图completely undeterministic decision――完全不确定型决策complexity――计算复杂性congruence method――同余法connected component――连通分支connected graph――连通图connected graph――连通图constraint condition――约束条件constraint function ――约束函数constraint matrix――约束矩阵constraint method――约束法constraint ――约束continuous game――连续对策convex combination――凸组合convex polyhedron ――凸多面体convex set――凸集core――核心corner-point ――顶点（角点）cost coefficient――费用系数cost function――费用函数cost――费用criterion ; test number――检验数critical activity ――关键工序critical path method ――关键路径法（CMP ）critical path scheduling ――关键路径cross job ――交叉作业curse of dimensionality――维数灾customer resource――顾客源customer――顾客cut magnitude ――截量cut set ――截集cut vertex――割点cutting plane method ――割平面法cycle ――回路cycling ――循环Ddecision fork――决策结点decision maker决――策者decision process of unfixed step number――不定期决策过程decision process――决策过程decision space――决策空间decision variable――决策变量decision决－－策decomposition algorithm――分解算法degenerate basic feasible solution ――退化基本可行解degree――度demand――需求deterministic inventory model――确定贮存模型deterministic type decision――确定型决策diagram method ――图解法dictionary ordered method ――字典序法differential game――微分对策digraph――有向图directed graph――有向图directed tree――有向树disconnected graph――非连通图distance――距离domain――定义域dominate――优超domination of strategies――策略的优超关系domination――优超关系dominion――优超域dual graph――对偶图Dual problem――对偶问题dual simplex algorithm ――对偶单纯形算法dual simplex method――对偶单纯形法dummy activity――虚工序dynamic game――动态对策dynamic programming――动态规划Eearliest finish time――最早可能完工时间earliest start time――最早可能开工时间economic ordering quantity formula――经济定购批量公式edge ――边effective set――有效集efficient solution――有效解efficient variable――有效变量elementary circuit――初级回路elementary path――初级通路elementary ――初等的element――元素empty set――空集entering basic variable ――进基变量equally liability method――等可能性方法equilibrium point――平衡点equipment replacement problem――设备更新问题equipment replacing problem――设备更新问题equivalence relation――等价关系equivalence――等价Erlang distribution――爱尔朗分布Euler circuit――欧拉回路Euler formula――欧拉公式Euler graph――欧拉图Euler path――欧拉通路event――事项expected value criterion――期望值准则expected value of queue length――平均排队长expected value of sojourn time――平均逗留时间expected value of team length――平均队长expected value of waiting time――平均等待时间exponential distribution――指数分布external stability――外部稳定性Ffeasible basis ――可行基feasible flow――可行流feasible point――可行点feasible region ――可行域feasible set in decision space――决策空间上的可行集feasible solution――可行解final fork――结局结点final solution――最终解finite set――有限集合flow――流following activity ――紧后工序forest――森林forward algorithm――前向算法free variable ――自由变量function iterative method――函数迭代法functional basic equation――基本函数方程function――函数fundamental circuit――基本回路fundamental cut-set――基本割集fundamental system of cut-sets――基本割集系统fundamental system of cut-sets――基本回路系统Ggame phenomenon――对策现象game theory――对策论game――对策generator――生成元geometric distribution――几何分布goal programming――目标规划graph theory――图论graph――图HHamilton circuit――哈密顿回路Hamilton graph――哈密顿图Hamilton path――哈密顿通路Hasse diagram――哈斯图hitchock method ――表上作业法hybrid method――混合法Iideal point――理想点idle period――闲期implicit enumeration method――隐枚举法in equilibrium――平衡incidence matrix――关联矩阵incident――关联indegree――入度indifference curve――无差异曲线indifference surface――无差异曲面induced subgraph――导出子图infinite set――无限集合initial basic feasible solution ――初始基本可行解initial basis ――初始基input process――输入过程Integer programming ――整数规划inventory policy―v存贮策略inventory problem―v货物存储问题inverse order method――逆序解法inverse transition method――逆转换法isolated vertex――孤立点isomorphism――同构Kkernel――核knapsack problem ――背包问题Llabeling method ――标号法latest finish time――最迟必须完工时间leaf――树叶least core――最小核心least element――最小元least spanning tree――最小生成树leaving basic variable ――出基变量lexicographic order――字典序lexicographic rule――字典序lexicographically positive――按字典序正linear multiobjective programming――线性多目标规划Linear Programming Model――线性规划模型Linear Programming――线性规划local noninferior solution――局部非劣解loop method――闭回路loop――圈loop――自环（环）loss system――损失制Mmarginal rate of substitution――边际替代率Marquart decision process――马尔可夫决策过程matching problem――匹配问题matching――匹配mathematical programming――数学规划matrix form ――矩阵形式matrix game――矩阵对策maximum element――最大元maximum flow――最大流maximum matching――最大匹配middle square method――平方取中法minimal regret value method――最小后悔值法minimum-cost flow――最小费用流mixed expansion――混合扩充mixed integer programming ――混合整数规划mixed Integer programming――混合整数规划mixed Integer ――混合整数规划mixed situation――混合局势mixed strategy set――混合策略集mixed strategy――混合策略mixed system――混合制most likely estimate――最可能时间multigraph――多重图multiobjective programming――多目标规划multiobjective simplex algorithm――多目标单纯形算法multiple optimal solutions ――多个最优解multistage decision problem――多阶段决策问题multistep decision process――多阶段决策过程Nn- person cooperative game ――n人合作对策n- person noncooperative game――n人非合作对策n probability distribution of customer arrive――顾客到达的n 概率分布natural state――自然状态nature state probability――自然状态概率negative deviational variables――负偏差变量negative exponential distribution――负指数分布network――网络newsboy problem――报童问题no solutions ――无解node――节点non-aligned game――不结盟对策nonbasic variable ――非基变量nondegenerate basic feasible solution――非退化基本可行解nondominated solution――非优超解noninferior set――非劣集noninferior solution――非劣解nonnegative constrains ――非负约束non-zero-sum game――非零和对策normal distribution――正态分布northwest corner method ――西北角法n-person game――多人对策nucleolus――核仁null graph――零图Oobjective function ――目标函数objective( indicator) function――指标函数one estimate approach――三时估计法operational index――运行指标operation――运算optimal basis ――最优基optimal criterion ――最优准则optimal solution ――最优解optimal strategy――最优策略optimal value function――最优值函数optimistic coefficient method――乐观系数法optimistic estimate――最乐观时间optimistic method――乐观法optimum binary tree――最优二元树optimum service rate――最优服务率optional plan――可供选择的方案order method――顺序解法ordered forest――有序森林ordered tree――有序树outdegree――出度outweigh――胜过Ppacking problem ――装箱问题parallel job――平行作业partition problem――分解问题partition――划分path――路path――通路pay-off function――支付函数payoff matrix――支付矩阵payoff――支付pendant edge――悬挂边pendant vertex――悬挂点pessimistic estimate――最悲观时间pessimistic method――悲观法pivot number ――主元plan branch――方案分支plane graph――平面图plant location problem――工厂选址问题player――局中人Poisson distribution――泊松分布Poisson process――泊松流policy――策略polynomial algorithm――多项式算法positive deviational variables――正偏差变量posterior――后验分析potential method ――位势法preceding activity ――紧前工序prediction posterior analysis――预验分析prefix code――前级码price coefficient vector ――价格系数向量primal problem――原问题principal of duality ――对偶原理principle of optimality――最优性原理prior analysis――先验分析prisoner’s dilemma――囚徒困境probability branch――概率分支production scheduling problem――生产计划program evaluation and review technique――计划评审技术(PERT) proof――证明proper noninferior solution――真非劣解pseudo-random number――伪随机数pure integer programming ――纯整数规划pure strategy――纯策略Qqueue discipline――排队规则queue length――排队长queuing theory――排队论Rrandom number――随机数random strategy――随机策略reachability matrix――可达矩阵reachability――可达性regular graph――正则图regular point――正则点regular solution――正则解regular tree――正则树relation――关系replenish――补充resource vector ――资源向量revised simplex method――修正单纯型法risk type decision――风险型决策rooted tree――根树root――树根Ssaddle point――鞍点saturated arc ――饱和弧scheduling (sequencing) problem――排序问题screening method――舍取法sensitivity analysis ――灵敏度分析server――服务台set of admissible decisions(policies) ――允许决策集合set of admissible states――允许状态集合set theory――集合论set――集合shadow price ――影子价格shortest path problem――最短路线问题shortest path――最短路径simple circuit――简单回路simple graph――简单图simple path――简单通路Simplex method of goal programming――目标规划单纯形法Simplex method ――单纯形法Simplex tableau――单纯形表single slack time ――单时差situation――局势situation――局势slack variable ――松弛变量sojourn time――逗留时间spanning graph――支撑子图spanning tree――支撑树spanning tree――生成树stable set――稳定集stage indicator――阶段指标stage variable――阶段变量stage――阶段standard form――标准型state fork――状态结点state of system――系统状态state transition equation――状态转移方程state transition――状态转移state variable――状态变量state――状态static game――静态对策station equilibrium state――统计平衡状态stationary input――平稳输入steady state――稳态stochastic decision process――随机性决策过程stochastic inventory method――随机贮存模型stochastic simulation――随机模拟strategic equivalence――策略等价strategic variable, decision variable ――决策变量strategy (policy) ――策略strategy set――策略集strong duality property ――强对偶性strong ε-core――强ε-核心strongly connected component――强连通分支strongly connected graph――强连通图structure variable ――结构变量subgraph――子图sub-policy――子策略subset――子集subtree――子树surplus variable ――剩余变量surrogate worth trade-off method――代替价值交换法symmetry property ――对称性system reliability problem――系统可靠性问题Tteam length――队长tear cycle method――破圈法technique coefficient vector ――技术系数矩阵test number of cell ――空格检验数the branch-and-bound technique ――分支定界法the fixed-charge problem ――固定费用问题three estimate approach一―时估计法total slack time――总时差traffic intensity――服务强度transportation problem ――运输问题traveling salesman problem――旅行售货员问题tree――树trivial graph――平凡图two person finite zero-sum game二人有限零和对策two-person game――二人对策two-phase simplex method ――两阶段单纯形法Uunbalanced transportation problem ――产销不平衡运输问题unbounded ――无界undirected graph――无向图uniform distribution――均匀分布unilaterally connected component――单向连通分支unilaterally connected graph――单向连通图union of sets――并集utility function――效用函数Vvertex――顶点voting game――投票对策Wwaiting system――等待制waiting time――等待时间weak duality property ――弱对偶性weak noninferior set――弱非劣集weak noninferior solution――弱非劣解weakly connected component――弱连通分支weakly connected graph――弱连通图weighed graph ――赋权图weighted graph――带权图weighting method――加权法win expectation――收益期望值Zzero flow――零流zero-sum game――零和对策zero-sum two person infinite game――二人无限零和对策。

H3C交换机限速技巧全攻略

H3C交换机限速技巧全攻略H3C华为交换机限速有以下方法：line-rate(lr)speedtraffic-limitqos carH3C华为交换机端口限速二层较为准确（如：lr,speed),三层不准确（如：traffic-linit,qos car)lr :E050：(可信度100%)[Quidway-Ethernet0/1]line-rate ?INTEGER<1-100> Target rate(MbpsS5500：(可信度100%)[S5500-GigabitEthernet1/0/1]qos lr outbound cir ?INTEGER<64-1000000> Committed Information Rate(kbps), it must be a multiple of 64speed : (可信度100%)[S5500-GigabitEthernet1/0/1]speed ?10 Specify speed of current port 10Mb/s100 Specify speed of current port 100Mb/s1000 Specify speed of current port 1000Mb/sauto Enable port's speed negotiation automaticallytraffic-limit : (可信度50%,当设定50M时，带宽为7M左右；当设定10M时，带宽为1M左右)[Quidway E050-Ethernet0/1]traffic-limit inbound ip-group 2000 ?INTEGER<1-100> Target rate(Mbps)link-group Apply the link-based aclrule Specify the ID of acl ruleqos car :(s5500)(可信度50%,当设定9.6M时，带宽为5M左右) acl number 2000rule 0 permit source 10.0.0.0 0.0.0.255traffic classifier liukong operator andif-match acl 2000traffic behavior liukongcar cir 9600 cbs 200000 ebs 4000 green pass red discard yellow passqos policy liukongclassifier liukong behavior liukonginterface GigabitEthernet1/0/1qos apply policy liukong inbound补充说明：交换机端口限速2000_EI系列以上的交换机都可以限速!限速不同的交换机限速的方式不一样!2000_EI直接在端口视图下面输入LINE-RATE (4 )参数可选!端口限速配置1功能需求及组网说明端口限速配置『配置环境参数』1. PC1和PC2的IP地址分别为10.10.1.1/24、10.10.1.2/24『组网需求』1. 在SwitchA上配置端口限速，将PC1的下载速率限制在3Mbps，同时将PC1的上传速率限制在1Mbps2数据配置步骤『S2000EI系列交换机端口限速配置流程』使用以太网物理端口下面的line-rate命令，来对该端口的出、入报文进行流量限速。

华为网络资料关于8011 QoS介绍

QoS服务，网络在流量参数描述的范围内，预留资
源以承诺满足该请求

DiffServ模型：当网络出现拥塞时，根据业务的不同服务等级约定，有差别地进行流量ห้องสมุดไป่ตู้制和转发来解决拥塞问题
Best-Effort 模型
Best-Effort是单一的服务模型，也是最简单的服务
模型。
应用程序可任意发送任意报文，不需要事先得到批
准或通知网络
网络尽最大可能发送这些报文，但对时延，可靠性
等性能不提供任何保障
Best-Effort
service是目前Internet的缺省服务模型，
主要实现技术是先进先出队列(FIFO)
IntServ 模型

为应用提供可控制的、端到端的服务网络单元支持QoS的控制机制应用程序向网络申请特定的QoS服务
NE40&80支持的流分类规则
流分类方式
简单流分类
流分类规则
IP Precedence DSCP 1、入队列
动作
2、优先级映射（remark）
MPLS EXP
802.1P优先级复杂流分类 IP报文的五元组分片报文的类型源MAC地址 1、CAR 2、NAT 3、Remark
时间段Time-Control/Time- 4、重定向 Range 5、策略路由
8011即将发布版本：V3R2
V1R2和V3R2版本均支持DiffServ模型
概述

根据DiffServ模型，NE40&80在网络边缘路由器实施复杂流分类，在网络核心路由器实施简单流分类。

Diff-Serv边缘路由器复杂流分类流量监管
流量整形

10-congestion讲义2009

其他拥塞控制方式？TCP检测拥塞的方式The only way Tahoe, Reno and NewReno can detect congestion is by creating congestion! They carefully probe for congestion by slowly increasing their sending rate. When they find (create), congestion, they cut sending rate at least in half!网络资源管理（2）拥塞避免资源分配：公平排队TCP的典型行为This slow advance and rapid retreat approach results in a saw-toothed sending rate, and highly erratic throughput.其他拥塞控制方法What if TCP could detect congestion without causing congestion? ©2009秋季 ©2009秋季高等计算机网络北航计算机学院 2拥塞避免拥塞避免(congestion avoidance) 预测拥塞在何时发生，并在分组被丢弃之前降低主机的发送速率拥塞避免机制Random Early Detection (RED) Explicit Congestion Notification (ECN)两种方法 router-centric: RED Gatewaysimplicit and measure of congestion is loss probability or queueing delayhost-centric: TCP VegasTCP/AQM (active queue management)©2009秋季 ©2009秋季高等计算机网络北航计算机学院 4随机早期检测RED：动机20世纪90年代早期，Sally Floyd和Van Jacobson提出现象：突发流量消耗缓冲区，导致丢包 TCP通过慢启动降低负载弃尾排队规则导致突发丢包重复发送丢失的分组，导致负载和延迟的进一步增加全局同步问题 Global synchronization 大量TCP连接进入慢启动流量降低，网络利用率下降同时离开慢启动阶段之后，导致突发流量慢反馈问题缓冲区满作为反馈指示Feedback comes when buffer is completely full … even though the buffer has been filling for a whileRTT增加Plus, the filling buffer is increasing RTT … and the variance in the RTT改进：尽早反馈Get one or two connections to slow down, not all of them Get these connections to slow down before it is too late©2009秋季高等计算机网络北航计算机学院5©2009秋季高等计算机网络北航计算机学院61RED的基本方法解决方法：监测队列长度Router notices that the queue is getting backlogged … and randomly drops packets to signal congestion随机早期检测RED 设计目标拥塞避免，并且保持：Low delay High throughput确定何时丢弃分组（丢包概率）Drop probability increases as queue length increases If buffer is below some level, don’t drop anything … otherwise, set drop probability as function of queue避免全局同步（Global synchronization）Current systems inform connections to back off implicitly by dropping packets实现：和主机控制算法相结合（Reno）Probability避免偏向突发流量（ bursty traffic）Discard arriving packets will do this限制平均队列长度Hence control on average delayAverage Queue Length7 8©2009秋季高等计算机网络北航计算机学院©2009秋季高等计算机网络北航计算机学院RED: 参数基本方法Probabilistically drop Discard Probability packets Probabilistically mark packetsMarking requires ECN bit (RFC 2481)1RED: 分组丢弃计算平均队列长度 avg_len avg_len =（1-Weight）× avg_len + Weight×SampleLen If (avg_len < min_th) If (avg_len > max_th) 分组入队列分组丢弃按概率P 丢弃参数min_th – minimum threshold max_th – maximum threshold avg_len – average queue length avg_len = (1-w)*avg_len + w*sample_len ©2009秋季高等计算机网络If (avg_len >= min_th and avg_len < max_th) 到达的分组Discard Probability (P) min_th max_th queue_len Average Queue Length 100 min_th max_th queue_len Average Queue Length北航计算机学院 9©2009秋季高等计算机网络北航计算机学院10RED: 分组丢弃（续）P = max_P×(avg_len – min_th)/(max_th – min_th) Improvements to spread the drops P’ = P/(1 – count*P), 其中 • Count：自最后一次丢包后，连续排入队列的分组数量说明：P’随count值的增加而缓慢增加，避免在单个连接上的多重丢包RED的特性Drops packets before queue is fullIn the hope of reducing the rates of some flowsDrops packet in proportion to each flow’s rateHigh-rate flows have more packets … and, hence, a higher chance of being selectedDiscard ProbabilityDrops are spaced out in timeWhich should help desynchronize the TCP sendersmax_P 1 P 0 min_th max_th queue_len Average Queue Length avg_len北航计算机学院 11Tolerant of burstiness in the trafficBy basing the decisions on average queue length©2009秋季高等计算机网络©2009秋季高等计算机网络北航计算机学院122RED的问题RED的参数敏感性How early to start dropping packets? What slope for the increase in drop probability? What time scale for averaging the queue length?主动队列管理AQM一类通用策略：Active Queue ManagementRED可能有副作用RED uses avg. queue length, may introduce large feedback delay, lead to instability根据平均队列长度丢弃或标记分组优点:signal end systems earlier absorb burst better avoids synchronization0 min_th max_th queue_lenAverage Queue Length 14Discard ProbabilityRED实现机制But, often not used due to the challenges of tuning right1相关研究©2009秋季高等计算机网络北航计算机学院 13©2009秋季高等计算机网络北航计算机学院其他 AQM 机制Adaptive RED (ARED) BLUE Virtual Queue Random Early Discard (REM) Proportional Integral Controller Adaptive Virtual QueueImproved AQMs are designed based on control theory to provide better faster response to congestion and more stable systemsExplicit Congestion Notification (ECN)显式拥塞通知ECN (RFC 2481):Routers mark packets instead of dropping them Receiver returns marks to sender in ACK packets Sender adjusts its window accordingly利用IP头部的两位:ECT: ECN-capable transport (set to 1)：源端能够处理拥塞通知 CE: congestion experienced (set to 1)：拥塞指示©2009秋季高等计算机网络北航计算机学院15©2009秋季高等计算机网络北航计算机学院16Explicit Congestion Notification (ECN)早期丢包Good: gives early feedback Bad: has to drop the packet to give the feedback基于源的拥塞避免机制TCP Variation: TCP Vegas1994年，Brakmo 和 Peterson提出相对于TCP Reno的三个变化修改拥塞避免机制不等待计时器超时，如果实际吞吐量小于期望吞吐量，减小拥塞窗口 (AIAD)拥塞通知Router marks the packet with an ECN bit … and sending host interprets as a sign of congestion新的重传机制动机：如果发送方无法收到三个重复的ACK(due to lost segments or window size is too small.)，如何处理？方法：收到一个重复ACK后，发送方进行重传，如果有： RTT estimate > timeout.挑战Must be supported by the end hosts and the routers borrow two of the Type-Of-Service bits in the IPv4 packet header修改慢启动动机：发送方在不引起丢包的情况下发现正确的窗口大小17 高等计算机网络北航计算机学院 18©2009秋季高等计算机网络北航计算机学院©2009秋季3TCP Vegas方法将测量到的吞吐量变化率和理想的吞吐量变化率向比较测量和控制连接正在发送的“额外”数据量超出了可用带宽的数据量windowTCP Vegas拥塞发生的指示：RTT增长平滑发送速率SSCAtimeConverges, no retransmission … provided buffer is large enough©2009秋季高等计算机网络北航计算机学院19©2009秋季高等计算机网络北航计算机学院20动机70 60 50 40 30 20 10 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 Time (seconds) 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 KB算法计算RTT最小值let BaseRTT be the minimum of all measured RTTs (commonly the RTT of the first packet)Congestion Window 观测到的吞吐量1100 900 700 500 300 100 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 Time (seconds) 5.0 5.5 6.0 6.57.0 7.5 8.0 8.5Average send rate at source计算期望吞吐量（ExpectedRate） ExpectedRate = CongestionWindow / BaseRTT 源端计算每个RTT的当前发送速率（ActualRate）比较 ActualRate和 ExpectedRate,并调整拥塞窗口大小 Diff = ExpectedRate – ActualRate （Diff≥0） (两个阈值，α < β) if Diff < α （差距小，可能没有充分利用带宽，增加窗口）increase CongestionWindow linearlyQueue size in routerSending KBps10else if Diff >β （差距大，拥塞可能性增加，减小窗口）decrease CongestionWindow linearly5elseleave CongestionWindow unchanged0.5 1.0 1.5 2.0 2.5 3.0©2009秋季高等计算机网络Average 北航计算机学院 in router Q length3.5 4.0 4.5 Time (seconds)5.05.5 6.0 6.57.0 7.5 8.0 8.521©2009秋季高等计算机网络北航计算机学院22TCP Vegas例子70 60 50 40 30 20 10Vegas 总结当前吞吐量和期望吞吐量比较If current difference is smaller, increase window size linearly If current difference is larger, decrease window size linearly拥塞窗口0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.0Time (seconds)慢启动（Slow Start）机制的改变doubling the window every other RTT, rather than every RTT and of using a boundary in the difference between throughputs to exit the Slow Start phase, rather than a window size value.阴影为α和β之间的区域240 200 160 120 80 40 0.5 1.0 1.5 2.0 2.5Expected throughput3.0Actual Throughput©2009秋季3.5 4.0 4.5 5.0 Time (seconds)北航计算机学院5.56.06.57.07.58.0高等计算机网络23©2009秋季高等计算机网络北航计算机学院244关于TCP的思考Assumes that all sources cooperate Assumes that congestion occurs on time scales greater than 1 RTT Only useful for reliable, in order delivery, non-real time applications Vulnerable to non-congestion related loss (e.g. wireless) Can be unfair to long RTT flows资源分配：公平排队©2009秋季高等计算机网络北航计算机学院25©2009秋季回顾：资源分配的几种类型三种分类方法Router-Centric vs. Host-centric Reservation-Based vs. Feedback-Based Window-Based vs. Rate-based资源分配机制的评价标准有效性（effectively）吞吐量throughput and 时延delay 问题: 增加吞吐量，避免链路空闲，就会增加路由器队列的长度，导致分组的延迟增加。

Nokia 7250 IXR-10 IXR-6 IXR-s 集成路由器说明书

Interconnect routers complement IP edge and core router platforms to deliver enhanced, cost-effective IP network architectures. The 7250 IXR delivers a comprehensive set of IP/MPLS, synchronization and quality of service (QoS) capabilities. Flexible traffic management includes big buffering, per-port queuing, shaping and policing.High-density aggregationThe 7250 IXR is optimized for high-density aggregation, supporting up to 57.6 Tb/s(7250 IXR-10), 28.8 Tb/s (7250 IXR-6) or 1.6 Tb/s (7250 IXR-s) of system capacity, and is equipped with high-performance 100GE (Gigabit Ethernet), 50GE 2, 40GE, 25GE, 10GE and GE interfaces to scale networks to meet evolving traffic demands.Differentiated service supportPer-service, hierarchical queuing features support differentiated QoS, which is ideal for any-Gaggregation and fixed-mobile network convergence. These features also help industrial enterprises attain IT/OT (informational technology/operational technology) convergence by simultaneously carrying both their business and operational traffic.Nokia 7250 IXR-10/IXR-6/IXR-s Interconnect RoutersRelease 20The Nokia 7250 Interconnect Router (IXR) family addresses evolving demands driven by the cloud, 5G and the Internet of Things. The IXR-10, IXR-6 and IXR-s1 routers enable high-scale interconnectivity in data centers and across WANs and aggregation networks in service provider, enterprise and webscale environments.7250 IXR-107250 IXR-s7250 IXR-61 The 7250 IXR-10, IXR-6 and IXR-s are part of the 7250 IXR product family. Additional data sheets are available for other models in this product family.The 7250 IXR10, IXR-6 and IXR-s are referred to collectively as the 7250 IXR throughout this data sheet.2 50GE is a future software deliverable.High availabilityThe 7250 IXR sets the benchmark for high availability. The 7250 IXR-10 and IXR-6 systems support a full suite of 1+1 control, 5+1 fabric,and redundant fan and power configurations.In addition to full hardware redundancy, the robust Nokia Service Router Operating System (SR OS) supports numerous features to maximize network stability, ensuring that IP/MPLS protocols and services run without interruption. These features include innovative nonstop routing, nonstop services and stateful failover. AutomationThe 7250 IXR uses the Nokia SR OS and is managed by the Nokia Network Services Platform (NSP). The Nokia NSP offers a rich set of service management features that automate new service delivery and reduce operating cost.Standards-based software-defined networking (SDN) interfaces enable best-path computation to be offloaded to path computation elements (PCEs) such as the Nokia NSP. The 7250 IXR operates as a path computation client (PCC), collecting and reporting per-link and per-service delay, jitter and loss metrics as well as port utilization levels, for efficient path computation. Software featuresThe 7250 IXR supports, but is not limited to,the following features.Services• Point-to-point Ethernet pseudowires/virtual leased line (VLL)• Ethernet Virtual Private Network (EVPN)–Virtual Private Wire Service (EVPN-VPWS)–Virtual Private LAN Services (EVPN-VPLS):IPv4 and IPv6 support, including VirtualRouter Redundancy Protocol (VRRP)–Multihoming with single active or active/active • Multipoint Ethernet VPN services with VPLS based on Targeted Label Distribution Protocol (T-LDP) and Border Gateway Protocol (BGP)• Routed VPLS with Internet Enhanced Service (IES) or IP-VPN, IPv4 and IPv6• Ingress and egress VLAN manipulation for Layer 2 services• IP VPN (VPRN), Inter-Autonomous System (Inter-AS) Option A, B and C• IPv6 VPN Provider Edge (6VPE)Network protocols• Segment routing–Intermediate System-to-Intermediate System(SR-ISIS) and Open Shortest Path First(SR-OSPF)–Traffic engineering (SR-TE)• MPLS label edge router (LER) and label switching router (LSR) functions–Label Distribution Protocol (LDP)–Resource Reservation Protocol with trafficengineering (RSVP-TE)• BGP - Labeled Unicast (BGP-LU) (IETF RFC 3107) route tunnels• IP routing–Dual-stack Interior Gateway Protocol (IGP)–Multi-topology, multi-instance IntermediateSystem to Intermediate System (IS-IS)–Multi-instance OSPF–Multiprotocol BGP (MP-BGP)–BGP-LU support in edge, area border router(ABR) and autonomous system boundaryrouter (ASBR) roles–Usage-triggered download of BGP labelroutes to Label - Forwarding Information Base(L-FIB)–Accumulated IGP (AIGP) metric for BGP–BGP route-reflector for EVPN and IP-VPNwith VPNv4 and VPNv6 address families (AFs) • Layer 3 Multicast – base routing–Internet Group Management Protocol (IGMP)–Protocol Independent Multicast – Sparse Mode(PIM-SM), Source Specific Multicast (SSM)–Multicast Listener Discovery (MLD)• Layer 3 Multicast - VPRN (7250-IXR-s)–Next-generation multicast VPNs (NG-MVPN)–SSM with multicast LSPv4 (mLDPv4)–IGMP/MLD–IGMP/MLD on Routed VPLS Interface• Layer 2 Multicast–IGMP/MLD snoopingSDN• SR-TE LSPs, RSVP-TE LSPs–PCC initialized, PCC controlled–PCC initialized, PCE computed (7250 IXR-s)–PCC initialized, PCE controlled (7250 IXR-s)• SR-TE LSPs: PCE initialized, PCE controlled(7250 IXR-s)• Topology discovery: BGP-Link State (BGP LS) IPv4 and IPv6• Telemetry: streaming interface, service delay and jitter statisticsLoad balancing and resiliency• Nonstop routing (IXR-10 and IXR-6)• Segment routing topology independent and remote loop-free alternate (TI-LFA and rLFA)• LDP LFA• IEEE 802.3.ad Link Aggregation Group (LAG) and multi-chassis (MC) LAG• Pseudowire and LSP redundancy• IP and MPLS load balancing by equal-cost multipath (ECMP)• VRRP• Configurable polynomial and hash seed shift • Entropy label (IETF RFC 6790)• RSVP-TE Fast Reroute (FRR)• BGP Edge and Core Prefix Independent Convergence (BGP PIC)Platform• Ethernet IEEE 802.1Q (VLAN) and 802.1ad (QinQ) with 9k jumbo frames• Detailed forwarded and discarded countersfor service access points (SAPs) and network interfaces in addition to port-based statistics: per Virtual Output Queue (VoQ) packet and byte counters (7250 IXR-s)• Dynamic Host Configuration Protocol (DHCP) server for IPv4 IES, VPNv4• DHCP relay, IPv4 and IPv6, IES, IP-VPN,EVPN-VPLS• Accounting recordsQoS and traffic management• Hierarchical QoS (7250 IXR-s)–Hierarchical egress schedulers and shapersper forwarding class, SAP, network interfaceor port–Port sub-rate• Intelligent packet classification, including MAC, IPv4, IPv6 match-criteria-based classification • Granular rate enforcement with up to 32 policers per SAP/VLAN, including broadcast, unicast, multicast and unknown policers• Hierarchical policing for aggregate rate enforcement• Strict priority, weighted fair queuing schedulers • Congestion management via weighted random early discard (WRED)• Egress marking or re-markingSystem management• Network Management Protocol (SNMP)• Model-driven (MD) management interfaces–Netconf–MD CLI–Remote Procedure Call (gRPC)• Comprehensive support through Nokia NSPOperations, administration and maintenance • IEEE 802.1ag, ITU-T Y.1731: Ethernet Connectivity Fault Management for both fault detection and performance monitoring, including delay, jitter and loss tests• Ethernet bandwidth notification with egress rate adjustment• IEEE 802.3ah: Ethernet in the First Mile• Bidirectional Forwarding Detection IPv4 and IPv6• Two-Way Active Measurement Protocol (TWAMP), TWAMP Light• A full suite of MPLS OAM tools, including LSP and virtual circuit connectivity verification ping • Service assurance agent• Mirroring with slicing support:–Port–VLAN–Filter output: Media Access Control (MAC),IPv4/IPv6 filters–Local/remote• Port loopback with MAC swap• Configuration rollback• Zero Touch Provisioning (ZTP) capable (7250 IXR-s) Security• Remote Authentication Dial-In User Service (RADIUS), Terminal Access ControllerAccess Control System Plus (TACACS+), and comprehensive control-plane protection capabilities• MAC-, IPv4- and IPv6-based access control lists and criteria-based classifiers• Secure Shell (SSH)Hardware overview7250 IXR-10 and IXR-6 platformsThe 7250 IXR-10 and IXR-6 share common integrated media module (IMM) cards, control processor modules (CPMs) and power supplyunits (PSUs).Each chassis uses an orthogonal direct cross-connect architecture, with IMMs connecting in front and switch fabrics and fans connecting at the rear. The lack of a backplane, midplane or midplane connector system provides a compact chassis design, optimal cooling and easy capacity upgrades. The 7250 IXR supports a 5+1 switch fabric design for full fabric redundancy with graceful degradation. Fans and switch fabrics are separate, ensuring a complete separation of cooling from the dataplane and enabling non-service-impacting fan replacement options. The system uses a complete Faraday Cage design to ensure EMI containment, a critical requirement for platform evolution that will support next-generation application-specific integrated circuits (ASICs).7250 IXR-10 and IXR-6 control plane Control-plane performance is a key requirementin networking. Multicore CPUs with support for symmetric multiprocessing (SMP) provide leading capabilities in task distribution and concurrent processing, leveraging the hardened capabilitiesof the SR OS. This is a capability common to all platforms in the 7250 IXR product series.The 7250 IXR-10/IXR-6 supports dual-redundant CPMs for hot-standby control-plane redundancy and supports a fully distributed control infrastructure with dedicated CPUs per line card. Compared to single monolithic control plane systems, this distributed architecture provides optimized control plane processing without any detrimental impacts to the central CPM during system maintenance, IMM commissioning and heavy data loads. The distributed architecture also improves system security.Power suppliesThe 7250 IXR-10/IXR-6 platforms support 12and 6 PSUs respectively, allowing for full N+M(N is active and M is the number of protecting power supplies) power supply redundancy and full power feed redundancy. In contrast to systems with fewer power supplies, the 7250 IXR provides added headroom for power growth for system enhancements with next-generation ASICs.On the IXR-10/IXR-6, two PSU variants are available: a low-voltage DC PSU (LVDC) and a combined high-voltage DC (HVDC) and AC PSU. The PSUs are fully interchangeable between the chassis variants. The HVDC PSU option enables OPEX and CAPEX savings as a result of the power-supply and infrastructure design.The 7250 IXR-s supports two PSUs with 1+1 redundancy with support for either AC or LVDC power options.Technical specificationsTable 1. 7250 IXR6-10/IXR-6/IXR-s specificationsSystem configuration Dual hot-standby CPMs Dual hot-standby CPMs Single integrated CPM System throughput:Half duplex (HD) IMIXtraffic57.6 Tb/s28.8 Tb/s 1.6 Tb/sSwitch fabric capacity per module: Full duplex (FD) • 5.76 Tb/s• Single-stage fabric with gracefuldegradation• Separate fan tray from switch fabric• 2.88 Tb/s• Single-stage fabric with gracefuldegradation• Separate fan tray from switch fabricIntegratedCard slot throughput:FD per slot3.6 Tb/s 3.6 Tb/s n/aCard slots84n/aService interfaces n/a n/a• 6 x QSFP28/QSFP+100/40GE• 48 x SFP+/SFP 10/1GEControl interfaces Console, management, Synchronous Ethernet (SyncE)/1588, OES, BITS,Bluetooth, USB*, 1PPS, SD slot Console, management, USB, SD slotTiming and synchronization • Built-in Stratum 3E clock• ITU-T Synchronous Ethernet (SyncE)• IEEE 1588v2–Boundary clock (BC), slave clock (SC)–Profiles: IEEE 1588v2 default, ITU-T G.8275.1• Nokia Bell Labs IEEE 1588v2 algorithm• IETF RFC 5905 Network Time Protocol (NTP)• Building Integrated Timing Supply (BITS) ports (T1, E1, 2M) and pulse-persecond (1PPS) timing• Built-in Stratum 3E clock• ITU-T SyncE• ITU-T G.8262.1 eEEC• IEEE 1588v2–BC–Profile: ITU-T G.8275.1• ITU-T G.8273.2 Class B, C**• IETF RFC 5905 NTP• Support for GNSS SFPMemory buffer size Per card (see T able 2)Per card (see T able 2)8 GBRedundant hardware• Dual redundant CPMs• Switch fabric redundancy (5+1)• Power redundancy (M+N)• Fan redundancy (N+1)• Power redundancy (1+1)• Fan redundancy (5+1)Dimensions• Height: 57.78 cm (22.75 in);13 RU• Width: 44.45 cm (17.5 in)• Depth: 81.28 cm (32.0 in)Fits in standard 19-in rack • Height: 31.15 cm (12.25 in);7 RU• Width: 44.45 cm (17.5 in)• Depth: 81.28 cm (32.0 in)Fits in standard 19-in rack• Height: 4.35 cm (1.75 in);1 RU• Width: 43.84 cm (17.26 in)• Depth: 51.5 cm (20.28 in)Fits in standard 19-in rack* Future software deliverable** Class C for noise generation. Future support for RS-FEC.Power• 12 PSUs with N+M redundancy• LVDC (single feed): -40 V DC to-72 V DC• HVDC: 240 V to 400 V• AC: 200 V AC to 240 V AC,50 Hz/60 Hz• Front-bottom mounted • 6 PSUs with N+M redundancy• LVDC (single feed): -40 V DC to-72 V DC• HVDC: 240 V to 400 V• AC: 200 V AC to 240 V AC,50 Hz/60 Hz• Front-bottom mounted• 2 PSUs with 1+1redundancy• LVDC (single feed):-40 V DC/-72 V• AC: 200 V AC to 240 V AC,50 Hz/60 Hz• Rear mountedCooling• 3 trays of 3 ultra-quiet fans• Fan trays separate from switchfabric• Safety electronic breaks on removal• Front-to-back airflow• Fan filter door kit (optional)• 3 trays of 2 ultra-quiet fans• Fan trays separate from switchfabric• Safety electronic breaks on removal• Front-to-back airflow• Fan filter door kit (optional)• 6 trays of 1 ultra-quietfan each• Fan trays separate fromswitch fabric• Safety electronic breakson removal• Front-to-back airflowNormal operatingtemperature range0°C to +40°C (32°F to +104°F) sustainedShipping and storagetemperature-40°C to 70°C (-40°F to 158°F) Normal humidity5% to 95%, non-condensing Note: Throughout this table, n/a = not applicable.Optical breakout solutions available on QSFP28/QSFP+ ports:• 7210 IXR-10, IXR-6: 4 x 10GE and 4 x 25GE• 7210 IXR-s: 4 x 10GETable 2. Nokia 7250 IXR-10 and IXR-6 IMM cards36-port 100GE• 36 x 100GE QSFP28/QSFP+ 100/40GE• MACsec on all ports*• 48 GB packet buffer2-port 100GE + 48-port 10GE • 2 x 100GE QSFP28/QSFP+ 100/40GE • 48 x SFP+/SFP 10/1GE• MACsec on all ports*• 8 GB packet bufferTable 3. Platform density7250 IXR-s• 288 x 100/40GE• 384 x 10/1 GE + 16 x 100/40GE • 144 x 100/40GE• 192 x 10/1GE + 8 x 100/40GE• 6 x 100/40GE•48 x 10/1GE* Future software deliverableStandards compliance3Environmental• ATIS-0600015.03• ATT-TP-76200• ETSI EN 300 019-2-1; Storage Tests, (Class 1.2)• ETSI EN 300 019-2-2; Transportation Tests,(Class 2.3)• ETSI EN 300 019-2-3; Operational Tests, (Class 3.2)• ETSI EN 300 753 Acoustic Noise (Class 3.2)• GR-63-CORE• GR-295-CORE• GR-3160-CORE• VZ.TPR.9205• VZ.TPR.9203 (CO)Safety• AS/NZS 60950.1• CSA/UL 62368-1 NRTL• EN 62368-1 CE Mark• IEC 60529 IP20• IEC/EN 60825-1• IEC/EN 60825-2• IEC 62368-1 CB Scheme Electromagnetic compatibility• AS/NZS CISPR 32 (Class A)• ATIS-600315.01.2015• BSMI CNS13438 Class A• BT GS-7• EN 300 386• EN 55024• EN 55032 (Class A)• ES 201 468• ETSI EN 300 132-3-1• ETSI EN 300 132-2 (LVDC)• ETSI EN 300 132-3 (AC)• FCC Part 15 (Class A)• GR-1089-CORE• ICES-003 (Class A)• IEC 61000-3-2• IEC 61000-3-3• IEC CISPR 24• IEC CISPR 32 (Class A)• IEC 61000-6-2• IEC 61000-6-4• IEC/EN 61000-4-2 ESD• IEC/EN 61000-4-3 Radiated Immunity• IEC/EN 61000-4-4 EFT• IEC/EN 61000-4-5 Surge• IEC/EN 61000-4-6 Conducted Immunity • IEC/EN 61000-4-11 Voltage Interruptions • ITU-T L.1200• KCC Korea-Emissions & Immunity(in accordance with KN32/35)• VCCI (Class A)Directives, regional approvals and certifications • DIRECTIVE 2011/65/EU RoHS• DIRECTIVE 2012/19/EU WEEE• DIRECTIVE 2014/30/EU EMC• DIRECTIVE 2014/35/EU LVD• MEF CE 3.0 compliant• NEBS Level 3–Australia: RCM Mark–China RoHS: CRoHS–Europe: CE Mark–Japan: VCCI Mark–South Korea: KC Mark–Taiwan: BSMI Mark3 System design intent is according to the listed standards. Refer to product documentation for detailed compliance status.7Data sheetAbout NokiaWe create the technology to connect the world. Powered by the research and innovation of Nokia Bell Labs, we serve communications service providers, governments, large enterprises and consumers, with the industry’s most complete, end-to-end portfolio of products, services and licensing.From the enabling infrastructure for 5G and the Internet of Things, to emerging applications in digital health, we are shaping the future of technology to transformthe human experience. Nokia operates a policy of ongoing development and has made all reasonable efforts to ensure that the content of this document is adequate and free of material errors and omissions. Nokia assumes no responsibility for any inaccuracies in this document and reserves the right to change, modify, transfer, or otherwise revise this publication without notice.Nokia is a registered trademark of Nokia Corporation. Other product and company names mentioned herein may be trademarks or trade names of their respective owners. © 2020 NokiaNokia OyjKaraportti 3FI-02610 Espoo, Finland。

计算机英语词汇

计算机英语词汇:计算机编程英语词汇(2)疯狂代码 / ĵ:http://DeveloperUtil/Article41908.html icon 图标IDE (Integrated Development Environment)集成开发环境IDL (Interface Definition Language) 接口定义语言identier 标识符idle time 空闲时间and only 当且仅当IL (Intermediate Language) 中间语言、中介语言image 图象IME 输入法immediate base 直接基类immediate derived 直接派生类immediate updating 即时更新 (for database)implicit transaction隐式事务 (for database)incremental update 增量更新 (for database)index 索引 (for database)implement 实现implementation 实现、实现品implicit 隐式import 导入increment operator 增加操作符infinite loop 无限循环infinite recursive 无限递归information 信息infrastructure 基础设施inheritance 继承、继承机制inline 内联inline expansion 内联展开initialization 化initialization list 化列表、值列表initialize 化inner join 内联接 (for database)in-place active 现场激活instance 例子instantiated 具现化、实体化(常应用于template)instantiation 具现体、具现化实体(常应用于template)egrate 集成、整合egrity 完整性、致性egrity constra完整性约束 (for database)erprocess communication (IPC)进程间通讯(IPC) eracts 交互erface 接口for GUI 界面eroperability 互操作性、互操作能力erpreter 解释器rospection 自省invariants 不变性invokeisolation level 隔离级别 (for database)iterate 迭代iterative 反复、迭代iterator 迭代器iteration 迭代(回圈每次轮回称为个iteration) item 项、条款、项目JIT compilation JIT编译即时编译key 键 (for database)key column 键列 (for database)laser 激光late binding 迟绑定left outer join 左向外联接 (for database)level 阶、层例high level 高阶、高层library 库letime 生命期、寿命link 连接、链接linkage 连接、链接linker 连接器、链接器literal constant 字面常数list 列表、表、链表list box 列表框livelock 活锁 (for database)load 装载、加载load balancing 负载平衡loader 装载器、载入器local 局部local object 局部对象lock 锁log 日志login 登录login security mode登录安全模式 (for database)lookup table 查找表 (for database)loop 循环loose coupling 松散耦合lvalue 左值machine code 机器码、机器代码macro 宏tain 维护managed code 受控代码、托管代码Managed Extensions 受控扩充件、托管扩展managed object 受控对象、托管对象mangled namemanest 清单manipulator 操纵器(iostream预先定义种东西)many-to-many relationship 多对多关系 (for database)many-to-one relationship 多对关系 (for database)marshal 列集member 成员member access operator 成员取用运算子(有dot和arrow两种) member function 成员member initialization list成员值列表memberwise 以member为单元…、members 逐…memberwise copymemory 内存memory leak 内存泄漏menu 菜单message 消息message based 基于消息message loop 消息环message queuing消息队列metadata 元数据metaprogramming元编程method 思路方法micro 微middleware 中间件middle tier 中间层modeling 建模modeling language 建模语言modier 修饰字、修饰符modem 调制解调器module 模块most derived 最底层派生类mouse 鼠标mutable 可变mutex 互斥元、互斥体multidimensional OLAP (MOLAP) 多维OLAP(MOLAP) (for database) multithreaded server application 多线程服务器应用multiuser 多用户multi-tasking 多任务multi-thread 多线程multicast delegate 组播委托、多点委托named parameter 命名参数named pipe 命名管道名字空间、命名空间native 原生、本地native code 本地码、本机码Native Image Generator (NGEN)本地映像生成器nested 嵌套类nested query 嵌套查询 (for database)nested table 嵌套表 (for database)network 网络network card 网卡nondependent nameobject 对象object based 基于对象object file 目标文件object model 对象模型object oriented 面向对象object pooling 对象池化ODBC data source ODBC数据源 (for database)ODBC driver ODBC驱动 (for database)ODR (one-definition rule)OLE Automation objects OLE自动化对象 (for database)OLE Automation server OLE自动化服务器 (for database)OLE DB consumer OLE DB使用者 (for database)OLE DB for OLAP 用于OLAPOLE DB (for database)OLE DB provider OLE DB提供者 (for database)one-to-many relationship 对多关系 (for database)one-to-one relationship 对关系 (for database)online analytical processing (OLAP) 联机分析处理(OLAP) (for database)online redo log 联机重做日志 (for database)online transaction processing (OLTP) 联机事务处理(OLTP) (for database)Open Data Services (ODS) 开放式数据服务(ODS) (for database)Open Database Connectivity (ODBC) 开放式数据库连接(ODBC) (for database) operand 操作数operating system (OS) 操作系统operation 操作operator 操作符、运算符option 选项optimizer 优化器outer join 外联接 (for database)overflow 上限溢位(相对于underflow)overhead 额外开销overload 重载overload resolution 重载决议overloaded function 重载overloaded operator 被重载操作符override 覆写、重载、重新定义package 包packaging 打包palette 调色板parallel 并行parameter 参数、形式参数、形参parameter list 参数列表parameterize 参数化parent 父类parentheses 圆括弧、圆括号parse 解析parser 解析器part 零件、部件partial specialization 局部特化pass by address 传址(函式引数传递方式)(非正式用语) pass by reference 传地址、按引用传递pass by value 按值传递pattern 模式PDA (personal digital assistant)个人数字助理PE (Portable Executable) file 可移植可执行文件performance 性能persistence 持久性PInvoke (platform invoke service) 平台服务pixel 像素placement deleteplacementplaceholder 占位符platform 平台POD (plain old data (type))POI (po of instantiation)poer 指针poll 轮询pooling 池化polymorphism 多态pop up 弹出式port 端口postfix 后缀precedence 优先序(通常用于运算子优先执行次序)prefix 前缀preprocessor 预处理器primary key (PK)主键(PK) (for database)primary table 主表 (for database)primary template原始模板primitive type 原始类型pr 打印prer 打印机procedure 过程procedural 过程式、过程化process 进程profile 评测profiler 效能(性能)评测器programprogrammer 员programming编程、设计progress bar 进度指示器project 项目、工程property 属性protocol 协议pseudo code伪码qualied 经过资格修饰(例如加上scope运算子) qualied namequalier 修饰符quality 质量queue 队列race condition 竞争条件(多线程环境常用语)radian 弧度radio button 单选按钮raise 引发(常用来表示发出个exception) random number 随机数range 范围、区间rank 等级raw 未经处理readOnly只读record 记录 (for database)record 记录集 (for databaserecursive 递归re-direction 重定向refactoring 重构refer 引用、参考reference 引用、参考reference counting引用计数referential egrity (RI)引用完整性(RI) (for database) register 寄存器reflection 反射refresh data 刷新数据 (for database)regular expression 正则表达式relational database 关系数据库remote 远程remote request 远程请求represent 表述表现resolve 解析、决议resolution 解析过程result 结果集 (for database)retrieve data 检索数据返回type 返回类型value 返回值right outer join 右向外联接 (for database)revoke 撤销robust 健壮robustness 健壮性roll back 回滚 (for database)roll forward 前滚 (for database)routine 例程row 行 (for database)row lock 行锁 (for database)row 行集 (for database)RPC (remote procedure call)RPC(远程过程)runtime 执行期、运行期、执行时、运行时rvalue 右值save 保存savepo 保存点 (for database)SAX (Simple API for XML)scalable 可伸缩、可扩展schedule 调度scheduler 调度schema 模式、纲目结构scroll bar滚动条scope 作用域、生存空间scope operator 生存空间操作符scope resolution operator 生存空间解析操作符screen 屏幕SDK (Software Development Kit)软件Software开发包sealed 密封类search 查找semantics 语义semaphore 信号量sequential container序列式容器server 服务器、服务端serial 串行serialization/serialize 序列化server cursor服务端游标、服务器游标 (for database)session 会话 (for database)ter 设值shared lock 共享锁 (for database)sibling 同级side effect 副作用signature 签名single-threaded 单线程slider滑块slot 槽smart poer 智能指针SMTP (Simple Mail Transfer Protocol) 简单邮件传输协议 snapshot 截屏图snapshot 快照 (for database)specialization 特化specication 规范标准、规格splitter 切分窗口SOAP (simple object access protocol) 简单对象访问协议software 软件Softwaresource code 源码、源代码SQL (Structured Query Language) 结构化查询语言 (for database) stack 栈、堆栈stack unwinding 叠辗转开解(此词用于exception主题)standard library 标准库standard template library 标准模板库stateless 无状态statement 语句、声明cursor 静态游标 (for database)SQL statements 静态SQL语句 (for database)stored procedure 存储过程 (for database)status bar 状态条stream 流串stub 存根subobject子对象subquery 子查询 (for database)subroutine 子例程subscript operator 下标操作符sub 子集subtype 子类型support 支持suspend 挂起symbol 记号syntax 语法system databases 系统数据库 (for database)system tables 系统表 (for database)table 表 (for database)table lock 表锁 (for database)table-level constra 表级约束 (for database)tape backup 磁带备份 (for database)target 标,目标task switch 工作切换TCP (Transport Control Protocol) 传输控制协议template 模板template-idtemplate argument deduction 模板参数推导template explicit specialization 模板显式特化template parameter 模板参数template template parametertemporary object 临时对象temporary table 临时表 (for database)text 文本text file 文本文件thin client 瘦客户端third-party 第 3方thread 线程thread-safe 线程安全throw 抛出、引发(常指发出个exception)token 符号、标记、令牌(看场合)trace 跟踪transaction 事务 (for database)transaction log 事务日志 (for database)transaction rollback 事务回滚 (for database)transactional replication 事务复制 (for database)translation unit 翻译单元traverse 遍历trigger 触发器 (for database)two-phase commit 两阶段提交 (for database)tupletwo-phase lookup 两阶段查找type 类型UDDI(Universary Description, Discovery and Integration)统描述、查询和集成 UML (unied modeling language)统建模语言unary function 单参unary operator 元操作符unboxing 拆箱、拆箱转换underflow 下限溢位(相对于overflow)Union query 联合查询 (for database)UNIQUE constras UNIQUE约束 (for database)unique index 唯索引 (for database)unmanaged code 非受控代码、非托管代码unmarshal 散集unqualied 未经限定、未经修饰URI (Unorm Resource identier) 统资源标识符 URL (Unorm Resource Locator) 统资源定位器 user 用户user erface 用户界面value types 值类型variable 变量vector 向量(种容器有点类似.gif' />) viable 可行video 视频view 视图VEE (Virtual Execution Engine)虚拟执行引擎vendor 厂商view 视图 (for database)virtual function 虚virtual machine 虚拟机virtual memory 虚拟内存vowel 元音字母Web Services web服务WHERE clause WHERE子句 (for database)wildcard characters 通配符 (for database)wildcard search 通配符搜索 (for database) window 窗口window function 窗口window procedure 窗口过程Windows authentication Windows身份验证wizard 向导word 单词word processor 字处理器wrapper 包装、包装器write enable 写启用 (for database)write-ahead log 预写日志 (for database)write-only 只写WSDL (Web Service Description Language)Web Service描述语言XML Message Interface (XMI) XML消息接口XML (eXtensible Markup Language) 可扩展标记语言XSD (XML Schema Definition) XML模式定义语言XSL (eXtensible Stylesheet Language) 可扩展样式表语言XSLT (eXtensible Stylesheet Language Transformation)可扩展样式表语言转换 xxx based 基于xxxxxx oriented 面向xxx 2008-12-17 1:34:00疯狂代码 /。

完整LTE缩略语

TPC TPMI TSTD TTI TX U UCI UDP UDPAP UE UL UL-SCH UM UMB UMTS UpPTS URL USIM USSD UTC UTRA UTRAN V VLAN VMIMO VoIP VP VRB VSWR W WAP WAP GW WCDMA WiMAX WLAN WRR
COD CP CPC CPE CPRI CQI CRC C-RNTI CS CS CSFB CSG D DAI D-AMPS DBCH D-BCH DC DCCH DC-HSDPA DCI DCS DFT DHCP DiffServ DL DL-SCH DM DM RS DMRS DOA DOS DRB DRS DRX DSCP
X X2 ZC
英文全称（English） 16 Quadrature Amplitude Modulation The Second generation The Third generation 3rd Generation Partnership Project 3rd Generation Partnership Project 2 Multi-band,MIMO,Multi-Standard_Radio Remote RadioUnit The Fourth Generation 64 Quadrature Amplitude Modulation Authentication Authorzation and Accounting Adaptive Antenna System Acknowledgement Acknowledgement/Negative-Acknowledgement Access Control List Average Cell Stay Interval Application Header Assisted-GPS Authentication Header Access Description Data Acknowledged Mode Aggregate Maximum Bit Rate Adaptive Modulation and coding AMR Adaptive MultiRate Advanced Mobile Telephone System Adaptive MIMO switching Automatic Neighbour Relation average packet arrival interval access point name Allocation and retention priority Averrage revenue per user （Automatic Repeat Request） access stratum Advanced Wireless Services

计算机专业英语单词

计算机专业英语词汇指与计算机硬件、软件、⽹络等多⽅⾯有关的英语词汇，主要包括硬件基础、计算机系统维护、计算机⽹络基础、软件、程序设计语⾔、计算机⽹络技术、IT职场英语等词汇。

下⾯为⼤家带来计算机专业英语单词，快来看看吧。

计算机专业英语单词1-10 第⼀单元 Processor 处理机 Primary storage 主存储器 bit 位 hearsay 传说 CPU 中英处理器 control unit 控制部件 arithmetic and logic unit 算术逻辑部件 integral parts 不可缺的部件 tape and disk磁带和磁盘 DRAM动态随机存储器 SRAM静态随机存储器 Register 寄存器 a state of the art ⽬前⼯艺⽔平 chip 芯⽚ VDT 视频显⽰终端 secondary storage 辅助存储器 at a premium⾮常珍贵 reallocate 重新分配 capacity 容量 coaxial cable 同轴电缆 program and data 程序和数据 instruction 指令 location 单元 RAM随机存取存储器 Hardwired 硬连线 EPROM可擦可编程只读存储器 Cache ⾼速缓存 Throughput 吞吐量 read-mostly 以读为主 EEPROM电可擦编程ROM Nonvolatility ⾮易失性 Updatable 可修改的 in place 在适当的地⽅ semiconductor 半导体 flash memory 闪存 functionality 功能 byte-level 字节级 be referred to as 称作 virtually 事实上 house 存放 expansion 扩充 peripheral 外围的 slot 插槽 power supply 电源 system board 系统板 storage bay 存储机架 floppy 软盘第⼆单元 optical laser disk 光盘 laser beam激光束 score 刻痕 microscopic pit 微⼩的`凹点 light-sensitive 光敏感的 deflect 偏转 access arm存取臂 inviting 令⼈⼼动的 fluctuation 波动 emerge 显现 stabilize 稳定 gigabyte 千兆字节 cd 光盘 magneto-optical disk 磁光盘 entrepreneur 企业家 video 视频的拓展阅读： A (Active-matrix)主动矩阵 (Adapter cards)适配卡 (Advanced application)⾼级应⽤ (Analytical graph)分析图表 (Analyze)分析 (Animations)动画 (Application software) 应⽤软件 (Arithmetic operations)算术运算 (Audio-output device)⾳频输出设备 (Access time)存取时间 (access)存取 (accuracy)准确性 (ad network cookies)⼴告⽹络信息记录软件 (administrator)管理员 (Add-ons)插件 (Address)地址 (Agents)代理 (Analog signals)模拟信号 (Applets)程序 (Asynchronous communications port)异步通信端⼝ (Attachment)附件 AGP(accelerated graphics port)加速图形接⼝ ALU (arithmetic-logic unit)算术逻辑单元 AAT(Average Access Time) 平均存取时间 ACL(Access Control Lists)访问控制表 ACK(acknowledgement character)确认字符 ACPI (Advanced Configuration and Power Interface)⾼级配置和电源接⼝ ADC(Analog to Digital Converter)模数转换器 ADSL(Asymmetric Digital Subscriber Line)⾮对称⽤户数字线路 ADT(Abstract Data Type)抽象数据类型 AGP(Accelerated Graphics Port)图形加速端⼝ AI(Artif icial Intelligence)⼈⼯智能 AIFF(Audio Image File Format)声⾳图像⽂件格式 ALU(Arithmetic Logical Unit) 算术逻辑单元 AM(Amplitude Modulation)调幅 ANN(Artificial Neural Network)⼈⼯神经⽹络 ANSI(American National Standard Institute)美国国家标准协会 API(Application Programming Interface)应⽤程序设计接⼝ APPN(Advanced Peer-to-Peer Network)⾼级对等⽹络 ARP(Address Resolution Protocol)地址分辨/ 转换协议 ARPG(Action Role Playing Game)动作⾓⾊扮演游戏 ASCII (American Standard Code for Information Interchange)美国信息交换标准代码 ASP(Active Server Page)活动服务器⽹页 ASP(Application Service Provider)应⽤服务提供商 AST(Average Seek Time)平均访问时间 ATM(asynchronous transfer mode)异步传输模式 ATR (Automatic Target Recognition) ⾃动⽬标识别 AVI (Audio Video Interleaved)声⾳视频接⼝ B (Bar code)条形码 (Bar code reader)条形码读卡器 (Basic application)基础程序 (Binary coding schemes)⼆进制编码⽅案 (Binary system)⼆进制系统 (Bit)⽐特 (Browser)浏览器 (Bus line)总线 (Backup tape cartridge units)备份磁带盒单元 (Bandwidth)带宽 (Bluetooth)蓝⽛ (Broadband)宽带 (Bus)总线 B2B(Busines s to Business)商业机构对商业机构的电⼦商务 B2C(Business to Consumer)商业机构对消费者的电⼦商务 BBS(bulletin board system)电⼦公告牌系统 BER(Bit Error Rate)误码率 BFS (Breadth First Search) ⼴度优先搜索 BGP(Border Gateway Protocol)边缘⽹关协议 BIOS(basic input/output system)基本输⼊输出系统 BISDN(Broadband- Integrated Services Digital Network)宽带综合业务数字⽹ BLU(Basic Link Unit)基本链路单元 BOF(Beginning Of File)⽂件开头 BPS(Bits Per Second)每秒⽐特数 BRI(Basic Rate Interface)基本速率接⼝ BSP(Byte Stream Protocol)字节流协议 BSS(Broadband Switching System)宽带交换系统 C (Cables)连线 (Cell)单元箱 (Chain printer)链式打印机 (Character and recognition device)字符标识识别设备 (Chart)图表 (Chassis)⽀架 (Chip)芯⽚ (Clarity)清晰度 (Closed architecture)封闭式体系结构 (Column)列 (Combination key)结合键 (computer competency)计算机能⼒ (connectivity)连接，结点 (Continuous-speech recognition system)连续语⾔识别系统 (Control unit)操纵单元 (Cordless or wireless mouse)⽆线⿏标 (Cable modems)有线调制解调器 (Channel)信道 (Chat group)谈话群组 (Client)客户端 (Coaxial cable)同轴电缆 (cold site)冷⽹站 (Commerce servers)商业服务器 (Communication channel)信道 (Communication systems)信息系统 CD(Compact disc)光盘 (computer abuse amendments act of 19941994)计算机滥⽤法案 (computer crime)计算机犯罪 (computer ethics)计算机道德 (computer fraud and abuse act of 1986)计算机欺诈和滥⽤法案 (computer matching and privacy protection act of 1988)计算机查找和隐私保护法案 (Computer network)计算机⽹络 (computer support specialist)计算机⽀持专家 (computer technician)计算机技术⼈员 (computer trainer)计算机教师 (Connection device)连接设备 (Connectivity)连接 (cookies-cutter programs)信息记录截取程序 (cookies)信息记录程序 (cracker)解密⾼⼿ (Cyber cash)电⼦货币 (Cyberspace)计算机空间 (chart)图表 (closed architecture )封闭式体系结构 C2C(Consumer-to-consumer)个⼈对个⼈ CPU (central processing unit)中央处理器 CISC (complex instruction set computer)复杂指令集计算机 CRT( cathode-ray tube)阴极射线管 AD(Computer Aided Design)计算机辅助设计 CAE(Computer-Aided Engineering)计算机辅助⼯程 CAI(Computer Aided Instruction)计算机辅助教学 CAM(Computer Aided Manufacturing)计算机辅助管理 CASE(Computer Assisted Software Engineering)计算机辅助软件⼯程 CAT(Computer Aided Test)计算机辅助测试 CATV(Community Antenna Television)有线电视 CB(control bus)控制总线 CCP(Communication Control Procrssor)通信控制处理机 CD(Compact Disc)压缩光盘，只读光盘 CD-R(Compact Disc-Recordable)可录光盘，只写⼀次的光盘 CDFS(Compact Disk File System)密集磁盘⽂件系统 CDMA(Code Division Multiple Access)码分多路访问 CD-MO(Compact Disc-Magneto Optical)磁光式光盘 CD-ROM(compact disc read-only memory)只读光盘 CD-RW(compact disc rewritable)可读写光盘 CGA(Color Graphics Adapter)彩⾊显⽰器 CGI(common gateway interface)公共⽹关接⼝ CI(Computational Intelligence)计算智能 CISC(Complex Instruction Set Computer) 复杂指令集计算机 CMOS(Complementary Metal Oxide Semiconductor)互补⾦属氧化物半导体存储器 COM(Component object model)组件对象模型 CORBA(Common Object Request Broker Architecture)公共对象请求代理结构 CPU(central proces sing unit)中央处理单元 CRC(cyclical redundancy check)循环冗余校验码 CRM(Client Relation Management)客户关系管理 CRT(Cathode-Ray Tube)阴极射线管,显⽰器 CSMA(Carrier Sense Multi -Access)载波侦听多路访问 CSU(Channel Service Unit)信道服务单元 CU(Control Unit)控制单元 D DB(Database)数据库 (database files)数据库⽂件 (Database manager)数据库管理 DBMS(Database manager system)数据库管理系统 (Data bus)数据总线 (Data projector)数码放映机 (Desktop system unit)台式电脑系统单元 (Destination file)⽬标⽂件 (Digital cameras)数码照相机 (Digital notebooks)数字笔记本 (Digital video camera)数码摄影机 (Discrete-speech recognition system)不连续语⾔识别系统 (Document)⽂档 (document files)⽂档⽂件 (Dot-matrix printer)点矩阵式打印机 (Dual-scan monitor)双向扫描显⽰器 (Dumb terminal)⾮智能终端 (data security)数据安全 (Data transmission specifications)数据传输说明 (database administrator)数据库管理员 (Data play)数字播放器 (Demodulation)解调 (denial of service attack)拒绝服务攻击 (Dial-up service)拨号服务 (Digital cash)数字现⾦ (Digital signals)数字信号 (Digital subscriber line)数字⽤户线路 (Digital versatile disc)数字化通⽤磁盘 (Digital video disc)数字化视频光盘 (Direct access)直接存取 (Directory search)⽬录搜索 (disaster recovery plan)灾难恢复计划 (Disk caching)磁盘驱动器⾼速缓存 (Diskette)磁盘 (Disk)磁碟 (Distributed data processing system)分部数据处理系统 (Distributed processing)分布处理 (Domain code)域代码 (Downloading)下载 DVD(Digital Versatile Disc)数字多功能光盘 DVD-R(DVD-Recordable)可写DVD DVD-RAM(DVD- Random Access Memory)DVD随机存取器 DNS(Domain name system)域名服务器 DAC(Digital to Analogue Converter)数模转换器 DAO(Data Access Object)数据访问对象 DAP(Directory Acces s Protocol)⽬录访问协议 DBMS(Database Management System)数据库管理系统 DCE(data communication equipment)数据通信设备 DCE(Distributed Computing Environment)分布式计算环境 DCOM(Distributed COM)分布式组件对象模型 DDB(Distributed DataBase)分布式数据库 DDE(Dynamic Data Exchange)动态数据交换 DDI(Device Driver Interface)设备驱动程序接⼝ DDK(Driver Development Kit)驱动程序开发⼯具包 DDN(Data Digital Network)数据数字⽹ DEC(Digital Equipment Corporation)数字设备公司 DES(Data Encryption Standard)数据加密标准 DFS(Depth First Search) 深度优先搜索 DFS(Distributed File System)分布式⽂件系统 DHCP(Dynamic Host Configuration Protocol)动态主机配置协议 DIB(Dual Independent Bus)双独⽴总线 DIC(Digital Image Control)数字图像控制 DLC(Data Link Control)数据链路控制 DLL(Dynamic Link Library)动态链接库 DLT(Data Link Terminal)数据链路终端 DMA(Direct Memory Access)直接内存访问 DMSP(Distributed Mail System Protocol)分布式电⼦邮件系统协议 DNS(Domain Name System)域名系统 DOM(Document Object Mode)⽂档对象模型 DOS(Disk Operation System)磁盘操作系统 DQDB(Distributed Queue Dual Bus)分布式队列双总线 DRAM(Dynamic Random Access Memory)动态随机存取存储器 DSD(Direct Stream Digital)直接数字信号流 DSL(Digital Subscriber Line)数字⽤户线路 DSM(Distributed Shared Memory)分布式共享内存 DSP(Digital Signal Processing)数字信号处理 DTE(Data Terminal Equipment)数据终端设备 DVD(Digital Versatile Disc)数字多功能盘 DVD-ROM(DVD-Read Only Memory)计算机⽤只读光盘 DVI(Digital Video Interactive)数字视频交互 E (e-book)电⼦阅读器 (Expansion cards)扩展卡 (end user)终端⽤户 (e-cash)电⼦现⾦ (e-commerce)电⼦商务 (electronic cash)电⼦现⾦ (electronic commerce)电⼦商务 (electronic communications privacy act of1986)电⼦通信隐私法案 (encrypting)加密术 (energy star)能源之星 (Enterprise computing)企业计算化 (environment)环境 (Erasable optical disks)可擦除式光盘 (ergonomics)⼈类⼯程学 (ethics)道德规范 (External modem)外置调制解调器 (extranet)企业外部⽹ EC(Embedded Controller)嵌⼊式控制器 EDIF(Electronic Data Interchange Format)电⼦数据交换格式 EEPROM(Erasable and Electrically Programmable ROM)电擦除可编程只读存储器 EGA(Enhanced Graphics Adapter)彩⾊显⽰器,分辨率为 640×350 ,可以显⽰ 16 种颜⾊ EGP(External Gateway Protocol)外部⽹关协议 EISA(Extended Industry Standard Architecture)增强⼯业标准结构 EMS(Expanded Memory Specification)扩充存储器规范 EPH(Electronic payment Handler)电⼦⽀付处理系统 EPROM(Erasable Programmable ROM)可擦除可编程只读存储器 ERP(Enterprise Resource Planning)企业资源计划 ETM(ExTended Memory)扩展存储器 F (Fax machine)传真机 (Field)域 (Find)搜索 (FireWire port)⽕线端⼝ (Firmware)固件 (Flash RAM)闪存 (Flatbed scanner)台式扫描器 (Flat-panel monitor)纯平显⽰器 (floppy disk)软盘 (Formatting toolbar)格式化⼯具条 (Formula)公式 (Forum)论坛 (Function)函数 (fair credit reporting act of 1970)公平信⽤报告法案 (Fiber-optic cable)光纤电缆 (File compression)⽂件压缩 (File decompression)⽂件解压缩 (filter)过滤 (firewall)防⽕墙 (firewall)防⽕墙 (Fixed disk)固定硬盘 (Flash memory)闪存 (Flexible disk)可折叠磁盘 (Floppies)磁盘 (Floppy-disk cartridge)磁盘盒 (Formatting)格式化 (freedom of information act of 1970)信息⾃由法案 (frequency)频率 (frustrated)受挫折 (Full-duplex communication)全双通通信 FAT(File Allocation Table)⽂件分配表 FCB(File Control Block)⽂件控制块 FCFS(First Come First Service)先到先服务 FCS(Frame Check Sequence)帧校验序列 FDD(Floppy Disk Device)软盘驱动器 FDDI(Fiber-optic Data Distribution Inter face)光纤数据分布接⼝ FDM(Frequency-Division Multiplexing)频分多路 FDMA(Frequency Division Multiple Address)频分多址 FEC(Forward Error Correction) 前向纠错 FEK(File Encryption Key)⽂件密钥 FEP(Front Ef fect Processor)前端处理机 FET(Field Effect Transistor)场效应晶体管 FIFO(First In First Out)先进先出 FM(Frequency Modulation)频率调制 FPU(Float Point Unit)浮点部件 FRC(Frame Rate Control)帧频控制 FTAM(File Transfer Access and Management)⽂件传输访问和管理 FTP(File Transfer Protocol)⽂件传输协议 G (General-purpose application)通⽤运⽤程序 (Gigahertz)千兆赫 (Graphic tablet)绘图板 (green pc)绿⾊个⼈计算机 (Group by) 排序 GAL(General Array Logic)通⽤逻辑阵列 GCR(Group-Coded Recording)成组编码记录 GDI(Graphics Device Interface)图形设备接⼝ GIF(Graphics Interchange Format)⼀种图⽚⽂件格式,图形转换格式 GIS(Geographic Information System)地理信息系统 GPI(Graphical Programming Interface)图形编程接⼝ GPIB(General Purpose Interface Bus)通⽤接⼝总线 GPS(Global Positioning System)全球定位系统 GSX(Graphics System Extension)图形系统扩展 GUI(Graphical User Interface)图形⽤户接⼝ H (handheld computer)⼿提电脑 (Hard copy)硬拷贝 (hard disk)硬盘 (hardware)硬件 (Help)帮助 (Host computer)主机 (Home page)主页 (Hyperlink)超链接 (hacker)⿊客 (Half-duplex communication)半双通通信 (Hard-disk cartridge)硬盘盒 (Hard-disk pack)硬盘组 (Head crash)磁头碰撞 (header)标题 (help desk specialist)帮助办公专家 (helper applications)帮助软件 (Hierarchical network)层次型⽹络 (history file)历史⽂件 (hits)匹配记录 (horizontal portal)横向⽤户 (hot site)热⽹站 (Hybrid network)混合⽹络 HPSB (high performance serial bus)⾼性能串⾏总线 HDTV(high-definition television)⾼清晰度电视 HDC(Hard Disk Control)硬盘控制器 HDD(Hard Disk Drive)硬盘驱动器 HDLC(High-level Data Link Control)⾼级数据链路控制 HEX(HEXadecimal)⼗六进制 HPFS(High Performance File System)⾼性能⽂件系统 HPSB(High Performance Serial Bus)⾼性能串⾏总线 HTML(Hyper Text Markup Language)超⽂本标记语⾔ HTTP(Hyper Text Transport Protocol)超⽂本传输协议 I (Image capturing device)图像获取设备 IT(information technology)信息技术 (Ink-jet printer)墨⽔喷射印刷机 (Integrated package)综合性组件 (Intelligent termina)l智能终端设备 (Intergrated circuit)集成电路 (implements )实现接⼝ (Interface cards)接⼝卡 (Internal modem)内部调制解调器 (internet telephony)⽹络电话 (internet terminal)互联⽹终端 (Identification)识别 (i-drive)⽹络硬盘驱动器 (illusion of anonymity)匿名幻想 (index search)索引搜索 (information pushers)信息推送器 (initializing )初始化 (instant messaging)计时信息 (internal hard disk)内置硬盘 (Internet hard drive) ⽹络硬盘驱动器 (intranet)企业内部⽹ ISA (industry standard architecture)⼯业标准结构体系 IRC(internet relay chat)互联⽹多线交谈 IAC(Inter-Application Communications)应⽤间通信 IC(Integrated Circuit)集成电路 ICMP(Internet Control Mes sage Protocol)因特⽹控制消息协议 ICP(Internet Content Provider)因特⽹内容服务提供商,是 ISP中提供信息服务的⼀种机构 IDC(International Development Center)国际开发中⼼ IDE(Integrated Development Environment)集成开发环境 IDL(Interface Definition Language)接⼝定义语⾔ IEEE(Institute of Electrical and Electronics Engineering)电⼦电器⼯程师协会 IGP(Interior Gateway Protocol)内部⽹关协议 IIS(Internet Information Service)因特⽹信息服务 IP(Internet Protocol)因特⽹协议 IPC(Inter-Process Communication)进程间通信 IPSE(Integrated Project Support Environments)集成⼯程⽀持环境 IPX(Internet Packer Exchitecture)互联⽹报⽂分组交换 ISA(Industry Standard Architecture)⼯业标准结构,是 IBM PC/ XT总线标准 ISDN(Integrated Service Digital Network)综合业务数字⽹ ISO(International Standard Organization)国际标准化组织 ISP(Internet Service Provider)因特⽹服务提供者 ITU(International Telecom Union)国际电信联盟 J (joystick)操纵杆 JDBC(Java Database Connectivity) J ava数据库互联 JPEG(Joint Photographic Experts Group)联合图⽚专家组 JSP(Java Server Page) Java 服务器页⾯技术 JVM(Java Virtual Machine)Java虚拟机 K (keyword search)关键字搜索 KB(Kilobyte)千字节 KBPS(Kilobits Per Second)每秒千⽐特 KMS(Knowledge Management System)知识管理系统 L (laser printer)激光打印机 (Layout files)版式⽂件 (Light pen)光笔 (Locate)定位 (Logical operations)逻辑运算 (Lands)凸⾯ (Line of sight communication)视影通信 (Low bandwidth)低带宽 (lurking)潜伏 LCD (liquid crystal display monitor)液晶显⽰器 LAN(Local Area Network)局域⽹ LBA(Logical Block Addressing)逻辑块寻址 LCD(Liquid Crystal Display)液晶显⽰器 LDT(Logic Design Translator)逻辑设计翻译程序 LED(Light Emitting Diode)发光⼆极管 LIFO(Last In First Out)后进先出 LP(Linear Programming)线性规划 LPC(Local Procedure Call)局部过程调⽤ LSIC(Large Scale Integration Circuit)⼤规模集成电路 M (Main board)主板 (Mark sensing)标志检测 (Mechanical mouse)机械⿏标 (Memory)内存 (Menu)菜单 (Menu bar)菜单栏 (Microprocessor)微处理器 (Microseconds)微秒 (Modem card)调制解调器 (Monitor)显⽰器 (Motherboard)主板 (Mouse) ⿏标 (Multifunctional device)多功能设备 (Magnetic tape reels)磁带卷 (Magnetic tape streamers)磁带条 (mailing list)邮件列表 (Medium band)媒质带宽 (metasearch engine)整合搜索引擎 (Microwave)微波 (Modem)解调器 (Modulation)解调 MAN(Metropolitan area network)城域⽹ MICR(magnetic-ink character recognition)磁墨⽔字符识别器 MAC(Medium Access Control)介质访问控制 MAN(Metropolitan Area Network)城域⽹ MBR(Master Boot Record)主引导记录 MC(Memory Card)存储卡⽚ MCA(Micro Channel Architecture)微通道结构 MDA(Monochrome Display Adapter)单⾊显⽰适配卡 MFM(Modified Frequency Modulation)改进调频制 MIB(Management Information Bass)管理信息库 MIDI(Musical Instrument Digital Interface) 乐器数字接⼝ MIMD(Multiple Instruction Stream,Multiple Data Stream)多指令流,多数据流 MIPS(Million Instructions Per Second)每秒百万条指令 MIS(Management Information System)管理信息系统 MISD(Multiple Instruction Stream,Single Data Stream)多指令流,单数据流 MMDS(Multi-channel Multipoint Distribution Service)多波段多点分发服务器 MMU(Memory Management Unit)内存管理单元 MPC(Multimedia PC)多媒体计算机 MPEG(Moving Picture Expert Group) ⼀种视频和⾳频的国际标准格式 MPLS(Multi-Protocol Label Switching)多协议标记交换 MPS(Micro Processor System)微处理器系列 MTBF(Mean Time Between Failures)平均故障间隔时间 MUD(Multiple User Dimension)多⽤户空间 N (Net PC)⽹络计算机 (Network adapter card)⽹卡 (Network personal computer)⽹络个⼈电脑 (Network terminal)⽹络终端 (Notebook computer)笔记本电脑 (Notebook system unit)笔记本系统单元 (Numeric entry)数字输⼊ (national information infrastructure protection act of1996)国际信息保护法案 (national service provider)全国性服务供应商 (Network architecture)⽹络体系结构 (Network bridge)⽹桥 (Network gateway)⽹关 (network manager)⽹络管理员 (newsgroup)新闻组 (no electronic theft act of1997)⽆电⼦盗窃法 (Node)节点 (Nonvolatile storage)⾮易失性存储 NOS(Network operation system)⽹络操作系统 NAOC(No-Account Over Clock)⽆效超频 NAT(Network Address Translation) ⽹络地址转换 NC(Network Computer)⽹络计算机 NDIS(Network Device Interface Speci fication)⽹络设备接⼝规范 NCM(Neural Cognitive Maps)神经元认知图 NFS(Network File System)⽹络⽂件系统 NIS(Network Information Services)⽹络信息服务 NNTP(Network News Transfer Protocol)⽹络新闻传输协议 NOC(Network Operations Center) ⽹络操作中⼼ NSP(Name Server Protocol)名字服务器协议 NTP(Network Time Protocol)⽹络时间协议 NUI(network user identification)⽹络⽤户标识 O (Object embedding)对象嵌⼊ (Object linking)⽬标链接 (Open architecture)开放式体系结构 OS(Operation System)操作系统 (Optical disk)光盘 (Optical mouse)光电⿏标 (Optical scanner)光电扫描仪 (Outline)⼤纲 (off-line browsers)离线浏览器 (Online storage)联机存储 OLE (object linking and embedding)对象链接⼊ OCR(optical-character recognition)字符识别器 OMR(optical-mark recognition)光标阅读器 OA(Of f ice Automation)办公⾃动化 OCR(Optical Character Recognition)光学字符识别 ODBC(Open Database Connectivity)开放式数据库互联 ODI(Open Data- link Interface)开放式数据链路接⼝ OEM(Original Equipment Manufactures)原始设备制造⼚家 OLE(Object Linking and Embedding)对象链接与嵌⼊ OMG(Object Management Group)对象管理组织 OMR(Optical-Mark Recognition)光标阅读器 OOM(Object Oriented Method)⾯向对象⽅法 OOP(Object Oriented Programming)⾯向对象程序设计 ORB(Object Request Broker)对象请求代理 OS(Operating System)操作系统 OSI(Open System Interconnect Reference Model)开放式系统互联参考模型 OSPF(Open Shortest Path First)开发最短路径优先 P (palmtop computer)掌上电脑 (Parallel ports)并⾏端⼝ (Passive-matrix)被动矩阵 (PC card)个⼈计算机卡 (Personal laser printer)个⼈激光打印机 (Personal video recorder card)个⼈视频记录卡 (Photo printer)照⽚打印机 (Pixel)像素 (Platform scanner)平版式扫描仪 (Plotter)绘图仪 (Plug and play)即插即⽤ (Plug-in boards)插件卡 (Pointer)指⽰器 (Pointing stick)指⽰棍 (Port)端⼝ (Portable scanner)便携式扫描仪 (Presentation files)演⽰⽂稿 (Presentation graphics)电⼦⽂稿程序 (Primary storage)主存 (Procedures)规程 (Processor)处理机 (Programming control language)程序控制语⾔ (Packets)数据包 (Parallel data transmission)平⾏数据传输 (Peer-to-peer network system点)对点⽹络系统 (person-person auction site)个⼈对个⼈拍卖站点 (physical security)物理安全 (Pits)凹⾯ (plug-in)插件程序 (privacy )隐私权 (proactive )主动地 (programmer)程序员 (Protocols)协议 (provider)供应商 (project )项⽬⼯程 (proxy server)代理服务 (pull products)推取程序 (push products)推送程序 PDA(personal digital assistant)个⼈数字助理 PCI(peripheral component interconnect)外部设备互连总线 PCMCIA (Personal Memory Card International Association)个⼈计算机存储卡国际协会 PBX(Private Branch Exchange)⽤户级交换机 PC(Personal Computer)个⼈计算机 PCB(Process Control Block)进程控制块 PCI(Peripheral Component Interconnect)外部连接互联,是⼀种局部总线 PCM(Pulse Code Modulation)脉冲编码调制 PCS(Personal Communications Service) 个⼈通信业务 PDA(Personal Digital As sistant)个⼈数字助理 PDF(Portable Document Format)便携式⽂档格式 PDN(Public Data Network)公共数据⽹ PHP(Personal Home Page)个⼈⽹页 PIB(Programmable Input Buffer)可编程输⼊缓冲区 PMMU(Paged Memory Management Unit)页⾯存储管理单元 POP(Post Of f ice Protocol)邮局协议 POST(Power-On Self -Test)加电⾃检 PPP(Peer-Peer Protocol)端对端协议 PPP(Point to Point Protocol)点到点协议 PPSN(Public Packed-Switched Network)公⽤分组交换⽹ PR(Performance Rate)性能⽐率 PROM(Programmable ROM)可编程只读存储器 PSN(Processor Serial Number)处理器序列号 Q QC(Quality Control)质量控制 QLP(Query Language Proces sor)查询语⾔处理器 QoS(Quality of Service)服务质量 R (RAM cache)随机⾼速缓冲器 (Range)范围 (Record)记录 (Relational database)关系数据库 (Replace)替换 (Resolution)分辨率 (Row)⾏ (Read-only)只读 (Reformatting)重组 (regional service provider)区域性服务供应商 (reverse directory)反向⽬录 (right to financial privacy act of 1979)财产隐私法案 (Ring network)环形⽹ RAD(Rapid Application Development)快速应⽤开发 RAI(Remote Application Interface)远程应⽤程序界⾯ RAID(Redundant Array Independent Disk) 冗余列阵磁盘机 RARP(Reverse Address Resolution Protocol)反向地址解析协议 RAM(Random Acces s Memory)随机存储器 RAM(Real Address Mode)实地址模式 RAID(Redundant Arrays of Inexpensive Disks)冗余磁盘阵列技术 RAS(Remote Access Service)远程访问服务 RCP(Remote CoPy)远程复制 RDA(Remote Data Access)远程数据访问 RDO (Remote Data Objects) 远程数据对象 RF(Radio Frequency) 射频，⽆线电频率 RIP(Raster Image Protocol)光栅图像处理器 RIP(Routing Information Protocol)路由选择信息协议 RISC(Reduced Instruction Set Computer)精简指令集计算机 ROM(Read Only Memory)只读存储器 RPC(Remote Procedure Call)远程过程调⽤ RPG(Role Play Games)⾓⾊扮演游戏 RPM(Revolutions Per Minute)转/分 RTS(Request To Send)请求发送 RTSP(Real Time Streaming Protocol) 实时流协议 S (Scanner)扫描器 (Search)查找 (Secondary storage device)辅助存储设备 (Semiconductor)半导体 (Serial ports)串⾏端⼝ (Server)服务器 (Shared laser printer)共享激光打印机 (shakedown test )调试 (Sheet)表格 (Silicon chip)硅⽚ (Slots)插槽 (Smart card)智能卡 (Soft copy)软拷贝 (Software suite)软件协议 (Sorting)排序 (Source file)源⽂件 (Special-purpose application)专⽤⽂件 (Spreadsheet)电⼦数据表 (Standard toolbar)标准⼯具栏 (Supercomputer)巨型机 (System )系统 (System cabinet )系统箱 (System clock)时钟 (System software)系统软件 (Satellite/air connection services)卫星⽆线连接服务 (search engines)搜索引擎 (search providers)搜索供应者 (search services )搜索服务器 (Sectors)扇区 (security)安全 (Sending and receiving devices)发送接收设备 (Sequential access)顺序存取 (Serial data transmission)单向通信 (signature line)签名档 (snoopware)监控软件 (software copyright act of1980)软件版权法案 (software piracy)软件盗版 (Solid-state storage)固态存储器 (specialized search engine)专⽤搜索引擎 (spiders)⽹页爬⾍ (spike)尖峰电压 (Star network)星型⽹ (Strategy)⽅案 (subject)主题 (subscription address)预定地址 (Superdisk)超级磁盘 (surfing)⽹上冲浪 (surgeprotector)浪涌保护器 (systems analyst)系统分析师... SACL(System Access Control List) 系统访问控制列表 SAF(Store And Forward)存储转发 SAP(Service Acces s Point)服务访问点 SCSI(Small Computer System Interface)⼩型计算机系统接⼝ SDLC(Synchronous Data Link Control)同步数据链路控制 SGML(Standard Generalized Markup Language)标准通⽤标记语⾔ SHTTP(Secure Hype Text Transfer Protocol)安全超⽂本传递协议 SMP(Symmetric Multi-Processor)对称式多处理器 SMTP(Simple Mail Transport Protocol)简单邮件传输协议 SNA(System Network Architecture)系统⽹络结构 SNMP(Simple Network Management Protocol)简单⽹络管理协议 SNR(Signal Noise Ratio)信噪⽐ SNTP(Simple Network Time Protocol)简单⽹络时间协议 SONC(System On a Chip)系统集成芯⽚ SONET(Synchronous Optic Network)同步光纤⽹ SPC(Stored-Program Control)存储程序控制 SQL(Structured Query Language)结构化查询语⾔ SRAM(Static Random Access Memory)静态随机存储器 SRPG(Strategies Role Play Games) 战略⾓⾊扮演游戏 SSL(Secure Sockets Layer)安全套接层 STDM(Synchronous Time Division Multiplexing)同步时分复⽤ STG(Shoot Game)射击类游戏 STP(Shielded Twisted-Pair)屏蔽双绞线 SVGA (Super Video Graphics Array) 超级视频图形阵列 T (Table)⼆维表 (Telephony)电话学 (Television boards)电视扩展卡 (Terminal) 终端 (Template)模板 (Text entry)⽂本输⼊ (Thermal printer )热印刷 (Thin client)瘦客 (Toggle key)触发键 (Toolbar)⼯具栏 (Touch screen)触摸屏 (Trackball)球 (TV tuner card)电视调谐卡 (Two-state system))双状态系统 (technical writer)技术协作者 (technostress)重压技术 (telnet)远程登录 (Time-sharing system)分时系统 (Topology)拓扑结构 (Tracks)磁道 (traditional cookies)传统的信息记录程序 (Twisted pair)双绞 TCB(Transmission Control Block)传输控制块 TCP(Transmis sion Control Protocol)传输控制协议 TCP/IP(Transmission Control Protocol / Internet Protocol)传输控制协议/ ⽹间协议 TDM(Time Division Multiplexing)时分多路复⽤ TDMA(Time Division Multiplexing Address)时分多址技术 TDR(Time-Domain Reflectometer)时间域反射测试仪 TFT(Thin Film Transistor Monitor)薄膜晶体管显⽰器 TFTP(Trivial File Transfer Protocol)简单⽂件传送协议 TIFF(Tag Image File Format)标记图形⽂件格式 TIG(Task Interaction Graph)任务交互图 TLI(Transport Layer Interface)传输层接⼝ TM(Traffic Management)业务量管理，流量管理 TPS(Transactions Per Second)(系统)每秒可处理的交易数 TSR(Terminate and Stay Resident)终⽌并驻留 TTL(Transistor-Transistor Logic)晶体管—晶体管逻辑电路 TWX(Teletypewriter Exchange)电传电报交换机 U (Unicode)统⼀字符标准 (uploading)上传 (usenet)世界性新闻组⽹络 UART(Universal Asynchronous Receiver Transmitter)通⽤异步收发器 UDF(Universal Disk Format)通⽤磁盘格式 UDP(User Datagram Protocol)⽤户数据报协议 UHF(Ultra High Frequency)超⾼频 UI(User Interface)⽤户界⾯，⽤户接⼝ UIMS(User Interface Management System)⽤户接⼝管理程序 UNI(User Network Interface)⽤户⽹络接⼝ UPA(Ultra Port Architecture)超级端⼝结构 UPS(Uninterruptible Power Supply)不间断电源 URI(Uniform Resource Identi fier)环球资源标识符 URL(Uniform Resource Locator)统⼀资源定位器 USB(Universal Serial Bus)通⽤串⾏总线 UTP(Unshielded Twisted-Pair)⾮屏蔽双绞线 UXGA(Ultra Extended Graphics Array)超强图形阵列 V (Virtual memory)虚拟内存 (Video display screen)视频显⽰屏 (Voice recognition system)声⾳识别系统 (vertical portal)纵向门户 (video privacy protection act of 1988)视频隐私权保护法案 (virus checker)病毒检测程序 (virus)病毒 (Voiceband)⾳频带宽 (Volatile storage)易失性存储 (voltage surge)电涌 VAD(Virtual Addres s Descriptors)虚拟地址描述符 VAGP(Variable Aperature Grille Pitch) 可变间距光栅 VAN(Value Added Network)增值⽹络 VAP(Value-Added Process)增值处理 VAS(Value-Added Server)增值服务 VAX(Virtual Address eXtension)虚拟地址扩充 VBR(Variable Bit Rate)可变⽐特率 VC(Virtual Circuit)虚拟线路 VCPI(Virtual Control Program Interface)虚拟控制程序接⼝ VDD(Virtual Device Driver s)虚拟设备驱动程序 VDR(Video Disc Recorder)光盘录像机 VDT(Video Display Terminals)视频显⽰终端 VDU(Visual Display Unit)视频显⽰单元 VFS(Virtual File System)虚拟⽂件系统 VGA(Video Graphics Adapter)视频图形适配器 VIS(Video Information System)视频信息系统 VLAN(Virtual LAN)虚拟局域⽹ VLIW(Very Long Instruction Word)超长指令字 VLSI(Very Large Scale Integration)超⼤规模集成 VMS(Virtual Memory System)虚拟存储系统 VOD(Video On Demand)视频点播系统 VON(Voice On Net)⽹上通话 VR(Virtual Reality)虚拟现实 VRML(Virtual Reality Modeling Language)虚拟现实建模语⾔ VRR(Vertical Refresh Rate)垂直刷新率 VTP(Virtual Terminal Protocol)虚拟终端协议 W (Wand reader )条形码读⼊ (Web )⽹络 (Web appliance )环球⽹设备 (Web page)⽹页 (Web site address)⽹络地址 (Web terminal)环球⽹终端 (Webcam)摄像头 (What-if analysis)假定分析 (Wireless revolution)⽆线⾰命 (Word)字长 (Word processing)⽂字处理 (Word wrap)⾃动换⾏ (Worksheet file) ⼯作⽂件 (web auctions)⽹上拍卖 (web broadcasters)⽹络⼴播 (web portals)门户⽹站 (web sites)⽹站 (web storefront creation packages)⽹上商店创建包 (web storefronts)⽹上商店 (web utilities)⽹上应⽤程序 (web-downloading utilities)⽹页下载应⽤程序 (webmaster web)站点管理员 (web)万维⽹ (Wireless modems)⽆线调制解调器 (wireless service provider)⽆线服务供应商 WWW(world wide web)万维⽹ (worm)蠕⾍病毒 (Write-protect notch)写保护⼝ WAN(Wide area network)⼴域⽹ (Web server)Web 服务器 (well-connected )连接良好 (well-known services )公认的服务。

fundamentals of queueing theory

fundamentals of queueing theoryQueueing theory is a branch of mathematics that deals with the study of waiting lines or queues. It is widely used in various fields such as telecommunications, traffic engineering, computer networks, manufacturing, and service industries. The theory provides a framework for analyzing the behavior of systems where customers arrive randomly and are served by one or more servers.The fundamental concept of queueing theory is the queue itself. A queue is a line of customers waiting to be served. The theory seeks to understand the behavior and characteristics of queues, including the average waiting time, the length of the queue, and the number of customers served per unit time. One of the key components of queueing theory is the arrival process. The arrival process determines the rate at which customers arrive at the queue. The arrival process can be described as Poisson, where customers arrive randomly and independently of each other. Alternatively, the arrival process can be modeled as a deterministic process, where customers arrive at fixed intervals.The service process is another important component of queueing theory. The service process determines the time ittakes to serve a customer. The service process can be modeled as an exponential distribution, where the time taken to serve a customer is random and follows a specific probability distribution.The queueing system also has one or more servers that serve the customers. The server can be modeled as a single server or multiple servers. In a single server system, customers are served one at a time, while in a multiple server system, customers can be served by multiple servers simultaneously. One of the key metrics used in queueing theory is the average waiting time. The average waiting time is the time a customer spends waiting in the queue before being served. The average waiting time depends on several factors, including the arrival rate, the service rate, the number of servers, and the queue discipline.The queue discipline refers to the way customers are served in the queue. There are several queue disciplines, including first-come, first-served (FCFS), last-come, first-served (LCFS), and priority-based. The queue discipline can have a significant impact on the average waiting time and the length of the queue.In conclusion, queueing theory is an important field ofmathematics that provides a framework for understanding waiting lines or queues. The theory is used in various fields to analyze the behavior of systems with random arrivals and service times. The fundamental concepts of queueing theory include the arrival process, service process, queue discipline, and server configuration. The theory provides a range of metrics to analyze the behavior of queues, including the average waiting time, the length of the queue, and the number of customers served per unit time.。

计算机网络专业词汇中英对照

《计算机网络》中英文对照Chapter 1End system P28 端系统Modem P29 调制解调器（俗称：猫）Base station P29 基站Communication link P30 通信链路Physical media P30 物理介质Coaxial cable P30 同轴电缆Fiber optics P30 光纤Radio spectrum P30 射频频谱Transmission rate P30 传输速率Packets P30 （数据）包，或分组Routers P30 路由器Link-layer switches P30 链路层交换机Path P30 路径ISP (Internet Service Provider) P30 网络服务提供商TCP (Transmission Control Protocol) P31 传输控制协议IP ( Internet Protocol) P31 网际协议Intranets P31 内网API (Application Programming Interface) P32 应用程序编程接口Network edge P35 网络边缘Access Networks P38 接入网Ethernet P42 以太网Network core P48 网络核心Circuit Switching P50 电路转换Packet Switching 分组交换FDM (frequency-division multiplexing) P50 频分多路复用TDM (time-division multiplexing) P50 时分多路复用Statistical Multiplexing 统计复用Store-and-forward 存储转发Queuing delays P53 排队延迟Transmission delay P60 传输延迟，或发送延迟Propagation delay P60 传播延迟Throughput P59 吞吐量Internet backbone P57 骨干网Delay P59 延迟，或时延Loss P59 丢包Packet-Switched Network P59 分组交换网络Nodal processing delay P60 节点处理延迟End-to-end delay P66 端到端延迟Instantaneous throughput P68 瞬时吞吐量Network interface card P74 网络接口卡（即网卡）Message P75 消息，或报文Segment P75 （报文）段Datagram P75 数据报Frames P75 帧Packet sniffer P82 数据包监听器Protocol Stack 协议栈Peer entities 对等实体Chapter 2 应用层Server farm P110 服务器集群Infrastructure P110 基础设施，或基础架构Self-scalability P111 自扩展性Timing P114 实时性Bandwidth-sensitive applications P115带宽敏感应用Connection-oriented service P117 面向连接的服务Directory service P121 目录服务Base HTML file P122 基本HTML文件Stateless protocol P124 无状态协议RTT (round-trip time ) P126 往返时间Web proxy caches P128 网页代理缓存Status line P130 状态行Out-of-band P141 （频）带外（的）In-band P141 带内（的）User agents P144 用户代理Mail servers P144 邮件服务器Pull protocol P148 拉式协议Push protocol p148 推式协议Host aliasing P158 主机别名Canonical hostname P158 规范主机名Mail server aliasing P158 邮件服务器别名Load distribution P158 负载分配Top-level domain (TLD) servers P161 顶级域名服务器Authoritative DNS servers P161 权威域名服务器Iterative queries P168 迭代查询Resource records (RRs) P165 资源记录Overlay network P179 覆盖网Nonpersistent HTTP 非持久HTTP，或非坚持HTTP Persistent HTTP 持久性HTTP，或坚持的HTTPPeer-to-Peer (P2P) Network 对等网络Socket programming 套接字编程Chapter 3 传输层Multiplexing and demultiplexing P226 复用与分用Unidirectional data transfer P241 单向数据传送Finite-state machine (FSM) P242 有限状态机Positive acknowledgments P243 肯定确认Negative acknowledgments P243 否定确认Countdown timer P250 （倒数）计时器Cumulative acknowledgment P258 累积确认Receive buffer P269 接收缓冲区，或接收缓存Resource-management cells 资源管理单元Source (port number) 源端口号Destination (port number) 目的端口号Checksum 校验和Pipelined protocols 流水线（型）协议Go-back-N 回退NSelective Repeat 选择重传Timeout （定时器）超时Fast Retransmit 快速重传Flow Control 流量控制Three way handshake 三次握手sequence number 序列号（简写为seq）acknowledgement number 确认号（简写为ack；注意与大小的ACK不同）Congestion Control 拥塞控制additive increase, multiplicative decrease 加性增乘性减Slow Start 慢启动congestion-avoidance 拥塞避免fast recovery 快速恢复duplicate (ACK) 冗余（ACK）Random Early Detection 随机早期检测Chapter 4 网络层Forwarding table P338 转发表Virtual-circuit networks P343 虚电路网络Datagram networks P343 数据报网络Signaling message P346 信令报文Content Addressable Memory P354 内容可寻址存储器Crossbar switch P356 纵横开关Active queue management 主动队列管理Head-of-the-line (HOL) 队头Classless interdomain routing (CIDR) P371 无类域间路由Plug-and-play P376 即插即用Anycast P386 任播Interior gateway protocols P414 内部网关协议Routing information Protocol P414 路由信息协议（RIP）Open shortest Path First OSPF P414 开放最短路径优先Area border routers P419 区域边界路由器Sequence-number-controlled flooding P430 序列号控制的洪泛，或带序列号的受控洪泛Reverse path forwarding (RPF) P431 逆向路径转发Rendezvous point P433 汇聚点Longest prefix matching 最长前缀匹配Scheduling 调度Fragmentation 分片，或分段Fragment Offset 报文段偏移量Network Address Translation (NAT) 网络地址转换NAT traversal NAT穿越Multicast 组播，或多播Unicast 单播Tunneling 隧道技术Link-State Routing Algorithm 链路状态路由算法Distance Vector Routing Algorithm 距离向量路由算法Count to Infinity Problem 无穷计数问题Hierarchical Routing 分层路由autonomous systems 自治系统BGP (Border Gateway Protocol) 边界网关协议in-network duplication 网内复制broadcast storm 广播风暴spanning tree 生成树redundant packets 冗余数据包Chapter 5 数据链路层，或链路层Broadcast channels P461 广播信道Trailer fields P464 尾部字段Link access P464 链路接入，或链路访问Network interface card P466 网络接口卡（即网卡）Parity checks P469 奇偶校验Forward error correction (FEC) P471 前向纠错Cyclic Redundancy Check 循环冗余校验Polynomial code P472 多项式码（即CRC码）Multiple access P475 多路接入Random access protocols P477 随机接入协议CSMA/CD P484 带冲突检测的载波侦听多路访问CSMA/CA 带冲突避免的载波侦听多路访问Token passing protocol P487 令牌传递协议ARP P491 地址解析协议Preamble P497 前导（字段）Exponential backoff P502 指数回退，或指数退避Repeater P504 中继器Virtual-channel identifier P520 虚拟信道标识Cell-loss priority P520 信元丢失优先权Label-switched router P524 标签交换路由器Framing （封装）成帧error detection 误差检测，或检错Channel Partitioning 信道分割式（MAC协议）Taking turns MAC protocol 轮流式MAC协议Collision 冲突，或碰撞Time Slot 时隙Slotted ALOHA 时隙ALOHAUnslotted ALOHA 无时隙ALOHANonpersistent CSMA 非坚持CSMA1-persistent CSMA 1坚持CSMAp-persistent CSMA p坚持CSMAToken Ring 令牌环(Wireless) LAN （无线）局域网Hub 集线器Collision domain 冲突域Bridge 网桥欢迎您的下载，资料仅供参考！致力为企业和个人提供合同协议，策划案计划书，学习资料等等打造全网一站式需求。

Congestion-ControlPPT课件

Source 3
Router Router
Router
Destination 1
Destination 2
• Taxonomy
– router-centric versus host-centric – reservation-based versus feedback-based – window-based versus rate-based
Fall 2006
.
3
Evaluation
• Fairness • Power (ratio of throughput to delay)
Throughput/delay
Fall 2006
Optimal load
Load
.
4
Queuing Discipline
• First-In-First-Out (FIFO)
• Objective: adjust to changes in the available capacity • New state variable per connection: CongestionWindow
– limits how much data source has in transit
Congestion Control
Outline
Queuing Discipline Reacting to Congestion Avoiding Congestion Quality of Service
Fall 2006
.
1
Issues
• Two sides of the same coin
• Challenge
– determining the available capacity in the first place – adjusting to changes in the available capacity

计算机网络缩写词

Chapter 1ISPs = Internet Service Providers 因特网服务提供者TCP= Transmission Control Protocol 传输控制协议IP = Internet Protocol 网际协议UDP = User Datagram Protocol 用户数据报协议RFC = Request for comments 注解请求API= Application Programming Interface应用程序编程接口FDM = frequency division multiplexing 频分多路复用TDM= time division multiplexing 时分多路复用POP = Points of Presence 入网点，网络连接点DoS= denial of service attacks 服务器拒绝攻击Chapter 2HTTP = Hypertext Transfer Protocol 超文本传输协议SMTP = simple mail transfer protocol 简单邮件传送协议RTT = round-trip time 循环时间FTP = file transfer protocol 文件传输协议MIME =multipurpose Internet mail extensions 多用途网际邮件扩展IMAP = Internet mail access protocol 互联网邮件访问协议POP3 = post office protocol-version3 邮局协议-版本3DNS = domain name system 域名系统TLD = top-level domain 顶级域名RR = resources records 储存信息Chapter 3MSS = maximum segment size 最大数据段AIMD = additive-increase, multiplicative-decrease 加增乘减CA = congestion avoidance 拥塞避免SR = selective repeat 选择重传SS = slow start 慢启动GBN = Go-Back-N 多帧滑动窗口与后退N帧协议MTU = maximum transmission unit 最大传输单元Chapter 4NAT = network address translation 网络地址转换ICMP = Internet Control Message Protocol 互联网控制报文协议CBR = Constant bit rate 恒定比特率ABR = Available bit rate 可用比特率VC = virtual-circuit 虚电路CAM = Content addressable memories 内容可寻址内存AQM = active queue management 主动队列管理RED = Random Early Detection 随机早期检测HOL = head-of-the-line 线路前部TOS = type of service 服务类型TTL = time to live 寿命CIDR = Classless Interdomain Routing 无类别域间选路DHCP = Dynamic Host Configuration Protocol 动态主机配置协议UPnP = Universal Plug and Play 通用即插即播IGMP = Internet Group Management Protocol 互联网组管理协议LS = link-state 链路状态DV = Distance-Vector 距离向量AS = autonomous system 自治系统RIP = Routing Information Protocol 选路信息协议OSPF = Open Shortest Path First 开放最短路径优先BGP = Border Gateway Protocol 边界网关协议RPF = reverse path forwarding 反向路径转换DVMRP = Distance-Vector Multicast Routing Protocol 距离向量多播选路协议Chapter 5NIC = network interface card 网络接口卡PPP = Point-to-Point Protocol 点对点协议ARP = address resolution protocol 地址解析协议LAN = local area network 局域网WAN = Wide Area Network 广域网MAN = metropolitan area network 城域网ATM = Asynchronous Transfer Mode 异步传输方式CRC = Cyclic Redundancy Check 循环冗余检测FEC = forward error correction 前向纠错EDC = error detection and correction 差错检测和纠错MAC = Medium/Media Access Control 介质访问控制CDMA = Code Division Multiple Access 码分多址FDMA = frequency division multiple access 频分多址TDMA= Time Division Multiple Access 时分多址HDLC = High-level Data Link Control 高级数据链路控制MPLS = Multiprotocol Label Switching 多协议标签交换AAL = ATM Adaptation Layer ATM适配层CSMA = carrier sense multiple access 载波侦听多路访问CSMA/CD = Carrier Sense Multiple Access with Collision Detect 具有碰撞检测的载波侦听多路访问CSMA/CA = Carrier Sense Multiple Access with Collision Avoidance 带有冲突避免的载波侦听多路访问MA 多址multiple access。

WRED调度算法说明

RED reduces the chances of tail drop by selectively dropping packets when the output interface begins to show signs of congestion. By dropping some packets early rather than waiting until the buffer is full, RED avoids dropping large numbers of packets at once and minimizes the chances of global synchronization. Thus, RED allows the transmission line to be used fully at all times.
Prerequisites
In order to use DWRED, Distributed Cisco Express Forwarding switching must be enabled on the interface. Refer to the Cisco Express Forwarding feature documentation for conﬁguration information.
2 Release 11.1(17)CC
Average Queue Size
Supported MIBs and FCs
This feature supports the CISCO-WRED-MIB. For descriptions of supported MIBs and how to use MIBs, see Cisco’s MIB website on CCO at /public/sw-center/netmgmt/cmtk/mibs.shtml. No RFCs are supported by this feature.

路由器QOS配置命令参考

RGOS™ 命令参考手册QOS配置目录RGOS™ 命令参考手册 (1)第一章配置QOS命令 (1)1.1 QOS配置命令 (1)1.1.1 bandwidth (policy-map class) (2)1.1.2 class (policy-map) (3)1.1.3 class-map (4)1.1.4 custom-queue-list (5)1.1.5 debug qos (6)1.1.6 debug ip rtp (7)1.1.7 debug ip tcp (7)1.1.8 drop (8)1.1.9 fair-queue (9)1.1.10 hold-queue (10)1.1.11 ip rtp compression-connections (11)1.1.12 ip rtp header-compression (11)1.1.13 ip rtp priority (12)1.1.14 ip tcp compression-connections (13)1.1.15 ip tcp header-compression (14)1.1.16 match access-group (15)1.1.17 match input-interface (16)1.1.18 match ip dscp (16)1.1.19 match ip precedence (17)1.1.20 match not (18)1.1.21 match protocol (19)1.1.22 max-reserved-bandwidth (19)1.1.23 policy-map (20)1.1.24 police (21)1.1.25 priority (23)1.1.26 priority-group (24)1.1.27 priority-list default (25)1.1.28 priority list interface (26)1.1.29 priority-list protocol (27)1.1.30 priority-list queue-limit (29)1.1.31 queue-limit (30)1.1.32 queue-list default (31)1.1.33 queue-list interface (32)1.1.34 queue-list protocol (33)1.1.35 queue-list queue byte-count (34)1.1.36 queue-list queue limit (35)1.1.37 rate-limit (36)1.1.38 random-detect (38)1.1.39 random-detect dscp (39)1.1.40 random-detect dscp-based (40)1.1.41 random-detect prec-based (41)1.1.42 random-detect precedence (42)1.1.43 random-detect exponential-weighting-constant (43)1.1.44 service-policy (44)1.1.45 set ip dscp (44)1.1.46 set ip precedence (45)1.1.47 shape average (46)1.1.48 shape peak (47)1.1.49 shape max-buffers (48)1.1.50 traffic-shape group (49)1.1.51 traffic-shape rate (50)1.2 显示相关命令 (51)1.2.1 show class-map (51)1.2.2 show ip rtp header-compression (52)1.2.3 show ip tcp header-compression (53)1.2.4 show rate-limit (53)1.2.5 show policy-map (54)1.2.6 show queue (60)1.2.7 show traffic-shape (61)1.2.8 show traffic-shape queue (62)1.2.9 show traffic-shape statistics (63)第一章配置QOS命令1.1QOS配置命令QOS配置命令有：z bandwidth (policy-map class)z class (policy-map)z class-mapz custom-queue-listz debug qosz debug ip rtpz debug ip tcpz dropz fair-queuez hold-queuez ip rtp compression-connectionsz ip rtp header-compressionz ip tcp compression-connectionsz ip tcp header-compressionz match access-groupz match input-interfacez match ip dscpz match ip precedencez match notz match protocolz max-reserved-bandwidthz policy-mapz policez priorityz priority-groupz priority-list defaultz priority-list interfacez priority-list protocolz priority-list queue-limitz queue-limitz queue-list defaultz queue-list interfacez queue-list protocolz queue-list queue byte-countz queue-list queue limitz rate-limitz random-detectz random-detect dscpz random-detect dscp-basez random-detect prec-basedz random-detect precedencez random-detect exponential-weighting-constantz service-policyz set ip dscpz set ip precedencez shape averagez shape peakz shape max-buffersz traffic-shape groupz traffic-shape ratez show class-mapz show ip rtp header-compressionz show ip tcp header-compressionz show rate-limitz show policy-mapz show queuez show traffic-shapez show traffic-shape queuez show traffic-shape statistics1.1.1bandwidth (policy-map class)本命令将为规则映射表中引用的类映射表分配带宽。

极限网络ExtremeSwitching X450-G2系列产品数据表说明书

Data SheetExtremeSwitching ™ X450-G2 SeriesScalable advanced aggregation switch with ExtremeXOS® modular operating system.The ExtremeSwitching X450-G2 series is based on Extreme Networks revolutionary ExtremeXOS, a highly resilient OS that provides continuous uptime, manageability and operational efficiency. Each switch offers the same high-performance, nonblocking hardware technology, in the Extreme Networks tradition of simplifying network deployments through the use of common hardware and software throughout the network.The X450-G2 switches are effective campus edge switches with IEEE802.3at PoEplus. The X450-G2 series is also an option for DSLAM or CMTS aggregation, or for active Ethernet access.Comprehensive Security Management• Role-based policy and host integrity enforcement, and identity management• Universal Port Dynamic Security Profiles to provide fine granular security policies in the network • Threat detection and response instrumentation to react to network intrusion with CLEAR-Flow Security Rules Engine • Denial of Service (DoS) protection and IP security against man-in-the-middle and DoS attacks to harden the network infrastructure • Role-based Policy enables support for policy profiles to secure and provision network resources based upon the role the user or device plays within the network.HighlightsPerformance• 48-port or 24-port Gigabit Ethernet models• 4 ports of SFP+ 10GbE/1GbE or 4 ports of SFP 1GbE on front faceplate • All configurations Non-blocking full duplex• Copper and PoE-Plus models • Built-in 21Gbps stacking ports on rear panel for all models (SummitStack-V84)• Optional SummitStack-V 40 Gbps stacking across two 10Gb front- panel portsFeatures• Secure Network Accessthrough Rolebased policy or Identity Management • Front-to-Back airflow • Modular PoE power supplies• 850W of PoE-Plus budget with 1 PSU • 1440W of PoE-Plus Budget with 2 PSUs• Y .1731 OAM Measurements in hardware for accuracy • Energy Efficient Ethernet – IEEE 802.3az• Hot-swappable fan tray and PoEpower suppliesFlexible Port ConfigurationAll models come equipped with either 4 ports of SFP+ 10 GbE or 4 ports of SFP 1GbE resident on the faceplate of each model.High-Performance StackingUp to eight X450-G2 switches can be stacked usingtwo different methods of stacking: SummitStack-V, and SummitStack-V84. Each X450-G2 unit comes equipped with 2 ports of 21 Gigabit stacking ports via a QSFP interface. Standard passive 40Gb copper cables can be used for stacking X450-G2s together. SUMMITSTACK-V — Flexible Stacking Over10 Gigabit EthernetExtremeXOS supports the SummitStack-V capability using 2 of the native 10 GbE ports on the faceplate as stacking ports, enabling the use of standard cabling and optics technologies used for 10 GbE SFP+. SummitStack-V provides long-distance stacking connectivity of up to 40 km while reducing the cable complexity of implementing a stacking solution. SummitStack-V is compatible withX440-G2, X450-G2 and X460-G2 switches with 10Gb uplinks, as well as X480, X670, X670V, X670-G2 and X770 switches. SummitStack-V enabled 10 GbE ports must be physically direct-connected with all switches running the same version of ExtremeXOS.SUMMITSTACK-V84 — High-Speed Stacking Over Dedicated Stacking PortsThe X450-G2 also supports high-speed 84 Gbps stacking, which is ideal for demanding applications where a high volume of traffic traverses through the stacking links,yet bandwidth is not compromised through stacking. SummitStack-V84 is supported over passive copper QSFP cables (up to 7m). SummitStack-V84 is only supported on X450-G2 switches running the same version of ExtremeXOS.NOTE: SummitStack-V84 is NOT interoperable with SummitStack-V80 Intelligent SwitchingThe X450-G2 Series supports sophisticated and intelligent Layer 2 switching, as well as Layer 3 IPv4/IPv6 routing including policy-based switching/routing, Provider Bridges, bidirectional ingress and egress Access Control Lists, and bandwidth control by 8 Kbps granularity both for ingress and egress.IEEE 802.3AT PoE-PlusIEEE 802.3af Power over Ethernet has been widely usedin the campus enterprise edge network for Ethernet-powered devices such as wireless access points, Voiceover IP phones, and security cameras. Ethernet port extenders such as Extreme Networks ReachNXT™ 100-8t can also utilize PoE, making installation and management easier and reducing maintenance costs. The newer IEEE 802.3at PoEplus standard expands upon Power over Ethernet by increasing the power limit up to 30 watts, and by standardizing power negotiation by using LLDP. TheX450-G2 supports IEEE 802.3at PoE-plus and supports standards-compliant PoE devices today and into the future. Role-Based PolicyUtilizing ExtremeManagement Policy Management, the role-based policy framework empowers a network administrator to define distinct roles or profiles that represent industry specific operational groups that may exist in an education or a business environment (e.g., administrator, teacher, student, guest). Each defined role is granted individualized access to specific network services and applications and these access privileges remain associated with users as they move across both wired and wireless network access points. Users can be authenticated via IEEE 802.1X, MAC address, or web authentication, and then assigned a pre-defined operational role. Network operations can be seamlessly tailored to meet business-oriented requirements by providing each role with individualized access to network services and applications, thus aligning network resource utilization with business goals and priorities.Audio Video BridgingThe X450-G2 series supports IEEE 802.1 Audio Video Bridging (AVB) to enable reliable, real-time audio/video transmission over Ethernet. AVB technology delivers the quality of service required for today’s high-definition and time-sensitive multimedia streams.Ordering NotesThe X450-G2 base switches do not ship with fan trays —these must be ordered separately. The X450-G2 PoE switches support modular power supplies and these must be ordered separately. The non-PoE X450-G2 switches have a fixed internal power supply so a power supply does not need to be ordered separately.SpecificationsPerformance and Scale• Less than 4 microsecond latency (64-byte)• Layer 2/MAC Addresses: 68K • IPv4 LPM Entries: 16K• IPv6 LPM (64-bit) Entries: 8K • IPv6 LPM (128-bit) Entries: 256• 4094 VLAN/VMANs• 9216 Byte Max Packet Size (Jumbo Frame)• 128 load sharing trunks, up to 32 members per trunk • 1,024 ingress bandwidth meters•Ingress and egress bandwidth policing/rate limiting per flow/ACL• 8 QoS egress queues/port• Egress bandwidth rate shaping per egress queue andper port*Includes stacking ports.• Rate Limiting Granularity: 8 Kbps• All ports Full Duplex - half duplex operation is not supported• Policy Capabilities • Policy Profiles: 63• Rules per Profile: Up to 1464• Authenticated Policy Users per Switch: Up to 6,144• Authenticated Policy Users per Port: Up to 6,144• Unique Permit/Deny Rules per switch: 1464• MAC Rules: 512• IPv4 Rules: 1280• IPv6 Rules: 256• L2 Rules: 184• Rate Limiting: Per Class of ServiceNOTE: Policy and rule limits here reflect support available in EXOS 22.4.External PortsPhysicalNOTE: Switch weights include installed fan module. PoE switches do not include PSUs.* Please refer to the Summit Family Switches Hardware Installation Guide for packaged weight and dimensions.LED Indicators• Per port status LED including power status • System Status LEDs: management, fan and power • 7 segment display of stack numberPowerThe Non-PoE SwitchesCPU/Memory• 64-bit MIPS Processor, 1 GHz clock, dual core • 1GB ECC DDR3 DRAM • 4GB eMMC Flash • 4MB packet bufferPoE Power Supply Units (Only Front-to-Back Supplies Are Supported)† - The power supplies will continue to operate +- 10% of the rated input to accommodate temporary loss of input voltage regulationPoE-Plus Power BudgetEnvironmental Specifications• EN/ETSI 300 019-2-1 v2.1.2 - Class 1.2 Storage • EN/ETSI 300 019-2-2 v2.1.2 - Class 2.3 Transportation • EN/ETSI 300 019-2-3 v2.1.2 - Class 3.1e Operational • EN/ETSI 300 753 (1997-10) - Acoustic Noise • ASTM D3580 Random Vibration Unpackaged 1.5 GEnvironmental Compliance• EU RoHS: 2011/65/EU • EU WEEE: 2012/19/EU • China RoHS: SJ/T 11363-2006• T aiwan RoHS: CNS 15663 (2013.7)Operating Conditions• T emp: 0° C to 50° C (32° F to 122° F)• Humidity: 10% to 95% relative humidity, non-condensing • Altitude: 0 to 5,000 meters (16,404 feet) – PoE switches• Altitude: 0 to 2,000 meters (6,562 feet) – non- PoE switches• Shock (half sine): 30 m/s2 (3 G), 11 ms, 6 shocks • Random vibration: 3 to 500 Hz at 1.5 G rmsPackaging and Storing Specifications• T emp: -40° C to 70° C (-40° F to 158° F)• Humidity: 10% to 95% relative humidity, non-condensing • Packaged Shock (half sine): 180 m/s2 (18 G), 6 ms, 600 shocks• Packaged Vibration: 5 to 62 Hz at velocity 5 mm/s, 62 to 500 Hz at 0.2 G• Packaged Random Vibration: 5 to 20 Hz at 1.0 ASD w/–3 dB/oct. from 20 to 200 Hz• Packaged Drop Height: 14 drops minimum on sides and corners at 42 inches (<15 kg box)Regulatory and Safety• North American ITE• UL 60950-1 2nd edition A2:2014, Listed Device (U.S.)• CSA 22.2 No. 60950-1 2nd edition 2014 (Canada)• EN 60825-1:2007/IEC 60825-1:2007 Class 1(Lasers Safety)• CDRH Letter of Approval (US FDA Approval)• European ITE• EN 60950-1:2006+A11:2009+A1:2010+A12:2011+A2:2013 2nd Ed.• EN 60825-1:2007/IEC 60825-1:2007 Class 1(Lasers Safety)• 2014/35/EU Low Voltage Directive• International ITE• CB Report & Certificate per IEC 60950-1 :2005+A1:2009+A2:2013 + National Differences• AS/NZS 60950-1 (Australia /New Zealand)EMI/EMC Standards• North American EMC for ITE• FCC CFR 47 part 15 Class A (USA)• ICES-003 Class A (Canada)• European EMC Standards• EN 55032: 2015 Class A• EN 55024: 2010• EN 61000-3-2: 2014 (Harmonics)• EN 61000-3-3: 2013 (Flicker)• EN 300 386 v1.6.1 (EMC T elecommunications)• 2014/30/EU EMC Directive• International EMC Certifications• CISPR 32:2015, Class A (International Emissions)• AS/NZS CISPR32: 2015• CISPR 24:2010 Class A (International Immunity)• IEC 61000-4-2:2008/EN 61000-4-2:2009Electrostatic Discharge, 8kV Contact, 15 kV Air,Criteria B• IEC 61000-4-3:2010/EN 61000-4-3:2006 +A1:2008+A2:2010 Radiated Immunity 10V/m, Criteria A• IEC 61000-4-4:2012. / EN 61000-4-4:2012 Transient Burst, 1 kV, Criteria A• IEC 61000-4-5:2014 /EN 61000-4-5:2014 Surge, 1 kV L-L, 2 kV L-G, Level 3, Criteria B• IEC 61000-4-6:2013/EN 61000-4-6:2014 ConductedImmunity, 0.15-80 MHz, 10Vrms, 80%AM (1kHz)Criteria A• IEC/EN 61000-4-11:2004 Power Dips & Interruptions, >30%, 25 periods, Criteria CCountry Specific• VCCI Class A (Japan Emissions)• ACMA RCM (Australia Emissions)• CCC Mark• KCC Mark, EMC Approval (Korea)Telecom Standards• CE 2.0 CompliantIEEE 802.3 Media Access Standards • IEEE 802.3ab 1000BASE-T• IEEE 802.3z 1000BASE-X• IEEE 802.3ae 10GBASE-X• IEEE 802.3at PoE Plus• IEEE 802.3az (EEE)Fan and Acoustic Noise* Sound Pressure is presented for comparison per ISO 7779**Declared Sound Power is presented in accordance with ISO-7779, ISO 9296 per ETSI/EN 300 753AccessoriesModular Fan Tray for All x450-G2 Switches• X460/X450-G2 fan module FB• Front-to-back airflow fan module for X460/X450-G2 series switchesExternal Redundant Power Supplies forNon-PoE SwitchesAll X450-G2 series non-PoE switches ship with one fixed internal power supply. If redundancy is required, an external RPS can be attached to the switch.Modular Power Supplies for PoE X450-2 Switches• STK-RPS-150PS• 150 watt non-PoE redundant power supply for X450-G2 switches• EPS-C2• External Power System Chassis 2. Accepts up to three 750W AC PoE PSU 48V power supplies.Accepts up to 5 EPS-CBL-2x7 or up to 1 EPS-CBL-2x9 cables.• EPS-CBL-2x7• External Power System Cable (1M) that connects EPS to any X440 or X450-G2 non-PoE switch forproviding redundant DC power.• 750W AC PSU• AC Power Supply module for EPS-C2 Chassis Redundant Power SupplyThe STK-RPS-150PS can be rack mounted into the two slotRPS chassis STK-RPS-150CH2 where the power supplies are horizontally mounted or the eight slot RPS chassis STK-RPS-150CH8 where the power supplies are vertically mounted.All X450-G2 series PoE switches support modular power supplies and do NOT ship with a power supply. Either a 715 watt or 1100 watt power supply needs to be added.Only front-to-back power supplies and fans are certified for use in the X450-G2 PoE switches.• 715W PoE AC PSU FB• 715W PoE AC PSU with front-to-back airflow is compatible with X450-G2-24p/48p switches andprovides 500 watts of PoE-plus power budget perone supply. When two PSUs are installed, the totalPoE-plus power budget becomes 1031 watts.• 1100W PoE AC PSU FB• 1100W PoE AC PSU with front-to-back airflow is compatible with X450-G2-24p/48p switches andprovides 850 watts of PoE-plus power budget perone supply. When two PSUs are installed, the totalPoE-plus power budget becomes 1440 watts.*Optional: Redundant or Additive Power Supply ordered separately**Required: First Power Supply ordered separatelyOrdered EmptyShipped EmptyOrdered Empty Shipped Empty*Ordering InformationOrdering Information (cont.)/contact Phone +1-408-579-2800 ©2017 Extreme Networks, Inc. All rights reserved. Extreme Networks and the Extreme Networks logo are trademarks or registered trademarks of Extreme Networks, Inc. in the United States and/or other countries. All other names are the property of their respective owners. For additional information on Extreme Networks Trademarks please see /company/legal/trademarks. Specifications and product availability are subject to change without notice. 9718-1217-1911Ordering Information (cont.)NOTE: PoE Power Supplies and fan tray MUST be ordered separately. Only non-PoE switches ships with a fixed internal power supply1 1Gb Mode Only2 Supported configuration is to populate every other SFP+ port in system, with a maximum of half the 10Gb SFP+ ports configured with 10GBASE-T transceivers. An adjacent SFP+ port should remain unused for every 10GBASE-T SFP+ installed.。

AXIS M3106-LVE Mk II 网络摄像头说明文档说明书

DatasheetAXIS M3106-LVE Mk II Network CameraDiscreet,outdoor-ready4MP video surveillance with built-in IR illuminationAXIS M3106-LVE Mk II is an affordable,outdoor-ready fixed mini dome with a flat-faced design that suppresses ing WDR technology and IR illumination,it provides compact HDTV surveillance even in challenging light conditions or total darkness.The smart design allows for easy repainting,or using the optional black accessory casing to blend the camera into its environment.Axis Zipstream technology reduces bandwidth and storage requirements.A variety of accessories are available for flexible and easy installation.>Built-in IR illumination>Quad HD/4MP video>Wide Dynamic Range(WDR)>Axis Zipstream technology>Smart design for easy,flexible installationAXIS M3106-LVE Mk II Network Camera CameraImage sensor1/3"progressive scan RGB CMOSLens M12mount,Fixed iris,Fixed focus2.4mm,F2.2Horizontal field of view:130°Vertical field of view:73°Day and night Automatically removable infrared-cut filterMinimum illumination Color:0.3lux at50IRE,F2.2 B/W:0.06lux at50IRE,F2.2 0lux with IR illumination onShutter speed1/31500s to1/5sCamera angle adjustment Pan:±180°Tilt:0°to60°(0°=lens directed at a right angle to camera base) Rotation:±95°Can be directed in any direction and see the wall/ceilingVideoVideo compression H.264(MPEG-4Part10/AVC)Main and High Profiles H.265(MPEG-H Part2/HEVC)Main Profile Motion JPEGResolution2688x1520to320x240Frame rate Up to25/30fps with power line frequency50/60HzVideo streaming Multiple,individually configurable streams in H.264,H.265and Motion JPEGAxis Zipstream technology in H.264and H.265Controllable frame rate and bandwidthVBR/MBR H.264/H.265Multi-viewstreamingUp to2individually cropped out view areas in full frame rate Pan/Tilt/Zoom Digital PTZImage settings Compression,Color,Brightness,Sharpness,Contrast,Whitebalance,Exposure control,WDR:up to100dB depending onscene.Rotation:0°,90°,180°,270°including Corridor Format,Text and image overlay,Privacy masks,Mirroring of images NetworkSecurity Password protection,IP address filtering,HTTPS a encryption,IEEE802.1x(EAP-TLS)a network access control,Digestauthentication,User access log,Centralized CertificateManagement,brute force delay protection,signed firmwareSupported protocols IPv4,IPv6USGv6,HTTP,HTTPS a,SSL/TLS a,QoS Layer3DiffServ, FTP,SFTP,CIFS/SMB,SMTP,Bonjour,UPnP TM,SNMP v1/v2c/v3 (MIB-II),DNS,DynDNS,NTP,RTSP,RTP,TCP,UDP,IGMP,RTCP, ICMP,DHCP,ARP,SOCKS,SSH,LLDP,MQTT v3.1.1System integrationApplication Programming Interface Open API for software integration,including VAPIX®and AXIS Camera Application Platform;specifications at AXIS Video Hosting System(AVHS)with One-Click Connection ONVIF®Profile G,ONVIF®Profile S,and ONVIF®Profile T, specification at Analytics IncludedAXIS Video Motion Detection,active tampering alarmSupportedAXIS Digital Autotracking,AXIS Fence Guard,AXIS Motion Guard,AXIS Loitering Guard,AXIS People Counter,AXIS Queue Monitor,AXIS Occupancy Estimator,AXIS Direction Detector,AXIS Tailgating Detector,AXIS Random SelectorSupport for AXIS Camera Application Platform enablinginstallation of third-party applications,see /acap Event triggers Analytics,Edge storage events,Virtual inputs through API Event actions File upload:FTP,SFTP,HTTP,HTTPS,network share,emailNotification:email,HTTP,HTTPS,TCP,SNMP trapVideo recording to edge storageSend video clipPre-and post-alarm video bufferingOverlay textData streaming Event dataBuilt-ininstallation aidsPixel counterGeneralCasing IP66-,NEMA250Type4X,and IK08-rated,ASA polymer casingEncapsulated electronics,Captive screws(Torx10)Color:White NCS S1002-BFor repainting instructions and impact on warranty,contactyour Axis partnerSustainability PVC freeMemory512MB RAM,256MB FlashPower Power over Ethernet(PoE)IEEE802.3af/802.3at Type1Class3Typical:5.1W,Max.:7.9WConnectors RJ4510BASE-T/100BASE-TX PoEIR illumination Power-efficient,long-life850nm IR LEDs.Range of reach15m(50ft)or more depending on the sceneStorage Support for microSD/microSDHC/microSDXC cardSupport for SD card encryptionSupport for recording to network-attached storage(NAS)For SD card and NAS recommendations see Operatingconditions–30°C to50°C(–22°F to122°F)Humidity10–100%RH(condensing)Storageconditions-40°C to65°C(-40°F to149°F)Approvals EMCEN55022Class B,EN55024,IEC62471,EN61000-6-1,EN61000-6-2,FCC Part15Subpart B Class B,ICES-003Class B,VCCI Class B,RCM AS/NZS CISPR22Class B,KCC KN32Class A,KN35EnvironmentIEC60068-2-1,IEC60068-2-2,IEC60068-2-78,IEC60068-2-14,IEC60068-2-6,IEC60068-2-27,IEC/EN62262IK08,IEC/EN60529IP66,NEMA250Type4X,IEC60721-3-4Class4M3SafetyIEC/EN/UL62368-1,IS13252NetworkNIST SP500-267Dimensions Height:94mm(3.7in)ø101mm(4.0in)Weight370g(0.81lb)IncludedaccessoriesInstallation Guide,Windows decoder1-user license,Torx L-key,Connector guardOptionalaccessoriesAXIS T94B02D Pendant kitAXIS T94B01P Conduit Back BoxAXIS T94B02M J-Box/Gang Box PlateAXIS M31-LVE Casing,BlackAxis MountsAXIS Surveillance microSDXC™CardFor more accessories,see VideomanagementsoftwareAXIS Companion,AXIS Camera Station,Video managementsoftware from Axis’Application Development Partners availableon /vmsLanguages English,German,French,Spanish,Italian,Russian,SimplifiedChinese,Japanese,Korean,Portuguese,Traditional Chinese Warranty Axis3-year warranty and AXIS Extended Warranty option,see/warrantya.This product includes software developed by the OpenSSL Project for use in the OpenSSL Toolkit.(),and cryptographic software written by Eric Young(*****************).Environmental responsibility:/environmental-responsibility©2016-2021Axis Communications AB.AXIS COMMUNICATIONS,AXIS,ARTPEC and VAPIX are registered trademarks ofAxis AB in various jurisdictions.All other trademarks are the property of their respective owners.We reserve the right tointroduce modifications without notice.T10093343/EN/M12.3/2101。

QoS常见问题

QoS常见问题前⾔本⽂讨论多数常见问题(常见问题)相关对服务质量(QoS)。

⼀般问题问。

什么是服务质量(QoS) ？问。

什么是拥塞、延迟和抖动？问。

MQC 是什么？问。

service-policy is supported only on VIP interfaces with DCEF enabled 消息意味着什么？Q.多少类服务质量(QoS)策略⽀持？A.在 12.2 之前的 Cisco IOS 版本中，最多可以定义 256 个类，如果将相同的类重复⽤于不同策略，在每个策略内最多可以定义 256 个类。

如果您有⼆个策略，两个策略的级别总数都不应超过 256。

如果策略包括基于类别的加权公平队列(CBWFQ) (意味着在任何类别内包含带宽[或优先]语句)，所⽀持的全部类别数量是64。

在 Cisco IOS12.2(12)，12.2(12)T 和 12.2(12)S 版本中，256 全局类别映射的限制被更改，并且可以配置多达 1024 个全局类映射，并在同⼀策略映射中使⽤ 256 个类映射。

问。

当服务策略应⽤时，路由更新和点对点协议(PPP)/⾼级数据链路控制(HDLC) Keepalive如何被处理？A. Cisco IOS 路由器采⽤以下两种机制设置控制数据包的优先级：问。

服务质量(QoS)⽀持的在接⼝配置与集成路由和桥接？答：不能。

当接⼝配置为⽤于 IRB 时，您⽆法配置 QoS 功能。

答：分类和标记问。

什么是服务质量(QoS)预分类？问。

哪些数据包报头字段可以重新标记？可⽤的值有哪些？问。

能否根据 URL 设置流量的优先级？问。

⽀持什么平台和Cisco IOS软件版本基于⽹络的应⽤程序识别(NBAR) ？A.以下版本的 Cisco IOS 软件引⼊了对 NBAR 的⽀持：平台最低 Cisco IOS 软件版本720012.1(5)T710012.1(5)T366012.1(5)T364012.1(5)T362012.1(5)T260012.1(5)T170012.2(2)T注意：需要启⽤ Cisco 快速转发 (CEF) 才能使⽤ NBAR。

simulink模块的分类及用途解析教学内容

simulink模块的分类及用途Commsim 2001 Education模块化通信仿真软件产品编号：808-110(单),112 (10), 115 (25)Commsim 2001是一个理想的通信系统的教学软件。

它很适用于如’信号与系统’、’通信’、’网络’ 等课程，难度适合从一般介绍到高级。

使学生学的更快并且掌握的更多。

Commsim200含有200多个通用通信和数学模块，包含工业中的大部分编码器，调制器，滤波器，信号源,信道等，Commsin2001中的模块和通常通信技术中的很一致，这可以确保你的学生学会当今所有最重要的通信技术。

要观察仿真的结果，你可以有多种选择：时域，频域，XY图，对数坐标，比特误码率，眼图和功率谱。

Scalable Fun cti on alityLike all other Electronics Workbench products Commsim 2001 is available in three tiers for the education community:Single: For use by professors/teachers in the creation of lectures, lessons, assignments etcLab: For use by students in on-campus computer labsStudent：A special version for use by students on home PCs onlyHow Commsim is UsedCommsim 2001 is a powerful yet easy to use simulation tool that provides fast, accurate viewing of signals at anypoint in your system, via a natural sequence of steps. This power is presented to the user through an intuitive GUI(graphicalUser Interface) enabling drag and drop simplicity, just like all of the other products in the Electronics Workbench Family.Features at a Glan ce:* Industry's Largest Library«200+ Blocks«Communication & Math Blocks«Build your own Blocks/Models«Drag and Drop Diagram Construction* Analog, Digital & Mixed Systems«Automatic Wiring* Analog and Digital Modulators/Demodulators«Wide variety of Encoders/Decoders«Adaptive Equalizers«Vector and Matrix Operations* All popular Channel Models* Filter Design Wizard and Response Viewer«PLLs* RF Elements and Accurate Distortion* Complex Math* Complex Envelope Representation* Continuous, Discrete and Hybrid Simulation* Autorestart and Single Step Algorithms« Euler, Trapezoidal and Runge Kutta Integration Methods * Look-up Table Wizard* Signal Probes«Large variety of Plot Options«Mathcad, Matlab OLE IntegrationPlac ing and Conn ect ing BlocksPlace desired blocks from the library by dragging and dropping(from either the menusor the toolbar) any of the over 200 functional blocks available. Once placed, connecting blocks is extremely straightforward-just click on one block's output then on other blocks input and Commsim takes care of the rest. Its that simple!You can also make use of hierarchical blocks to break up more complex systems, each of whichcan be assigned its own symbol.Blocks LibrariesThe science of understanding and teaching communication systems lies in being aware of a widevariety of "functional blocks" of technology available to "construct" the optimal transmitter or receiver, given a particular type of signal and channel.Commsim 2001 helps you to ensure your students learn all of today's most important communication technologies by delivering blocks to match all of the commonly used techniques in communications.The commsimlibrary contains the industry's largest selection of coders, modulators, filters, sources, channels etc. You can even create your own blocks using equations or lower level functional blocks.Library BlocksBecause the right library is so essential to a good communications simulator, we have explained each family of blocks in detail. Simply click on the family to view more information.ChannelsEncoding/DecodingModulators/DemodulatorsOther Communication BlocksBasic BlocksChann elsModeling the medium through which a transmitted signal must pass is essential to accurately capture delay and distortion effects. Channels include copper wire, fiber, free space, etc.Cha nnel Blocks Modeled in Commsim 2001* Add.White Gaussian Noise (Complex & Real)* Binary Symmetric Channel* Jakes MobileMultipathPropagation Loss * Rice/Rayleigh Fading« Rummler Multipath« TWTAEn cod in g/Decod ingSingle encoding is performed to increase the reliability of information transfer and can include companding and quantization (analog signals) or forward error correction (using convolutional or trellis cooling on digital signals).Commsim 2001 in cludes the followi ng En coders/Decoders* Block Interleaver* Convolutional Encoder«Convolutional Interleaver* Gray Decoder«Gray Encoder* Trellis Decoder« Viterbi Decoder (Hard & Soft)Modulators/DemodulatorsCommsim provides the following analog and digital modulators/demodulation blocks, a subset of which use coherent methods(require phase synchronization in demodulation):Commsim 2001 in cludes the followi ng Modulators/Demodulators* AM* DQPSK* pi/4-DQPSK* FM* FSK* I/Q* MSK* PM* PAM (4,8)* PPM* PSK (2,4,8,16)* QAM (16,32,64,256)* SQPSK・DQPSK・pi/4-DQPSK Detector« FM Demodulator・PPM Demodulator« PSK Detector (2,4,8,16)«PAM Detector (2,4,8,16)・QAM Detector (16,32,64,256)Other BlocksCommsim 2001 also provides many other communication blocks (filters, PLLs, digital etc.) and general mathematical functions (complex math, estimatio, etc.)Communication & General Mathematical Blocks Modeled in Commsim 2001• Addtion• Conjugate•Conversions (Complex &Real)• Division• Inverse• Multiplication• Power• Square Root*Adaptive Equalizer(Complex & Real)* File FIR* FIR* IIR* MagPhase* Sampled FileFIR* Sampled FIR* Binary Counter* Bits to Symbol* Divide by N* D Flip Flop * JK Flip Flop* Mux/Demux *Paralell toSerial* Queue*Serial toParalell* Symbol to Bits• Charge Pump• PLL Loop Filters (2nd &3rd Order)•Type 2 PhaseDetector•Type3Phase/Frequency Detector•Type4Phase/Frequency DetectorBasic BlocksCommsir2001 offers over 90 blocks for linear, non linear, continous, discrete-time, time varying, and hybrid system design.Basic Blocks Modeled in Commsim 2001* Animation* Annotation* Arithmetic* BooleanDDEIntegrationLinear SystemsMatlab InterfaceMatrix OperationsNonlinearOptimizationRandom GeneratorSignal ConsumerSignal ProducerTime DelayTranscendentalCDM軀信系统的MATLA仿真学习好资料张广森，王虎（中国民航学院通信工程系，天津300300 ）摘要：在简要介绍MATLAB^言的基础上，对使用MATLAB^言仿真的CDMA 通信系统进行描述。

LLQ

LLQ配置LLQ 把数据包放到优先队列中，这些队列的数据包会被优先转发，队列中的数据包没有转发完之前不会转发其它类别的数据。

class-map match-any MAP1match protocol httpmatch access-group 100class-map match-any MAP2match protocol telnetmatch protocol sshclass-map match-any MAP3match ip precedence 5match ip dscp efpolicy-map LLQclass MAP1bandwidth percent 30queue-limit 128class MAP2bandwidth percent 20class MAP3priority percent 10class class-defaultfair-queue 256random-detectinterface Serial0/0service-policy output LLQR1#show policy-map int s0/0Serial0/0Service-policy output: LLQClass-map: MAP1 (match-any)0 packets, 0 bytes5 minute offered rate 0 bps, drop rate 0 bps Match: protocol http0 packets, 0 bytes5 minute rate 0 bpsMatch: access-group 1000 packets, 0 bytes5 minute rate 0 bpsQueueingOutput Queue: Conversation 265Bandwidth 30 (%)Bandwidth 463 (kbps)Max Threshold 128 (packets) (pkts matched/bytes matched) 0/0(depth/total drops/no-buffer drops) 0/0/0Class-map: MAP2 (match-any)0 packets, 0 bytes5 minute offered rate 0 bps, drop rate 0 bpsMatch: protocol telnet0 packets, 0 bytes5 minute rate 0 bpsMatch: protocol ssh0 packets, 0 bytes5 minute rate 0 bpsQueueingOutput Queue: Conversation 266Bandwidth 20 (%)Bandwidth 308 (kbps)Max Threshold 64 (packets) (pkts matched/bytes matched) 0/0(depth/total drops/no-buffer drops) 0/0/0Class-map: MAP3 (match-any)0 packets, 0 bytes5 minute offered rate 0 bps, drop rate 0 bpsMatch: ip precedence 50 packets, 0 bytes5 minute rate 0 bpsMatch: ip dscp ef (46)0 packets, 0 bytes5 minute rate 0 bpsQueueingStrict PriorityOutput Queue: Conversation 264Bandwidth 10 (%)Bandwidth 154 (kbps) Burst 3850 (Bytes)(pkts matched/bytes matched) 0/0(total drops/bytes drops) 0/0Class-map: class-default (match-any)24 packets, 1760 bytes5 minute offered rate 0 bps, drop rate 0 bpsMatch: anyQueueingFlow Based Fair QueueingMaximum Number of Hashed Queues 256(total queued/total drops/no-buffer drops) 0/0/0exponential weight: 9class Transmitted Random drop Tail drop Minimum Maximum Mark pkts/bytes pkts/bytes pkts/bytes thresh thresh prob0 24/1760 0/0 0/0 20 40 1/101 0/0 0/0 0/0 22 40 1/102 0/0 0/0 0/0 24 40 1/103 0/0 0/0 0/0 26 40 1/104 0/0 0/0 0/0 28 40 1/105 0/0 0/0 0/0 30 40 1/106 0/0 0/0 0/0 32 40 1/107 0/0 0/0 0/0 34 40 1/10 rsvp 0/0 0/0 0/0 36 40 1/10。

交换机QOS配置模板

交换机QOS配置模板2009-5-12 来源:ruijie 作者:ruijie 【大中小】点击：1766 次police在class 配置模式下使用此命令为该数据流中定义policer，目前的policer 支持限制该数据流的带宽和为带宽超限部分指定处理动作。

police rate-bps burst-byte [exceed-action{drop | dscp dscp-value}]rate-bps 每秒钟的带宽限制量，对于10/100M 以太网接口来说取值范围是1～100Mbsp，对于1000M 以太网接口来说取值范围是8～1000Mbsp。

burst-byte 猝发流量限制值，单位是比特（byte）。

exceed-action drop 丢弃带宽超限部分的报文。

exceed-action dscp dscp-value 改写带宽超限部分报文的DSCP值。

dscp-value 的取值范围是0, 8, 10, 16, 18, 24, 26, 32, 34, 40, 46, 48, 56.缺省值缺省没有设置任何policer。

命令模式class 配置模式。

使用指导目前的policer 支持限制该数据流的带宽和为带宽超限部分指定处理动作；rate-bps 是每秒钟的带宽限制量，对于10/100M 以太网接口来说取值范围是1～100Mbsp，对于1000M 以太网接口来说取值范围是8～1000Mbsp；burst-byte是猝发流量限制值，单位是比特（byte）。

您可以在命令中指定关键字drop 来丢弃带宽超限部分的报文；您也可以在命令各种指定dscpdscp-value来改写带宽超限部分报文的DSCP 值；使用show policy-map 命令查看设置。

配置示例：Switch(config)#access-list 15 permit tcp host 192.1.1.1Switch(config)#class-map class1Switch(config-cmap)#match access-group 15Switch(config-cmap)#exitSwitch(config)# policy-map policy1Switch(config-pmap)#class class1Switch(config-pmap-c)#police 100000 exceed-action dscp 22Switch(config-pmap-c)#set ip dscp 8Switch(config-pmap-c)#exitSwitch(config-pmap)#exitSwitch(config)#interface fastethernet 0/2Switch(config-if)#service-policy input policy命令描述class-map 创建一个class map，并进入class map 配置模式。

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Rate And Queue Controlled Random Drop (RQRD):A Buffer Management Scheme forInternet RoutersMansour J.Karam,Fouad A.TobagiAbstract—A buffer management scheme destined to be deployed in In-ternet routers should provide an adequate handling of all trafﬁc types,in-cluding UDP and TCP trafﬁc as well as fairness among competingﬂows.In core routers,keeping per-ﬂow state and taking per-ﬂow actions is strongly discouraged,because of the scalability issues that ensue.Consequently, CSFQ[12]adopts a distributed architecture,and uses rate information to provide fairness in core routers.However,we show that CSFQ is sensitive to the setting of its parameters and often leads to a reduction in aggregate throughput.In this paper,we present Rate and Queue controlled Random Drop(RQRD),a buffer management scheme which is based on CSFQ’s dis-tributed architecture,but adds queue size information,as in RED,and pro-vides two drop precedences to achieve all the objectives above.We show that RQRD provides an adequate service in the context of both the present and the future Internet.I.I NTRODUCTIONThe Internet must support trafﬁc types which are very differ-ent in nature,generated by various applications using either the TCP or UDP transport protocol.In today’s Internet,trafﬁc of all types is served by a single FIFO queue and share the same bandwidth resources on the link.The traditional view which is that TCP trafﬁc is the real and useful trafﬁc,whereas UDP traf-ﬁc is only an additional nuisance1has led to the development of buffer management schemes either aimed to serve TCP trafﬁc, or to protect TCP trafﬁc from competing UDPﬂows(e.g.,RED [4],CSFQ[12]).However,in the context of an Integrated Ser-vices network,UDP is not always undesirable,despite its non-responsive nature.(For example,in the case of a video stream, the excessive loss of packets renders the stream useless at the receiver.)Consequently,(1)it is important for a buffer manage-ment scheme to provide a service that is adequate to both UDP and TCP trafﬁc.In addition,it should be able to differentiate between different UDPﬂows,in support of applications such as layered video and voice.Moreover,(2)a buffer management scheme should be equipped to provide fairness among compet-ingﬂows.For example,unfriendly UDP trafﬁc should not starve competing TCPﬂows.Also,if different customers are paying for the same service,each should be capable of getting the same service rate from the network.Nevertheless,no per-ﬂow state should be kept in routers given the scalability issues that ensue. Also,fairness should not be achieved at the expense of through-put.Finally,(3)a buffer management scheme should be robust. It should perform effectively for a wide range of conditions in terms of buffer size,trafﬁc characteristics and trafﬁc mix.Also, its performance should not be too sensitive to the setting of its parameters.The authors are with the Computer Systems Laboratory,Stanford University, Stanford CA94305USA(e-mail:{mans,tobagi}@).This belief is triggered by the original vocation of the Internet,which is to serve TCP data trafﬁc,and is reinforced by the responsive nature of TCP trafﬁc.Since keeping per-ﬂow state and taking per-ﬂow actions is strongly discouraged,the design of such a scheme is a chal-lenging task.For example,RED uses queue size information to improve TCP throughput but is neither equipped to provide fairness among various competingﬂows,nor is effective in the presence of UDP trafﬁc;on the other hand,CSFQ uses rate in-formation to protect TCP trafﬁc from competing UDPﬂows, but(as we show in this paper)can lead to a massive reduction in achievable throughput.In this paper,we present Rate and Queue controlled Ran-dom Drop(RQRD).Based on CSFQ’s distributed architecture, RQRD takes into account both rate(just as CSFQ)and queue size(just as RED)information to achieve the objectives de-scribed above.We start in Section II with an overview of prior work.In Section III,we state our assumptions and describe the details of the RQRD algorithm.In Section IV,we use simula-tion to compare RQRD to existing queue management schemes. Finally,Section V summarizes the results of this paper.A longer version of this paper including the algorithm pseudocode can be found at .II.P RIOR W ORKAccording to Drop Tail(DT[5])which,owing to its simplic-ity,is used in most routers today,incoming packets thatﬁnd the queue full are simply dropped.Yet,DT suffers from a number of shortcomings,preventing it from acting effectively in the pres-ence of congestion:ﬁrst,there is no way of ensuring fairness amongﬂows traversing a Drop Tail queue;second,in the case of TCP trafﬁc,DT queues have been shown to introduce global synchronization in the network,leading to both a decrease in the average throughput and an increase in the average delay through the link[5].To avoid DT’s shortcomings,RED[4]attempts to avoid buffer overﬂow by controlling the queue size so it is kept at a reasonably low level.Alternatively,CSFQ[12]attempts to reduce the effect of congestion on individualﬂows by allocating to eachﬂow a minimum portion of the resources,independently of other trafﬁc in the network.In this section,we present a de-scription of RED and CSFQ.A.Random Early Detection(RED)RED[4]is a mechanism that attempts to provide a high ag-gregate throughput while keeping the queue size small by drop-ping packets probabilistically before the buffer overﬂows,using for that purpose a probability drop function that increases with the average queue size2.Designed for TCP trafﬁc,the assump-The average queue size itself is computed using an Exponential Weighted Moving Average(EWMA)when the queue is non-empty[4].(In case the queuetion is that marking a packet causes the source to reduce its rate of transmission(by reducing the TCP window size).[4]shows that by getting rid of global synchronization,RED is capable of reducing the average queue size,while increasing the aver-age throughput on the link.However,RED is shown to be sen-sitive to the setting of its parameters([3],[7]).[3]alsoﬁnds that unless the buffer size is large enough,RED is incapable of avoiding buffer overﬂow.In addition,[7]ﬁnds that in some situ-ations RED does not bear any progress in terms of fairness when compared to DT.Finally,RED is not equipped to insure fairness among a number of streamsﬂowing through the buffer;in par-ticular,in case UDP and TCP trafﬁc are mixed together,TCP gets a signiﬁcantly lower portion of the link bandwidth.In light of RED’s shortcomings,other approaches have been investigated through the development of competing schemes, e.g.,BLUE[3].Also,a number of buffer management schemes that are based on RED have been developed,in order to alleviate the lack of fairness that results from the basic RED algorithm, e.g.RIO([2],[10],[6],[11])and CHOKe[8].B.Core-Stateless Fair Queuing(CSFQ)Similarly to RED,CSFQ[12]assumes that routers are equipped with FIFO queues.As in RED,admittance to the queue is controlled by an algorithm which computes a drop probability for each packet that arrives to the queue.However, whereas RED uses the queue size as a control parameter,CSFQ uses rate information in an attempt to insure fairness among the ﬂows sharing the buffer.The Internet core is assumed to be par-titioned into different administrative domains,called core net-works.In order to avoid keeping per-ﬂow information and per-forming per-ﬂow actions in core routers,CSFQ is a distributed algorithm,where edge and core routers3exercise different,com-plementary functions.Edge Router Function.Edge routers keep a table of all ﬂows entering the core network;they estimate the rate of each ﬂow and insert this estimate as a label in the packet.More speciﬁcally,upon the arrival of a packet belonging toﬂow i at time t,the current rate of thatﬂow is estimated usingand are is idle,then a different formula is used,so the queue average size decreases exponentially with the queue idle time[4].)Routers sitting at the edge of the domain,and those sitting inside the domain are called edge and core routers,respectively.As described in[12],the weight used()results in a rate estimate that converges asymptotically to the real puted using the same exponential averaging method used by the edge router for.Denoting by the total link bandwidth,the fair share esti-mation algorithm is as follows.A congestion bit is deﬁned, which value depends on and.More speciﬁcally,is initialized to0.If exceeds for a time period exceed-ing,is set to1,indicating that packets must be dropped in order to prevent buffer overﬂow.Conversely,If is less than for a time period exceeding a window,is reset to 0.The fair share is updated once each period.In caseat time t,is simply set to the largest per-ﬂow rate seen at the input of the queue during the period.In case,then is updated usinginstead of.In addition,the expression for becomes.Also,the optimal value of depends on the ex-pected trafﬁc burstiness,so cannot always be set optimally in a realistic en-vironment,where trafﬁc burstiness constitutes a dynamic phenomenon.In fact, simulation will shed some light on the undesirable dependence of achievable throughput on in case CSFQ is used.(See Section IV.)III.RQRD A LGORITHMRQRD is based on the distributed architecture used in CSFQ. RQRD provides two drop precedences to differentiate loss sen-sitive trafﬁc,such as voice and video trafﬁc from other trafﬁc in the network.Edge routers implementing RQRD keep for each ﬂow7,in addition to the estimate the rate of theﬂow the drop precedence of thatﬂow,.We assume two priority levels for dropping(1designating the highest level,0the lowest).Flows that do not tolerate any packet drop belong to level1(e.g.,the base layer of an UDP video stream).Flows that tolerate packet drop belong to level0,and can include both TCP and UDP traf-ﬁc.is estimated just as in CSFQ.(See Section II-B.)Each packet is stamped with both and prior to its transmission into the transit network.An RQRD core router delays any dropping action until both the queue size increases signiﬁcantly and the aggregate rate ex-ceeds the total link bandwidth,indicating that the transient con-gestion experienced will most likely become persistent.In order to achieve this goal,RQRD uses two drop probability functions, a rate dependent and a queue size dependent.Drop Probability.relates to the fair share,as estimated by a core router,and.In case s=1,,meaning that the packet is only dropped in case of buffer overﬂow.In case s=0,the drop probability is function of r(t)and,exactly as in CSFQ,using the formula shown in Section II-B.The fair share estimation performed in core routers is done in a manner that is very similar to CSFQ,except that the drop precedence of incoming packets is also taken into account.In particular,an RQRD core router estimates the total rate of pack-ets of drop priority0at the queue input,,and the total rate of packets of priority0and1admitted to the queue,and ,respectively;for that,it uses the same exponential aver-aging method described in Section II-B.The value of a link congestion bit,is obtained as in CSFQ(Section II-B),except that is replaced here with,which rep-resents the service rate for packets of drop priority0.The fair share is then updated exactly like in CSFQ.Queue Dependant Drop Probability.In addition,RQRD uses a queue dependent drop probability function,which,as in RED,is a non-decreasing function of the average queue size .The value of is obtained as follows:as in RED,we deﬁne and to be two thresholds to which is compared,and to be the total buffer size.We also deﬁne a buffer congestion bit,,and set its value according to the position of with respect to,and.More speciﬁcally,is initialized to0.If exceeds for a time period greater than a given time window,then is set to1.is only reset to0when drops back below and stays under that value for a time period exceeding .is always set to0when and to1when .For,depends on the value of.(See Figure1.)If,then the algorithm uses an optimistic drop function that increases slowly with Q.Conversely,when,then RQRD uses a more aggressive drop function.Therefore,unlike RED is As in CSFQ,the operation of RQRD is independent of what is considered a ﬂow.Hence,we intentionally keep the deﬁnition of the worldﬂow imprecise.work scenario.at the input of the queue at time t is relabeled using,where and constitute the original and new labels,respectively,and represents the drop proba-bility associated to the incoming packet.Also,extending the algorithm to support heterogeneous rates is done exactly as in CSFQ.(See Section II-B.)IV.S IMULATION R ESULTSIn this section,we conduct simulation experiments that shed a light on the potential beneﬁts of RQRD.The general sce-nario(see Figure2)consists ofﬂows entering the core network through a number of edge routers,and then forwarded to a core router.We are interested in per-ﬂow average throughput mea-surements at the output of the queue.We use=10Mb/s, and experiment with values for the total buffer size varying from64to512KBytes.We experiment with different round trip times by considering propagation delays ranging from one to 20ms.(Unless stated otherwise,we use a propagation delay of 1ms,that is a round trip time of2ms.)In the RQRD algorithm, we use the same value for all constants pertaining to the estima-tion of the different parameters(that is,K,,,,, and).As for and,the default chosen val-ues are.However,we experiment with othercombinations to understand their effect on the algorithm.For RED,we use,, and(wherefor less bursty(e.g.smtp,nntp)TCP trafﬁc.We assume that the minimum available bandwidth offered to this queue is known,through the use of a Weighted Fair Queue-ing scheduling algorithm10.Since RQRD is designed to achieve both CSFQ’s and RED’s advantages,its performance is com-pared to both.Also,we compare RQRD to DT,since it is im-portant to make sure that the improvement achieved warrants the complexity introduced.The simulation experiments conducted are grouped in three categories.In a future differentiated ser-vices network,UDP and TCP trafﬁc will be separated in differ-ent queues;hence,weﬁrst assess the beneﬁts of RQRD when applied to UDP trafﬁc alone(Section IV-A),and TCP trafﬁc alone(Section IV-B).Also,since RQRD is primarily intended to provide an adequate support of UDP and TCP trafﬁc in today’s networks,we include a set of experiments that demonstrate the performance of RQRD when applied to a mixture of UDP and TCP trafﬁc(section IV-C).A.RQRD Applied to UDP Trafﬁc AloneWe start with an experiment used in[12]where N sources,to transmit UDPﬂows with Source transmitting at an average rateis allocated to each of theﬂows,leading to; conversely,a considerably unfair algorithm will allocate to each ﬂow a portion of the link bandwidth that is proportional to its input rate yielding.As shown in Figure3a,CSFQ is the most capable in providing fairness in such a setting.Clearly, In our simulations,we experiment with a single-queue system.(Accord-ingly,the minimum available bandwidth consists of the total link bandwidth.)for CSFQ so extra burstiness is allowed when the buffer size is increased[12].)We conclude from thisﬁrst experiment that un-like DT and RED,RQRD is capable of providing a theoretical fairness comparable to that obtained with CSFQ.We now consider a realistic scenario in which statistically identical VBR streams share the link.In real life,this sce-nario represents,for example,the transmission of VBR video streams over the link.The important measure in this case con-sists of the loss rate experienced by video trafﬁc.(See Figure 4.)We consider values of ranging from to, where represents the average aggregate UDP arrival rate. The results show that in all cases,the best queue management scheme is simply DT.In fact,since trafﬁc is bursty and sources are non responsive,preventive drop becomes harmful.We can see from the results that RQRD matches very closely RED’s be-havior and drops slightly more packets than DT.(This indicates that the congestion bit is rarely set to1.)Comparatively, with CSFQ,transient burstiness that could have been stored in the buffer is unnecessarily dropped instead,resulting in heavy packet drop,particularly when the average arrival rate is small11. In another experiment,we consider the mixture of CBR and VBR UDP trafﬁc.This experiment models,for example,a situ-These results suggest that mechanisms aimed at taking into account queue size in CSFQ(that is,reducing with buffer overﬂow,and avoiding packet drop when the queue size is less than half the total buffer size,as described in Section II-B)are not sufﬁcient.In order to conﬁrm this fact,we repeat all experiments described in this paper with a version of CSFQ that is stripped from these two amendments:the results obtained with the two RQRD conﬁgurations match almostexactly.Fig.5.Per-ﬂow loss rate for CBR UDPﬂows sharing a link.The rate proportion isVBR.Fig.6.Average per-ﬂow rate for TCPﬂows sharing a link versus. ation where CBR and VBR video streams share the link.In our setting,one third of the trafﬁc volume(in Mb/s)consists ofVBR ﬂows.We consider values ranging from25to90%of ,and values of ranging from8to64.As can be seen fromFigure5,CSFQ consistently drops VBR trafﬁc the most.When the total arrival rate to the link is large,this behavior results in a lower drop rate for CBR trafﬁc,a desirable result in line with the fairness objective that CSFQ is striving to achieve.However, when is small,then the excessive drop of VBR packets does not help reducing the drop rate of CBR trafﬁc,which is the highest with CSFQ.Conversely,RQRD drops signiﬁcantly less VBR packets.Also,when is large,RQRD is almost as capable in protecting CBR trafﬁc as CSFQ.In fact,RQRD’s ability to tailor its drop probability function based on the queue size using a hysteresis function allows it to differentiate more effectively between situations where congestion is transient(in which case packet drop is kept low)and those in which conges-tion is persistent(in which case adequate packet drop is applied).B.RQRD Applied to TCP Trafﬁc AloneWe now investigate RQRD’s ability to provide an adequate handling of TCP trafﬁc.Weﬁrst consider the simple case of statistically identical TCPﬂows mixed on a link.As can be seen from Figure6,CSFQ performs poorly when is small: in fact,CSFQ falsely assumes that dropping packets at a rateFig.7.Average rates for TCP connections sharing the same link;have a round trip time of40ms.(streams each)which traverse links that have different propagation delays:ms and ms for Groups1and2,respectively;as a result, TCP trafﬁc from Group1is more aggressive,capturing most of the buffer resources.The experiment is intended to verify whether CSFQ is capable of insuring fairness among competing TCPﬂows.In fact,CSFQ falls short in this respect.For exam-ple,even though the plots corresponding to in Figure 7reveal that for KBytes,the use of CSFQ leads to an increase in the average rate of theﬂows belonging to Group 2from0.16to0.18Mb/s,at the expense of a reduction in the average rate ofﬂows pertaining to Group1from0.25Mb/s to0.22Mb/s,these results are not consistent for all values of(e.g.,and).Also,as observed in the previous experiment,CSFQ performs poorly when either the number of ﬂows is small or the buffer size is less than256KBytes.Con-versely,RQRD and RED are very close in their performance. Compared to DT,aggregate throughput is slightly improved by getting rid of global pared to CSFQ,ag-gregate throughput is in all cases higher,in most cases by a sig-niﬁcant amount12.Similar results are obtained for an experiment in which two groups(ofversus Bytes,versus5). Summary.Even though the use of CSFQ leads,in some situ-ations to a desirable increase in fairness among TCPﬂows,thisresult is not consistent,and depends on factors such as the sizeof the buffer,the number ofﬂows sharing the link and the settingof the parameter used in the algorithm.Perhaps more impor-tantly,the results show that if either the buffer is too small,orthe number of TCPﬂows is too small,CSFQ leads to a drasticdecrease in aggregate throughput.In this case,the use of RQRDdoes not lead to an improved fairness among competing TCPﬂows,but provides an aggregate throughput that matches very closely that provided by RED,and which is never noticeably lower than that provided by Drop Tail.C.RQRD Applied to both UDP and TCP TrafﬁcIn this section,we investigate RQRD’s ability to deal withTCP and UDP trafﬁc when mixed in the same FIFO queue.We start with a scenario in which we investigate RQRD’s ability to protect TCPﬂows from a high volume,non-adaptive UDPﬂow. In this respect,we consider the following setting:one UDPﬂow, transmitting at a rate Mb/s is combined with TCPﬂows.As shown in Figure8,with DT and RED,TCP traf-ﬁc is starved almost totally by the ill-behaved UDPﬂow.On the other hand,both RQRD and CSFQ drop enough UDP packets so TCP throughput increases to reasonable levels13.(CSFQ per-forms slightly better than RQRD,owing to its ability to drop the ill-behaved UDP trafﬁc consistently,proportionally to its input rate.)Similar results are obtained for.We now consider a set of realistic scenarios in which16UDPCBR streams,having an aggregate average arrival rate of5Mb/s(that is,Fig.9.UDP loss rate and TCP per-ﬂow average rate versus for TCPﬂows sharing the link with16CBR UDPﬂows having an aggregate average rate of5Mb/s.(16UDP,5TCPﬂows.)。