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‹#› PROPRIETARY AND CONFIDENTIAL
Spirent Testcenter Manual-based Schedule 示例 六) 示例(六
发包次序(续上页胶片):
• L.12 ns 以后,第五条测试流(Nominal- Best Effort - Delta 4)发送3个burst,每个burst
• D.12ns 以后,第三条测试流( Nominal- Best Effort - Delta 2)发送5个burst,每个burst
含22个包, burst内22个包的发送速率是90%线速(900Mbps),Burst 之间的间隔是323ns
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Spirent Testcenter Manual-based Schedule 示例
在千兆口上设置的如下图所示Manual Schedule 序列 发包次序:
• A.第一条测试流(High Priority - Stedy State - AF31)发送1个burst,含10个包,burst内
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简单解释 Microburst
“It is a traffic pattern that's like a spike except microbursts are short in time, such as 100 microseconds”-Pramod Srivatsa, manager, server access virtualization at Cisco Microburst 是类似尖刺的流量模 型,Microburst 持续的时间很短, 比如100微秒或以下。 Microburst具有随机性 Microburst 可表现在流量,地址 学习,burst时间
• J.12 ns 以后,重复步骤D-J, 重复2次 • K.12ns以后, 第三条测试流(Nominal- Best Effort - Delta 2)发送346个burst,每个
burst含3个包,burst内3个包的发送速率是24%线速(240Mbps), Burst 之间的间隔是145ns
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含90个包,burst内90个包的发送速率是72%线速(720Mbps),Burst之间的间隔是12ns
• M.12 ns 以后,第六条测试流(Nominal- Best Effort - Delta 5)发送99个burst,每个
Spirent Testcenter Manual-based Schedule 示例 三) 示例(三
发包次序(续上页胶片):
• E.12 ns 以后,第四条测试流(Nominal- Best Effort - Delta 3)发送7个burst,每个burst
含34个包,burst内34个包的发送速率是80%线速(800Mbps),Burst之间的间隔是12ns
Testing the Microburst
How to measure the SLA over a Microburst with Spirent TestCenter
PROPRIETARY AND CONFIDENTIAL
传统意义上的Burst 统意义上的
传统意义上的Burst 是测试流随 时间采用统一的方式变化. 这种统一的变化方式通常是方波 的方式,由以下几个参数定义:
• F.12 ns 以后,第三条测试流( Nominal- Best Effort - Delta 2)发送19个burst,每个
burst含56个包, burst内56个包的发送速率是70%线速(700Mbps),Burst 之间的间隔是 167ns
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• 一个Burst 内帧的数目(Burst Size) Burst (Burst • IBG (Interburst Gap) • Burst cycle count
Rate
• 峰值速率(通常是100%线速)
传统意义上的Burst,通常测试 队列和缓冲的深度
Time
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10个包的发送速率是10%线速(100Mbps)
• B.12ns 以后,第一条测试流(High Priority - Stedy State - AF31)再发送一个burst,含
10个包, burst内10个包的发送速率是10%线速(100Mbps)
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传统Burst 不能完全测试真实世界的流量模型 解决之道:采用Microburst.
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什么是 Microburst
“In real-world traffic conditions, with differentiated traffic under SLA mandates (The Service Flow), a microburst is a pseudo-random, multi vector expansion and contraction within very short periods of time. Typically, variability happens by rate, unlearned address density, period density. For a Device Under Test (DUT) to successfully manage the microburst, the service flow SLA must be maintained.”
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典型案例-Microburst 的影响 型案例-
银行或者证券交易所
业务特征
• 一次交易(如股票竞价,银行交易等)的数据量不大 • 交易频率高,同时有大量交易发生 • 对网络架构或者网络中的交换机,很容易产生Microburst Microburst
不能正确处理 Microburst的影响
• 数据丢失-竞价失败或者交易失败 • 时延过大-交易延误,交易阻塞 •பைடு நூலகம்应用失步,影响一系列决策行为
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Spirent Testcenter Manual-based Schedule: Microburst 实现
Spirent Testcenter Manual-based Schedule 示例 四) 示例(四
发包次序(续上页胶片):
• G.12 ns 以后,第五条测试流(Nominal- Best Effort - Delta 4)发送34个burst,每个
burst含3个包,burst内3个包的发送速率是60%线速(600Mbps),Burst之间的间隔是234ns
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Model for Microburst
A traffic microburst is a traffic condition that simultaneously expands instantaneous rate, layer 2 address density, layer 3 address density, QoS Codepoint density within sudden pseudo random scale capped by the physical medium limits (such as maximum packets per second). To variablized a microburst, we must define variables. The first variable is delta (∆=2 mSec is typical) is the time window of change. This is the measurement window where metrics are dynamically expanding. Next, beta and beta’ represent the address density within a delta window (∂=10 Random, unique MAC +IP addresses per delta, pre burst is typical) and (∂’ is the address density per delta within the burst). Each burst will use a gamma statistical distribution as a weighting factor:
Rate over Burst =
=1
Δ∗
β ( )
−1 −
Unique Addresses over Burst = Δ
|η| =1
∂∗
β ( )
−1 −
Also, the Max rate may not be larger than the natural medium. Address need to be truly random (Like RFC-4814, to prevent summarization)
X represents maximum PPS of the medium, α and β are provided parameters to skew the shape. Finally, there is a simple uniform random distribution ,η, that will pick the number of bursting windows of deltas. Thus, a rate over burst of a microburst may be modeled as: |η|
Spirent Testcenter Manual-based Schedule 示例 二) 示例(二
发包次序(续上页胶片):
• C.12 ns 以后,第二条测试流(Nominal- Best Effort - Delta 1)发送3个burst,每个burst
含19个包,burst内19个包的发送速率是100%线速(1000Mbps),Burst 之间的间隔是 1344ns
Spirent Testcenter Manual-based Schedule 示例 五) 示例(五
发包次序(续上页胶片):
• I.12 ns 以后,第四条测试流(Nominal- Best Effort - Delta 3)发送12个burst,每个
burst含7个包,burst内7个包的发送速率是24%线速(240Mbps),Burst之间的间隔是13ns
• H.12 ns 以后,第二条测试流( Nominal- Best Effort - Delta 1)发送12个burst,每个
burst含77个包, burst内77个包的发送速率是55%线速(550Mbps),Burst 之间的间隔是 123ns
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The Problem
现实世界的流量不是简单传统意义上的Burst, 因为传统意义上的 Burst 有下列缺乏现实意义的特征:
• 统一分布 • 均匀地址密度 • 可预测
被测设备真实工作特征:
• 需要把新的地址加入FIB 数据库,这些新地址出现的速率是瞬时变化的 • 当新的流量对系统产生压力时候,维护流量的完整性 • 根据不同的参数保证SLA (DiffServ, VLAN PRI, etc) • 能够处理瞬时的,完全不相同,不可重复的流量变化。
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