Cisco Cisco Nexus 5010 Switch Libro bianco

 

 

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In the preceding output, cnt denotes the minimum, maximum, and average latency, in nanoseconds, of packets 

entering 1/6 and egressing 1/1. 

A linear histogram can show you the number of packets seen in a given latency range. For instance, suppose you 

want to count packets for the following ranges of latencies (in nanoseconds) separately: 800 to 849, 850 to 899, 

900 to 949, and 950 to 999. You can do this by using a linear histogram. 

You first configure a latency base value for the table to 800 ns. Then you program a step value of 50 ns. Using 

these two values, you partition the entry into four separate counters: 

if base ≤ latency < base + step, increment CNT0 

if base + step ≤ latency < base + 2 * step, increment CNT1 

if base + 2 * step ≤ latency < base + 3 * step, increment CNT2 

if base + 3 * step ≤ latency < base + 4 * step, increment CNT3 

This histogram mode is linear because the latency ranges are increased linearly using the step value. 

Following is a sample of latency measurement output in Linear Histogram mode. Eth 1/1 is the egress port and 1/6 

is the ingress port. 

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Egress Port: Ethernet1/1 Ingress Port: Ethernet1/6 Mode: Linear Histogram 

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| Range|       800-840|            840-880|               880-920|      920-960| 

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|  cnt |          123009|                556009|            640003|      450243| 

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In the preceding output, cnt is the number of packets in the specified user-configured latency range. A base value 

of 800 ns and a step value of 40 ns were configured. 

An exponential histogram provides the binning of latencies for ranges increasing exponentially. For instance, 

suppose that you want to count the packets in the following ranges of latencies: 850 to 899, 900 to 999, 1000 to 

1199, and 1200 to 1599. You can achieve this by using the Exponential Histogram mode with the base value set to 

800 and the step value set to 50 ns. 

The exponential binning would count the packets as follows: 

if base + step * 2^0 ≤ latency < base + step * 2^1, increment CNT0 

if base + step * 2^1 ≤ latency < base + step * 2^2, increment CNT1 

if base + step * 2^2 ≤ latency < base + step * 2^3, increment CNT2 

if base + step * 2^3 ≤ latency < base + step * 2^4, increment CNT3 

Following is a sample of latency measurement output in Exponential Histogram mode. Eth 1/1 is the egress port 

and 1/6 is the ingress port. 

switch# show hardware profile latency monitor interface ethernet 1/1 interface ethernet 1/6 

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