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This chapter contains the following sections:
Active Latency Monitoring provides a real-time view of the latency that is incurred by the packets while traveling through the switch on a per port basis. The latency measurement is FIFO measurement. Functionally, as soon as the packet enters the switch, the ASIC adds a timestamp to it. When it is scheduled to go out of the egress port, the egress port calculates the latency for each packet that is going out of that port based on current time and the ingress timestamp on the packet.
Note | Active latency monitoring is currently not available for Cisco Nexus N3548 Series switches. This feature is only supported for Cisco Nexus N3548-X Series switches. |
Each egress port maintains the information in the frame count and the latency register, along with the minimum and maximum latency on that port. The software periodically reads the frame count (default 3 seconds) and the total latency to calculate the average latency per port. Based on per port latency information, the software calculates the average switch latency.
Active Latency Monitoring has the following limitations and guidelines:
To configure active latency monitoring, complete the following steps:
Note | The average or maximum latency threshold is in nanoseconds. The software sampling interval value is between 1 to 30 seconds. The default values for the parameters are: |
See the following examples that provide a real-time view of the latency incurred by the packets:
switch# show hardware profile latency monitor summary 10/13/2015 06:55:58 Device instance 0 Total Switch ============ 3s 30s 1hr All Time Min Latency (ns) 390 375 n/a 369 Max Latency (ns) 775 1844 n/a 1950 Avg Latency (ns) 612 721 n/a 754 Std Deviation 205.24 117.23 n/a 69.17 Ethernet1/1 =========== 3s 30s 1hr All Time Min Latency (ns) 775 762 n/a 762 Max Latency (ns) 775 1757 n/a 1950 Avg Latency (ns) 775 838 n/a 870 Std Deviation n/a 83.87 n/a 100.93 <snip> Ethernet1/13 ============ 3s 30s 1hr All Time Min Latency (ns) 671 646 n/a 644 Max Latency (ns) 671 1844 n/a 1844 Avg Latency (ns) 671 736 n/a 740 Std Deviation n/a 100.16 n/a 93.76 switch# show hardware profile latency monitor summary detail 10/13/2015 06:57:00 Device instance 0 Format: timestamp ifindex fcnt min_latency max_latency avg_latency 10/13/2015 06:56:58 Ethernet1/1 fcnt 2 min_latency 565 max_latency 571 avg_latency 568 10/13/2015 06:56:55 Ethernet1/1 fcnt 1 min_latency 576 max_latency 576 avg_latency 576 10/13/2015 06:56:52 <snip> Ethernet1/2 fcnt 0 min_latency 4294967295 max_latency 0 avg_latency 0 10/13/2015 06:56:55 Ethernet1/2 fcnt 0 min_latency 4294967295 max_latency 0 avg_latency 0 10/13/2015 06:56:52 switch# # show hardware profile latency monitor summary clear-timestamp 10/13/2015 06:56:31 Device instance 0 Egress Port Last Clear Timestamp ============================================ Total Switch 10/13/2015 06:54:35 Ethernet1/1 10/13/2015 06:54:35 Ethernet1/2 10/13/2015 06:54:35 <snip> Ethernet1/47 10/13/2015 06:54:35 Ethernet1/48 10/13/2015 06:54:35 switch# show hardware profile latency monitor summary brief 10/13/2015 06:57:27 Device instance 0 Egress Port Avg Latency (ns) ======================================== Total Switch 769 Ethernet1/1 874 Ethernet1/2 1682 <snip> Ethernet1/47 n/a Ethernet1/48 n/a switch# show hardware profile latency monitor summary sort 10/13/2015 06:57:34 Device instance 0 Egress Port Avg Latency (ns) ======================================== Ethernet1/2 1682 Ethernet1/5 1664 Ethernet1/1 871 Ethernet1/13 765 Ethernet1/6 507 Ethernet1/3 n/a switch# show hardware profile latency monitor summary top 10/13/2015 06:57:44 Device instance 0 Egress Port Avg Latency (ns) ======================================== Ethernet1/2 1682 Ethernet1/5 1664 <snip> Ethernet1/6 500 Ethernet1/3 n/a