strong variation in Ping Round Trip Time Tests in WLAN

[ciscoprolin]

Dear All,

do you if try to ping the Default Gateway from our eduroam wlan the Ping RTT is varying between 1 or 2 and up to 101ms within a short time. This can be observed in different Location even when the AP has low interference and the Client has a good RSSI of about -50dB.

Do you have any idea what acceptable RTT values are in the wireless lan (802.1x-based wlan with EAP-PEAP) ? Is there an official guide which I can consult about this and also how to optimize this behavior ?

Thanks very much,

Thorsten

[Vengatesa Prasath]

Hi

Ping is not a reliable tool to test. It is always recommended to perform Iperf test or file transfer to check the performance.

You can verify if the client have better SNR or RSSI value.. Following command will give Rssi and snr value:

---- Show client detail <mac of client>

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[Vengatesa Prasath]

Adding to my above post..

To do Iperf test you can refer: https://supportforums.cisco.com/t5/wireless-mobility-documents/iperf-test-for-measuring-the-throughput-speed-of-a-wlan-client/ta-p/3142047

Verify if the best practice is followed :

https://www.cisco.com/c/en/us/td/docs/wireless/technology/wlc/8-5/82463-wlc-config-best-practice.html#pgfId-380235

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[ciscoprolin]

Hi Vengathesa,

can you tell my why ping is not recommended for this purpose ? Is there a reason behind it ? The RSSI values (according to show client detail <MAC> ranges between -50 and -60 dBm.

Are there any other useful alternatives to iperf which don't require to run a piece of software on the destination in the LAN ?

Thanks very much for your help,

Thorsten

[Vengatesa Prasath]

Hi,

Ping on wlc is handled on best effort basis.

You could try with file transfer between wireless PC and wired PC. (Don't test file transfer between two wireless clients connected on same AP).

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[ciscoprolin]

Hi thanks,

does the same apply for pings from the wireless client to a wired client ? Will this also be handled by the WLC with lower priority ?

Thanks,

Thorsten

[Vengatesa Prasath]

yes, ICMP is not reliable tool to test throughput (especially in wireless).

[ciscoprolin]

Hi  thanks that's good to know - do you know how to measure the round trip time with iperf ? It only gives me bandwidth throughput and Total/Lost Datagrams - but we really like to know why according to ping there are so many spikes in the RTT.

Cheers