topic Re: XCC - wondering about ac-WiFi asymmetric client speed in ExtremeWireless (WiNG)

XCC - wondering about ac-WiFi asymmetric client speed

M_Nees — Tue, 21 Sep 2021 21:17:55 GMT

I got this XCC WLAN client report shown:

(XCC 5.36.02 - report truncated - AP310i)

XCC-V5.36.02# show clients apserial XXXXX-XXXXXX00000

Protocol   Radio  SSID       Aut./Priv.    OS         RSS(dBm)  Avg.Rate
                                                                (Mbps)
                                                              Sent/Recvd 

5.0ac|L|S  2      XX-MDE     None/WPA-PSK  Apple iOS  -55       360/6                      
5.0ac|L|S  2      XX-MDE     None/WPA-PSK  Apple iOS  -55       300/6                      
5.0ac|L|S  2      XX-MEDIEN  None/-        Apple iOS  -63       400/6                      
2.4n       1      XX-Mobile  None/WPA-PSK  Apple iOS  -96       0/0                        

XCC-V5.36.02#

i wondering about the asymmetric speed of this apple clients (while RSS is good).

It seems to be a general behaviour of smartphones (means android also). Windows clients seem to have symmetric speeds.

Is anybody able to explain this behavior ?

Also seeing some rates as a point number e.g. “102.3 Mbps”. Does XCC Controller calculates some averages ? If yes within which timerange ? (maybe during whole session or within a fix amount of time?)

How can i understand the displayed direction in this report - View of Controller/AP or View of client?

Given above example does this apple phone send or receive only with 6 Mbps ?

BR,

Matthias

Re: XCC - wondering about ac-WiFi asymmetric client speed

Gareth_Mitchell — Wed, 22 Sep 2021 15:39:43 GMT

Hi Matthias

Typically phones pull data down from the internet (downlink) rather than pushing it to the internet (uplink.) This is most likely what you are seeing, the average speed for the small amounts of data sent by the device is 6Mbps.

It’s also worth mentioning that the data rate used in wireless is variable, it can change frame by frame, depending on the RF environment.

The stats are averaged by the AP over 30 seconds and then reported to the controller.

The view of the controller/AP is what you are seeing there.

-Gareth

Re: XCC - wondering about ac-WiFi asymmetric client speed

M_Nees — Thu, 23 Sep 2021 13:26:59 GMT

Hi,

thanks for reply.

one point causes some headache … what’s the benefit/reason that smartphones request only small datarates /eg 6Mbps)?

In legacy wifi networks (pre ac/ax) small datareate means (in my opinion) wasting limited and worthful airtime?

Is there some technique in ac / ax networks that solve that opposite needs?

BR,

Matthias

Re: XCC - wondering about ac-WiFi asymmetric client speed

Gareth_Mitchell — Thu, 23 Sep 2021 16:32:51 GMT

Hi Matthias

It’s more that the volume of data is low rather than only using slow 802.11 data-rates, this would cause the average to be lower

To be sure, you can take a wireless trace and see the volume of data being used by the device, and in the radiotap header you can see the data-rates used. I normally have a column in wireshark to show the rate for each frame.

You are right about lower data-rates consuming more airtime than higher, however this is the 802.11 data-rate, not the average throughput data-rate seen on the controller sample above.

I hope this makes sense?

-Gareth

Re: XCC - wondering about ac-WiFi asymmetric client speed

M_Nees — Fri, 24 Sep 2021 01:23:03 GMT

Hi Gareth,

today i take the time an do some testings.

Getting wireshark traces within XCC GUI in now much more easier compare to legacy identify.

Analysing the wireshark traces (radio 2) show me the needed background information:

if the client does not communicate much, than the AP/Controller see mostly 802.11 radio overhead packtes which are send at min. basic rate (here 6Mbps)
(for example a smartphone which is automatic connected to SSID, but no need to communicate)
if the client communicate later more real traffic, it will be send with best possible speed - depends on RSS, wifi technology, available channels and channel bonding etc.
(Windows clients mostly having communication with someone)
confirm every data packet also having a 802.11 data rate (if tcpdump is done on a radio interface) - and this rate changes/adapts
IEEE 802.11ac-2013 wikipedia article (https://en.wikipedia.org/wiki/IEEE_802.11ac-2013) give me a good overview about the possible data rates - and to my surprise there a lot of possibles rates - also the seen point number rates.
Averages are done by 30 secs steps - TxRate and Rxrate are always defined in APs view

BR,

Matthias

Re: XCC - wondering about ac-WiFi asymmetric client speed

M_Nees — Fri, 24 Sep 2021 01:33:06 GMT

Here an example of a done wireshark trace within a quite lab environment:

Re: XCC - wondering about ac-WiFi asymmetric client speed

StephanH — Fri, 24 Sep 2021 03:04:41 GMT

Hello Matthias,

confirm every data packet also having a 802.11 data rate (if tcpdump is done on a radio interface) - and this rate changes/adapts

please note that the speed, Wireshark shows, is not really included or transmitted in the wireless packet.
This and other information that can be seen in the traces belong to the so-called pseudo headers and are read by programs such as Wireshark from the driver! Also the radio tap header is a pseudo header.

Re: XCC - wondering about ac-WiFi asymmetric client speed

StephanH — Fri, 24 Sep 2021 03:12:30 GMT

IEEE 802.11ac-2013 wikipedia article (https://en.wikipedia.org/wiki/IEEE_802.11ac-2013) give me a good overview about the possible data rates - and to my surprise there a lot of possibles rates - also the seen point number rates.

A complete overview of all current MCS depending on the different wifi standards and number of spatial streams can be found here: http://mcsindex.com/

Re: XCC - wondering about ac-WiFi asymmetric client speed

Gareth_Mitchell — Fri, 24 Sep 2021 15:32:05 GMT

Hi Matthias

It sounds like you have got to the bottom of this question now. As Stephan said, there are a lot of factors in choosing data rates as shown in mcsindex website, guard interval, modulation etc all come into play. Each device will also use its own algorithm, almost all of which are proprietary and closed source.

Laptops generally have much more capable antennas and larger batteries that allows them to use higher data rates than smartphones.

If you have any more questions please let us know.

Have a good weekend.

-Gareth