Are the AMSDU settings even doing something?

RouterOS Beginner Basics
1

Based on the post of user bpwl and under my own expirience there is absolutely no change of the values in the VHT capabilities and/or HT capabilities part of the beacons. Whatever I set into the AMSDU limit or threshold (0,3839,1024,8192,..)- everytime I see only Max A-MSDU length: 3839 and Max A-MPDU length exponent 65535 bytes (3895 and 262143 for VHT).
I’ve tried it with and without capsman managing the interface. So far I’m using 3839 anyway and set priorities according dscp bits. I’m not going after some fancy super high speeds (as I have some old RBs with 100M upload ports), but I’d like to give my users the best performance I can afford.

My setup:
x86 CAPsMAN ROS 7.9.1
RB951/wAP ac/CAP ac/.. etc. CAPs ROS 7.9.1

Scanner method: Atheros 9285 b/g/n int. wifi + Realtek 8811CU ac USB with LizardSystem Wifi-scanner 21.03

2

Frankly - I may mixed things up. But - let’s say MT always advertises 3839 A-MSPDU field.

Maximum A-MSDU length Indicates maximum A-MSDU length. See 9.7b (A-MSDU operation).
Set to 0 for 3839 octets
Set to 1 for 7935 octets

But what is the point of default value of 8192 in the amsdu-limit (integer [0..8192]; Default: 8192) and amsdu-threshold (integer [0..8192]; Default: 8192)?

3

I also long set the AMSDU to the 3839 myself. But can’t say I’ve ever verified the effect…

I’ve found that setting distance=indoor is pretty critical to getting stable Wi-Fi on the older Atheros chips.

/interface wireless set [find] distance=indoor

(also in winbox under Advanced tab, if you click show advanced settings)

As a guess, if that setting “distance=dynamic”, I’d try your test again with “indoor”. My thought is that setting might muck with AMSDU things, but dunno.

4

Yes - indeed, the Distance field should be another name for the ack-timeout variable

5

Exactly. Still have some RB953s with only 5Ghz/n in field…with distance=indoor, 20Mhz, longer group key timeout, and lower AMSDU… really haven’t had complaints even though they going on 10 years old…even modern ax smartphones/etc. happily use 802.11n from them.

But never actually confirmed the AMSDU was working. I recall some iPad long ago that had problems staying connected, and lower AMSDU fixed – so just always set it since then.

Not familiar enough the with 802.11 specs to know here… but if you think RouterOS isn’t setting something right from sniffer, it’s worth a bug report at help.mikrotik.com.

6

if the clients (cpes) are not mikrotik set AMSDU to 7935 for compat..