I read this thread and tried recommendations here (but this may apply to older LEDE/OWRT builds).
How does one modify Wireless MTU? There is currently no GUI option ( I don't mind making a PR to add it ) - although trying in /etc/config/wireless yields no change if I supply option mtu 2000 under config wifi-iface 'wifinet0' or config wifi-device 'radio0' - any tips?
It results in 31: wlan1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000 link/ether xx:xx:xx:df:39:72 brd ff:ff:ff:ff:ff:ff
I also tried the Fragmentation Threshold advanced wifi option. Nothing there either. Some hardware is just hard-coded/cannot do it?
That has to be supported by hardware/driver on both sides of the connection with the same size configured. Otherwise it will be fragmented. It usually has to be enabled explicit. Also I doubt you will see any effect nowdays. CPUs even on routers are powerfull enough. Beside that there is no standard for jumbo frames. So each device/driver is supporting sizes what it want.
Well if there is a standard defined for MSDU size then I'm in hope that industry will make use of it. But I think this will be a premium feature. So they would optimize this values to their own technology/equipment first targeting companies with wider areas in competition with 5G. IMO It will take years hitting the consumer/SOHO market.
One problem you can run into with Wi-Fi is frame payloads can be larger than the standard ethernet payload.
This is IMO the most important point. Like I said already above (fragmentation).
At some point traffic is hitting WAN interface also.
IMO is the usecase for packet size optimisation limited to the network you are running your services (beside the internet using PathMTU). So from the point of an enduser/private user it does not really much for us. Expect you are a heavy LAN user. I might be wrong so don't take that what I've written as in stone written.