On Fri, Apr 09, 2021 at 03:38:15PM +0200, Andi Depressivum wrote:
Actual OpenWRT trunk on TP-Link C7 / C2600 devices. Can decrease to anything lower than 1500 but cannot raise above 1500.
Hm, yes, many/most ethernet devices don't support jumbo frames.
You could test with iperf3 and its --set-mss option if smaller, unfragmented frames have a better performance.
A few more options to solve this are then:
* using the DHCP MTU option on the DHCP server (though many DHCP clients do not properly support this) * use iptables MSS clamping (only works for TCP and routed traffic) * on a gateway router, set a route to the internet with a lower MTU, which then results in "ICMP packet too big" messages back to the client with containing the desired MTU and the initial host should retry with a smaller packet size (only works for routed traffic)
Or if you have full control of all hosts in the network you can also reduce the MTU on the hosts.
Also note batman-adv v2021.0 had some performance improvements for frames fragmented by batman-adv:
https://www.open-mesh.org/news/100 -> * https://git.open-mesh.org/batman-adv.git/commit/92064deda9b063ca2d5a53b307c6... * https://git.open-mesh.org/batman-adv.git/commit/0966d5424bb87e86303730148851... * https://git.open-mesh.org/batman-adv.git/commit/3e3ff987876d3be70d928561acbe...
Regards, Linus