For a long time I have not considered this problem, but it drives me crazy.
I have three routers ap01,ap02 and ap03, the ISP router is connected to ap01 via ethernet.
The ap01 is WDS master (5GHz) and the other two are WDS clients.
Additionally there is a WLAN for the clients (2,4GHz) on each AP, this WLAN is the same on all three (same name, same password).
AP01.wlan 192.168.0.1/24 (bridge 2,4Ghz and 5Ghz)
AP02.wlan 192.168.0.2/24 (bridge 2,4Ghz and 5Ghz)
AP03.wlan 192.168.0.3/24 (bridge 2,4Ghz and 5Ghz)
ISP router 192.168.1.254
Actually everything works, everybody can communicate with everybody, everything is good.
But the performance sucks, if there is nothing going on in the network and I am connected to my PC on ap03 and ping on the lan ip of ap01 (PC=192.168.0.101 -> ap01.eth=192.168.1.1), then I have about 1-4ms latency, which is ok.
But if I run a Youtube video on the PC I have a latency of 120ms avg on the same ap01 at 10 pings.
I know that I have not given you much information yet, I wanted to explain the topology first.
On all routers OpenWrt 19.07.2 is running, I have no QoS activated, all interfaces belong to the same FW group.
Please help me.