TCP should use the same TOS for datagrams containing only TCP
control information as it does for datagrams which contain user
data. Windows does exacly that, so triple check that you are dissecting payload when checking.
Although it might seem intuitively correct to always
request that the network minimize delay for segments containing
acknowledgements but ...
I come back on this topic because I had the same troubles to implement my qdisc on a port of my bridge.
The first solution with tc filter does not work for me. And the arp solution seems to be a good one but is problematic when you use DHCP, because it pass through Layer 2 of OSI model, while arp bridge pass through Layer 3 (I saw that you could use dhcp-...