[Cake] overheads or rate calculation changed?

[Andy Furniss]

Been running a cake cobolt from april for some time using

tc qdisc add dev ppp0 handle 1:0 root cake bandwidth 19690kbit raw 
overhead 34 diffserv4 dual-srchost nat rtt 200ms

tc -s qdisc ls dev ppp0 (ppp0 is pppoe)

qdisc cake 1: root refcnt 2 bandwidth 19690Kbit diffserv4 dual-srchost 
nat rtt 200.0ms noatm overhead 56 via-ethernet

Which is backed off a couple of kbit and tests well (overhead 33 + udp 
flood is over limit)

With current cobalt + current tc the same command is under rate - I 
don't know if its rate calculation or overheads calc changed.

overhead 20 (-14) is still under but overhead 12 (-22) is over.

I was hoping one of those would be correct, but no.

Any ideas/known changes?