[LARTC] CBQ and excess bandwidth

[Patrick Nagelschmidt <dto@gmx.net>]

i've got a problem with bounded and unbounded classes using cbq. i want to create
two classes for my outbound network connection, one for the normal data and one
only for ack-packets:

tc qdisc add dev ppp0 root handle 1: cbq bandwidth 10Mbit avpkt 1000 mpu 64

tc class add dev ppp0 parent 1:0 classid 1:1 cbq bandwidth 10Mbit rate 768kbit allot 1514 weight 76.8kbit prio 8 maxburst 20 avpkt 1000 bounded

tc class add dev ppp0 parent 1:1 classid 1:2 cbq bandwidth 10Mbit rate 16kbit allot 1514 weight 16kbit prio 1 maxburst 20 avpkt 1000

tc class add dev ppp0 parent 1:1 classid 1:3 cbq bandwidth 10Mbit rate 112kbit allot 1514 weight 11.2kbit prio 7 maxburst 20 avpkt 1000 [bounded]
[...]

with 1:3 set to bounded this works perfectly and i get ~90kb/s downstream with an
upload running at the same time. BUT i dont want to limit class 1:3 if class 1:2 
has excess bandwidth. i thought it should be enough to remove the 'bounded' from 
class 1:3 to share excess bandwidth from class 1:2. 
but if i do so, class 1:3 uses bandwidth of class 1:2 even if no excess bandwidth
is available from 1:2. 1:3 is simply 'stealing'. without the 'bounded' i get ~25kb/s
downstream if i upload. and this means not all ack-packets have been sent as fast 
as possible, regardless that the ack-class has the highest priority. 

anyone got an idea what i've done wrong?

thanks in advance

Patrick Nagelschmidt 


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