CBQ rates

Pawel Krawczyk (kravietz@ceti.pl)
Fri, 18 Jun 1999 04:28:48 +0200

Could anyone help with the following problem? Below are tc command
creating two CBQ leaf classes - bulk and interactive one, each with
assigned flow rate:

# root and parent classes
tc qdisc add $DEV root handle 1: cbq $BAND $AVPKT mpu 64
tc class add $DEV parent 1: classid 1:1 cbq $BAND rate 33600bps $ALLOT \
cell 8 weight 1 prio 8 maxburst 5 $AVPKT

# bulk class has rate of 24000 bps and SFQ qdisc
tc class add $DEV parent 1:1 classid 1:2 est 1sec 8sec cbq $BAND \
rate 24000bps $ALLOT weight 1 prio 6 maxburst 5 $AVPKT split 1:0 bounded isolated
tc qdisc add $DEV parent 1:2 sfq quantum 576b perturb 15

# interactive class has rate of 9600bps, same qdisc and higher priority (2)
tc class add $DEV parent 1:1 classid :3 est 2sec 16sec cbq $BAND \
rate 9600bps $ALLOT weight 1 prio 2 maxburst 10 avpkt 200b split 1:0
tc qdisc add $DEV parent 1:3 sfq quantum 576b perturb 15

Where DEV is name of dynamically allocated ppp interface, ALLOT is "580b"
(576 MTU + 4 bytes for PPP header), AVPKT is "500b", BAND - "33600bps".

Below is what really gets added to the kernel:

class cbq 1: root rate 33600bps (bounded,isolated) prio no-transmit
class cbq 1:1 parent 1: rate 33600bps prio no-transmit
class cbq 1:2 parent 1:1 leaf 8003: rate 24000bps (bounded,isolated) prio 6
class cbq 1:3 parent 1:1 leaf 8004: rate 75Kbit prio 2

The 9600bps gets changed to 75Kbit, which seems to be nonsense. Why does
it happen so? Or maybe is there any better method to optimize usage of
such PPP link? Any help will be greatly appreciated.

Pawel Krawczyk, CETI internet, Krakow. http://www.ceti.pl/~kravietz/
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