[LARTC] time window in CBQ

[Andreani Luca <landreani@seltatel.it>]

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Dear list,

I have two linux boxes acting as VoIP Gateway in the following
configuration:

     
        IP Phone ----------+                 +------------------+
+------------------+                  +---------------- IP Phone
		         |-----------eth0-| Linux BOX1
|-hdlc0----------hdlc0-| Linux BOX2 |-hdlc0-----------|
        PC ----------------- -+                 +------------------+
+-----------------+                   +--------------- PC

The hdlc link is 64 kbps.

I tried to make a configuration in order to guarantee the bandidth of the
VoIP calls versus the data traffic between the two PCs.
I used CBQ + Prio and U32 filter. The ip Phones mark the packet with TOS
0x40. I also need the entire bandidth available for data traffic
when there are no calls.

I used the following configuration:


insmod /lib/modules/2.4.17_mvl21-sandpoint/kernel/net/sched/sch_cbq.o

insmod /lib/modules/2.4.17_mvl21-sandpoint/kernel/net/sched/sch_prio.o

insmod /lib/modules/2.4.17_mvl21-sandpoint/kernel/net/sched/cls_u32.o

tc qdisc del dev $int root

tc qdisc add dev $int root handle 1:0 cbq bandwidth $banda avpkt 1000 cell 8

tc class add dev $int parent 1:0 classid 1:1 cbq bandwidth $banda rate
$banda maxburst 20 avpkt 500

tc class add dev $int parent 1:1 classid 1:2 cbq bandwidth $banda rate
$banda_voce maxburst 20 avpkt 500

tc class add dev $int parent 1:1 classid 1:3 cbq bandwidth $banda rate
$banda_dati maxburst 1 avpkt 500

tc qdisc add dev $int parent 1:2 handle 20: prio

tc qdisc add dev $int parent 1:3 handle 30: prio

tc filter add dev $int parent 1:0 protocol ip prio 1 u32 match ip tos 0x40
0xff flowid 1:2

tc filter add dev $int parent 1:0 protocol ip prio 1 u32 match ip tos 0x00
0xff flowid 1:3


According to the test I performed, the configuration works because the VoiP
traffic has its bandwidth, however the voice quality is absolutely bad. This
occurs because
the bandidth is given in "avarage" while I need a more "instant" bandidth.
How can I reduce the time window used to calculate the rate of the VoIP
class. Note (in the script) that I tried setting maxburst=1 for the best
effort class but had no result,

thanks for help,

P.S. any other configuration suggested for my application will be very
appreciated...

Luca Andreani

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