Dear all,
I tested bandwidth throttling using TC CBQ using the simplest configuration
with "bounded" on Pentium 3 , 648 Computers and it is puzzling to me
that the bandwidth throttling mechanism does not work very nicely at very high
throughput.
I attached only a class 10:1 to the root class and configured the
"bounded" desired rate on this class. I chose to use the default fifo
queue which is generated automatically when class 10:1 is created to reduce
complication.
I injected a constant flow of 80Mbps of UDP 1250 Bytes packets for 3 cases.
Case 1: The rate of 10:1 was "bounded" to 10Mbit, I received an
outgoing
flow of 11.6Mbps.
Case 2: The rate of 10:1 was "bounded" to 20Mbit, I received an
outgoing
flow of 25.6Mbps.
Case 3: The rate of 10:1 was "bounded" to 40Mbit, I received an
outgoing
flow of 63.6Mbps.
Below is my configuration for case 3:
$TC qdisc add dev $DEV root handle 10: cbq bandwidth 100Mbit avpkt 1000
cell 8 mpu 64 ewma 8
$TC class add dev $DEV parent 10:0 classid 10:1 cbq bandwidth 100Mbit rate
40Mbit allot 1514 weight 1Mbit prio 8 maxburst 63 avpkt 1000 ewma 8 bounded
$TC filter add dev $DEV parent 10:0 protocol ip prio 100 u32 match ip dst
192.168.13.0/24 flowid 10:1
I must admit that the results were not very enticing. Why is it that additional
20Mbps of traffic can burst through the "bounded" class 10:1 in case
3?
I changed my injected traffic from 80Mbps to 50Mbps in case 3 and I got an
outgoing traffic of 50Mbps (it was not bounded at 40Mbps !!).
It can be seen that the bounding mechanism does not depend much on the incoming
traffic. I tried changing the avpkt value from 1000 to 1250 but nothing
changes. Did I do anything wrong in my config or anyone can offer me any
explanation.Has it anything to do with the not-so-fined grain of the estimator?
I would appreciate a lot for any pointers.
Thanks and kind regards,
cheewei
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