[LARTC] Changing TBF rate on the fly results in drops?

[Francesco Zampognaro]

Hi everybody, it is my first message here. I tried to browse  
throughout older posts but I found no immediate answer.

I need to change rate of a tbf queue while ip packets are already  
enqueued by it. If I go:

tc qdisc replace|change|link dev eth0 root tbf rate 180kbit burst 1540  
limit 15400

as results all enqueued packets seems to disappear. I can see that from a:

tc -s qdisc ls dev eth0

where backlog suddenly goes down to zero packets. Iperf performances  
also confirm that. Using custom kernel 2.6.20.1 on Ubuntu 6.06.

Where can I look to understand what is going on? Can I do something  
else to get the same result (shaping outgoing traffic dynamically and  
very often without losses)?


Thanks in advance!

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Francesco
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