Re: [LARTC] Question: traffic shaping (tc-htb)

[Andy Furniss <andy.furniss@dsl.pipex.com>]

John Smith wrote:
> Hello *!
> My trafficshaping (tc-htb) drops packets very early, at least i suspect
> this. It drops about 30% fo the packets. The traffic-generating appication
> is running locally on the shaping host. I think i can lower this rate by
> increasing the packet-buffer, because the locally application will slow down
> with increasing buffer (tcp/ip). But i can´t find any options for that, i
> cycled the manual several times. Is there a solution?
> 
> 
> 
> 
> see output of "tc -s -d class show dev ppp0" (main class):
>     class htb 1:10 parent 1:1 prio 1 quantum 1800 rate 144000bit
>         ceil 480000bit burst 1779b/8 mpu 0b overhead 0b cburst 2199b/8
>         mpu 0b overhead 0b level 0
>     Sent 57567157 bytes 40609 pkts (dropped 16033, overlimits 0)
>     rate 460328bit 40pps
>     lended: 12845 borrowed: 27764 giants: 0
>     tokens: -74623 ctokens: -28826
> 
> This class is the only one with packet drops. Does tc use the kernels
> network packet queue?

HTB uses the txqueuelength of the interface if you don't add a queue to 
the leaf class. For my ppp0 that's 3 which is a bit short - even so I 
just did a test and only got 10% loss so maybe your generator app/kernel 
version of tcp is a bit over aggressive. I did 1 tcp stream with netperf 
on 2.6.12-rc1.

So either add a queue to the leaf and specify a length or before you 
start htb do ifconfig ppp0 txqueuelen 30 or whatever.


Andy.


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