Re: [LARTC] HTB burst, cburst parameters

[Amit Kucheria <amitk@ittc.ku.edu>]

On Tue, 11 Dec 2001, devik wrote:

> > Hmm...so if i understand this correctly, 'burst' controls 'rate' and
> > 'cburst' controls 'ceil'?
> 
> exactly.
> 
> > Lets say that i am generating bursty fixed length UDP traffic i.e.1470
> > bytes every 5000us.
> > Now for a pkt size of 1470 bytes and 'rate' and 'ceil' being 1.536Mbit
> > what would be the ideal values of burst and cburst?
> 
> So one 1.5k packet then 5ms pause, other 1.5 packet ... ok ?
> It leads to rate cca 1500/5ms = 300kBps = 2.4mbit.
> 
> Because is exceeds your 1.5mbit rate so that the burst value
> is not so important. Just use minimal value:
> 
> burstmin = 1.5mbit/8*10ms = 2k
> 
> devik

Using those parameters puts the cap on my bandwidth real hard, not at all 
accuate. Infact, my connections go haywire. Here are the results.
-----------------------------------------------------------------
testbed16 [30] % sudo ./T1-using-htb
TC=/usr/bin/tc
DEVICEÞv eth1
BANDWIDTHºndwidth 10Mbit
LIMITBW=1Mbit
AVPKT=avpkt 1470
SRC\x192.168.157.2
DEST\x192.168.158.2
tc qdisc add dev eth1 root handle 1: htb
tc class add dev eth1 parent 1: classid 1:1 htb rate 1Mbit ceil 1Mbit burst 2k
-----------------------------------------------------------------
testbed16 [32] % showinfo eth1
----------------------------------
            QDISC logs
----------------------------------
qdisc htb 1: dev eth1 r2q 10 default 1 dcache 0
 deq_util 1/1000000 deq_rate 0 trials_per_deq 0 dcache_hits 0
 Sent 2946644 bytes 2105 pkts (dropped 1209, overlimits 9640) 

 ----------------------------------
            CLASS logs
----------------------------------
class htb 1:1 root prio 0 rate 1Mbit ceil 1Mbit burst 2Kb cburst 2Kb 
 Sent 2946644 bytes 2105 pkts (dropped 1209, overlimits 8506) 
 rate 283bps 
 lended: 2105 borrowed: 0 giants: 0 injects: 0
 tokens: 15491 ctokens: 15491
-----------------------------------------------------------------

When i increase the burst size to say 100k i get better thruput but still 
not equivalent to the ceil.

Regards,
Amit
-- 
The statement below is true.
The statement above is false.
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                  Amit Kucheria
          EECS Grad. Research Assistant
         University of Kansas @ Lawrence
   (R)+1-(785)-830 8521 ||| (O)+1-(785)-864 7774
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