: However I have a doubt on [1]. When packets arrive to an HTB
: filter, it first checks to see if there are ctokens available.
: How come if there are, it then checks for tokens instead of just
: dequeuing at full speed. And if there are none: shouldn´t it THEN
: check for tokens instead of discarding right away?
I would like to quibble about terminology here. A filter selects a
destination class (which contains a qdisc). Filters have absolutely
nothing to do with tokens. Once a packet has been filtered, it
enters its destination class.
Roughly speaking, the class does the following:
1. check to see if there are tokens availabledequeue
2. check to see if there are ctokens available dequeue
3. wait until tokens become availablegoto 2 (1?)
Once a packet is in an HTB class, the packet will not get discarded
by the class until the class itself has a tremendous backlog and
needs to drop the packet. An HTB class will delay the transmission
of the packet until tokens are available. This is the core feature
which provides the shaping capability.
: Also, could you give me an advice or reference on the following?
: I need a child class to allow passage to a video stream that I
: KNOW has mean X kbps and seldom peaks of Y kbps and T seconds.
: Would the best way be to just configure mean=X, ceil=Y? Or should
: I configure mean=ceil=X and calculate a cburst that´ll allow
: passage of the peaks? Or maybe a third option.
I cannot recommend an optimal calculation method, though I would
start with X kbps as the rate and Y kbps * T as the burst. After
that, I'd increase rate and decrease burst until there was no
choppiness in the transmitted video stream.
Good luck,
-Martin
: - Original Message - From: Martin A. Brown
: [EMAIL PROTECTED]
: To: VideoIP [EMAIL PROTECTED]
: Cc: lartc lartc@mailman.ds9a.nl
: Sent: Wednesday, July 13, 2005 2:14 AM
: Subject: Re: [LARTC] HTB: ¿how do burst/cburst work exactly?
:
:
:
: Hello,
:
: : I´ve read all the definitions of burst and cburst and I´ve tried
: : playing with the parameters and graphing the output of the filter
: : to see its effects, but STILL I can´t figure out how the
: : parameters work exactly.
: :
: : Could anyone give a better explanation than the manpage?
:
: Have you tried Stef's site? He has a good page [0] that talks about
: the various tests he did while experimenting with HTB burst and
: cburst parameters?
:
: Some time ago, I took a stab at creating a visual representation [1]
: of a hypothetical HTB configuration [2]. In order to understand
: when cburst is used, look for the diamond-shaped boxes in the
: diagram which talk about tokens and ctokens.
:
: Every HTB class has two buckets.
:
: rate bucket is of burst size, traffic uses tokens
: ceil bucket is of cburst size, traffic uses ctokens
:
: My diagram may give you the framework to understand exactly how they
: are used if it's still unclear to you, but Stef's site will give you
: much better detail on the results of using burst and cburst. Of the
: scenarios he describes, I like the results of Test 7 the best. The
: only guideline that struck me after reading his results was to
: prefer burst and cburst usage on parent classes.
:
: Good luck,
:
: -Martin
:
: [0] http://www.docum.org/docum.org/tests/htb/burst/
: [1] http://linux-ip.net/traffic-control/htb-class.png
: [2] http://linux-ip.net/traffic-control/diagram.html
:
:
--
Martin A. Brown --- Wonderfrog Enterprises --- [EMAIL PROTECTED]___
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