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Date:      Fri, 6 Jun 2014 23:31:57 +1000 (EST)
From:      Ian Smith <smithi@nimnet.asn.au>
To:        bycn82 <bycn82@gmail.com>
Cc:        'Luigi Rizzo' <rizzo@iet.unipi.it>, "'Alexander V. Chernikov'" <melifaro@ipfw.ru>, 'FreeBSD Net' <net@freebsd.org>
Subject:   RE: [CFT]: ipfw named tables / different tabletypes
Message-ID:  <20140606222753.W15833@sola.nimnet.asn.au>
In-Reply-To: <000401cf80d8$ad1bb840$075328c0$@gmail.com>
References:  <20140521204826.GA67124@onelab2.iet.unipi.it> <537E1029.70007@FreeBSD.org> <20140522154740.GA76448@onelab2.iet.unipi.it> <537E2153.1040005@FreeBSD.org> <20140522163812.GA77634@onelab2.iet.unipi.it> <538B2FE5.6070407@FreeBSD.org> <539044E4.1020904@ipfw.ru> <000c01cf80be$41194370$c34bca50$@gmail.com> <20140605134256.GA81234@onelab2.iet.unipi.it> <000001cf80cd$5dc1d9b0$19458d10$@gmail.com> <20140605155402.GA81905@onelab2.iet.unipi.it> <000401cf80d8$ad1bb840$075328c0$@gmail.com>

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On Fri, 6 Jun 2014 00:10:26 +0800, bycn82 wrote:

Hi Bill,

 > Sorry for waste you time to explain it again, I will read the code first.

Especially the code provided in free tutorials by your busy professor ..

 > And the latest patch of `PPS` should be OK, I checked the logic carefully this time. I sent it out last weekend.
 > 
 > logic as below, PPS actually will be fulfilled using `PPT`,(N packets per M ticks).

I think a few people have pointed out likely problems with 'packets per 
tick(s)', and that people tend to prefer packets per second as a more 
natural and familiar concept.  I can see use cases for that, especially 
when applied by easily updateable (and soon, saveable) tables.

Remember that HZ may be set at boot time, and will at times by people 
experimenting with, as one example, dummynet latency versus cpu use, so 
rulesets specifying packets per tick would need also to be modified to 
match, which won't happen.  Packets per second is independent of HZ and 
far easier to comprehend.  See inetd(8) for a typical PPM example, while 
PPS makes more sense for a firewall.

I wonder if something like Bresenham's Linedrawing Algorithm might help?

cheers, Ian



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