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From: "Richard Scheffenegger" <rscheff@gmx.at>
To: <BeckW@telekom.de>, <sgunderson@bigfoot.com>,
	<bloat@lists.bufferbloat.net>
Subject: Re: [Bloat] Not all the world's a WAN
Date: Tue, 23 Aug 2011 09:37:32 +0200	[thread overview]
Message-ID: <BCA035584D37472A9CB3E6E9C6525456@srichardlxp2> (raw)
In-Reply-To: <AAE428925197FE46A5F94ED6643478FEA91BE93823@HE111644.EMEA1.CDS.T-INTERNAL.COM>

Some do. i.e. l3 capable switches, broadcom scorpio (and later) can do ecn 
marking based on l2 buffer occupancy.

see the paper from stanford/microsoft about dctcp - ecn marking based on 
instantaneous buffer occupancy and proportional tcp reaction (rather than 
halving cwnd) per rtt...

rgds
----- Original Message ----- 
From: <BeckW@telekom.de>
To: <sgunderson@bigfoot.com>; <bloat@lists.bufferbloat.net>
Sent: Friday, August 19, 2011 4:59 PM
Subject: Re: [Bloat] Not all the world's a WAN


>> [...]so over short intervals the switch's aggregate incoming bandwidth 
>> (multiple 10GbE links from
>> servers) is larger than its outgoing bandwidth (single 10GbE link to 
>> client).
>
> Well, this kind of burstiness is the reason why we have buffers at all.
>
> Restricting the window size limits the TCP speed and keeps it this way 
> from overflowing the buffer outside of bursty periods.
>
> ECN marking helps TCP to distinguish between really available bandwidth 
> and 'fake' bandwidth that just fills up a buffer, at least if the feedback 
> loop is fast enough. Do ethernet switches support ECN marking?
>
> _______________________________________________
> Bloat mailing list
> Bloat@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat 


  reply	other threads:[~2011-08-23  6:45 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-08-18  1:26 Patrick J. LoPresti
2011-08-18  3:57 ` Stephen Hemminger
2011-08-18  7:45   ` Neil Davies
2011-08-18  5:08 ` Steinar H. Gunderson
2011-08-19 14:59   ` BeckW
2011-08-23  7:37     ` Richard Scheffenegger [this message]
2011-08-23  7:44 ` Richard Scheffenegger

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