On Fri, 8 Jun 2012, Bill Bogstad wrote:
On Fri, Jun 8, 2012 at 8:35 AM, Edward Ned Harvey <[email protected]> wrote:
From: Bill Bogstad [mailto:[email protected]]
Sent: Thursday, June 07, 2012 11:35 AM
I'm going to have to disagree with this. A congested link SHOULD
drop TCP packets so that congestion control knows to slow down.
It's actually this thinking which results in deploying equipment and
software that creates buffer bloat.
What are you calling buffer bloat?
I'm (attempting) to use the term as I understand Jim Getty does. He
coined the term in 2010 on his blog:
http://gettys.wordpress.com/2010/12/03/introducing-the-criminal-mastermind-bufferbloat/
If you aren't familiar with ongoing work on this issue, you shouldn't
have trouble finding information about it. This recent CACM article
by Jim Gettys and Kathleen Nichols might be a good place to start:
http://cacm.acm.org/magazines/2012/1/144810-bufferbloat/fulltext
In addition, the Linux 3.3 kernel has new code in it to attempt to
start dealing with the problem. I'm not going to respond to the rest
of your note until you let me know that I'm using the term incorrectly
or that it isn't relevant to a discussion about whether networks
should ever drop packets.
A simple explanation buffer bload comes from understanding that if a 10
mbs link is presented with 12 mbs of traffic, 20% of the traffic must be
dropped. If there is 10 seconds worth of buffer, then all the traffic not
dropped is delayed 10 seconds. Because dropped packets will generally
cause sources to slow down, the traffic presented will generally slow down
to something very close to capacity and very few dropped packets, but with
10 seconds of delay for every packet - not at all optimal.
dan feenberg
Thanks,
Bill Bogstad
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