Subject: [aqm] splat start?

From: Dave Taht <[email-masked]>
Date: Sat, 9 May 2015 19:18:36 -0700

One of the things bugging me lately is that we actually have a lot of
forms of "slow start"
on the table - HyStart, Initial Spreading, reno vs cubic, dctcp, IW2,
IW4, IW10, TSO offloads, the effect of GRO on it, etc. I dont know
what is in QUIC, either.

I would love a comprehensive guide to exactly the behaviors of "slow
start" in every tcp known to man and some sane way to refer to them
all in a cross reference and a spreadsheet.

Does something like that exist? Just the "* start" behavior.

The world has spent way too much time analyzing congestion avoidance mode.

-- 
Dave Täht

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From: Tim Shepard <[email-masked]>
Date: Sun, 10 May 2015 00:23:59 -0400

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From: Tim Shepard <[email-masked]>
Date: Sun, 10 May 2015 00:59:55 -0400

> all in a cross reference and a spreadsheet.

That reminded me of a loose end from something I noticed a year or so
ago...  that hystart is sometimes problematic, and the magic numbers
in hystart vary in different versions of linux.  It is problematic in
that sometimes hystart limits the throughput rather dramtically
(compared to what can be obtained when switching linux's
tcp_congestion_control algorithm to "reno") and it is also problematic
that different versions of linux have different versions of hystart
(with different magic numbers compiled in).

The situation I recall was where hystart was limiting the congestion
window in situations where one of its two mechanisms was being
triggered prematurely over a short (low RTT) path that involved
802.11n or 802.11ac wireless hop with high capacity which was the
bottleneck.

And this reminds me of Bob's other observations on this list yesterday
regarding what he found in Linux code.  (But in that case, it was, in
linux PIE which is not used by default anywhere AFAIK, but both of
hystart's mechanisms seem to be on by default in linux's default TCP
congestion control algorithm these days.   Oops.)

			-Tim Shepard
			 [email-masked]

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From: Mirja Kühlewind <[email-masked]>
Date: Mon, 11 May 2015 14:26:32 +0200

Hi Dave,

Michael Scharf performed his PhD thesis on start up mechanisms. Here is one of his papers (from 2009):

Scharf, M.: Work in Progress: Performance Evaluation of Fast Startup Congestion Control Schemes
Proceedings of the 8th IFIP-TC6 Networking Conference (Networking 2009), Lecture Notes in Computer Science (LNCS) 5550, Aachen, May 2009

I guess he can further comment on this own (cc’ed).

Mirja

> Am 10.05.2015 um 04:18 schrieb Dave Taht <[email-masked]>:
> 
> _______________________________________________
> aqm mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/aqm

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From: Dave Taht <[email-masked]>
Date: Mon, 11 May 2015 10:38:08 -0700

> Michael Scharf performed his PhD thesis on start up mechanisms. Here is one of his papers (from 2009):

Am I the only person that works in spreadsheets to model stuff? :(

> Proceedings of the 8th IFIP-TC6 Networking Conference (Networking 2009), Lecture Notes in Computer Science (LNCS) 5550, Aachen, May 2009

Thank you. I did not know that work had also fed back into RFC6928.

https://www.bell-labs.com/researchers/537/

thesis here. But I will need a spare weekend to read it.

http://www.ikr.uni-stuttgart.de/Content/Publications/Archive/Sf_Diss_40112.pdf

-- 
Dave Täht
Open Networking needs **Open Source Hardware**

https://plus.google.com/u/0/+EricRaymond/posts/JqxCe2pFr67