netdev - Re: TCP Appropriate Byte Counting per default off

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Wed, 03 Mar 2010 10:33:31 +0100
From:	Alexander Zimmermann <Alexander.Zimmermann@...s.rwth-aachen.de>
To:	Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
Cc:	David Miller <davem@...emloft.net>, Netdev <netdev@...r.kernel.org>
Subject: Re: TCP Appropriate Byte Counting per default off


Am 03.03.2010 um 09:48 schrieb Ilpo Järvinen:

> On Wed, 3 Mar 2010, Alexander Zimmermann wrote:
> 
>> Hi David, hi Ilpo,
>> 
>> I wonder why ABC is off per default? What are the reasons?
>> Should we turn it on per default?
>> 
>> From algorithmic point of view I see no flaws just
>> benefits.
>> 
>> With RFC5681 ABC is recommended.
>> OSX uses ABC per default.
> 
> As Alexey once put it, ABC is very BSD specific algorithm.
> 
> Out of two goals of ABC, protection against split ACKs is achieved in 
> Linux by other means (see tcp_clean_rtx_queue and flags it gives to 
> elsewhere). Thus, you can kind of think that we do APC already :-). The 
> other part, faster increase during slow start, isn't currently done though 
> it would be relatively simple to implement (I think I even have some, 
> possibly unfinished, patch to do that lying around somewhere I wrote 
> someday).

Related to that is a scenario that I have in mind: reverse path reordering.
With ABC we are more robust, ie, open cwnd as normal during SS 

> 
> ABC is not that necessary when window is counted in packets. And besides 
> that, it was found to somewhat hurt small segment flows. There are some 
> messages in archives in the timeframe ABC was disabled (plus there might 
> have been some even older than that).
> 
> -- 
> i.

//
// Dipl.-Inform. Alexander Zimmermann
// Department of Computer Science, Informatik 4
// RWTH Aachen University
// Ahornstr. 55, 52056 Aachen, Germany
// phone: (49-241) 80-21422, fax: (49-241) 80-22220
// email: zimmermann@...rwth-aachen.de
// web: http://www.umic-mesh.net
//

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html