From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <rick.jones2@hpe.com>
Received: from g2t2353.austin.hpe.com (g2t2353.austin.hpe.com [15.233.44.26])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256
 bits)) (No client certificate requested)
 by lists.bufferbloat.net (Postfix) with ESMTPS id DAD413B260;
 Fri, 20 May 2016 13:21:19 -0400 (EDT)
Received: from g2t2360.austin.hpecorp.net (g2t2360.austin.hpecorp.net
 [16.196.225.135])
 by g2t2353.austin.hpe.com (Postfix) with ESMTP id 0F0C444;
 Fri, 20 May 2016 17:21:19 +0000 (UTC)
Received: from [16.103.148.51] (tardy.usa.hp.com [16.103.148.51])
 by g2t2360.austin.hpecorp.net (Postfix) with ESMTP id 7C43A50;
 Fri, 20 May 2016 17:21:18 +0000 (UTC)
To: Jonathan Morton <chromatix99@gmail.com>
References: <CEE3BB80-E6D4-4851-8406-54DBCC0B36AB@gmail.com>
 <22371476-B45C-4E81-93C0-D39A67639EA0@gmx.de>
 <A714A489-BA53-4FCF-BECC-1C092619C556@gmail.com>
 <alpine.DEB.2.02.1605200638530.1578@nftneq.ynat.uz>
 <991C8B50-192E-431A-819F-F1C5954FF64F@gmx.de>
 <alpine.DEB.2.02.1605200654280.1578@nftneq.ynat.uz>
 <4C5D0005-2CAA-4C90-BF0D-7177874872AC@gmail.com> <573F394B.5060009@hpe.com>
 <26FFB878-5E6B-47B8-8DFD-A8765421655F@gmail.com> <573F42DF.9010108@hpe.com>
 <F6FDE6B5-B8E8-4E57-A147-75B578035DF8@gmail.com>
Cc: David Lang <david@lang.hm>, cake@lists.bufferbloat.net,
 codel@lists.bufferbloat.net
From: Rick Jones <rick.jones2@hpe.com>
Message-ID: <573F478E.9000206@hpe.com>
Date: Fri, 20 May 2016 10:21:18 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101
 Thunderbird/38.8.0
MIME-Version: 1.0
In-Reply-To: <F6FDE6B5-B8E8-4E57-A147-75B578035DF8@gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
X-Mailman-Approved-At: Fri, 20 May 2016 13:38:14 -0400
Subject: Re: [Cake] [Codel]  Proposing COBALT
X-BeenThere: cake@lists.bufferbloat.net
X-Mailman-Version: 2.1.20
Precedence: list
List-Id: Cake - FQ_codel the next generation <cake.lists.bufferbloat.net>
List-Unsubscribe: <https://lists.bufferbloat.net/options/cake>,
 <mailto:cake-request@lists.bufferbloat.net?subject=unsubscribe>
List-Archive: <https://lists.bufferbloat.net/pipermail/cake>
List-Post: <mailto:cake@lists.bufferbloat.net>
List-Help: <mailto:cake-request@lists.bufferbloat.net?subject=help>
List-Subscribe: <https://lists.bufferbloat.net/listinfo/cake>,
 <mailto:cake-request@lists.bufferbloat.net?subject=subscribe>
X-List-Received-Date: Fri, 20 May 2016 17:21:20 -0000

On 05/20/2016 10:07 AM, Jonathan Morton wrote:
>
>> On 20 May, 2016, at 20:01, Rick Jones <rick.jones2@hpe.com> wrote:
>>
>> But I haven't seen that EMSGSIZE happen with netperf UDP tests -
>> could be though I've never run them in an environment which
>> triggered PTMUD.
>
> It’s entirely possible that netperf and/or iperf3 are (ab)using the
> IP_MTU_DISCOVERY socket option mentioned.

I cannot speak to iperf, but netperf doesn't manipulate 
IP_MTU_DISCOVERY.  It will set IP_RECVERR for a UDP_STREAM test, and 
will by default set SO_DONTROUTE (*) for UDP_STREAM but no IP_MTU_DISCOVERY.

happy benchmarking,

rick jones

* QA engineers doing link up/down testing with UDP_STREAM on test 
systems not air-gapped from the production networks are dangerous 
creatures...