From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f181.google.com (mail-wi0-f181.google.com [209.85.212.181]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 5FDE02021A8 for ; Sat, 14 Jul 2012 14:50:00 -0700 (PDT) Received: by wibhm2 with SMTP id hm2so1296367wib.10 for ; Sat, 14 Jul 2012 14:49:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=F3SpISXuJV4GhL87W/WJkzDerjFl4gM6svz8sp8C2xs=; b=J4GyqZCatDeIU9tGJn1n2bZjTLqiKv0kPQqpmZFaw2afQSHsiEL6DJya7vlROO83fx hQ+dh3/Dqlp17mmpNHA7yz33s3n+SLOFKHsAz0zKnkrZnwuAO6gR4HexqT14y7a941Um 5y3Sr7ufxwn3ADk2dEozXP3OZ+yw7N6KJBTdKg3OdvrIdxYQuEXWk7Ot26WtI6S5o1u1 Sbc5la5QF1Fzwl1OhjdbvWubIZhMcJHwA5Z1RugyeuuUJoSxSh4gVGXbFPYR1aDwxSGV dox64NbgFIZjpXdpIkuLj7JNK8W2n5mVLAHBBiInVhxAsRbmzsLMoAkqnYCkAB+IsFBN USOA== MIME-Version: 1.0 Received: by 10.180.98.138 with SMTP id ei10mr7303731wib.1.1342302596974; Sat, 14 Jul 2012 14:49:56 -0700 (PDT) Received: by 10.223.96.132 with HTTP; Sat, 14 Jul 2012 14:49:56 -0700 (PDT) In-Reply-To: <5000D10E.4070208@pollere.com> References: <5000D037.7030103@pollere.com> <5000D10E.4070208@pollere.com> Date: Sat, 14 Jul 2012 17:49:56 -0400 Message-ID: From: Dave Taht To: Kathleen Nichols , Fred Baker Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: codel@lists.bufferbloat.net Subject: Re: [Codel] Fwd: Re: [tsvwg] new draft on CoDel AQM X-BeenThere: codel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: CoDel AQM discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 14 Jul 2012 21:50:00 -0000 I'm not sure if fred is on the codel list... On Fri, Jul 13, 2012 at 9:53 PM, Kathleen Nichols wro= te: >> >>> 3.3. About the interval >>> >>> The interval constant is loosely related to RTT since it is chosen >>> to give endpoints time to react without being so long that >>> response times suffer. A setting of 100ms works well across a >>> range of RTTs from 10ms to 1 second (excellent performance is >>> achieved in the range from 10 ms to 300ms). For devices intended >>> for the normal, terrestrial internet interval SHOULD have the value >>> of 100ms. >> >> For very low RTT environments, such as data centers, or very high >> delay environments such as multi-hop satcom, is "interval" a >> configuration constant? Eric Dumazet has run many of his (targetted at data center) 10GigE benchmarks with a target delay of 500us and an interval of 20, with the default packet limit of 10k packets. 5ms is an eternity at those speeds. Overrunning the packet limit results in "interesting" drop tail behavior, too. The reference linux implementation allows for setting target, interval, ecn enablement and packet limits. Additionally the fq_codel implementation allows for alternate quantums and number of flows in the hashing algorithm. Having not read this draft... I do have some real world cautions to make. IF an ethernet driver (under linux) isn't soft limited (htb or hfsc) or has does NOT have BQL enabled, the underlying buffering in the stack can/will defeat codel/fq_codel's management utterly. On wifi, which features wildly random delays in the .2-20 second range, I am presently getting poor utilization at 13ms and 27ms targets in fq_codel. I frankly didn't expect much at this stage of the game there (only got one of the core patches last week) - there's too much work left to be done at the wifi driver layer to draw any conclusions from the data points I have so far. I think the ecn implementation of codel in linux needs to be thunk on harde= r. >> >> > > Well, there are words about that in Section 5. Testing and analysis can > determine > appropriate settings for those circumstances. > > This seems to just be cross-posted to a Cisco internal list? This was > not meant for IETF > discussion? > > > _______________________________________________ > Codel mailing list > Codel@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/codel --=20 Dave T=E4ht http://www.bufferbloat.net/projects/cerowrt/wiki - "3.3.8-6 is out with fq_codel!"