From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yk0-x22a.google.com (mail-yk0-x22a.google.com [IPv6:2607:f8b0:4002:c07::22a]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 800F521F985 for ; Tue, 11 Aug 2015 10:35:05 -0700 (PDT) Received: by ykdz80 with SMTP id z80so61493835ykd.2 for ; Tue, 11 Aug 2015 10:35:05 -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; bh=tULLAy9EgKN5Hj+KYkw/SiEvCZfkZbkF8GouWaPeN0M=; b=J+J8MH98jqd0icGU2WCXhCVC9D0XZ2YNrZrMzLGJsX9WAnQJVZBHXSFsm2WPaLTeGR +hdLyzFRH37yH9c/sLuFweWHHViXQSbhj7VBbuyzUsZMwd1zziZYlIf6KV4u/+f0Cnbj nsW79o7jEcylTNQ81Xl+S/QebpOLzIebRxWZhYTfUA1OYQwjhi5IW3ZwyN7BFurA5Rad HjZiuD35jTeJ1f2h6CgN9FaGXGpQf4XmIaeFRBZ5D6+JmnB3XupKtA2nWX2LcLuenIU5 HBBfLeqWxsd/05ydOjc9XBPjd+dHvqlo68+RvTgByyR2yLThclNvYY00dmWMXnFvym+T MrnQ== MIME-Version: 1.0 X-Received: by 10.170.41.144 with SMTP id 138mr26966439ykj.45.1439314504930; Tue, 11 Aug 2015 10:35:04 -0700 (PDT) Received: by 10.37.214.203 with HTTP; Tue, 11 Aug 2015 10:35:04 -0700 (PDT) Received: by 10.37.214.203 with HTTP; Tue, 11 Aug 2015 10:35:04 -0700 (PDT) In-Reply-To: <274D3A0FA900FD47AA6B56991AAA32FDC53BB45E@wtl-exchp-1.sandvine.com> References: <274D3A0FA900FD47AA6B56991AAA32FDC53BB45E@wtl-exchp-1.sandvine.com> Date: Tue, 11 Aug 2015 20:35:04 +0300 Message-ID: From: Jonathan Morton To: Jeff Weeks Content-Type: multipart/alternative; boundary=001a1137d442c95b42051d0c8583 Cc: codel@lists.bufferbloat.net Subject: Re: [Codel] drop state short-circuit... 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: Tue, 11 Aug 2015 17:35:34 -0000 --001a1137d442c95b42051d0c8583 Content-Type: text/plain; charset=UTF-8 The logic is that if the stored count was effectively controlling the queue, we want to keep using that value if the network is still under load. If 16 intervals (1.6 seconds) pass without re-entering drop state, we can assume the link is no longer saturated (by this flow) and reset count. I think the value 16 itself is mostly arbitrary. I'm a bit skeptical of the way count is saved and restored in the reference versions - it's hard to follow. Cake's version explicitly keeps the old value, but halves it, allowing it to grow back to its original value if required. It would also be reasonable to scale the backoff with time, rather than thresholding it. - Jonathan Morton --001a1137d442c95b42051d0c8583 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable

The logic is that if the stored count was effectively contro= lling the queue, we want to keep using that value if the network is still u= nder load.=C2=A0 If 16 intervals (1.6 seconds) pass without re-entering dro= p state, we can assume the link is no longer saturated (by this flow) and r= eset count.

I think the value 16 itself is mostly arbitrary.

I'm a bit skeptical of the way count is saved and restor= ed in the reference versions - it's hard to follow.=C2=A0 Cake's ve= rsion explicitly keeps the old value, but halves it, allowing it to grow ba= ck to its original value if required.=C2=A0 It would also be reasonable to = scale the backoff with time, rather than thresholding it.

- Jonathan Morton

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