Re: [quicwg/base-drafts] Changing the Default QUIC ACK Policy (#3529)

Jana Iyengar <> Fri, 29 May 2020 06:41 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id BBC453A090A for <>; Thu, 28 May 2020 23:41:29 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -3.1
X-Spam-Status: No, score=-3.1 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, HTML_IMAGE_ONLY_32=0.001, HTML_MESSAGE=0.001, MAILING_LIST_MULTI=-1, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (1024-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id Ve7r8VpQC5BI for <>; Thu, 28 May 2020 23:41:28 -0700 (PDT)
Received: from ( []) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 651E83A0908 for <>; Thu, 28 May 2020 23:41:28 -0700 (PDT)
Received: from ( []) by (Postfix) with ESMTP id 71C918C0F24 for <>; Thu, 28 May 2020 23:41:27 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=pf2014; t=1590734487; bh=tuy8yiyTo2zASVcB+0mzfylwMfKgZ3Unk8nPbsCAMuE=; h=Date:From:Reply-To:To:Cc:In-Reply-To:References:Subject:List-ID: List-Archive:List-Post:List-Unsubscribe:From; b=pn9a0L9akXSuePWnHQfV0KgO8KNW2H3JUtlSw+chpBhPxzCRGzMNgQgXsNIkRa7ez 0sAcujfYvZ/vXwZy8SzVJIB+n4b0Ywjfv1H9X3bN+GtvaDbiTga97xB6gylfaGT4Qf rXuDvIwQAV56EWDEYa7xZXUguUWSdUVCYEXXlnJQ=
Date: Thu, 28 May 2020 23:41:27 -0700
From: Jana Iyengar <>
Reply-To: quicwg/base-drafts <>
To: quicwg/base-drafts <>
Cc: Subscribed <>
Message-ID: <quicwg/base-drafts/issues/3529/>
In-Reply-To: <quicwg/base-drafts/issues/>
References: <quicwg/base-drafts/issues/>
Subject: Re: [quicwg/base-drafts] Changing the Default QUIC ACK Policy (#3529)
Mime-Version: 1.0
Content-Type: multipart/alternative; boundary="--==_mimepart_5ed0ae976230c_180c3fc729acd96c1492cf"; charset="UTF-8"
Content-Transfer-Encoding: 7bit
Precedence: list
X-GitHub-Sender: janaiyengar
X-GitHub-Recipient: quic-issues
X-GitHub-Reason: subscribed
X-Auto-Response-Suppress: All
Archived-At: <>
X-Mailman-Version: 2.1.29
List-Id: Notification list for GitHub issues related to the QUIC WG <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Fri, 29 May 2020 06:41:30 -0000

@gorryfair : I understand your position. While I agree that ack thinning happens with TCP, it is not what I expect to find on a common network path. And as far as I know, the endpoints still implement the RFC 5681 recommendation of acking every other packet.

What you are arguing is that _with ack thinners in the network_ TCP's behavior on _those_ network paths is different. However, I do not believe we understand the performance effects of these middleboxes, that is, how they might reduce connection throughput when the asymmetry is not a problem. Importantly,  I don't think we should be specifying as default what some middleboxes might be doing without fully understanding the consequences of doing this. Please bear in mind that Chrome's ack policy of 1:10 works with BBR, not with Cubic or Reno. 

I do not believe there is a magic number at the moment, and as @kazuho noted, even 1:10 is not a small enough ratio under some conditions. Given this, and given that we know 1:2 is used by TCP endpoints, it makes the most sense to specify that as the suggested guidance. The new text proposed in #3706 describes the tradeoff involved, and the rationale for using 1:2. I am strongly against doing anything substantially different without _overwhelming information_.

You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub: