Re: Two Notable Ack Frequency Issues

Ian Swett <> Tue, 14 September 2021 02:04 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 2F1443A0B89 for <>; Mon, 13 Sep 2021 19:04:18 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -18.098
X-Spam-Status: No, score=-18.098 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_MED=-0.499, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, ENV_AND_HDR_SPF_MATCH=-0.5, HTML_MESSAGE=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, USER_IN_DEF_DKIM_WL=-7.5, USER_IN_DEF_SPF_WL=-7.5] autolearn=ham autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (2048-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id L-PaFq3ENCei for <>; Mon, 13 Sep 2021 19:04:14 -0700 (PDT)
Received: from ( [IPv6:2607:f8b0:4864:20::b2e]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 422FB3A0B88 for <>; Mon, 13 Sep 2021 19:04:14 -0700 (PDT)
Received: by with SMTP id s16so24805068ybe.0 for <>; Mon, 13 Sep 2021 19:04:14 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=WwF0VkDu8ZJJ7dRMrns3BvZqTM22GvlLoOhA5hxGUq8=; b=LixYxscc6OCnykZfw7/tI6KcudfSVQp8MWlWo5sBBjksrix2iSPC5GB1qh1c90DO5+ MGq8lP5GmjPm//eIMSanphD7cN/xuevfVcvSHwpOGZB69XvdhtDWIbz1v91wTweddvjy G8+c90s3Gz+2/XV7RtMm9jSVCWMrYe1iIF9XP+GFgHa9RkOeAuqjUmrKPeh1YP9u18p7 86c2HM8OfdX2PYw/qVBDbhvQqXOACkNhtP8c1DUdHevO9pA/eRC5Peeujby/IcvwQJMK AmGtKviPwLVLXNPnDnFsaCN4Fp5v8J5VnsPp7dZdLxM5LG2bSDQbCtL8fNh+f6wGkjlC W2sQ==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=WwF0VkDu8ZJJ7dRMrns3BvZqTM22GvlLoOhA5hxGUq8=; b=0KKB5VW+GwpkfftO5L1PBB564JrKxDo0zf+XeVgqkvVYIDymeF2BRZ5YWbsUilSWhy Em5K3lbNBYXbb13aRVsRqqiLDTzdjrA+/Q4lEmS0Ube+i68nfeN5kl808xJHZXIqEhhD TpbxRg15/6odGu6M3LaxN3HJP0qv3e8X2e/c6WWf10EgdXwgsM8sW9qfjPUuHAwj3MXQ owb6c36uQotYt4XveVepkR1aeGyrWa12HZHZ1m5Rlq0A2//svjXswX2Bpj7u3gRdlkzh 40rdPI+iRQ5lJXWYoVFkBfwg3RlPgY39PiB7A8FBFbHKbEh0wy5w1fnIZo+itFU3u8wW mOSQ==
X-Gm-Message-State: AOAM530XOpyKzhtIInpEbMLGx5WQDpflH321iFR4XsfLTF2X+uMs5kCj aGGHtpMVMHiinnhr4PrJEOnZyqZLpIH2ptafjj8rLK3ftW0=
X-Google-Smtp-Source: ABdhPJyA9Et6gOWUyzC/oVq9qzBojPEkNiTwU1oU/pB+ZPb0wMr9VebuS11iYVnLcZYVTNwKA+fPNJ5azNZCCjjGTds=
X-Received: by 2002:a25:3002:: with SMTP id w2mr17846886ybw.76.1631585052267; Mon, 13 Sep 2021 19:04:12 -0700 (PDT)
MIME-Version: 1.0
References: <> <> <> <> <>
In-Reply-To: <>
From: Ian Swett <>
Date: Mon, 13 Sep 2021 22:04:01 -0400
Message-ID: <>
Subject: Re: Two Notable Ack Frequency Issues
To: Roberto Peon <>
Cc: Martin Thomson <>, "" <>
Content-Type: multipart/alternative; boundary="0000000000007685ee05cbeaff8e"
Archived-At: <>
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Main mailing list of the IETF QUIC working group <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Tue, 14 Sep 2021 02:04:19 -0000

Thanks for all the feedback, I've substantially changed my PR on NO_ACK to
be DELAY_ACK.  I already have a use case for DELAY_ACK, so I think it's
potentially quite useful.  I'd also like to change how peers ACK(or rather
do not ACK) PADDING only packets, but I have not done that in this
<> PR.

I also left a recent comment
<> on
the ECN issue, since I'm not 100% sure all endpoints that use ECN will want
the Accurate ECN response.  I'm not sure we're in a good place to redesign
ECN response, but I suggested what I thought were the 3 most
straightforward options.

On IMMEDIATE_ACK, it both solves a clear problem(PN skipping no longer
elicits an immediate ACK when 'Ignore Order' is true) as well as following
in the footsteps of the TCP drafts.  Additionally, it was discussed at the
last IETF, and the only outstanding question I am aware of from that
discussion was what to name the frame (
Slides 7 to 11
the relevant slides.

>From the minutes on IMMEDIATE_ACK, the last two points are:

*Matt:* seems like most people are in favor of option 2, 1-byte frame (or
semi-PING frame, see jabber). Doing option 1 (header bit) is probably not
*Jana:* will go ahead with option 2. If strong disagreement, please comment
on issue <>.

Thanks, Ian