Re: [quicwg/base-drafts] Add more context and text around ACK frequency (#3706)

Martin Thomson <notifications@github.com> Thu, 28 May 2020 23:53 UTC

Return-Path: <noreply@github.com>
X-Original-To: quic-issues@ietfa.amsl.com
Delivered-To: quic-issues@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 2557B3A0FC8 for <quic-issues@ietfa.amsl.com>; Thu, 28 May 2020 16:53:33 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -3.101
X-Spam-Level:
X-Spam-Status: No, score=-3.101 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_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: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=github.com
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 2q1HBu60Kw5N for <quic-issues@ietfa.amsl.com>; Thu, 28 May 2020 16:53:31 -0700 (PDT)
Received: from out-1.smtp.github.com (out-1.smtp.github.com [192.30.252.192]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 689BA3A0FC6 for <quic-issues@ietf.org>; Thu, 28 May 2020 16:53:31 -0700 (PDT)
Received: from github-lowworker-c5134a3.ac4-iad.github.net (github-lowworker-c5134a3.ac4-iad.github.net [10.52.23.55]) by smtp.github.com (Postfix) with ESMTP id C1673C605F9 for <quic-issues@ietf.org>; Thu, 28 May 2020 16:53:30 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=github.com; s=pf2014; t=1590710010; bh=JEmPkdIno1mGWNgDl2J2xeHdSmaBcrv7uDDOP1Wi2eQ=; h=Date:From:Reply-To:To:Cc:In-Reply-To:References:Subject:List-ID: List-Archive:List-Post:List-Unsubscribe:From; b=JCP1Zi2KrSrcsozOBNZCx8K/zVWtTQyPJT2DFJv9GOJgsg/Wp1a4qYvw/hlMEtHCM bQcK3fGtuNqyBWx38WH4TTh3f1aDrXdVPbMz/ZsMb3oPrpV41LJ3uLGYeTndjG+9TB uuhDC/+44DzeO2nT1z3g9KGYqfIQC3lgC/w3zWfU=
Date: Thu, 28 May 2020 16:53:30 -0700
From: Martin Thomson <notifications@github.com>
Reply-To: quicwg/base-drafts <reply+AFTOJK6M5JI7U6N7YQRJ4WF43QX7VEVBNHHCKUVTR4@reply.github.com>
To: quicwg/base-drafts <base-drafts@noreply.github.com>
Cc: Subscribed <subscribed@noreply.github.com>
Message-ID: <quicwg/base-drafts/pull/3706/review/420566327@github.com>
In-Reply-To: <quicwg/base-drafts/pull/3706@github.com>
References: <quicwg/base-drafts/pull/3706@github.com>
Subject: Re: [quicwg/base-drafts] Add more context and text around ACK frequency (#3706)
Mime-Version: 1.0
Content-Type: multipart/alternative; boundary="--==_mimepart_5ed04efab09b8_22773fe05c4cd96c176022"; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: list
X-GitHub-Sender: martinthomson
X-GitHub-Recipient: quic-issues
X-GitHub-Reason: subscribed
X-Auto-Response-Suppress: All
X-GitHub-Recipient-Address: quic-issues@ietf.org
Archived-At: <https://mailarchive.ietf.org/arch/msg/quic-issues/9XbBGFK8BX4NeGKuccxM4OspLyQ>
X-BeenThere: quic-issues@ietf.org
X-Mailman-Version: 2.1.29
List-Id: Notification list for GitHub issues related to the QUIC WG <quic-issues.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/quic-issues>, <mailto:quic-issues-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/quic-issues/>
List-Post: <mailto:quic-issues@ietf.org>
List-Help: <mailto:quic-issues-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/quic-issues>, <mailto:quic-issues-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 28 May 2020 23:53:33 -0000

@martinthomson approved this pull request.

Thanks!  This appears to be much better.  And it points in the right direction without being overly prescriptive.

>  
-Packets containing only ACK frames are not congestion controlled, so there are
-limits on how frequently they can be sent.  An endpoint MUST NOT send more than
-one ACK-frame-only packet in response to receiving an ack-eliciting packet.  An
-endpoint MUST NOT send a non-ack-eliciting packet in response to a
-non-ack-eliciting packet, even if there are packet gaps which precede the
-received packet. Limiting ACK frames avoids an infinite feedback loop of
-acknowledgements, which could prevent the connection from ever becoming idle.
-However, the endpoint acknowledges non-ACK-eliciting packets when it sends an
-ACK frame.
+### Acknowledgement Frequency
+
+A receiver determines how frequently to send acknowledgements in response to
+ack-eliciting packets. This determination involves a tradeoff however.

```suggestion
ack-eliciting packets. This determination involves a tradeoff.
```

>  
-Packets containing only ACK frames are not congestion controlled, so there are
-limits on how frequently they can be sent.  An endpoint MUST NOT send more than
-one ACK-frame-only packet in response to receiving an ack-eliciting packet.  An
-endpoint MUST NOT send a non-ack-eliciting packet in response to a
-non-ack-eliciting packet, even if there are packet gaps which precede the
-received packet. Limiting ACK frames avoids an infinite feedback loop of
-acknowledgements, which could prevent the connection from ever becoming idle.
-However, the endpoint acknowledges non-ACK-eliciting packets when it sends an
-ACK frame.
+### Acknowledgement Frequency
+
+A receiver determines how frequently to send acknowledgements in response to
+ack-eliciting packets. This determination involves a tradeoff however.
+
+Endpoints rely on timely acknowledgment to detect loss; see Section X of

We'll need a value for X.

```suggestion
Endpoints rely on timely acknowledgment to detect loss; see Section 5 of
```

> -limits on how frequently they can be sent.  An endpoint MUST NOT send more than
-one ACK-frame-only packet in response to receiving an ack-eliciting packet.  An
-endpoint MUST NOT send a non-ack-eliciting packet in response to a
-non-ack-eliciting packet, even if there are packet gaps which precede the
-received packet. Limiting ACK frames avoids an infinite feedback loop of
-acknowledgements, which could prevent the connection from ever becoming idle.
-However, the endpoint acknowledges non-ACK-eliciting packets when it sends an
-ACK frame.
+### Acknowledgement Frequency
+
+A receiver determines how frequently to send acknowledgements in response to
+ack-eliciting packets. This determination involves a tradeoff however.
+
+Endpoints rely on timely acknowledgment to detect loss; see Section X of
+{{QUIC-RECOVERY}}. Window-based congestion controllers, such as the one in
+Section X of {{QUIC-RECOVERY}}, rely on acknowledgments to manage their sending

```suggestion
Section 6 of {{QUIC-RECOVERY}}, rely on acknowledgments to manage their sending
```

> +packets. Better knowledge of network conditions or further research and
+experimentation might suggest alternative acknowledgment strategies with better
+performance characteristics. This recommendation is general in nature and
+consistent with recommendations for TCP endpoint behavior {{?RFC5681}}.

I think maybe we can swap the last two sentences, so that "this recommendation" is better bound to the first sentence.

> @@ -3555,6 +3563,16 @@ messages are delayed or lost.  Note that the same limitation applies to other
 data sent by the server protected by the 1-RTT keys.
 
 
+### PADDING Frames Consume Congestion Window
+
+Packets containing PADDING frames are considered to be in flight for congestion
+control purposes {{QUIC-RECOVERY}}. Sending only PADDING frames might cause the
+sender to become limited by the congestion controller with no acknowledgments
+forthcoming from the receiver. Therefore, a sender SHOULD ensure that other
+frames are sent periodically in addition to PADDING frames to elicit acknowledgments from

Check line length.

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/quicwg/base-drafts/pull/3706#pullrequestreview-420566327