Re: [quicwg/base-drafts] Rework section on persistent congestion (#3961)

Jana Iyengar <notifications@github.com> Sat, 01 August 2020 02:22 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 3AA003A106C for <quic-issues@ietfa.amsl.com>; Fri, 31 Jul 2020 19:22:55 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -3.1
X-Spam-Level:
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: 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 ARpCJ9IVusho for <quic-issues@ietfa.amsl.com>; Fri, 31 Jul 2020 19:22:53 -0700 (PDT)
Received: from out-18.smtp.github.com (out-18.smtp.github.com [192.30.252.201]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 810CA3A1069 for <quic-issues@ietf.org>; Fri, 31 Jul 2020 19:22:53 -0700 (PDT)
Received: from github-lowworker-1ac52d7.ash1-iad.github.net (github-lowworker-1ac52d7.ash1-iad.github.net [10.56.25.52]) by smtp.github.com (Postfix) with ESMTP id A3A5C3403FB for <quic-issues@ietf.org>; Fri, 31 Jul 2020 19:22:52 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=github.com; s=pf2014; t=1596248572; bh=uejLjALTONtJXOz0dhbNZofrxBkf55GqtyOHOYmA8DU=; h=Date:From:Reply-To:To:Cc:In-Reply-To:References:Subject:List-ID: List-Archive:List-Post:List-Unsubscribe:From; b=OOVkCvp7dSNoQJkkXGeeyxbsVEXVAx9WDS2bbgCyQJiAMXL6MOc9orH8TO92rcqZM S/C23FCreMz+vQUwWkRj34NT4AngD4wLSsPdh9F5iYjH2xPnYCcA9D/JHr9TYCt6r8 xXGdTvImDPHyCr+8RA7riO5WJ2mY1Zwi5A+TtXAc=
Date: Fri, 31 Jul 2020 19:22:52 -0700
From: Jana Iyengar <notifications@github.com>
Reply-To: quicwg/base-drafts <reply+AFTOJK26K3YEYLJYN4KLTQV5GCZPZEVBNHHCPPLSJE@reply.github.com>
To: quicwg/base-drafts <base-drafts@noreply.github.com>
Cc: Subscribed <subscribed@noreply.github.com>
Message-ID: <quicwg/base-drafts/pull/3961/review/459542454@github.com>
In-Reply-To: <quicwg/base-drafts/pull/3961@github.com>
References: <quicwg/base-drafts/pull/3961@github.com>
Subject: Re: [quicwg/base-drafts] Rework section on persistent congestion (#3961)
Mime-Version: 1.0
Content-Type: multipart/alternative; boundary="--==_mimepart_5f24d1fc9297b_21e116f830747e"; 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
X-GitHub-Recipient-Address: quic-issues@ietf.org
Archived-At: <https://mailarchive.ietf.org/arch/msg/quic-issues/av9TYSMmARZUN7mFYgx6XyoCn4E>
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: Sat, 01 Aug 2020 02:22:55 -0000

@janaiyengar commented on this pull request.

Thanks, Ian, I've incorporated most of your comments.

> +data with silence periods between them restarts the PTO timer every time it
+sends, potentially preventing the PTO timer from expiring for a long period of
+time, even when no acknowledgments are being received. The use of a duration
+enables a sender to establish persistent congestion without depending on the
+occurrence of PTOs.
+
+### Establishing Persistent Congestion
+
+A sender establishes persistent congestion on receiving an acknowledgement, if
+the following conditions are true:
+
+* there are at least two ack-eliciting packets that are declared lost;
+
+* a prior RTT sample existed at the time these packets were sent;
+
+* the duration between the send times of these packets exceeds the

This isn't correct. @marten-seemann had an example where:
- 1 - 10 are sent
- on ack, 1-4 and 6-9 are marked lost
- 1-4 have a period that exceeds the PC threshold. 

The text here allows for this to result in persistent congestion. I've changed the text here to be clearer.

> +reduced to the minimum congestion window (kMinimumWindow).  This response of
+collapsing the congestion window on persistent congestion is functionally
+similar to a sender's response on a Retransmission Timeout (RTO) in TCP
+({{RFC5681}}) after Tail Loss Probes ({{RACK}}).

Trimmed and rephrased.

-- 
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/3961#pullrequestreview-459542454