[quicwg/base-drafts] CC state after a change of path? (#2685)

Gorry Fairhurst <notifications@github.com> Fri, 10 May 2019 08:29 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 0E340120198 for <quic-issues@ietfa.amsl.com>; Fri, 10 May 2019 01:29:13 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.392
X-Spam-Level:
X-Spam-Status: No, score=-1.392 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HTML_IMAGE_ONLY_24=1.618, HTML_MESSAGE=0.001, MAILING_LIST_MULTI=-1, SPF_PASS=-0.001, T_DKIMWL_WL_HIGH=-0.01] autolearn=no 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 DFXU85o1us1V for <quic-issues@ietfa.amsl.com>; Fri, 10 May 2019 01:29:12 -0700 (PDT)
Received: from out-20.smtp.github.com (out-20.smtp.github.com [192.30.252.203]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 2782012017A for <quic-issues@ietf.org>; Fri, 10 May 2019 01:29:11 -0700 (PDT)
Date: Fri, 10 May 2019 01:29:10 -0700
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=github.com; s=pf2014; t=1557476950; bh=wFrZbC74EeLxKo/N2oci3/oB0a9gO9Nsr3/taGlHv1c=; h=Date:From:Reply-To:To:Cc:Subject:List-ID:List-Archive:List-Post: List-Unsubscribe:From; b=tY1gt6rEtW+HfzNQw7EJxDL6RYzhA4U/4WcKZ8AoTwr8ktPH7IAxsZX7Cpv9YQUIL SlJS87h7TJOyg1/P5NkumHVhfy0RQE8dwq7FlFeZjGSvNFE5glsAhDJb5EGzN3El+k P2jxd7DSt6BUWJz2GzjkunLBv0NiiuYOk6tzpnB0=
From: Gorry Fairhurst <notifications@github.com>
Reply-To: quicwg/base-drafts <reply+AFTOJK3T3OY2GSHT7GYPKI524JUNNEVBNHHBUYMJPU@reply.github.com>
To: quicwg/base-drafts <base-drafts@noreply.github.com>
Cc: Subscribed <subscribed@noreply.github.com>
Message-ID: <quicwg/base-drafts/issues/2685@github.com>
Subject: [quicwg/base-drafts] CC state after a change of path? (#2685)
Mime-Version: 1.0
Content-Type: multipart/alternative; boundary="--==_mimepart_5cd536561898d_52b63f9cba2cd96830809a"; charset="UTF-8"
Content-Transfer-Encoding: 7bit
Precedence: list
X-GitHub-Sender: gorryfair
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/YLq8HE-m4gJ7wAU95HasohJ9Hc0>
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: Fri, 10 May 2019 08:29:13 -0000

I think a normal transport assumption is that a change of path implies a (potential) loss of congestion state, and that the endpoint should reset the path CC parameters. 

Transport-ID: “On confirming a peer's ownership of its new address, an endpoint
SHOULD immediately reset the congestion controller and round-trip
time estimator for the new path.”

• Does the "reset" require setting the CC to the initial window value for a connection? I think so.
• Why not MUST? 

Transport-ID:  “An endpoint MUST NOT return to the send rate used for the previous
path unless it is reasonably sure that the previous send rate is
valid for the new path. “

This could therefore be seen as a “significant” departure from conventional approaches considered safe - and extends this to “reasonably sure”. 
• Is there a rationale for extending this to “reasonably sure”, because this seems bolder than permitted for a new TCP connection. How do people quantify reasonably sure, and why not just in this case grow from the Initial window? 

-- 
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/issues/2685