Re: [quicwg/base-drafts] Question on ECN validation (#3733)

Lars Eggert <> Mon, 08 June 2020 10:11 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 45A9D3A0850 for <>; Mon, 8 Jun 2020 03:11:38 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -1.483
X-Spam-Status: No, score=-1.483 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_24=1.618, 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 LNCPe__8e7Dy for <>; Mon, 8 Jun 2020 03:11:36 -0700 (PDT)
Received: from ( []) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 0FB1D3A084D for <>; Mon, 8 Jun 2020 03:11:36 -0700 (PDT)
Received: from ( []) by (Postfix) with ESMTP id 252868C0054 for <>; Mon, 8 Jun 2020 03:11:35 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=pf2014; t=1591611095; bh=5BD0UERPUA8BJf5kGoVh5StEWn0sI/Lo22oMor+bdhI=; h=Date:From:Reply-To:To:Cc:In-Reply-To:References:Subject:List-ID: List-Archive:List-Post:List-Unsubscribe:From; b=I9obOpCrYXdBvdlIFMR6QFzbigi3UzTtpfmeSEN8Xpy0zQNn692cuWSHGTkZl3Apd qSXNMGfXviboA4BuIbs8Lw6gZFD0Ea63W6qsk77SNHRlqMg0+u9mz0C2DN6BiqSpNq VUeu28JKLK406XihuJ5bk9u9KzhknOyg78VjbV9c=
Date: Mon, 08 Jun 2020 03:11:35 -0700
From: Lars Eggert <>
Reply-To: quicwg/base-drafts <>
To: quicwg/base-drafts <>
Cc: Subscribed <>
Message-ID: <quicwg/base-drafts/issues/3733/>
In-Reply-To: <quicwg/base-drafts/issues/>
References: <quicwg/base-drafts/issues/>
Subject: Re: [quicwg/base-drafts] Question on ECN validation (#3733)
Mime-Version: 1.0
Content-Type: multipart/alternative; boundary="--==_mimepart_5ede0ed716550_5d193f8c460cd96c112775"; charset="UTF-8"
Content-Transfer-Encoding: 7bit
Precedence: list
X-GitHub-Sender: larseggert
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: Mon, 08 Jun 2020 10:11:38 -0000

So let me tell you what my code is doing now to verify incoming ACK-ECNs, and then you tell me if this is correct:

I maintain ECN reference counter vectors (`ecn-ref`) per pn space. These hold the last counts received in an ACK-ECN from the peer.

I could new ACKs for ECN-marked packets that I send in a `new_ack`vector. (I only send ECN_ECT0 packets though, so this isn't really a vector, just a variable.)

When I receive a new ACK-ECN with ECN counts (`ecn_cnt`), I compute the `ecn_inc` vector as `ecn_ref - ecn_cnt`.

I then do the verification per Section

* (First bullet in is easy, omitted here)

* Second bullet in `ecn_inc[ECN_ECT0] + ecn_inc[ECN_ECT1] + ecn_inc[ECN_CE] <  new_ack[ECN_ECT0]` => verification failed

* Third bullet in `ecn_inc[ECN_ECT0] + ecn_cnt[ECN_CE] < new_ack[ECN_ECT0]` => verification failed. (Since I only send ECN_ECT0, I can omit looking at ECN_ACT1, I believe.)

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