Re: [babel] Warren Kumari's No Objection on draft-ietf-babel-v4viav6-07: (with COMMENT)

Juliusz Chroboczek <jch@irif.fr> Thu, 17 February 2022 17:13 UTC

Return-Path: <jch@irif.fr>
X-Original-To: babel@ietfa.amsl.com
Delivered-To: babel@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 49D3D3A0DEA; Thu, 17 Feb 2022 09:13:17 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.899
X-Spam-Level:
X-Spam-Status: No, score=-1.899 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
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 MnxRQheABsIR; Thu, 17 Feb 2022 09:13:15 -0800 (PST)
Received: from korolev.univ-paris7.fr (korolev.univ-paris7.fr [IPv6:2001:660:3301:8000::1:2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 27D543A0DCD; Thu, 17 Feb 2022 09:13:10 -0800 (PST)
Received: from mailhub.math.univ-paris-diderot.fr (mailhub.math.univ-paris-diderot.fr [81.194.30.253]) by korolev.univ-paris7.fr (8.14.4/8.14.4/relay1/82085) with ESMTP id 21HHD6TI003866; Thu, 17 Feb 2022 18:13:06 +0100
Received: from mailhub.math.univ-paris-diderot.fr (localhost [127.0.0.1]) by mailhub.math.univ-paris-diderot.fr (Postfix) with ESMTP id E55721038C1; Thu, 17 Feb 2022 18:13:06 +0100 (CET)
X-Virus-Scanned: amavisd-new at math.univ-paris-diderot.fr
Received: from mailhub.math.univ-paris-diderot.fr ([127.0.0.1]) by mailhub.math.univ-paris-diderot.fr (mailhub.math.univ-paris-diderot.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id 6l2iLTqZWJSF; Thu, 17 Feb 2022 18:13:05 +0100 (CET)
Received: from pirx.irif.fr (unknown [78.194.40.74]) (Authenticated sender: jch) by mailhub.math.univ-paris-diderot.fr (Postfix) with ESMTPSA id EA0BD1038BF; Thu, 17 Feb 2022 18:13:04 +0100 (CET)
Date: Thu, 17 Feb 2022 18:13:04 +0100
Message-ID: <87fsohpgbj.wl-jch@irif.fr>
From: Juliusz Chroboczek <jch@irif.fr>
To: Warren Kumari <warren@kumari.net>
Cc: The IESG <iesg@ietf.org>, draft-ietf-babel-v4viav6@ietf.org, babel-chairs@ietf.org, babel@ietf.org, d3e3e3@gmail.com
In-Reply-To: <164511238748.24903.3904656499206405256@ietfa.amsl.com>
References: <164511238748.24903.3904656499206405256@ietfa.amsl.com>
User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/27.1 Mule/6.0
MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue")
Content-Type: text/plain; charset="US-ASCII"
X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (korolev.univ-paris7.fr [194.254.61.138]); Thu, 17 Feb 2022 18:13:07 +0100 (CET)
X-Miltered: at korolev with ID 620E8222.002 by Joe's j-chkmail (http : // j-chkmail dot ensmp dot fr)!
X-j-chkmail-Enveloppe: 620E8222.002 from mailhub.math.univ-paris-diderot.fr/mailhub.math.univ-paris-diderot.fr/null/mailhub.math.univ-paris-diderot.fr/<jch@irif.fr>
X-j-chkmail-Score: MSGID : 620E8222.002 on korolev.univ-paris7.fr : j-chkmail score : . : R=. U=. O=. B=0.000 -> S=0.000
X-j-chkmail-Status: Ham
Archived-At: <https://mailarchive.ietf.org/arch/msg/babel/y1rUAKxCrdUDtP4zN3yy_-LtorQ>
Subject: Re: [babel] Warren Kumari's No Objection on draft-ietf-babel-v4viav6-07: (with COMMENT)
X-BeenThere: babel@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "A list for discussion of the Babel Routing Protocol." <babel.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/babel>, <mailto:babel-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/babel/>
List-Post: <mailto:babel@ietf.org>
List-Help: <mailto:babel-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/babel>, <mailto:babel-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 17 Feb 2022 17:13:25 -0000

> Is it *always* safe for a babel router to ignore a route? I really haven't
> thought about it enough (and the fact that it is DV based makes me think that
> it should be fine) but I'd like some reassurance that it is, especially in the
> case that a prefix is originated by multiple routers, and one of them gets
> filtered/ignored.

(I assume that by "safe" you mean "preserves Babel's loop-avoidance properties".)

Yes, dropping updates preserves Babel's loop-avoidance properties.  The
proof of the loop-avoidance properties of Babel never assumes that
a packet cannot be repeatedly lost (it only relies on the hypothesis that
a packet is never received before it is sent, i.e. that the happens-before
relation is acyclic).

An intuition that some people have found useful is that Babel is based on
principles similar to BGP: if something is trivial in BGP, then it's
probably easy in Babel; if something is tricky in BGP, then it's difficult
or impossible in Babel (for example, we don't know how to do aggregation
in Babel, since it's not clear how to map an AS-Set to a Babel feasibility
distance).

-- Juliusz