Re: [Lsr] Opsdir last call review of draft-ietf-ospf-ospfv2-hbit-10

Padma Pillay-Esnault <padma.ietf@gmail.com> Fri, 08 November 2019 01:08 UTC

Return-Path: <padma.ietf@gmail.com>
X-Original-To: lsr@ietfa.amsl.com
Delivered-To: lsr@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 853F4120147; Thu, 7 Nov 2019 17:08:10 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.998
X-Spam-Level:
X-Spam-Status: No, score=-1.998 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FREEMAIL_FROM=0.001, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=gmail.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 JwGQespn48IF; Thu, 7 Nov 2019 17:08:07 -0800 (PST)
Received: from mail-vs1-xe34.google.com (mail-vs1-xe34.google.com [IPv6:2607:f8b0:4864:20::e34]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 3DB5C120849; Thu, 7 Nov 2019 17:08:07 -0800 (PST)
Received: by mail-vs1-xe34.google.com with SMTP id m9so2674702vsq.7; Thu, 07 Nov 2019 17:08:07 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=A1TUxeERiQU4/wfEO83GV2Fclfel/96mBzklCgBkpTE=; b=jNhqJ0aQV6w5q6+RKv15QW0UaMvtM2TVDZNkXgyaETfiHQjmPFMa9RLsJ2NQW5mCAJ DsQOuViGi3hCacp8WzwD3K0394P5dsudQKWUhnfk+yjufHRb7XGG6Aa5YfOu7dXHvS7N tA17eS9wIETleAMY0DhANge3In3mG6ALPi2meSse53gTQbax5c/ZjEAGaWwhOf6hqLcD mOcoNe7e+erL/klPpEMK3PQ1LCTA/Fe8dgbjdfJlgLF1sGDgx+rWh111dfkzwENDYUBg ofXsEJNsm75o7wfDVg56zEKTUOGIETVV2/DAkMCrnMu5gtcECsbTgTVPdHcI6vxJ/3af pR6A==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=A1TUxeERiQU4/wfEO83GV2Fclfel/96mBzklCgBkpTE=; b=D3DYcoIGzV0ybUINuJ7aQ5ispkVQJoxR03UB/XLN4y1ISAk3PYroAUksxDHetbQ6Bx N0nKtXtGLjlF4fcf8NQwaLZ8f6X7FtbKMPhADM5+OmI3DlpBYQICcfGrOAlujgzV4gap cYCKCO97+EgnMHSREaFgb6yEQs7BTiUUy3+KQN589PHA7u8B377pCqWtegk7nVBu992R gfecQ0vOgNaJ5pwXN/G3aFjUoLNASqoSPoLb7p59UGFJPYiERmlHeKC2BTtJS8cxX0UI 0LfDSHjq8as721mJj6Ox0lxGW52QbdES3vDBPDwHHZfXp+F2C4QBmKK6frxko22ugbqG XjwA==
X-Gm-Message-State: APjAAAXBEQxjKfLCxB115R0mHIA7+J/brSaVdvIFRDUcj4TXi03GMVeM +jgobslpv+W10wKSYLssgZK+Dr7NbRPQETDjSTY=
X-Google-Smtp-Source: APXvYqx+yGAba7XdscIkE13yuGKKPdtuHFKGsMfzzr1AJ/GOOAiP3oQLqxxQIxEzhFGyiGRnu3fjB6CR9uw0KiAv8qU=
X-Received: by 2002:a67:b917:: with SMTP id q23mr5351360vsn.205.1573175286175; Thu, 07 Nov 2019 17:08:06 -0800 (PST)
MIME-Version: 1.0
References: <157316531939.2026.10004843645321945107@ietfa.amsl.com>
In-Reply-To: <157316531939.2026.10004843645321945107@ietfa.amsl.com>
From: Padma Pillay-Esnault <padma.ietf@gmail.com>
Date: Thu, 07 Nov 2019 17:07:54 -0800
Message-ID: <CAG-CQxpWmc7Gb+X0f5vCeABkShe5=GzKW4grLHrG=BfWi=OYdA@mail.gmail.com>
To: Tim Chown <tim.chown@jisc.ac.uk>
Cc: ops-dir@ietf.org, last-call@ietf.org, draft-ietf-ospf-ospfv2-hbit.all@ietf.org, lsr@ietf.org, Padma Pillay-Esnault <padma.ietf@gmail.com>
Content-Type: multipart/alternative; boundary="0000000000001a1c810596cb6ab8"
Archived-At: <https://mailarchive.ietf.org/arch/msg/lsr/w9RJ1JdYNVWcN4XDOQcACyC5MB8>
Subject: Re: [Lsr] Opsdir last call review of draft-ietf-ospf-ospfv2-hbit-10
X-BeenThere: lsr@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Link State Routing Working Group <lsr.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/lsr>, <mailto:lsr-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/lsr/>
List-Post: <mailto:lsr@ietf.org>
List-Help: <mailto:lsr-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/lsr>, <mailto:lsr-request@ietf.org?subject=subscribe>
X-List-Received-Date: Fri, 08 Nov 2019 01:08:11 -0000

Hi Tim

Thank you for your review and comments.

See below PPE.

On Thu, Nov 7, 2019 at 2:22 PM Tim Chown via Datatracker <noreply@ietf.org>
wrote:

> Reviewer: Tim Chown
> Review result: Has Nits
>
> I have reviewed this document as part of the Operational directorate's
> ongoing
> effort to review all IETF documents being processed by the IESG.  These
> comments were written with the intent of improving the operational aspects
> of
> the IETF drafts. Comments that are not addressed in last call may be
> included
> in AD reviews during the IESG review.  Document editors and WG chairs
> should
> treat these comments just like any other last call comments.
>
> The document describes a mechanism by which a node running OSPFv2 can repel
> transit traffic if it is on the shortest path (and an alternative path
> exists -
> though this is not wholly clear in the document). It defines a Host-bit
> (H-bit)
> that allows the router to advertise that it is not a transit router, and it
> describes the changes needed to support the H-bit within a domain, and
> mitigations against potential routing loops.
>
> General comments:
>
> Should the document also state that it updates RFC 2328?
>
>
PPE> No. This has been discussed previously during the AD review.
This feature is an optional feature and RFC2328 does not require it for
normal operations.


> I think the document could be clearer on the behaviour when the H-bit and
> MaxLinkMetric are used when there is only one path available, i.e. there
> is no
> redundant / alternative path.  Section 4 of RFC 6987 implies that if there
> is
> only one path the router can still be used as a transit router, by the
> nature
> of the definition of MaxLinkMetric.  The document has 3 or 4 places where
> it
> hints at behaviour, but I think it could be more explicit.
>
>
PPE>   This feature goes one step further than RFC 6987 which is a best
effort at stopping transit traffic.
We believe that the behavior is clear that a "host router" is NOT used for
transit  traffic regardless whether it is the last resort path or not.
Please note the CURRENT version does not restrict the feature on a specific
number of paths (last resort or not) or metric value (MaxlinkMetric or not)
or make any assumption in that way.

However, I proposed to add this text in an earlier thread  to make it even
more explicit.

CURRENT:
This document describes the Host-bit (H-bit) functionality that prevents
other OSPFv2 routers from using the host router for transit traffic in
OSPFv2 routing domains.

SUGGESTED NEW:
This document describes the Host-bit (H-bit) functionality that prevents
other OSPFv2 routers from using the host router by excluding it in path
calculations for transit traffic in OSPFv2 routing domains.



> It may be worth explicitly stating that OSPFv3 is not mentioned due to it
> having an R-bit defined for indicating whether a node/router can be used
> for
> transit traffic (see Sections 2.7 and A.2 of RFC 5340).
>
>
PPE> There was an earlier discussions regarding mentioning the OSPFv3
functionality and eventually these references were removed in subsequent
versions of the H-bit draft.
The R-bit is not exactly the same as H-bit, even though both are used for
the similar functionality, they rely on different mechanisms in the
protocol.


> The reasons given in Section 1 for the need for the H-bit are different to
> those given in Section 1 of RFC 6987 for the capability.  Should these be
> more
> consistent?   Also, the document later mentions “a router being gracefully
> isolated” as a reason, but this is not mentioned in Section 1.
>
>
PPE>  We believe that this the document covers this case in bullet 1 and
bullet 3 in section1.

CURRENT

1.  To isolate a router to avoid blackhole scenarios when there is a
       reload and possible long reconvergence times.
<...>
3.  Overloaded routers could use such a capability to temporarily
       repel traffic until they stabilize.

To make it even more explicit:

SUGGESTION
1. To gracefully isolate a router to avoid blackhole scenarios when there
is a
       reload and possible long reconvergence times.

Let me know if this addresses all your comments

Thanks
Padma

Nits:
>
> In the abstract:
> Change
> “This document defines a bit (Host-bit)”
> to
> “This document defines a Host bit (H-bit)”
> for consistency
> And “is a non-transit router.”” - remove the spurious “.
>
> Section 8:
> Where it says “beyond those already known in OSPF”, say OSPFv2.
>
>