Re: [Isis-wg] [Bier] BAR field length in draft-ietf-bier-isis-extensions and draft-ietf-bier-ospf-extensions

"IJsbrand Wijnands (iwijnand)" <> Wed, 21 February 2018 13:15 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 542F5127077; Wed, 21 Feb 2018 05:15:44 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -14.53
X-Spam-Status: No, score=-14.53 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_HI=-5, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_PASS=-0.001, T_RP_MATCHES_RCVD=-0.01, USER_IN_DEF_DKIM_WL=-7.5] 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 6W031RvKMOmh; Wed, 21 Feb 2018 05:15:42 -0800 (PST)
Received: from ( []) (using TLSv1.2 with cipher DHE-RSA-SEED-SHA (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 9E07812025C; Wed, 21 Feb 2018 05:15:42 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple;;; l=9549; q=dns/txt; s=iport; t=1519218942; x=1520428542; h=from:to:cc:subject:date:message-id:references: in-reply-to:mime-version; bh=8xaop7R8uwmBQOc3USbl/q4jYmFllMYNNuP1I2fBrV4=; b=Bg+QtWP0pnuwkQKjNiV7Zxz3YoulXCi/sGtKXtziQJ5OWx4y0PSdb3zq r380F8pH33lnjNYPvHDiAmKnYwF+5ZYTSLRdIh7LtH3wqHs5ardTgf/AF qxX8d9LogOQUpWxSrlvZjBW/IItgfzRbr7VcemZz5ztV3Hweg43e242m/ E=;
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-AV: E=Sophos; i="5.46,543,1511827200"; d="scan'208,217"; a="73271473"
Received: from ([]) by with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Feb 2018 13:15:41 +0000
Received: from ( []) by (8.14.5/8.14.5) with ESMTP id w1LDFfQY025920 (version=TLSv1/SSLv3 cipher=AES256-SHA bits=256 verify=FAIL); Wed, 21 Feb 2018 13:15:41 GMT
Received: from ( by ( with Microsoft SMTP Server (TLS) id 15.0.1320.4; Wed, 21 Feb 2018 07:15:41 -0600
Received: from ([]) by ([]) with mapi id 15.00.1320.000; Wed, 21 Feb 2018 07:15:40 -0600
From: "IJsbrand Wijnands (iwijnand)" <>
To: Tony Przygienda <>
CC: IJsbrand Wijnands <>, "Jeffrey (Zhaohui) Zhang" <>, "" <>, "" <>, "" <>, Eric Rosen <>
Thread-Topic: [Bier] BAR field length in draft-ietf-bier-isis-extensions and draft-ietf-bier-ospf-extensions
Date: Wed, 21 Feb 2018 13:15:40 +0000
Message-ID: <>
References: <> <> <> <> <> <> <> <> <>, <>
In-Reply-To: <>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-transport-fromentityheader: Hosted
Content-Type: multipart/alternative; boundary="_000_3D8AD227D32A453483B873D1C06FD635ciscocom_"
MIME-Version: 1.0
Archived-At: <>
Subject: Re: [Isis-wg] [Bier] BAR field length in draft-ietf-bier-isis-extensions and draft-ietf-bier-ospf-extensions
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: IETF IS-IS working group <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Wed, 21 Feb 2018 13:15:44 -0000


Future specifications may specify BART values that change the
interpretation of the BARM octet. Those specifications must handle backwards

ICE: This creates a potential dependency which I think we should avoid. I think there are possible use-cases where the combination of the two values could be valuable. But since we don’t yet know what that is, lets not speculate on it. Let keep both values as equal importance without interdependency.

And I happen to think that if this proposal has any merit this is precisely the paragraph we have to keep to make sure that not every possible BART value is being slaved to IGP

Ice: No, BART is not being slaved here. If BARM is 0, BART is all yours.

Registry Algorithm a.k.a as BARM then ... Without this section we would be mandating that BARM is always an IGP algorithm or FA so basically it would mandate IGP

Ice: Yes, BARM will be the IGP algorithm. That is to accommodate the people on the list who are of the opinion that aligning with IGP is important.

Algorithm registry as the only option to perform a calculation making BART possibly pretty much useless ... Having a registry being mapped 1:1 into  another registry known

Ice: I don't understand why you are saying this. If BARM is 0, BART is all yours. Its unfortunate that a large part of the discussion is dominated by perceived functionality in the form of BIER Algorithm, while there is no architecture draft that describes how it should work and no discussion has happen in any IETF meeting, which leaves us all guessing. I think Alia asked a very good question on the list regarding "constraints". It is not at all clear if BART is a Algorithm or a Constraint. I think from your response you're saying its both, which seems wrong IMO.. To me Alia's question is still open, but that that may be because I could not decipher the rest of your response.

as identity makes them both them the same thing by another name.

So, to get anywhere close to consensus let's get bit less creative maybe and stick to the four letters of the alphabet that the AD extended as a wide playing field and the WG seems to converge around ... Or otherwise stick to option F) unmodified and see who's
interested in it unless you insist on creating an option G) ...

Ice: Jeffrey brought option F to the list in order to discuss it, that is what we are doing, and that is how you can converge on a solution and reach consensus. That is better compared to a vote on an option and everybody walks away with a different interpretation of it.