Re: [Gen-art] Gen-ART Review of draft-ietf-trill-pseudonode-nickname-05

Donald Eastlake <d3e3e3@gmail.com> Sun, 20 September 2015 20:39 UTC

Return-Path: <d3e3e3@gmail.com>
X-Original-To: gen-art@ietfa.amsl.com
Delivered-To: gen-art@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id E16681B2D74; Sun, 20 Sep 2015 13:39:09 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.75
X-Spam-Level:
X-Spam-Status: No, score=-1.75 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, SPF_PASS=-0.001] autolearn=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 7LazKAKHURyY; Sun, 20 Sep 2015 13:39:08 -0700 (PDT)
Received: from mail-ob0-x235.google.com (mail-ob0-x235.google.com [IPv6:2607:f8b0:4003:c01::235]) (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 B2A1D1B2D72; Sun, 20 Sep 2015 13:39:08 -0700 (PDT)
Received: by obbmp4 with SMTP id mp4so35400982obb.3; Sun, 20 Sep 2015 13:39:08 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-type:content-transfer-encoding; bh=nn6FDFni2KZ9tPLG/VW635CoVpTewcDe0pMIYm5smVM=; b=bW1VQ8h48k2+7fZ8jvz/L+CEXeyxvx2VR4TonjF7HcLmUS5Ysb9gnn8LvPqvz1UeRr 8JW7LoX8PpIHqU+kYTCb0I3QvvLbJzvrA7DkMFCaerejdspHxNVorbtJxKfyAZBIAOGO gCEcwJSi7t1tE7+KRn2jCFVPcMQNC8yXmdKqjNu7QHgYAaKofD+/On8RTAntftvs1OJm 2wJtFk4JezKwPUVdBd+pFGdZ8rtpPxCPsc8SS/CGlzv3X+v4yIj/XNYg/WAiiHmmOhg5 sv5R0LrGVGzHb1ScRC71TO+xXEQvuf7cDSDV7BKYU6EseleLAI0W7SaWczEKDAXH7luk Jprg==
X-Received: by 10.182.53.229 with SMTP id e5mr9386735obp.68.1442781548057; Sun, 20 Sep 2015 13:39:08 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.76.144.65 with HTTP; Sun, 20 Sep 2015 13:38:53 -0700 (PDT)
In-Reply-To: <F779EA16-6E52-46BA-A555-6485CCC7E459@piuha.net>
References: <46A1A261-E9F4-414D-AAD8-9C85A8B53283@vigilsec.com> <4552F0907735844E9204A62BBDD325E7871A2CFE@nkgeml512-mbx.china.huawei.com> <CAF4+nEGAnyBVrv=Rbc0gfDijYsjraBW62ugC1Rwo07e6PSg_NA@mail.gmail.com> <53C61587-9F97-4664-9F84-603199B46D3E@vigilsec.com> <EBCEEEC6-1184-420F-BC8E-D19444A0A54A@piuha.net> <CAF4+nEEcz7fQLaXZSSGFrEECOfeLkhqUwrXbpjkxRnuybeefOA@mail.gmail.com> <F779EA16-6E52-46BA-A555-6485CCC7E459@piuha.net>
From: Donald Eastlake <d3e3e3@gmail.com>
Date: Sun, 20 Sep 2015 16:38:53 -0400
Message-ID: <CAF4+nEHOPSaiA=s_BVNHCNBSdfDTRK3nG5cGtCSAW1XVT3AVkg@mail.gmail.com>
To: Jari Arkko <jari.arkko@piuha.net>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Archived-At: <http://mailarchive.ietf.org/arch/msg/gen-art/HMVlMwoL8rpqmG7TNcDv374v2zw>
Cc: IETF Gen-ART <gen-art@ietf.org>, IETF <ietf@ietf.org>, "draft-ietf-trill-pseudonode-nickname.all@ietf.org" <draft-ietf-trill-pseudonode-nickname.all@ietf.org>
Subject: Re: [Gen-art] Gen-ART Review of draft-ietf-trill-pseudonode-nickname-05
X-BeenThere: gen-art@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: "GEN-ART: General Area Review Team" <gen-art.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/gen-art>, <mailto:gen-art-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/gen-art/>
List-Post: <mailto:gen-art@ietf.org>
List-Help: <mailto:gen-art-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/gen-art>, <mailto:gen-art-request@ietf.org?subject=subscribe>
X-List-Received-Date: Sun, 20 Sep 2015 20:39:10 -0000

On Fri, Sep 18, 2015 at 9:49 AM, Jari Arkko <jari.arkko@piuha.net> wrote:
> Donald,
>
>>> (Maybe this helps: I’m not actually sure why in a k-element set you order them based <something> mod k because that would seem to produce likely duplicates. Since your backup option in the case of duplicates is proper numeric sort, why just not do that and only that? E.g. "RBridges are sorted in byte string ascending order by their LAALP IDs, or if they are equal, by their System IDs considered as unsigned integers.” But it could also be that it is too early and I have not yet had enough Diet Coke…)
>>
>> I believe the idea is to quasi-randomize the order. The DF election is
>> per VLAN and a goal is to spread the multicast traffic across the
>> RBridges in the active-active edge group.
>
> It is a fine goal to randomise the order.
>
> My only observation of the current setup is that if you randomise a
> k-element group through "mod k” operation, you will likely have
> some number of collisions in the result. I don’t know enough
> about math to calculate the percentage. But for the sake of
> argument, if k=2 it seems that the likelihood of collision is 50%.
>
> And for every collision, your order becomes no longer random
> but simply numerical order of the identifiers. In our degenerate
> k=2 example it seems that in 50% of the cases you have a random
> order and 50% of the cases you have numerical order. I’m sure
> there would be other ways to randomise the order with less
> collisions, if avoiding numerical order is important.

Well, the way to randomize the order with quite low probability of
collisions is to sort by the hash of  (System IDj | LAALP IDi), for
example SHA-1(System IDj | LAALP IDi). Ties could still be broken by
System ID which is guaranteed to be unique but ties would be quite
rare. This seems like a minor localized change.

> Jari

Thanks,
Donald
=============================
 Donald E. Eastlake 3rd   +1-508-333-2270 (cell)
 155 Beaver Street, Milford, MA 01757 USA
 d3e3e3@gmail.com