Re: [Bier] Questions on draft-eckert-bier-te-arch-01

Caitlin Bestler <caitlin.bestler@nexenta.com> Fri, 09 October 2015 19:49 UTC

Return-Path: <caitlin.bestler@nexenta.com>
X-Original-To: bier@ietfa.amsl.com
Delivered-To: bier@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 295921A8795 for <bier@ietfa.amsl.com>; Fri, 9 Oct 2015 12:49:49 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.601
X-Spam-Level:
X-Spam-Status: No, score=-2.601 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_LOW=-0.7, SPF_PASS=-0.001] autolearn=ham
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 KxuEWb_0DHvd for <bier@ietfa.amsl.com>; Fri, 9 Oct 2015 12:49:47 -0700 (PDT)
Received: from mail-pa0-f52.google.com (mail-pa0-f52.google.com [209.85.220.52]) (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 C30B71A1B6A for <bier@ietf.org>; Fri, 9 Oct 2015 12:49:47 -0700 (PDT)
Received: by pabve7 with SMTP id ve7so36419411pab.2 for <bier@ietf.org>; Fri, 09 Oct 2015 12:49:47 -0700 (PDT)
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-type :content-transfer-encoding; bh=9dW9P1mJJ5Cr6kw56JhVorUdm0iJ4siQkoEwq8TurKc=; b=ZiJdiKO5bn59lSIUqIgf7euaWWp1stDZUKorag6TvR86tPqLO4Pg3ka7mbW88YBh49 Y4q+9pbuGqI0KPCdefQHyMwJb/K7BkdH7/L8jH+DCBJs0jlhC5LPqhwc5vK206aGcWDa Kb6FHypWZUlLKxprBe6pn8WpCfnYjEdjdjJSIZKpWqlsf2j6bOo74IZjEjRooujElW3g BbmxWrG/Ma+NnBoscF3IyuF58ZMAQrt3LFjMzrqOf9ZgCD/8DV2hhExjrWt296G3Zf68 xvAdCtSqlHFZQxscmeX/gEwlIMMdEWJ2DXzyEu5LvSMlvlkru92bq4Mv64Ani5gNTS7K aH6A==
X-Gm-Message-State: ALoCoQkn+L9jUn8PPuUTbJAH7y0OWcmBIFVQWNk2Ekejisl1JmsZ7ILkHBa8zspiPBCAfUrT4RUN
X-Received: by 10.66.119.135 with SMTP id ku7mr17035173pab.21.1444420187455; Fri, 09 Oct 2015 12:49:47 -0700 (PDT)
Received: from Macintosh.local (67-207-110-172.static.wiline.com. [67.207.110.172]) by smtp.googlemail.com with ESMTPSA id zc4sm4028682pbb.24.2015.10.09.12.49.45 (version=TLSv1/SSLv3 cipher=OTHER); Fri, 09 Oct 2015 12:49:46 -0700 (PDT)
To: Antoni Przygienda <antoni.przygienda@ericsson.com>, "bier@ietf.org" <bier@ietf.org>
References: <55DF5BAD.9060003@juniper.net> <20151007221035.GA26709@cisco.com> <20151009022602.GA32419@cisco.com> <5617EA57.4040909@nexenta.com> <2E4BB27CAB87BF43B4207C0E55860F180EAE0D74@eusaamb103.ericsson.se>
From: Caitlin Bestler <caitlin.bestler@nexenta.com>
Message-ID: <56181A58.4070500@nexenta.com>
Date: Fri, 09 Oct 2015 12:49:44 -0700
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:38.0) Gecko/20100101 Thunderbird/38.3.0
MIME-Version: 1.0
In-Reply-To: <2E4BB27CAB87BF43B4207C0E55860F180EAE0D74@eusaamb103.ericsson.se>
Content-Type: text/plain; charset="windows-1252"; format="flowed"
Content-Transfer-Encoding: 7bit
Archived-At: <http://mailarchive.ietf.org/arch/msg/bier/Jhrm1Zr1leCBu8CxBgz1H2oweSY>
Subject: Re: [Bier] Questions on draft-eckert-bier-te-arch-01
X-BeenThere: bier@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: "\"Bit Indexed Explicit Replication discussion list\"" <bier.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/bier>, <mailto:bier-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/bier/>
List-Post: <mailto:bier@ietf.org>
List-Help: <mailto:bier-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/bier>, <mailto:bier-request@ietf.org?subject=subscribe>
X-List-Received-Date: Fri, 09 Oct 2015 19:49:49 -0000


On 10/9/15 11:50 AM, Antoni Przygienda wrote:
> Study the architecture document for distinction between SI and subdomain.
>
> SIs are a concept to fit more than BSL of BFERs into a subdomain.
>
> A subdomain is something where you map a service on so you achieve separation or can separate clusters of receivers from each other. Each subdomain may follow a different topology, carry different type of service, use different assignment of BFR-ids and with that has a different distribution tree possibly.
>
> If you can play tricks with assignments to fit them into same SI, you are basically using SIs in a sense as sub-domain. This is maybe OK for you but won't work well if you need e.g. service speration in terms of scheduling or receivers joining/leaving subdomains and want to separate a subdomain from the impact of another subdomain.
>
> BIER is an architecture, not a 'multicast cookbook'. We kept it quite generic to allow for all kind of unexpected applicatons as you have it and give you simply a box of tools like SI, MT, subdomains to allow for mapping of your architectural entities into BIER abstractions to fit your needs  ...
>
> Thanks
>
> --- tony
>
>
Studying the architecture document it is apparent that the authors 
assume that there is some magic sauce
associated with the routing underlay associated with each sub-domain. 
But there is almost nothing mandated
about a sub-domain that is different from an SI slice of a sub-domain.

The SI slices of one sub-domain must use the same routing underlay. But 
nothing says that multiple sub-domains
cannot use the same routing underlay.

The BFR-IDs are unique to the sub-domain, and an SI is a slice of those 
IDs. But since BFR-IDs are assigned by a
mysterious process outside the scope of the document this does not seem 
terribly relevant unless you need a
BIER domain to have more than 2**16 ids.

Is there some reason why you could not replace the SI concept with 
simply have more sub-domains that mapped
to the same number of routing underlays?

You end up with at most 2**24 BFR-IDs in either case, and the same 
options for sizing the Bitstring.

Were the drafters assuming that a sub-domain was "expensive"? There's 
nothing in the draft that requires every
sub-domain to be a full cost sub-domain with a unique routing underlay.