Re: [RTG-DIR] RtgDir Review: draft-ietf-isis-segment-routing-msd-15

Jeff Tantsura <jefftant.ietf@gmail.com> Tue, 02 October 2018 18:28 UTC

Return-Path: <jefftant.ietf@gmail.com>
X-Original-To: rtg-dir@ietfa.amsl.com
Delivered-To: rtg-dir@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id A46CA130FFF; Tue, 2 Oct 2018 11:28:10 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.999
X-Spam-Level:
X-Spam-Status: No, score=-1.999 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_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 FzXg3A4cOpUW; Tue, 2 Oct 2018 11:28:07 -0700 (PDT)
Received: from mail-pg1-x52c.google.com (mail-pg1-x52c.google.com [IPv6:2607:f8b0:4864:20::52c]) (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 AA3D3130FF3; Tue, 2 Oct 2018 11:28:07 -0700 (PDT)
Received: by mail-pg1-x52c.google.com with SMTP id y18-v6so364363pge.0; Tue, 02 Oct 2018 11:28:07 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version; bh=qU5BAbkJVy+9tmbyxV0InDw1rrafYcaDfylzzHOBkgQ=; b=h2guzCGgqBa6H22pU+rJLOeaoHZSXVBTec5jAfzYp1sJSBVelKW55V7yXRKGnxwbvo XWqB8E9n8QhglXl5zCuDbbG+PsD7AfNBwpa66gPEMNUGgyXNKot/w+gFj53pBHCbako3 quqhXs2NgtrGHjWU0ze/iy7WGfRhf2l/PwHRJZX1/BEUjKKE1nH6smN6zwo54i3/DrKj WdLBgpf1U3vrXreXxf5XEeDFEXuqOBIRnU1WrclEdUGTKvawVVRx6x4wvV6UGTdTLGMv l7bPDVc+LQ9GAaN+mmFQxNKk/MA8H0FTLNftX/HKeplYkcmGGNl23wYmljOKZJ4JqLYo YTlw==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:message-id:in-reply-to :references:subject:mime-version; bh=qU5BAbkJVy+9tmbyxV0InDw1rrafYcaDfylzzHOBkgQ=; b=eOxTqItV+ugAhXHTTAxUm+b610v16P24c20XlMp5vwo34eCFJP4SX+OwRP+U7X4Ghv YUzhHd4vzKJ5ycOM/6P6X8MLk1HXmMgBArHE7/A7FFjIG1gMJ0f7jrdB+7BR9kLM2b38 gzPhC6boC6JHQrPT9yN0phhxnKufJ854gOTYm3PkOeWoPLbhQNaWL/Uh21wiE3vwdsd0 0LiELxTGvEG8LbBM2Hq2GgeTu+UGb5ilt5/vrsOhTdUeszGBwEKfZEYWpUad1P73rX7J gqVImZBpPeFxcqd9WUw1v4fAY7w50GGpENKZf0+yZu/6NxgO8XQXzwG/JaaRQOT9NwKr T/AQ==
X-Gm-Message-State: ABuFfojuhY+ahIWG/1FVb+TlPBgMxx54hnHaytZVM0u7rZnb8muDJV8K GfUDoB3g8m2kuOursCvkpkU=
X-Google-Smtp-Source: ACcGV61JvDV398Hmd/LH6TZtHsdwimu1M9bbtUgJxhaMu+2YXuGEaz3QXMl21Qp5gWlP4ODGhKCr7g==
X-Received: by 2002:a62:a0e:: with SMTP id s14-v6mr17539910pfi.153.1538504887184; Tue, 02 Oct 2018 11:28:07 -0700 (PDT)
Received: from [192.168.1.42] ([12.12.156.34]) by smtp.gmail.com with ESMTPSA id v189-v6sm12395751pfb.54.2018.10.02.11.28.05 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 02 Oct 2018 11:28:06 -0700 (PDT)
Date: Tue, 02 Oct 2018 11:27:59 -0700
From: Jeff Tantsura <jefftant.ietf@gmail.com>
To: "bruno.decraene@orange.com" <bruno.decraene@orange.com>, Alvaro Retana <aretana.ietf@gmail.com>, MEURIC Julien IMT/OLN <julien.meuric@orange.com>, "Les Ginsberg (ginsberg)" <ginsberg@cisco.com>
Cc: "rtg-ads@ietf.org" <rtg-ads@ietf.org>, "lsr@ietf.org" <lsr@ietf.org>, "rtg-dir@ietf.org" <rtg-dir@ietf.org>, "draft-ietf-isis-segment-routing-msd@ietf.org" <draft-ietf-isis-segment-routing-msd@ietf.org>
Message-ID: <e40be8f6-1160-4580-8d54-afc7d75ea560@Spark>
In-Reply-To: <413ebd13467d407cb6740c8b2af6d48d@XCH-ALN-001.cisco.com>
References: <cb33dfed-f14a-e079-78a7-83659aac7ffb@orange.com> <da219cdbe1db4edab2afb4dc03aa8656@XCH-ALN-001.cisco.com> <2414700a-0cf2-f663-8ab8-c312c4845ebb@orange.com> <f74187a7c96b40ebae4dccdd26bc29f3@XCH-ALN-001.cisco.com> <af362362-3c0c-6e42-562e-c6f7f16d14ff@orange.com> <CAMMESsy1Wn+O6iuuy_PdFxo6s6nSF0ztc__wyxR3u_WJBXe2CQ@mail.gmail.com> <7a22ba26220d45c8881c5bbf95f4b7e0@XCH-ALN-001.cisco.com> <4412_1538121729_5BADE001_4412_375_54_f1c05c2e-62d0-437b-af0b-a5a20073f31b@OPEXCLILM6F.corporate.adroot.infra.ftgroup> <a96fb91fd5f14532ac3e5203049af4c5@XCH-ALN-001.cisco.com> <16694_1538482569_5BB36189_16694_463_1_157d2475-3635-4182-bab6-55555b122ac9@OPEXCLILM5D.corporate.adroot.infra.ftgroup> <413ebd13467d407cb6740c8b2af6d48d@XCH-ALN-001.cisco.com>
X-Readdle-Message-ID: e40be8f6-1160-4580-8d54-afc7d75ea560@Spark
MIME-Version: 1.0
Content-Type: multipart/alternative; boundary="5bb3b8b5_310c50b3_40f"
Archived-At: <https://mailarchive.ietf.org/arch/msg/rtg-dir/REQzLRhZg86QIEd8n8Tamli8uuc>
Subject: Re: [RTG-DIR] RtgDir Review: draft-ietf-isis-segment-routing-msd-15
X-BeenThere: rtg-dir@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Routing Area Directorate <rtg-dir.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/rtg-dir>, <mailto:rtg-dir-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/rtg-dir/>
List-Post: <mailto:rtg-dir@ietf.org>
List-Help: <mailto:rtg-dir-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/rtg-dir>, <mailto:rtg-dir-request@ietf.org?subject=subscribe>
X-List-Received-Date: Tue, 02 Oct 2018 18:28:11 -0000

Gents,

I’m 100% with Les here, going into platform/asic specifics within this document would inevitably create ambiguity.

Cheers,
Jeff
On Oct 2, 2018, 11:20 AM -0700, Les Ginsberg (ginsberg) <ginsberg@cisco.com>, wrote:
> Bruno –
>
> Trimming the thread…
>
> [Les2:] Label imposition is meant to cover both the SWAP operation and the PUSH operation. In the example you provided above where a label stack of “12” is replaced by a label stack of “14,15” the number of labels “imposed” is 2.
> [Bruno2] In that case, I definitely think that the discussion was useful and that this point needs to be clarified in the document.
> Whether you choose to call that (1 POP, 2 PUSH) or (1 SWAP, 1 PUSH)  or simply a SWAP isn’t relevant here (though it might matter to folks like the RFC 3031 authors).
>
> With that ibn mind, here is proposed text:
>
> “Base MPLS Imposition MSD (BMI-MSD) signals the total number of MPLS
>    labels which can be imposed, including all service/transport/special
>    labels.  Imposition includes swap and/or push operations.
>
> If the advertising router performs label imposition in the context of
>    the ingress interface, it is not possible to meaningfully advertise
>    per link values.  In such a case only the Node MSD SHOULD be
>    advertised.”
>
> [Bruno2] Given that the term “imposition” does not seem to be defined within the IETF, I would still favor a formal definition not using it. e.g. “BMI-MSD advertises the ability to increase the depth of the label stack by BMI-MSD labels”.
> Alternatively, I’d propose the following rewording which seems clearer to me:
> OLD: Imposition includes swap and/or push operations.
> NEW: A swap operation counts as an imposition of one label; just like one push operation.
>
> [Les3:] This gets into implementation specific issues that I would really like to avoid.
> For example, some implementations perform one and only one  “operation”. Conceptually that may involve a swap and a push – but from the internal implementation POV it is simply one operation. And this may be true regardless of how many labels are involved. Other implementations might perform this in several discrete steps. The language we use here should not imply anything about how many labels are associated with a specific operation.
>
> The term “increase” isn’t accurate because in the case of a swap there is no increase, yet the label which is replaced is counted.
>
> https://tools.ietf.org/html/rfc3031#section-3.10 is relevant here.
>
> The term “imposition” is generic – and as Alvaro has pointed out is used in RFC 4221. And the language proposed above does define the relationship between “swap and push” and “imposition”.
>
> I appreciate your desire for clarity – and I am still open to new language – but at this point I still think what I proposed is  the most accurate.
>
>    Les
>
>
>
> Thanks,
> --Bruno
>