Re: [L2sm] Adoption poll for draft-wen-l2sm-l2vpn-service-model-03.txt

David Ball <> Wed, 04 January 2017 10:14 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 6C3FD128DF6 for <>; Wed, 4 Jan 2017 02:14:24 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -17.611
X-Spam-Status: No, score=-17.611 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_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, RP_MATCHES_RCVD=-3.1, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, T_KAM_HTML_FONT_INVALID=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 qjlNXEauK2lY for <>; Wed, 4 Jan 2017 02:14:21 -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 1CE5E12711D for <>; Wed, 4 Jan 2017 02:14:20 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple;;; l=22583; q=dns/txt; s=iport; t=1483524861; x=1484734461; h=subject:to:references:from:message-id:date:mime-version: in-reply-to; bh=O8KqSr/xKKjJBdZEENNSLpWUi65lzemek1pXEg4XSxE=; b=d/BgZDyy7sOfpOhmuUhCaKrtfUGur1bUylr/zE6SpBriqX1nOSxI9YJL 57sUsIp30eWQT49fG9DUETrxE4rVREL+5UQfDPZNlF/TdDt8aSlUKJBrZ ZUB72cigfJ6xAsIQ/PphmkSzQYaUNGqe9dosOW5GZbgkKKe0n5t3lZGH5 4=;
X-IronPort-AV: E=Sophos;i="5.33,458,1477958400"; d="scan'208,217";a="691049151"
Received: from (HELO ([]) by with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Jan 2017 10:14:19 +0000
Received: from [] ( []) by (8.14.5/8.14.5) with ESMTP id v04AEJbO010060; Wed, 4 Jan 2017 10:14:19 GMT
To: Scott Mansfield <>, Benoit Claise <>, "" <>, "" <>
References: <0d4501d24132$62ceb590$286c20b0$> <> <>
From: David Ball <>
Message-ID: <>
Date: Wed, 4 Jan 2017 10:14:18 +0000
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1
MIME-Version: 1.0
In-Reply-To: <>
Content-Type: multipart/alternative; boundary="------------08752243C1908FF56DCAB272"
Archived-At: <>
Subject: Re: [L2sm] Adoption poll for draft-wen-l2sm-l2vpn-service-model-03.txt
X-Mailman-Version: 2.1.17
Precedence: list
List-Id: "The Layer Two Virtual Private Network Service Model \(L2SM\)" <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Wed, 04 Jan 2017 10:14:24 -0000

Hi Scott,

I agree; but what is being proposed is not iteration, reuse and 
extension, which you rightly extol.  It is instead ignoring all the work 
that has gone before (not just the MEF yang models, but the 10+ years of 
work MEF has done in defining Carrier Ethernet services).

Benoit, to answer your points:

  * You are correct that MEF has a grand vision for the LSO
    architecture; time will tell whether that is achievable. However,
    the one small part of it that they are furthest progressed with is
    exactly the same area that is covered by L2SM.  I don't understand
    why you think L2SM is following a different architecture; in both
    cases what we are talking about is a model for the set of things
    that need to be agreed between the SP and the customer, right?
  * I can't speak for anyone else, but my criticism regarding the
    inclusion of "technology-specific parameters", as you put it, is not
    in respect of the PE-CE links.  I agree the technology details are
    needed there.  However, the draft also includes a lot of details
    about the technology used within the SP's network (i.e., PE-PE) -
    that is the detail which I think is not relevant and does not belong
    in a service model.
  * I do not understand what you mean when you say the MEF has worked on
    CE-based models.  A service model is not used between the CE and PE,
    it is used between the customer's management systems (as the client)
    and the SP's management systems (as the server).  There are
    differences in terminology for those systems, but fundamentally I
    don't see any difference between MEF and IETF approach here.  Can
    you clarify what you meant?

Benoit, you mentioned that, as vendors, we should listen more to 
operators.  I agree.  I would love to hear from the operators who 
support adoption of this draft what issues they see with the MEF models, 
and why they believe that starting again from scratch in IETF is a 
better option than working with MEF to improve on what they have already 
done, and then augmenting ("extending") it to fill in any gaps.  The MEF 
models are certainly far from perfect (and of course they are still WIP 
in MEF), but what I would like to understand is why you, as operators, 
think they are not a good starting point for solving the problems that 
led to the creation of this WG.


On 03/01/2017 19:19, Scott Mansfield wrote:
> I agree with Benoit.  There are many dimensions to the modeling space 
> and we can’t let the perfect be the enemy of the good.  Constant 
> communication and sharing will help alignment while allowing the 
> people that actually run networks to get what they need.  30+ years of 
> object-oriented software development (should have) taught all 
> designers/architects/programmers that the first iteration of a 
> solution is not the best and most optimized. Each iteration provides 
> the opportunity to abstract, refine, refactor, and extend.  Proper 
> information hiding and encapsulation is key.  Automation is very 
> important and we need to work together to ensure that whatever models 
> that are created are supported by tools that allow for effective reuse 
> and extensions.
> Regards,
> -scott.
> *From:*Benoit Claise []
> *Sent:* Thursday, December 22, 2016 8:44 AM
> *To:*;; Scott Mansfield 
> <>
> *Subject:* Re: [L2sm] Adoption poll for 
> draft-wen-l2sm-l2vpn-service-model-03.txt
> Dear all,
> A couple of reflections on L2SM, just before the end of year break.
> First, I want to quote one chairs slides 
> <> 
>     We really need this to be driven by Operators
>         - Of course, vendors can and should participate
>         - But be aware of how the data model is use
> I'm always baffled when vendors 'seem to) know better than the 
> operators what they need. I don't believe we have spent enough time 
> listening to the few operators in the room during the WG meeting.
> We have here a group of operators who want to do work in the IETF, and 
> we should respect that.
> Second, on the differences between IETF and MEF service management.
> MEF wants to go for the full LSO architecture (billing, SLA, order 
> management, etc.). Perfect.
> L2SM charter wants to do something similar to L3SM: a self-contained 
> service YANG module.
> It would be nice to try to fit the L2SM service models in the MEF LSO 
> architecture, but the L2SM work follows a different architectural 
> model to LSO, and that there is no value in trying to match the 
> functions across model at all costs. This should not invalidate either 
> approach, only observe that they are different.
> Third, exactly like the L3SM draft, the L2SM draft includes a number 
> of technology-specific parameters and these have caused people to 
> claim that the I-D must be describing a normalised or configuration 
> model. But (of course?) the parameters are needed to configure the 
> CE-PE access connections. This is a suitable point of differentiation 
> between MEF and L2SM that MEF has worked on CE-based models while L2SM 
> will work on PE-based models. Indeed, the IETF works on the networking 
> aspects. However, when a building is done somewhere else (typical 
> example, SLA management done in MEF), this L2SM YANG module should 
> only contain a place holder or a pointer.
> Fourth. Discussing those very topics live with Scott Mansfield (our 
> MEF - IETF liaison manager) during a workshop recently, we agree that 
> both IETF and MEF service models have a place. While we start to see 
> some consolidation in terms of YANG modules for device management, we 
> are only at the beginning of YANG service modules.
> I hope this is useful and that it clarifies the situation.
> Regards, Benoit
>     Hi,
>     Our charter mandates that we consider basing our work on
>     draft-wen-l2sm-l2vpn-service-model-03.txt
>     As we discussed in the meeting, that draft is not perfect. But when I asked the
>     room whether we thought that it would provide a good starting point that we
>     could work with to polish and adapt to become the I-D that we ultimately submit
>     for publication as an RFC, I believe I heard a good hum in favour and silence in
>     opposition.
>     So this email starts a formal poll for adoption. Please answer:
>     Do you think that the WG should adopt draft-wen-l2sm-l2vpn-service-model-03.txt?
>     If "yes," it would help if you could indicate whether you have read the draft
>     and how happy you are with it.
>     If "no", it is important that you provide reasons.
>     This poll will last for two weeks, ending on Saturday 3rd December.
>     Just to reassure everyone that adoption does not imply that anything is set in
>     stone: we expect the WG to continue to develop the content and change whatever
>     needs to be changed.
>     Thanks,
>     Adrian and Qin
>     _______________________________________________
>     L2sm mailing list
> <>
>     .
> _______________________________________________
> L2sm mailing list

David Ball