Re: [CCAMP] Objective function draft

Igor Bryskin <IBryskin@advaoptical.com> Wed, 19 September 2012 18:36 UTC

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From: Igor Bryskin <IBryskin@advaoptical.com>
To: Lou Berger <lberger@labn.net>, Gert Grammel <ggrammel@juniper.net>, "John E Drake" <jdrake@juniper.net>
Thread-Topic: [CCAMP] Objective function draft
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Date: Wed, 19 Sep 2012 18:36:40 +0000
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Cc: "ccamp@ietf.org" <ccamp@ietf.org>
Subject: Re: [CCAMP] Objective function draft
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Lou,

In the context of ENNI/UNI the multi-domain aspect is important, the multi-layer aspect is not important at all. Although, generally speaking, network and client physically exist in different layers (which by the way not always the case) they always peer each other in the same (client) layer, virtual topology exposed to the client also belongs to the same (client) layer.

Igor

-----Original Message-----
From: Lou Berger [mailto:lberger@labn.net] 
Sent: Wednesday, September 19, 2012 2:23 PM
To: Gert Grammel; Igor Bryskin; John E Drake
Cc: Julien Meuric; ccamp@ietf.org
Subject: Re: [CCAMP] Objective function draft

Gert/Igor/John,
	I sympathize with Julien's comments.  It seems to me that the draft intermingles the concepts of multi-domain (which includes UNI/ENNI) and multi-layer (which includes, for example MPLS over optical).  While there certainly is much commonality in mechanisms, I think the draft could be clearer on the conceptual definitions and discussions...

Lou

On 9/19/2012 1:00 PM, Gert Grammel wrote:
> Lets try to be more precise and write instead:
> 
> - "this document uses the term 'External Network Interface (E-NNI)' to describe this interface between two network domains. Both domains may switch on different layers and form a client/server relationship.
> 
> Although I agree with better readability of the BCP, we have to address the concern of the WG and be precise. So let's try perfecting our language ...
> 
> Gert
> 
> ________________________________________
> From: ccamp-bounces@ietf.org on behalf of Igor Bryskin
> Sent: Wednesday, September 19, 2012 12:25:58 PM
> To: Julien Meuric; John E Drake
> Cc: ccamp@ietf.org
> Subject: Re: [CCAMP] Objective function draft
> 
> Hi Julien,
> 
> This should say:
> - "this document uses the term 'External Network Network Interface (E-NNI)' to describe this interface between a client and server network domains".
> 
> The important thing is that there is a TE domain demarcation between network and its client. The similar demarcation exists between adjacent network domains in a multi-domain environment. In either case the domains are inter-connected via access/inter-domain links in the data plane and GMPLS-ENNI in the control plane.
> 
> Hope this helps.
> Igor
> 
> 
> 
> -----Original Message-----
> From: ccamp-bounces@ietf.org [mailto:ccamp-bounces@ietf.org] On Behalf 
> Of Julien Meuric
> Sent: Wednesday, September 19, 2012 11:59 AM
> To: John E Drake
> Cc: ccamp@ietf.org
> Subject: Re: [CCAMP] Objective function draft
> 
> Hi John.
> 
> Let me quote the introduction of draft-beeram-ccamp-gmpls-enni:
> - "this memo describes how introducing a representation of server 
> layer network resources into a client layer network topology enhances 
> client layer networking in the overlay model";
> - "this document uses the term 'External Network Network Interface (E-NNI)' to describe this interface between a client and server network".
> 
> E-NNI for client-server (and overlay): this is exactly where I start 
> to get confused... (draft-beeram-ccamp-gmpls-uni-bcp used to be easier 
> to follow on this.)
> 
> Julien
> 
> 
> On 09/19/2012 16:03, John E Drake wrote:
>> Julien,
>>
>> This is the terminology we have been using in draft-beeram.
>>
>> Yours irrespectively,
>>
>> John
>>
>>
>>> -----Original Message-----
>>> From: ccamp-bounces@ietf.org [mailto:ccamp-bounces@ietf.org] On 
>>> Behalf Of Julien Meuric
>>>
>>> Lou, Gert,
>>>
>>> You are right: my previous 1st sentence was too specific, 
>>> "inter-layer signaling" should be replaced by "client-server 
>>> signaling". We agree on that, it was not my intention to question that part.
>>>
>>> Regards,
>>>
>>> Julien
>>>
>>>
>>> Le 19/09/2012 13:46, Lou Berger a écrit :
>>>> Julien,
>>>>     Just to add to Gert's point about UNI/ENNI not being related to 
>>>> layers; you can find the same terminology in the context of 
>>>> MPLS-TP, see RFCs
>>>> 6215 and 5921.  We already have RFC4208 which provides the 
>>>> foundation of a GMPLS UNI, and the related RFC5787(bis) work.
>>>>
>>>> I personally see this as the foundation and context for this (and 
>>>> the
>>>> beeram) discussion.
>>>>
>>>> Lou
>>>>
>>>> On 9/19/2012 3:14 AM, Gert Grammel wrote:
>>>>> Hi Julien,
>>>>>
>>>>> Most of the discussions about UNI/ENNI are confusing. Let's start
>>> with the remark that UNI/ENNI are terms defined in G.709 and do not 
>>> relate to layers. They are reference points. You can think to place 
>>> them in the middle of the fiber between a router and a ROADM. Since 
>>> it is just fiber, it is pretty clear that no layer crossing is 
>>> happening there.
>>>>> In IETF we have the overlay concept which also doesn't relate to
>>> layers but to an administrative domain. Hence an operator can choose 
>>> to place a 'GMPLS-UNI' where he wants.
>>>>> Admittedly common wisdom places UNI as inter-layer communication 
>>>>> and
>>> here is where confusion starts. AFAIK the terms UNI-C and UNI-N as 
>>> well as the notion of a 'UNI-protocol' have been brought up in OIF.
>>> For whatever it is or was, initial UNI was from SDH/SONET client to 
>>> SDH/SONET server, hence again no layer crossing even at the protocol 
>>> level.
>>>>> If different layer switching is involved on both sides of an
>>> interface, the best reference is RFC5212 (requirements) and RFC6001.
>>> They define a consistent multi-layer switching and adaptation model.
>>>>> So in order to stay inside a consistent terminology we decided to 
>>>>> go
>>> strictly with IETF terminology. That's the best we can do for now.
>>>>> To your points:
>>>>> - the routing task involves both the IGP and the signaling 
>>>>> protocol, especially in case of loose hops or crankbacks;
>>>>> --> what you mean with routing task? Is it the routing process
>>> itself or something more?
>>>>> - the objective function only makes sense per LSP, which allows to
>>> consider it in LSP-related protocols (PCEP, RSVP-TE... as opposed to 
>>> IGPs or LMP).
>>>>> --> an objective function could make sense per LSP if routing
>>> information is insufficient. It starts with the assumption that a 
>>> router down the road may be able to find a better path than what the 
>>> ingress router does. Given that the ingress has no means to verify 
>>> if the objective has been followed this may turn out to become a 
>>> debugging nightmare.
>>>>> Gert
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> -----Original Message-----
>>>>> From: JP Vasseur (jvasseur) [mailto:jvasseur@cisco.com]
>>>>>
>>>>> I an completely sharing Julien's point of view.
>>>>>
>>>>> JP Vasseur
>>>>> Cisco Fellow
>>>>>
>>>>> Sent from my iPhone
>>>>>
>>>>> On 18 sept. 2012, at 05:27, "Julien Meuric"
>>> <julien.meuric@orange.com> wrote:
>>>>>> Hi Gert.
>>>>>>
>>>>>> As Daniele has just said, almost all the information in an inter-
>>> layer signaling can be seen as input/constraints to the routing 
>>> process. The IGP-TE brings some link-state information to some 
>>> network nodes so as to achieve path computation; the result is used 
>>> in the signaling protocol, on a per LSP basis. I would said that:
>>>>>> - the routing task involves both the IGP and the signaling
>>> protocol,
>>>>>> especially in case of loose hops or crankbacks;
>>>>>> - the objective function only makes sense per LSP, which allows 
>>>>>> to
>>> consider it in LSP-related protocols (PCEP, RSVP-TE... as opposed to 
>>> IGPs or LMP).
>>>>>> I feel that draft-beeram-ccamp-gmpls-_enni_ is clearly 
>>>>>> introducing
>>> some great confusion in the vocabulary: it is a superset of draft- 
>>> beeram-ccamp-gmpls-_uni_-bcp while removing the pointer to the ITU-T 
>>> reference point. A possible option is just to avoid those terms and 
>>> stick to protocols, namely RSVP-TE and IGP-TE.
>>>>>> Regards,
>>>>>>
>>>>>> Julien
>>>>>>
>>>>>>
>>>>>> Le 17/09/2012 23:22, Gert Grammel a écrit :
>>>>>>> Hi George,
>>>>>>>
>>>>>>> The objective function is in the end a routing information.
>>>>>>> Mixing
>>> routing and signaling in one protocol is something I don't feel 
>>> comfortable with.
>>>>>>> In other words, if routing is needed between client and server,
>>> UNI
>>>>>>> is the wrong choice. ENNI should be considered instead and 
>>>>>>> Draft-
>>> beeram-ccamp-gmpls-enni would be a good starting point.
>>>>>>>
>>>>>>> Gert
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> ________________________________________
>>>>>>> From: ccamp-bounces@ietf.org on behalf of George Swallow
>>>>>>> (swallow)
>>>>>>>
>>>>>>> Hi Julien -
>>>>>>>
>>>>>>> On 9/17/12 9:37 AM, "Julien Meuric" <julien.meuric@orange.com>
>>> wrote:
>>>>>>>> Hi George.
>>>>>>>>
>>>>>>>> Sorry for the late response. You are right: the minutes are not 
>>>>>>>> enough to trace the full discussion (which we also resumed 
>>>>>>>> right after the meeting). Let us start by thanking Adrian (as AD?
>>> former PCE co-chair?
>>>>>>>> author of... ;-) ) for bringing the PCE-associated vocabulary 
>>>>>>>> to
>>> a
>>>>>>>> common understanding.
>>>>>>>>
>>>>>>>> Actually my concern is sustained by 2 points:
>>>>>>>>
>>>>>>>> 1- The scope of the draft is about giving control of the 
>>>>>>>> routing objective function to the client node facing a transport layer.
>>>>>>>> I see already several existing solution to achieve it:
>>>>>>>> - a PCEP request from the signaling head node is an option 
>>>>>>>> (which is associated to the advertisement of the supported 
>>>>>>>> objectives in PCEP);
>>>>>>>> - building IGP adjacencies between client and transport edge
>>> nodes
>>>>>>>> (a.k.a. "border model") is another one.
>>>>>>>> In this context, it do not think extending RSVP-TE for this 
>>>>>>>> kind of application is worth the effort, since the requirement 
>>>>>>>> can already be addressed.
>>>>>>> As I understand it, in the optical and OTN cases, the border 
>>>>>>> model would not be popular as in many organizations this crosses 
>>>>>>> political boundaries.
>>>>>>>
>>>>>>> The point of the draft is to keep the UNI implementation simple
>>> and
>>>>>>> not require a PCEP on the uni-c or necessarily on the uni-n.  We 
>>>>>>> will keep the format aligned so if the UNI-N needs to make a 
>>>>>>> request of a PCS, it can do so rather simply.
>>>>>>>> 2- There are cases when previous options are ruled out of a 
>>>>>>>> given deployment. I do believe that it is not simply due to 
>>>>>>>> protocol exclusion, but rather to the fact that the SP wants 
>>>>>>>> transport routing decisions to remain entirely within the 
>>>>>>>> transport network (in order to fully leave the routing policy 
>>>>>>>> in the hands of
>>> people
>>>>>>>> doing the layer dimensioning). Thus, I feel this trade-off in
>>> path
>>>>>>>> selection tuning is rather unlikely to happen and I fear we may
>>> be
>>>>>>>> talking about RSVP-TE over-engineering here.
>>>>>>> The idea is simply to allow the client to express its
>>> needs/wishes.
>>>>>>> The UNI-N remains in control.  By policy it can use the 
>>>>>>> objective function or not.  Further if it does use the objective 
>>>>>>> function
>>> and
>>>>>>> fails to find a path it can either say that there was no path or
>>> it
>>>>>>> proceed to setup what it can.
>>>>>>>
>>>>>>>> (That is also why I preferred to consider your I-Ds separately 
>>>>>>>> during the CCAMP meeting.)
>>>>>>> Agreed.  I will ask for separate slots.  The discussion at the 
>>>>>>> end was rather disjointed.
>>>>>>>
>>>>>>>> However, my comments are mostly related to the client/transport 
>>>>>>>> relationship. If the I-D is extended to cover more use cases 
>>>>>>>> with wider scopes (Adrian has made interesting suggestions), 
>>>>>>>> turning the overlay interconnection into one among a longer 
>>>>>>>> list, then my conclusion may be different.
>>>>>>> I'm happy to widen the scope in this way.
>>>>>>>
>>>>>>> ...George
>>>>>>>
>>>>>>>> Regards,
>>>>>>>>
>>>>>>>> Julien
>>>>>>>>
>>>>>>>>
>>>>>>>> Le 11/09/2012 21:28, George Swallow (swallow) a écrit :
>>>>>>>>> Julien -
>>>>>>>>>
>>>>>>>>> Reading the CCAMP notes (which capture little of the actual
>>>>>>>>> discussion) I see that there may have been a perception in the 
>>>>>>>>> room that PCE functionality at the UNI-N was assumed (actual 
>>>>>>>>> or
>>> proxy).
>>>>>>>>> This is not the case. The reason for our draft is that with 
>>>>>>>>> the UNI, much of the functionality that resides at the headend 
>>>>>>>>> is moved to the UNI-N. So the UNI-C needs a way to express an 
>>>>>>>>> objective function even if there is no PCE.
>>>>>>>>>
>>>>>>>>> Operationally it seems burdensome to require a PCEP at the 
>>>>>>>>> UNI-C and a PCEP at the UNI-N, when all that is being done is 
>>>>>>>>> enabling the UNI-N to perform what the client would do if it 
>>>>>>>>> were connected to the network via a normal link.
>>>>>>>>>
>>>>>>>>> Do you still object to the draft?
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>>
>>>>>>>>> ŠGeorge
>>>>>>> _______________________________________________
>>>>>>> CCAMP mailing list
>>>>>>> CCAMP@ietf.org
>>>>>>> https://www.ietf.org/mailman/listinfo/ccamp
>>>>>>>
>>>>>>>
>>>>>> _______________________________________________
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>>>>>
>>>>>
>>>>>
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