Re: [CCAMP] Objective function draft

Julien Meuric <julien.meuric@orange.com> Wed, 19 September 2012 15:58 UTC

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Date: Wed, 19 Sep 2012 17:58:48 +0200
From: Julien Meuric <julien.meuric@orange.com>
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To: John E Drake <jdrake@juniper.net>
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Subject: Re: [CCAMP] Objective function draft
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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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