Re: [CCAMP] Objective function draft

Igor Bryskin <> Wed, 19 September 2012 16:26 UTC

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From: Igor Bryskin <>
To: Julien Meuric <>, John E Drake <>
Thread-Topic: [CCAMP] Objective function draft
Date: Wed, 19 Sep 2012 16:25:58 +0000
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Subject: Re: [CCAMP] Objective function draft
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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.

-----Original Message-----
From: [] On Behalf Of Julien Meuric
Sent: Wednesday, September 19, 2012 11:59 AM
To: John E Drake
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.)


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: [] 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) []
>>>> 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"
>> <> 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: on behalf of George Swallow 
>>>>>> (swallow)
>>>>>> Hi Julien -
>>>>>> On 9/17/12 9:37 AM, "Julien Meuric" <>
>> 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
>>>>>> _______________________________________________
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