Re: [CCAMP] Objective function draft

Dieter Beller <> Tue, 18 September 2012 09:54 UTC

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Date: Tue, 18 Sep 2012 11:53:09 +0200
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Hi Daniele, all,


I fully agree with your comments/clarifications.


On 18.09.2012 09:19, Daniele Ceccarelli wrote:

Fully agree on the second part of your statement. At the time of RFC4208 the UNI allowed the exchange of signaling and routing messages. Now that we're defining also the E-NNI i would prefer to have:

- UNI: signaling only
- E-NNI: signaling AND routing (i would prefer to call it reachability rather than routing, because it is not a topology info)

That said, i think that objective function (despite the correct comments from Julien) is not routing but a constraint. The ingress node of the overlay network asks the ingress node of the core network for a path computation with given constraints. 

Viceversa in the case of E-NNI if the objective function was exported to the overlay network as a "property" of a virtual link, then i agree it was routing (reachability) information.


-----Original Message-----
From: [] 
On Behalf Of Gert Grammel
Sent: lunedì 17 settembre 2012 23.22
To: George Swallow (swallow); Julien Meuric
Subject: Re: [CCAMP] Objective function draft

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.


From: on behalf of George Swallow (swallow)
Sent: Monday, September 17, 2012 12:19:21 PM
To: Julien Meuric
Subject: Re: [CCAMP] Objective function draft

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 
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 
I'm happy to widen the scope in this way.




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?



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