Re: [Pce] Urgent issue with draft-ietf-pce-stateful-pce : PCE advising PCC about no path

[Sudhir Cheruathur]

olicy to control the associated 
behavior => tear down, revoking delegation, keep existing path or whatever…

Optionally, we still need to agree if we consider NO-PATH object as a 
complement and optional object.

Brgds,


From: Pce [mailto:pce-boun...@ietf.org] On Behalf Of Olivier Dugeon
Sent: Wednesday, October 05, 2016 18:11
To: Aissaoui, Mustapha (Nokia - CA); MEURIC Julien IMT/OLN; 
pce@ietf.org<mailto:pce@ietf.org>
Subject: Re: [Pce] Urgent issue with draft-ietf-pce-stateful-pce : PCE advising 
PCC about no path


Hello all,

If I try to summarize, in one hand we have some implementations that use an 
empty ERO which lead in interoperability issues due to ambiguous 
interpretation, and in the other hand a clear non-ambiguous object i.e. NO-PATH 
which break implementation or at least impose strong modifications in existing 
code.

So, in order to advance on the subject, I would propose to add new code points 
to explicitly mention that the ERO is empty, and why is empty:  This solves the 
ambiguity while imposing smooth modification in today implementations as they 
just have to check a particular ERO code point (in replacement to check that 
the ERO is empty) instead processing a new object (i.e. NO-PATH).

There is two options for this new ERO code points:

a) At the ERO registry level. ERO is Class Type 20 and Class Num 1. The idea is 
to add a new Class Num = 2 i.e. Empty ERO with possibility to add different 
values to specify why it is empty e.g. 1 = NO-PATH, 2 = LOOSE-PATH ...

b) At the sub-object level. Within ERO Class Type 20 and Class Num 1, add new 
code points. eg. 38 = Empty-ERO NO-PATH, 39 = Empty-ERO Loose-Path ...

Option a) require to request a new registry and code points while option b) 
just require new code points in existing registry to IANA. Option a) allows to 
add a dedicated registry for Empty ERO with possibility to precisely describe 
why it is empty, while option b) mix the notion of Empty ERO and the reason why 
it is empty. Looking to implementation, option a) impose to look at Class Num 
when processing the ERO while option b) just need to look at sub-object.

Draft stateful could introduce this new ERO code points (whatever option a or 
b) and other drafts (initiated, synchronisation ...) could add there own needs 
regarding this empty ERO.

Comments are welcome.

Regards

Olivier
Le 05/10/2016 à 16:01, Aissaoui, Mustapha (Nokia - CA) a écrit :
I am of the same opinion too. Let us keep empty ERO in both the PCUpd and PCRpt 
messages to mean there is no valid path for the LSP. A PCC implementation 
receiving a PCUpd with an empty ERO for a non-zero PLSP-ID can decide if the 
outcome of this means to tear down the path or keep the existing working path. 
If the PCC wants to use the local CSPF or an IGP driven path, then it must 
first revoke the delegation as per existing procedures.

Regards,
Mustapha.

From: Pce [mailto:pce-boun...@ietf.org] On Behalf Of Julien Meuric
Sent: Wednesday, October 05, 2016 8:04 AM
To: pce@ietf.org<mailto:pce@ietf.org>
Subject: Re: [Pce] Urgent issue with draft-ietf-pce-stateful-pce : PCE advising 
PCC about no path


Hi all,

Chair hat on, I concur with the proposed plan: we need to stick to the current 
scope of the base stateful I-D and fix pending issues in there, new proposals 
like "partial delegation" do require a new document.

Thank you Dhruv and Stéphane for being proactive on that,

Julien

Oct. 05, 2016 - :
Hi Dhruv, Sudhir

I agree that what is achieved here is a partial delegation which is not inline 
with delegation in stateful pce draft which gives full control to PCE.

The use case described is interesting but I’m afraid that empty ERO was used 
for this purpose while there was no discussion at WG level to achieve consensus 
for this partial delegation solution. I would prefer that Juniper used a vendor 
specific flag for this behavior rather than using existing objects.
I would prefer to close the base stateful PCE draft before adding new features …

Partial delegation may be complex to handle as some people may want ERO to be 
controlled by PCC while constraints by PCE and some other may want the opposite 
(constraints by PCC and ERO by PCE) so this requires more discussion.

Brgds,

Stephane

From: Dhruv Dhody [mailto:dhruv.dh...@huawei.com]
Sent: Wednesday, October 05, 2016 06:09
To: Sudhir Cheruathur; LITKOWSKI Stephane OBS/OINIS; Harish Magganmane; 
Aissaoui, Mustapha (Nokia - CA); pce@ietf.org<mailto:pce@ietf.org>; 
draft-ietf-pce-stateful-...@tools.ietf.org<mailto:draft-ietf-pce-stateful-...@tools.ietf.org>
Cc: 'Dhruv Dhody'
Subject: RE: [Pce] Urgent issue with draft-ietf-pce-stateful-pce : PCE advising 
PCC about no path

Hi Sudhir/Harish,

Thanks for explaining your motivation but it is not as per the definition of 
“delegation”.
What you are suggesting is a new feature lets call it “partial delegation”. I 
hope we can discuss the merit and the procedures of this in a small 

Re: [Pce] Urgent issue with draft-ietf-pce-stateful-pce : PCE advising PCC about no path

[Sudhir Cheruathur]

Stephane/Dhruv/Mustapha,

>>I’m trying to understand what you really want to achieve here. Or do you want 
>>to have PCE updating LSP parameters/constraints but let the PCC compute path ?

We want to allow changing of other attributes of an LSP (such as BW/metric), 
but leave the path computation to the PCC. With this a PCC now has a choice to 
do a local CSPF or use IGP hop-by-hop. This choice can be enforced on the PCC 
with an empty ERO and local policy. When we want to drive this same behavior 
from the PCE then we could you use a NO-PATH object.

We could define flags in the NO-PATH object to tell the PCC what to do when a 
path is not available. The Nature of Issue is set to 0 (No path) and flags can 
be defined to specify the following

a)   Bring down the LSP

b)   Use local CSPF

c)   Use IGP based hop-by-hop.

Thanks
Redgs
Sudhir C



From: Pce  on behalf of "stephane.litkow...@orange.com" 

Date: Monday, October 3, 2016 at 1:27 AM
To: Harish Magganmane , "Aissaoui, Mustapha (Nokia - 
CA)" , "pce@ietf.org" , 
"draft-ietf-pce-stateful-...@tools.ietf.org" 

Subject: Re: [Pce] Urgent issue with draft-ietf-pce-stateful-pce : PCE advising 
PCC about no path

Hi Harish,

Thanks for your feedback.
I do not really understand why you map the empty ERO to a decision to possibly 
fallback computation to local.
As you mentioned, it could be a local PCC policy decision and this local policy 
could be to tear down the LSP instead of deferring ERO selection to the local 
router as you proposed.

The important point is the semantic of this empty ERO, not really the action 
taken. I understand in your email  that you still interpret it from a semantic 
point of view has an indication of no path, so you then can decide to defer ERO 
selection to the router. Because in the case, you want to have the PCE giving 
back path computation role to PCC, the PCE must use the delegate flag for this 
purpose and can revoke the delegation at anytime. I’m trying to understand what 
you really want to achieve here. Or do you want to have PCE updating LSP 
parameters/constraints but let the PCC compute path ?

Best Regards,

Stephane



From: Harish Magganmane [mailto:hmagganm...@juniper.net]
Sent: Saturday, October 01, 2016 00:53
To: LITKOWSKI Stephane OBS/OINIS; Aissaoui, Mustapha (Nokia - CA); 
pce@ietf.org; draft-ietf-pce-stateful-...@tools.ietf.org
Subject: Re: [Pce] Urgent issue with draft-ietf-pce-stateful-pce : PCE advising 
PCC about no path

Hi Stephane,

We are not in favor of using empty ERO as way to signal the tearing of an LSP. 
IMO empty ERO object should be interpreted to mean deferring the ERO selection 
to the router, perhaps through local policy on the PCC. For example PCC could 
choose between a local CSPF or a IGP based hop-by-hop.

In cases where we want PCE to explicitly control the behavior of the PCC when a 
path is not available, NO-PATH object can be used to dictate the behavior. One 
such behavior could be that of tearing down the LSP.

Thanks,
Harish

From: Pce > on behalf of 
"stephane.litkow...@orange.com" 
>
Date: Friday, September 30, 2016 at 8:33 AM
To: "Aissaoui, Mustapha (Nokia - CA)" 
>, 
"pce@ietf.org" >, 
"draft-ietf-pce-stateful-...@tools.ietf.org"
 
>
Subject: Re: [Pce] Urgent issue with draft-ietf-pce-stateful-pce : PCE advising 
PCC about no path

Hi Mustapha,

Your proposal works from my point of view, but it looks that it causes some 
trouble to another vendor so I would like these people (and others as well) to 
express their concerns regarding usage of empty ERO.

Thanks for pointing again your last proposal.

Best Regards,

Stephane


From: Aissaoui, Mustapha (Nokia - CA) [mailto:mustapha.aissa...@nokia.com]
Sent: Friday, September 30, 2016 17:08
To: LITKOWSKI Stephane OBS/OINIS; pce@ietf.org; 
draft-ietf-pce-stateful-...@tools.ietf.org
Subject: RE: Urgent issue with draft-ietf-pce-stateful-pce : PCE advising PCC 
about no path

Hi Stephane,
In the last email related to this issue, I made a proposal to Olivier and 
Robert commented on it. Would that be sufficient to address this interop issue?
https://mailarchive.ietf.org/arch/msg/pce/A1ADiw6Uvjn1ETjErqzgjdjXnsE

Mustapha.

From: Pce [mailto:pce-boun...@ietf.org] On Behalf Of 
stephane.litkow...@orange.com
Sent: Friday, September 30,