Re: [Pce] Poll for adoption: draft-litkowski-pce-association-diversity

[stephane.litkowski]

Hi Adrian,

We just posted a v01 that tried to address your comments.
Some encoding/procedures proposed still requires discussion for sure. Please 
let us know your feedback.

We have an on going discussion with the authors of the base association group 
draft. Your last point on security may be addressed by this document in a next 
revision as we think that it is a more general item.

Best regards,


A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Path Computation Element of the IETF.

Title   : Path Computation Element communication Protocol 
extension for signaling LSP diversity constraint
Authors : Stephane Litkowski
  Siva Sivabalan
  Colby Barth
  Dhruv Dhody
Filename: draft-ietf-pce-association-diversity-01.txt
Pages   : 17
Date: 2017-03-13

Abstract:
   This document introduces a simple mechanism to associate a group of
   Label Switched Paths (LSPs) via an extension to the Path Computation
   Element Communication Protocol (PCEP) with the purpose of computing
   diverse paths for those LSPs.  The proposed extension allows a PCC to
   advertise to a PCE the belonging of a particular LSP to a disjoint-
   group, thus the PCE knows that LSPs in the same group must be
   disjoint from each other.


The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-ietf-pce-association-diversity/

There's also a htmlized version available at:
https://tools.ietf.org/html/draft-ietf-pce-association-diversity-01

A diff from the previous version is available at:
https://www.ietf.org/rfcdiff?url2=draft-ietf-pce-association-diversity-01


Please note that it may take a couple of minutes from the time of submission 
until the htmlized version and diff are available at tools.ietf.org.

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/


-Original Message-
From: Adrian Farrel [mailto:adr...@olddog.co.uk] 
Sent: Saturday, January 14, 2017 18:08
To: 'Jonathan Hardwick'; pce@ietf.org
Cc: draft-litkowski-pce-association-divers...@ietf.org; pce-cha...@ietf.org
Subject: RE: [Pce] Poll for adoption: draft-litkowski-pce-association-diversity

> This is start of a two week poll on making
draft-litkowski-pce-association-diversity-01 a PCE working group document.

Hi,

I support the adoption of this draft, because it is clear that this function 
needs to be provided. But my review throws up a few things that should be 
worked on. None of my issues needs hold up adoption of the document so long as 
we can agree to look at them as the work goes forward. Note that a few of my 
comments might lead to reducing the available function, and other might suggest 
using existing mechanisms rather than adding new features.

Thanks,
Adrian

===

Could the Abstract make it a little clearer whether this signaling is to 
request a PCE to compute diverse group of LSPs, request that a PCE compute the 
path of an LSP that is diverse from some other group of existing LSPs, indicate 
to a PCC that it must set up a group of diverse LSPs, indicate to a PCC that an 
LSP that is to be set up must be diverse from some other group of LSPs, or 
report from a PCC to a PCE that a group of LSPs are diverse.

In other words, give some indication of what the feature is for.

---

Similarly, the Introduction needs to give some more clue. When it says "used to 
signal" it fails to indicate who signals to whom and at what stage in the 
process.

---

The document needs to make it clear why the SVEC object is not a suitable 
approach. I think this will follow from the previous two points but it is 
important to mention SVEC and clarify the relationship to that object which has 
previously been used to enable "related" computations.

---

The caption to Figure 1 might better read...

Figure 1 - Disjoint paths with different head-ends and tail-ends

---

"PCInit" should, I think, be "PCInitiate".

---

I want to note that diverse paths can often only be successfully computed if 
they are computed as a batch. Therefore, a mechanism that allows one PCC to 
request an LSP "disjoint from everything else in this group" is flawed unless 
the PCE has some way to know the whole of the group. 
Otherwise, the PCE will compute the path of the LSP as the CSPF because the 
group is empty and will later get a second request ("compute a second LSP 
disjoint from the group") that it might not be able to satisfy. This problem is 
compounded by increasing the size of the group without the PCE even knowing 
whether it has information about the whole group.

That fact does not detract from the protocol mechanism, but does, I think, mean 
that the use case of two or more separate PCCs (LERs) requesting LSPs to be 
divers

Re: [Pce] Poll for adoption: draft-litkowski-pce-association-diversity

[Jonathan Hardwick]

Thanks all for your replies.  This WG adoption poll has ended, with the result 
that the document will be adopted by the PCE working group.

Authors, please resubmit this document as 
draft-ietf-pce-association-diversity-00 (with no other changes).  As there were 
some comments during WG adoption, please address those comments and post any 
necessary updates in a version -01.

Best regards
Jon


From: Jonathan Hardwick
Sent: 11 January 2017 13:45
To: pce@ietf.org
Cc: pce-cha...@ietf.org; 'draft-litkowski-pce-association-divers...@ietf.org' 
<draft-litkowski-pce-association-divers...@ietf.org>
Subject: Poll for adoption: draft-litkowski-pce-association-diversity

This is start of a two week poll on making 
draft-litkowski-pce-association-diversity-01 a PCE working group document.
https://www.ietf.org/id/draft-litkowski-pce-association-diversity-01.txt


Please review the draft and send an email to the list indicating "yes/support" 
or "no/do not support".  If indicating no, please state your reasons.  If yes, 
please also feel free to provide comments you'd like to see addressed once the 
document is a WG document.



The poll ends on Wednesday January 25.



Thanks,

Jon, JP and Julien

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[Pce] Poll for adoption: draft-litkowski-pce-association-diversity

[Guennoun Mouhcine (mguennou)]

yes/support

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Mouhcine Guennoun
Engineer
mguen...@cisco.com
Phone:

Cisco Systems Limited
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CA
Cisco.com





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Re: [Pce] Poll for adoption: draft-litkowski-pce-association-diversity

[Adrian Farrel]

> This is start of a two week poll on making
draft-litkowski-pce-association-diversity-01 a PCE working group document.

Hi,

I support the adoption of this draft, because it is clear that this
function needs to be provided. But my review throws up a few things that
should be worked on. None of my issues needs hold up adoption of the 
document so long as we can agree to look at them as the work goes
forward. Note that a few of my comments might lead to reducing the
available function, and other might suggest using existing mechanisms
rather than adding new features.

Thanks,
Adrian

===

Could the Abstract make it a little clearer whether this signaling is
to request a PCE to compute diverse group of LSPs, request that a PCE 
compute the path of an LSP that is diverse from some other group of
existing LSPs, indicate to a PCC that it must set up a group of diverse 
LSPs, indicate to a PCC that an LSP that is to be set up must be diverse
from some other group of LSPs, or report from a PCC to a PCE that a
group of LSPs are diverse.

In other words, give some indication of what the feature is for.

---

Similarly, the Introduction needs to give some more clue. When it says
"used to signal" it fails to indicate who signals to whom and at what 
stage in the process.

---

The document needs to make it clear why the SVEC object is not a
suitable approach. I think this will follow from the previous two points
but it is important to mention SVEC and clarify the relationship to that
object which has previously been used to enable "related" computations.

---

The caption to Figure 1 might better read...

Figure 1 - Disjoint paths with different head-ends and tail-ends

---

"PCInit" should, I think, be "PCInitiate".

---

I want to note that diverse paths can often only be successfully computed
if they are computed as a batch. Therefore, a mechanism that allows one
PCC to request an LSP "disjoint from everything else in this group" is
flawed unless the PCE has some way to know the whole of the group. 
Otherwise, the PCE will compute the path of the LSP as the CSPF because
the group is empty and will later get a second request ("compute a 
second LSP disjoint from the group") that it might not be able to 
satisfy. This problem is compounded by increasing the size of the 
group without the PCE even knowing whether it has information about the
whole group.

That fact does not detract from the protocol mechanism, but does, I 
think, mean that the use case of two or more separate PCCs (LERs) 
requesting LSPs to be diverse from the group is either more complex (it
could use rerouting to achieve the results after performing a "global
concurrent reoptimization", or it could have additional protocol
mechanisms to scope the group), or subject to failures or suboptimal 
results.

Note that SVEC, SVEC list, and GCO were previous attempts to address
this specific problem. Just as OFs were previous ways of expressing the
computation result desired.

---

In 4.1 you have...

   A disjoint group can have two or more LSPs.  But a PCE may be limited
   in how many LSPs it can take into account when computing
   disjointness: usually PCEs are able to compute a pair of disjoint
   paths.  If a PCE receives more LSPs in the group than it can handle
   in its computation algorithm, it SHOULD apply disjointness
   computation to only a subset of LSPs in the group.  The subset of
   disjoint LSPs will be decided by the implementation.

I think it would be good to strike ": usually PCEs are able to compute a
pair of disjoint paths". That is an implementation detail and actually 
has no bearing on the protocol mechanism you define. That is, even if a
PCE can only compute one path, the "subset" of one will work. 
(Personally, I think PCEs should be able to handle arbitrary groups, but
I understand some algorithms differ.)

What is missing, however, is how the PCE in this case reports that it
did not perform the requested function, but still supplied paths. That 
is, the paths are not what was requested, but are supplied as though
they were. I believe the PCE MUST report this fact so that the PCC can
decide whether or not to use the paths.

---

Similarly

   Associating a particular LSP to multiple disjoint groups is
   authorized from a protocol perspective, however there is no insurance
   that the PCE will be able to compute properly the multi-disjointness
   constraint.

So the PCE that cannot handle this case needs to have a formal response
that lets the PCC know that something undesired has happened.

---

What is the interaction of the P flag and the OF?
If the OF says, for example, use the least load path, and yet the P flag
is set, what should the PCE do?
Perhaps this is what your text is trying to talk about.
Maybe then, this isn't specifically the "shortest path" flag, but is 
more a "satisfy all constraints and objective functions first without
considering the diversity constraint" flag.

Even so, you should talk about what 

Re: [Pce] Poll for adoption: draft-litkowski-pce-association-diversity

[Dhruv Dhody]

Hi WG, Authors,

Yes/Support   (but I have some concerns, that can be addressed once the 
document is a WG document)


(1)Strictness

a.   The document suggest local policies to decide the computation 
behavior, I would prefer to have normative text for better inter-operability. I 
think this point was also discussed during the IETF meeting.

b.  Also It would be helpful if we keep the proposal aligned to existing 
PCEP objects and mechanism

   i.  SVEC 
Flags (which are strict) [RFC5440]

 ii.  OF codes 
(which allow maximizing diversity, with no strictness guarantee) 
[draft-dhody-pce-of-diverse]

c.   I would propose following encoding change

   i.  Single 
disjoint association type (instead of 4)

 ii.  Add flags 
in DISJOINTNESS-INFORMATION-TLV for node, link, srlg (similar to SVEC - strict)

iii.  Add 
OF-Code also in the TLV



(2)I am not sure about this text in the section 3 -
   o  Configuration: in case the PCC is performing the path computation
  but the PCE (without computation engine) is managing the LSP
  parameters, the PCE should add the disjoint-group within the
  PCUpdate message to communicate to the PCC the disjointness
  constraint.


* I don't think the use of PCUpd in this way would be aligned to the 
Stateful PCE draft. Perhaps this needs to be discussed on its own.



(3)Some text should be added to suggest how this would work along with the 
protection association draft 
[draft-ananthakrishnan-pce-stateful-path-protection]. IMHO both association 
group should be used together when we would like to specify the diversity 
requirement of the protection LSP. Some text could be added here.

Based on the discussion with authors, I can provide text if required.

Regards,
Dhruv

From: Pce [mailto:pce-boun...@ietf.org] On Behalf Of Jonathan Hardwick
Sent: 11 January 2017 19:15
To: pce@ietf.org
Cc: draft-litkowski-pce-association-divers...@ietf.org; pce-cha...@ietf.org
Subject: [Pce] Poll for adoption: draft-litkowski-pce-association-diversity

This is start of a two week poll on making 
draft-litkowski-pce-association-diversity-01 a PCE working group document.
https://www.ietf.org/id/draft-litkowski-pce-association-diversity-01.txt


Please review the draft and send an email to the list indicating "yes/support" 
or "no/do not support".  If indicating no, please state your reasons.  If yes, 
please also feel free to provide comments you'd like to see addressed once the 
document is a WG document.



The poll ends on Wednesday January 25.



Thanks,

Jon, JP and Julien

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Re: [Pce] Poll for adoption: draft-litkowski-pce-association-diversity

[stephane.litkowski]

Support as author


From: Jonathan Hardwick [mailto:jonathan.hardw...@metaswitch.com]
Sent: Wednesday, January 11, 2017 14:45
To: pce@ietf.org
Cc: pce-cha...@ietf.org; draft-litkowski-pce-association-divers...@ietf.org
Subject: Poll for adoption: draft-litkowski-pce-association-diversity

This is start of a two week poll on making 
draft-litkowski-pce-association-diversity-01 a PCE working group document.
https://www.ietf.org/id/draft-litkowski-pce-association-diversity-01.txt


Please review the draft and send an email to the list indicating "yes/support" 
or "no/do not support".  If indicating no, please state your reasons.  If yes, 
please also feel free to provide comments you'd like to see addressed once the 
document is a WG document.



The poll ends on Wednesday January 25.



Thanks,

Jon, JP and Julien


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Re: [Pce] Poll for adoption: draft-litkowski-pce-association-diversity

[Siva Sivabalan (msiva)]

Yes/support

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Siva Sivabalan
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From: Siva Sivabalan (msiva)
Sent: Wednesday, January 11, 2017 1:10 PM
To: 'Jonathan Hardwick' <jonathan.hardw...@metaswitch.com>; pce@ietf.org
Cc: pce-cha...@ietf.org; draft-litkowski-pce-association-divers...@ietf.org
Subject: RE: Poll for adoption: draft-litkowski-pce-association-diversity

Support.

From: Jonathan Hardwick [mailto:jonathan.hardw...@metaswitch.com]
Sent: Wednesday, January 11, 2017 8:45 AM
To: pce@ietf.org<mailto:pce@ietf.org>
Cc: pce-cha...@ietf.org<mailto:pce-cha...@ietf.org>; 
draft-litkowski-pce-association-divers...@ietf.org<mailto:draft-litkowski-pce-association-divers...@ietf.org>
Subject: Poll for adoption: draft-litkowski-pce-association-diversity

This is start of a two week poll on making 
draft-litkowski-pce-association-diversity-01 a PCE working group document.
https://www.ietf.org/id/draft-litkowski-pce-association-diversity-01.txt


Please review the draft and send an email to the list indicating "yes/support" 
or "no/do not support".  If indicating no, please state your reasons.  If yes, 
please also feel free to provide comments you'd like to see addressed once the 
document is a WG document.



The poll ends on Wednesday January 25.



Thanks,

Jon, JP and Julien

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Re: [Pce] Poll for adoption: draft-litkowski-pce-association-diversity

[Jeff Tantsura]

yes/support

 

 

Cheers,

Jeff

 

From: Jonathan Hardwick [mailto:jonathan.hardw...@metaswitch.com] 
Sent: Wednesday, January 11, 2017 8:45 AM
To: pce@ietf.org
Cc: pce-cha...@ietf.org; draft-litkowski-pce-association-divers...@ietf.org
Subject: Poll for adoption: draft-litkowski-pce-association-diversity

 

This is start of a two week poll on making 
draft-litkowski-pce-association-diversity-01 a PCE working group document.

https://www.ietf.org/id/draft-litkowski-pce-association-diversity-01.txt

 

Please review the draft and send an email to the list indicating “yes/support” 
or “no/do not support”.  If indicating no, please state your reasons.  If yes, 
please also feel free to provide comments you'd like to see addressed once the 
document is a WG document.

 

The poll ends on Wednesday January 25.

 

Thanks,

Jon, JP and Julien

 

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Re: [Pce] Poll for adoption: draft-litkowski-pce-association-diversity

[Olivier Dugeon]

Yes/support

Olivier


Le 11/01/2017 à 14:44, Jonathan Hardwick a écrit :
>
> This is start of a two week poll on making 
> draft-litkowski-pce-association-diversity-01 a PCE working group document.
>
> https://www.ietf.org/id/draft-litkowski-pce-association-diversity-01.txt
>
>  
>
> Please review the draft and send an email to the list indicating 
> “yes/support” or “no/do not support”.  If indicating no, please state your 
> reasons.  If yes, please also feel free to provide comments you'd like to see 
> addressed once the document is a WG document.
>
>  
>
> The poll ends on Wednesday January 25.
>
>  
>
> Thanks,
>
> Jon, JP and Julien
>
>  
>
>
>
> ___
> Pce mailing list
> Pce@ietf.org
> https://www.ietf.org/mailman/listinfo/pce

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[Pce] Poll for adoption: draft-litkowski-pce-association-diversity

[Jonathan Hardwick]

This is start of a two week poll on making 
draft-litkowski-pce-association-diversity-01 a PCE working group document.
https://www.ietf.org/id/draft-litkowski-pce-association-diversity-01.txt


Please review the draft and send an email to the list indicating "yes/support" 
or "no/do not support".  If indicating no, please state your reasons.  If yes, 
please also feel free to provide comments you'd like to see addressed once the 
document is a WG document.



The poll ends on Wednesday January 25.



Thanks,

Jon, JP and Julien

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