Re: [CCAMP] [Technical Errata Reported] RFC4872 (3304)

[Lou Berger <[e-mail]>]

Dimitri,
	(hat off) while it is not explicit, there is nothing in the draft that
precludes it and some of us certainly reviewed the document at the time
with this in mind to ensure it wasn't.  Furthermore, as we heard in
Paris, there is at least one deployed implementation that implements
reversion with full LSP rerouting.

Based on the level of discussion, I suspect an info doc may be a better
way to go on this topic...

Lou

On 8/2/2012 8:24 AM, Papadimitriou, Dimitri (Dimitri) wrote:
> Lou, 
> 
> there is by definition no notion of "reversion" in full LSP
> re-routing. this is why there is no such description: it is less
> faster than e.g. protection but less resource-consuming (direct
> release of resources after establishment of the new LSP using
> make-before-break/RFC 3209) and more robust. see also RFC 4428 for
> more details.
> 
> -> so I am not sure to which revision placeholder of RFC 4872 you are
> talking as I miss the rationales for a "scenario" that increases
> recovery time *and* resource consumption.
> 
> Thanks,
> -dimitri.
>> -----Original Message-----
>> From: Lou Berger [mailto:[e-mail]] 
>> Sent: Wednesday, August 01, 2012 23:45
>> To: [e-mail]; 'Ong, Lyndon'
>> Cc: [e-mail]; [e-mail]; [e-mail]; 
>> Papadimitriou, Dimitri (Dimitri); [e-mail]; 
>> [e-mail]; 'Roch, Evelyne'
>> Subject: Re: [Technical Errata Reported] RFC4872 (3304)
>>
>>> There is, of course, a lot that could be done to make it 
>> clearer. But
>> is there
>>> really a need? We discussed the point. We agreed it is not 
>> prohibited
>> in the
>>> RFC. Can we not just move on?
>>
>> So it sounds like there's agreement that there's no technical 
>> errata here.
>>
>> Perhaps an alternate way to proceed is to replace this errata with an
>> editorial errata that states that a future revision of the RFC should
>> explicitly discuss how this scenario is covered?
>>
>> Comments/thoughts?
>>
>> Lou
>>
>> On 8/1/2012 11:01 AM, Adrian Farrel wrote:
>>> Hello again,
>>>
>>>> Thank you for the fast evaluation of the errata.  It 
>> sounds like the
>>> correction that I
>>>> suggested has ended up overspecifying the method to do 
>> reversion with full
>>>> rerouting when it is very possible to support a form of 
>> reversion that doesn't
>>>> involve maintaining the old LSP.
>>>
>>> Right, I understand that you want to allow the option of 
>> retaining the old
>>> working LSP. Also that you have no intention to remove the 
>> option of removing
>>> the old working LSP.
>>>
>>>> From your response I believe that you do agree that it was 
>> not the intent of
>>> the
>>>> original specification text to imply that reversion with 
>> full rerouting is not
>>> allowed
>>>
>>> Definitely not the intent to imply that reversion with full 
>> rerouting is not
>>> allowed.
>>> Does the text say or even imply this?
>>>
>>>> (or to require that the old LSP always be torn down in 
>> full rerouting)
>>>
>>> Also no intention to *require* the old LSP to be torn down. 
>>> My view is that the text is fully conformant with that.
>>> I understand that the text does not make an explicit 
>> statement of this.
>>>
>>>> so hopefully
>>>> with some more discussion we can determine if there is 
>> anything that could be
>>>> done to make that clearer.
>>>
>>> There is, of course, a lot that could be done to make it 
>> clearer. But is there
>>> really a need? We discussed the point. We agreed it is not 
>> prohibited in the
>>> RFC. Can we not just move on?
>>>
>>> Cheers,
>>> Adrian
>>>> -----Original Message-----
>>>> From: Adrian Farrel [mailto:[e-mail]]
>>>> Sent: Tuesday, July 31, 2012 6:28 PM
>>>> To: [e-mail]
>>>> Cc: [e-mail]; [e-mail]; 
>> dimitri.papadimitriou@alcatel-
>>>> lucent.be; [e-mail]; [e-mail]; 
>> [e-mail]; Ong,
>>>> Lyndon
>>>> Subject: RE: [Technical Errata Reported] RFC4872 (3304)
>>>>
>>>> Hi CCAMP,
>>>>
>>>> I find that this erratum is raised against two sections 
>> one of which I
>>> supplied text
>>>> for. If this get contentious, I will call on Stewart to 
>> call consensus and
>>> handle the
>>>> Erratum in the system.
>>>>
>>>> In my opinion, this proposal goes further than the 
>> intention of the authors/WG
>>> in
>>>> publishing 4872.
>>>>
>>>> With regard to the proposed addition to section 11...
>>>> The use of mb4b is already in scope. The existing text 
>> says "The new LSP
>>>> resources can be established using the make-before-break 
>> mechanism," so there
>>>> is no need to re-state "The new LSP can be established 
>> without tearing down
>>> the
>>>> old LSP".
>>>>
>>>> I think your concern here is whether the old LSP is ever 
>> torn down. I think
>>> that
>>>> you are worried that if the old LSP is torn down, it might 
>> be impossible to
>>> perform
>>>> reversion because, after repair, an attempt to revert 
>> (also using mb4b) might
>>> find
>>>> that key resources have been "stolen" by some other LSP. I 
>> don't see this as
>>> at all
>>>> different from the issue of the protection LSP itself. 
>> That is, it is of the
>>> nature of
>>>> LSP Rerouting as a protection mechanism that:
>>>> a. protection may fail because of lack of resources b. 
>> reversion may fail
>>> because
>>>> of lack of resources
>>>>
>>>> *If* reversion is so important, I don't quite see why 
>> protection is not
>>> important.
>>>> If protection is important then you should be using a 
>> proper protection
>>>> mechanism and not waiting for post facto rerouting. 
>> Furthermore, if you
>>> require
>>>> that the LSP be retained for restoration, why are you not 
>> using a protection
>>>> mechanism?
>>>>
>>>> But the general paradigm here is that you are willing to 
>> use the best
>>> available LSP
>>>> when it is set up in the first place, the best available 
>> LSP when you re-route
>>> after
>>>> failure, and the best available LSP when you "revert".
>>>>
>>>> Lastly, it *does* remain an _option_ to retain the failed 
>> LSP in order to
>>> switch
>>>> back. Nothing in the old text precludes that, although I 
>> understand that there
>>> is
>>>> an implication that it might be expected to be torn down.
>>>>
>>>> So I conclude that the proposed addition to section 12 is 
>> not what the
>>>> authors/WG intended.
>>>>
>>>> We should discuss further.
>>>>
>>>> Adrian
>>>>
>>>>> -----Original Message-----
>>>>> From: RFC Errata System [mailto:[e-mail]]
>>>>> Sent: 31 July 2012 17:39
>>>>> To: [e-mail]; [e-mail]; 
>> dimitri.papadimitriou@alcatel-
>>>>> lucent.be; [e-mail]; [e-mail]; 
>> [e-mail];
>>>>> [e-mail]
>>>>> Cc: [e-mail]; [e-mail]; [e-mail]
>>>>> Subject: [Technical Errata Reported] RFC4872 (3304)
>>>>>
>>>>>
>>>>> The following errata report has been submitted for 
>> RFC4872, "RSVP-TE
>>>>> Extensions in Support of End-to-End Generalized 
>> Multi-Protocol Label
>>>>> Switching (GMPLS) Recovery".
>>>>>
>>>>> --------------------------------------
>>>>> You may review the report below and at:
>>>>> http://www.rfc-editor.org/errata_search.php?rfc=4872&eid=3304
>>>>>
>>>>> --------------------------------------
>>>>> Type: Technical
>>>>> Reported by: Lyndon Ong <[e-mail]>
>>>>>
>>>>> Section: 11 & 12
>>>>>
>>>>> Original Text
>>>>> -------------
>>>>> Section 11 says:
>>>>>
>>>>>
>>>>>    (Full) LSP rerouting will be initiated by the head-end 
>> node that has
>>>>>    either detected the LSP failure or received a Notify 
>> message and/or a
>>>>>    PathErr message with the new error code/sub-code 
>> "Notify Error/LSP
>>>>>    Locally Failed" for this LSP.  The new LSP resources can be
>>>>>    established using the make-before-break mechanism, 
>> where the new LSP
>>>>>    is set up before the old LSP is torn down.  This is 
>> done by using the
>>>>>    mechanisms of the SESSION_ATTRIBUTE object and the 
>> Shared-Explicit
>>>>>    (SE) reservation style (see [RFC3209]).  Both the new 
>> and old LSPs
>>>>>    can share resources at common nodes.
>>>>>
>>>>> Section 12 says:
>>>>>
>>>>>    [No text on reversion for (full) LSP Rerouting.]
>>>>>
>>>>> Corrected Text
>>>>> --------------
>>>>> Section 11 should say:
>>>>>
>>>>>
>>>>>    (Full) LSP rerouting will be initiated by the head-end 
>> node that has
>>>>>    either detected the LSP failure or received a Notify 
>> message and/or a
>>>>>    PathErr message with the new error code/sub-code 
>> "Notify Error/LSP
>>>>>    Locally Failed" for this LSP.  The new LSP resources can be
>>>>>    established using the make-before-break mechanism, 
>> where the new LSP
>>>>>    is set up before the old LSP is torn down.  This is 
>> done by using the
>>>>>    mechanisms of the SESSION_ATTRIBUTE object and the 
>> Shared-Explicit
>>>>>    (SE) reservation style (see [RFC3209]).  Both the new 
>> and old LSPs
>>>>>    can share resources at common nodes.  The new LSP can 
>> be established
>>>>>    without tearing down the old LSP in case of reversion 
>> (see section 12).
>>>>>
>>>>> Section 12 should say:
>>>>>
>>>>>    For "(full) LSP Rerouting", reversion implies that the 
>> old LSP is not
>>>>>    torn down by the head-end node after the new LSP is 
>> established. For
>>>>>    reversion, the head-end node re-activates the old LSP 
>> after this has
>>>>>    recovered.
>>>>>
>>>>>
>>>>>
>>>>> Notes
>>>>> -----
>>>>> Current text in RFC 4872 describes reversion in the cases of 1+1
>>>>> bidirectional Protection, 1:N Protection with Extra Traffic and
>>>>> Rerouting Without Extra
>>>> Traffic,
>>>>> however it has no description of reversion with (Full) 
>> LSP Rerouting.
>>>>> For (full) LSP Rerouting, the description in Section 11 instead
>>>>> implies that
>>>> the old
>>>>> LSP is torn down. This has led to some confusion as to whether
>>>>> reversion with
>>>>> (full) LSP Rerouting is allowed or not allowed by the 
>> RFC. We believe
>>>>> this was
>>>> not
>>>>> intentional. The additions would make it clear that 
>> reversion can be
>>>>> supported with (Full) LSP Rerouting.
>>>>>
>>>>> Instructions:
>>>>> -------------
>>>>> This errata is currently posted as "Reported". If 
>> necessary, please
>>>>> use "Reply All" to discuss whether it should be verified 
>> or rejected.
>>>>> When a decision is reached, the verifying party (IESG) 
>> can log in to
>>>>> change the status and edit the report, if necessary.
>>>>>
>>>>> --------------------------------------
>>>>> RFC4872 (draft-ietf-ccamp-gmpls-recovery-e2e-signaling-04)
>>>>> --------------------------------------
>>>>> Title               : RSVP-TE Extensions in Support of End-to-End
>>> Generalized
>>>> Multi-
>>>>> Protocol Label Switching (GMPLS) Recovery
>>>>> Publication Date    : May 2007
>>>>> Author(s)           : J.P. Lang, Ed., Y. Rekhter, Ed., D. 
>> Papadimitriou, Ed.
>>>>> Category            : PROPOSED STANDARD
>>>>> Source              : Common Control and Measurement Plane
>>>>> Area                : Routing
>>>>> Stream              : IETF
>>>>> Verifying Party     : IESG
>>>
>>>
>>>
>>>
>>>
>>
> 
> 
>