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

["Ong, Lyndon" <[e-mail]>]

Hi Adrian,

Sorry, not so fast!  Let me make another proposal:

Section 11: 
Existing: 
   (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.  

New:
   (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 *while the old LSP is still in place*.  

Reasoning: No longer implies that the old LSP would necessarily be torn down.

Note the text in Section 12 states
   Reversion refers to a recovery switching operation, where the normal
   traffic returns to (or remains on) the working LSP when it has
   recovered from the failure.  *Reversion implies that resources remain
   allocated to the LSP that was originally routed over them even after
   a failure*.  It is important to have mechanisms that allow reversion
   to be performed with minimal service disruption and reconfiguration.

That could be interpreted to rule out Reversion with LSP Rerouting if you must tear down the old LSP.
Of course this could be fixed also (for example by deleting the statement).

Thanks,

Lyndon

-----Original Message-----
From: Adrian Farrel [mailto:[e-mail]] 
Sent: Wednesday, August 01, 2012 11:02 AM
To: Ong, Lyndon; [e-mail]
Cc: [e-mail]; [e-mail]; [e-mail]; [e-mail]; [e-mail]; [e-mail]; Roch, Evelyne
Subject: RE: [Technical Errata Reported] RFC4872 (3304)

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