Re: [mpls] PSC: draft-rhd-mpls-tp-psc-sd-00

Hi Sasha-

 I tend to agree.  I fully admit that PSC is a little inconsistent in these matters, in that it provides a place for SD in the alarm hierarchy but not in the state machine.  However, I see little point in adding all the SD state machinery before we have some sort of SD mechanism.  It may be that we come up with an SD mechanism that is more powerful than its analog in the transport world, and it might provide operators with significant flexibility that wouldn't be possible with the current proposal.

  Why come up with highway legislation that describes the rules of the road for flying hovercars prior to inventing the flying hovercar?

eric

> -----Original Message-----
> From: Alexander Vainshtein [mailto:Alexander.Vainshtein@ecitele.com]
> Sent: Sunday, April 21, 2013 11:45 AM
> To: Eric Osborne (eosborne)
> Cc: mpls@ietf.org; Rotem Cohen; Gideon Agmon; Yechiel Rosengarten; Shell
> Nakash
> Subject: RE: PSC: draft-rhd-mpls-tp-psc-sd-00
> 
> Eric, and all,
> The issue has been discussed actively in the past.
> 
> I can only re-state my position during these discussions, namely that there is no
> way to define a reasonable analog of Signal Degrade (SD) in MPLS and, by
> implication, in the MPLS-TP data plane. By "reasonable" here I mean a method
> that does not depend on the actual traffic going thru the LSP.
> 
> The fact that we could not reach any consensus for such a definition in the past
> is not, of course, a mathematical proof of non-existence of SD.
> But it is a good indication of a fundamental problem IMO.
> 
> As a consequence, IMHO and FWIW, there is no need in defining SD-related
> state transitions, behavior etc.
> 
> My 2c,
>      Sasha
> 
> > -----Original Message-----
> > From: mpls-bounces@ietf.org [mailto:mpls-bounces@ietf.org] On Behalf
> > Of Eric Osborne (eosborne)
> > Sent: Wednesday, April 17, 2013 3:26 PM
> > To: mpls@ietf.org
> > Subject: [mpls] PSC: draft-rhd-mpls-tp-psc-sd-00
> >
> > This thread is for discussing draft-rhd-mpls-tp-psc-sd-00.  The draft
> > provided extensions to the PSC state machine to handle Signal Degrade
> > (SD).  It does not define SD or provide scope around where or how SD
> > may be used.  There are some expired drafts that touch on the definition and
> use of SD, including:
> >
> > draft-zhl-mpls-tp-sd-03
> > draft-rkhd-mpls-tp-sd-03
> >
> > (this is not an exhaustive list.  It's the top two google hits.)
> >
> >
> > The questions I think are relevant are:
> >
> > - do we need an SD mechanism in MPLS-TP?
> > - if so, is it reasonable to define state transitions for it before we
> > have defined SD itself?
> > - if yes to both of the above, does this draft provide the right
> > behavior?  Are there alternative approaches?
> >
> > but of course any and all discussion is welcome.
> >
> >
> >
> > eric
> >
> > _______________________________________________
> > mpls mailing list
> > mpls@ietf.org
> > https://www.ietf.org/mailman/listinfo/mpls
> 
> 
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