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

Hi Alessandro, see inline.

> -----Original Message-----
> From: D'Alessandro Alessandro Gerardo
> [mailto:alessandro.dalessandro@telecomitalia.it]
> Sent: Tuesday, May 07, 2013 3:27 PM
> To: Eric Osborne (eosborne); mpls@ietf.org
> Cc: Cavazzoni Carlo; Allasia Andrea; Nervo Giacolino; Morro Roberto;
> ryoo@etri.re.kr; lifang@catr.cn; cts@etri.re.kr
> Subject: R: PSC: draft-rhd-mpls-tp-psc-priority-00
> 
> Hi Eric,
> You wrote "is it appropriate to make this priority swap?"
> My answer is yes, it shall be done for the reasons explained in liaison
> 1205, bullet 1.

Let me paraphrase the three points in those bullets, I want to make sure I understand them:

a. If the protection path fails then the removal of the FS will not be seen because the channel used to provide it is gone.
b. If there is SF-P and FS is issued by accident then this will cause an outage, which is Bad
c. (points to Annex 1): similar to (a) above, the loss of the protection channel means there will be an inconsistency in the protection state

Is that an accurate paraphrase?

> You wrote "- what do we need to change?  rfc5654?  rfc4427?  "
> No I don't believe it is required to change any RFC but RFC 6378

To me this decision is a matter of process rather than of technical behavior.  
I believe the current set of opinions is this:

a) some believe that rfc4427 requires the current set of priorities, as per LS1174 point #1 (http://datatracker.ietf.org/liaison/1174/)
b) some believe it does not, and that rfc6378 misinterpreted rfc4427

I think we all agree that the chain here is: 6378 must obey 5654, and that 5654 requires 4427.

So it's going to come down to - is 4427 written wrong but interpreted correctly, or written correctly but misinterpreted?
If we decide the former, we need to change 4427 and/or 5654 to clarify the requirement.
If we decide the latter, we do not need to change 4427 and can probably just change 6378.

Does that sound right?

eric

> 
> Best regards,
> Alessandro
> 
> ------------------------------------------------------------------
> Telecom Italia
> Alessandro Gerardo D'Alessandro
> Transport Innovation
> Via Reiss Romoli, 274 - 10148 Torino
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> 
> -----Messaggio originale-----
> Da: mpls-bounces@ietf.org [mailto:mpls-bounces@ietf.org] Per conto di
> Eric Osborne (eosborne)
> Inviato: mercoledì 17 aprile 2013 14:16
> A: mpls@ietf.org
> Oggetto: [mpls] PSC: draft-rhd-mpls-tp-psc-priority-00
> 
> This thread is for discussing draft-rhd-mpls-tp-psc-priority-00.  In
> brief, the draft proposes swapping the priorities between FS and SF-P
> (see section 4.3.2 of rfc6378).  This proposed swap has a long history,
> dating back to when PSC was an ID.  For some history, see
> 
> http://datatracker.ietf.org/liaison/1229/
> and
> http://datatracker.ietf.org/liaison/1234/
> 
> The questions that I think are relevant here are:
> 
> - is it appropriate to make this priority swap?
>   - are there alternative approaches?
>   - what do we need to change?  rfc5654?  rfc4427?
> - if we don't make the change, does this expose implementation to
> problems?
> - if we do make the change, how do we go about it?
> 
> but of course any and all discussion is welcome.
> 
> As with the other threads I'm going to leave my two cents out of this
> introductory email but I'll chime in when discussion starts.
> 
> 
> 
> 
> 
> eric
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