Re: [Pce] Review of draft-ietf-pce-stateful-pce-18

[Julien Meuric <[e-mail]>]

Jon, Lionel,

I believe Lionel got confused by the wording introduced in RFC 8051:
- no report, no update means stateless PCE;
- report, no update means passive stateful PCE;
- report and update means active (stateful) PCE.

More details below, [JM].

Thanks for the work,

Julien


Apr. 11, 2017 - [e-mail]:
> =====
> 
> [LM] active/passive mode are not  advertized in PCEP. s/if active 
> stateful PCE capability was not advertised/if stateful PCE
> capability was not advertised
> 
> Jon> ACK
> 
> =====
[JM] NACK! ;-)
Actually, the passive mode is advertised using the
Stateful-capability-object TLV with the U bit unset, the active mode by
setting the U bit.

> =====
> 
> Note that even if the update capability has not been advertised, a 
> PCE can still accept LSP Status Reports from a PCC and build and 
> maintain an up to date view of the state of the PCC's LSPs.
> 
> [LM] I don't undersand. Is it not in contradiction with
> 
> "If the PCEP Speaker on the PCE supports the extensions of this
> draft but did not advertise this capability, then upon receipt of a
> PCRpt message from the PCC, it MUST generate a PCErr with error- type
> 19 (Invalid Operation), error-value 5 (Attempted LSP State Report if
>  active stateful PCE capability was not advertised) (see Section
> 8.5) and it SHOULD terminate the PCEP session."
> 
> Or does it mean that there is another way than PCRpt message for the
>  PCC to send LSP status reports to the PCE?
> 
> Jon> ACK.  I think that the statement in the draft is bogus and I 
> propose to delete this sentence from it.
> 
> =====
[JM] I do not think that the text is bogus:
- case 1: no advertised capability on update but advertised on report
(i.e. passive stateful) => no error message;
- case 2: no advertised capability on update nor report (i.e. stateless)
=> error.

> =====
> 
> [LM] Would it be useful to discover (using another TLV) whether the 
> PCE is an active/passive stateful PCE, as in IGP-based capabilities 
> discovery mechanism?
> 
> Jon> This can be inferred immediately from the U flag in the 
> STATEFUL-PCE-CAPABILITY TLV.  Passive mode is synonymous with not 
> sending / handling PCUpd messages.
> 
> =====
[JM] The mechanism is there, but section 7.1.1 may deserve an explicit
use of the "passive/active" terms, to make sure the capability
terminology is aligned with the vocabulary in the IGP section.