Re: [Pce] LSP identifiers TLV optional for SR in RFC8664

[Dhruv Dhody <[e-mail]>]

Hi Samuel,

The feeling at the time was to get away from the RSVP-TE-thinking for SR
(and allow SR paths to be set up with minimal information needed). If I
recall correctly, the "MAY" was the "compromise" struck at the time to
allow SR paths to be set up without it but when use cases require these the
LSP-IDENTIFIER-TLV can be included.

On Tue, Feb 14, 2023 at 3:02 PM Samuel Sidor (ssidor) <[e-mail]>
wrote:

> Hi PCE-chairs,
>
>
>
> Since there is no reasonable explanation provided in the mailing list –
> does that mean that RFC is “broken” and we need Errata to fix it? E.g. by
> making LSP identifiers TLV mandatory?
>
>
>

Errata would not be the right approach. See
https://www.ietf.org/about/groups/iesg/statements/processing-errata-ietf-stream/

If the WG wants an explicit statement we would need to add this in an
existing WG document or propose a new one.



> Thanks,
> Samuel
>
>
>
> *From:* Pce <[e-mail]> *On Behalf Of * Samuel Sidor (ssidor)
> *Sent:* Thursday, February 9, 2023 1:29 PM
> *To:* [e-mail]
> *Subject:* [Pce] LSP identifiers TLV optional for SR in RFC8664
>
>
>
> Hi PCE WG,
>
>
>
> RFC8664 marked LSP identifiers TLV as optional:
>
>
>
> “The LSP-IDENTIFIERS TLV *MAY* be present for the above PST type.”
>
>
>
> https://www.rfc-editor.org/rfc/rfc8664.html#name-the-rp-srp-object
>
>
>
> But I don’t see any clarification in that RFC, how SR policy
> endpoints/LSP-ID (may be needed for MBB) or any other field from that TLV
> is supposed to be encoded in PCRpt message.
>
>
>
> I can imagine that SR policy endpoints can be retrieved from SR policy
> association (
> https://datatracker.ietf.org/doc/html/draft-ietf-pce-segment-routing-policy-cp#section-5.1),
> but that draft is still not supported by many implementations and it is not
> mentioned as MUST in RFC8664.
>
>
>

Specifically about endpoints, for PCC configured SR path you have it via
local configuration and for the PCE-initiated, END-POINTS object could also
be optionally included in PCInitiate message.



> So now it seems to be completely valid based on RFC8664 to send PCRpt with
> no LSP identifiers and no SR Policy association => with missing endpoints.
> Is that intentional or am I missing any statement from RFC, which is
> clarifying it?
>
>
>

IMHO It is intentional. See para 4 at
https://www.rfc-editor.org/rfc/rfc8281.html#section-5.3 about endpoints
(and it is valid for SR as well).

I see following options -
- Do Nothing
- Clarify "when" the LSP-IDENTIFIER-TLV MUST be included (could be in the
operational clarification draft)
- Update the text in RFC8664 to make LSP-IDENTIFIER-TLV "MUST" for SR Path
type

Thanks!
Dhruv (as a WG participant)



> I found some older discussion in mail archive:
>
> https://mailarchive.ietf.org/arch/msg/pce/rGVwtH6u3eUCMbRyR-gV1Cv2zDU/
>
> Where almost similar topic was discussed and where it was requested to
> make it mandatory, but there were a few mails exchanged with no conclusion.
>
>
>
> One more comment – even statement about LSP-identifiers in RFC8664 seems
> to be mentioned in wrong section - dedicated for RP/SRP object, which was
> never used for LSP identifiers TLV (that is supposed to be included in LSP
> object).
>
>
>
> Thanks,
>
> Samuel
>