Extension for Stateful PCE to allow Optional Processing of PCE Communication Protocol (PCEP) Objects
draft-ietf-pce-stateful-pce-optional-13

Section 3.2.1:  It seems like the use of the R flag changes how the PCE handles the P flag.  I'm not sure SHOULD (or BCP14 language) is optimal in this section.  Does the PCE try hard to respect the P flag, but if it can't, then it ignores it?  This sounds more like 'best effort'.  I can't tell if this also might apply to the case where the 'PCC SHOULD set the P flag by default'.  [note:  I'm well outside of my expertise area here, I'm just trying to interpret what is here in a logical fashion.]

Sections 3.2 and 3.3: Would a small table with P, R, and I flags against PCC, PCE, and maybe the various extensions/message types might help? 

Section 4:  The last () is a bit puzzling.  It might need some explanation.  Is there something specific that is anticipated?  RFC8253 is old enough that TLS1.3 wasn't published yet, but RFC 9325 obviously covers both TLS 1.2 and 1.3.

Thanks for this document. I have two questions:

### Section 2, why not MUST?

```
When the P flag is set in the PCRpt message received on a PCEP session on which the R bit was set by both peers, the object SHOULD be taken into account by the PCE.

```

Under what circumstances is it OK for the PCE to ignore an object whose P flag is set? In other words, why isn't this a MUST?

### Section 4, explicitly set aside

```
As per [RFC8231], it is RECOMMENDED that these PCEP extensions can only be activated on authenticated and encrypted sessions across PCEs and PCCs belonging to the same administrative authority, using Transport Layer Security (TLS) [RFC8253] as per the recommendations and best current practices in [RFC9325] (unless explicitly set aside in [RFC8253]).

```

I'm curious about the parenthetical comment. Can you provide an example of a recommendation or best current practice that was explicitly set aside in RFC 8253? I did go look at the Security Considerations of RFC 8253 and didn't see anything like that.

"Abstract", paragraph 0
> Abstract

The shepherd's write-up was done in 2022. Has there been no change in the document since then that would require an update to the writeup?

Section 1, paragraph 3
>    [RFC5440] defined the P flag (Processing-Rule) in the Common Object
>    Header to allow a PCC to specify in a Path Computation Request
>    (PCReq) message (sent to a PCE) whether the object must be taken into
>    account by the PCE during path computation or is optional.  The I
>    flag (Ignore) is used by the PCE in a Path Computation Reply (PCRep)
>    message to indicate to a PCC whether or not an optional object was
>    considered by the PCE during path computation.  Stateful PCE
>    [RFC8231] specified that the P and I flags of the PCEP objects
>    defined in [RFC8231] is to be set to zero on transmission and ignored
>    on receipt, since they are exclusively related to the path
>    computation requests.  The behaviour for P and I flag in other
>    messages defined in [RFC5440] and other extension was not specified.
>    This document specifies how the P and I flag could be used in the
>    stateful PCE model to identify optional objects in the Path
>    Computation State Report (PCRpt) [RFC8231], the Path Computation
>    Update Request (PCUpd) [RFC8231], and the LSP Initiate Request
>    (PCInitiate) [RFC8281] message.


I would have imagined that this would be a good place to introduce the fact that the document is trying to define a new flag (R) in this document.

Section 3.1, paragraph 3
>    The R flag MUST be set by both PCC and PCE to indicate support for
>    the handling of the P and I flag in the PCEP common object header to
>    allow relaxing some constraints by marking objects as 'optional to
>    process'.  If the PCEP speaker did not set the R flag but receives
>    PCEP objects with P or I bit set, it MUST behave as per the
>    processing rule in [RFC8231].  Note that while [RFC8231] stated that
>    P and I flags of the PCEP objects defined in [RFC8231] are set to 0
>    on transmission and ignored on receipt, it did not say anything about
>    already existing PCEP objects and thus the behaviour remained
>    undefined.  To safely use this feature, both peers need to set the R
>    flag.

It is unclear from this paragraph what it means when it states that "it did not say anything about already existing PCEP objects". Already existing PCEP objects that have the P and I flags set to 1?? It appears that the behavior of when it is set to 0 is known, so it would seem that we are talking about when the value is not set to 0. Can this be made clear?

Section 7, paragraph 0
> 7.  Manageability Considerations

It is great to see that this document has a separate manageability consideration section called out.

Section 7.2, paragraph 0
>    An implementation supporting this document SHOULD allow the operator
>    to view the capability defined in this document.  To serve this
>    purpose, the PCEP YANG module [I-D.ietf-pce-pcep-yang] could be
>    extended in the future.

Is this captured in the charter as a milestone, or in a draft that is being considered by the WG?

-------------------------------------------------------------------------------
NIT
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All comments below are about very minor potential issues that you may choose to
address in some way - or ignore - as you see fit. Some were flagged by
automated tools (via https://github.com/larseggert/ietf-reviewtool), so there
will likely be some false positives. There is no need to let me know what you
did with these suggestions.

Section 3.3.2, paragraph 1
> g in the common object header in a similar way as [RFC5440], i.e. if a PCEP 
>                               ^^^^^^^^^^^^^^^^
Consider replacing this phrase with the adverb "similarly" to avoid wordiness.

I have the same comment as Deb about the SHOULD in 3.2.1.

Thanks to Tianran Zhou for the OpsDir review: https://datatracker.ietf.org/doc/review-ietf-pce-stateful-pce-optional-10-opsdir-lc-zhou-2024-10-07/

I found this document quite difficult to read, but that may be because I'm unfamiliar with PCE. 

I have some nits:
1:The behaviour for P and I flag in other messages defined in [RFC5440] and other extension was not specified.
P: The behaviour for P and I flag in other messages defined in [RFC5440] and other extensions were not specified. 
C: I'm actually not sure what this sentence is trying to say -- is it that "the behavior for the flags, and also the behavior in other extensions" was not specified, or "the behavior of the flags which are specified in RFC5440 and other extensions" was not specified?


2: "In these cases, it would be useful to mark the objects as 'optional' and it could be ignored by the PCEP peer."
P: "In these cases, it would be useful to mark the objects as 'optional', and they could be ignored by the PCEP peer." (I think).

3: "Thus, this document specifies how the already existing P and I flag in the PCEP common object header could be used during the stateful ..."
P: "Thus, this document specifies how the already existing P and I flags in the PCEP common object header could be used during the stateful ..." (this occurs in many places in the document.)

4: "In case the bit is unset, it indicates that the PCEP Speaker would not handle the P and I flags in the PCEP common object header for stateful PCE messages."
P: "If the bit..."

5: "The P flag for the mandatory objects such as the LSP and the ERO (Explicit Route Object) object (intended path) MUST be set in the PCRpt message. "
P: "The P flag for the mandatory objects, such as the LSP and the ERO (Explicit Route Object) object (intended path), MUST be set in the PCRpt message."
C: It's really hard to read without the commas. This occurs in multiple places in the documents.

6: "On a PCEP session on which R bit was set by both peers, the PCC SHOULD set the P flag by default, "
P: "On a PCEP session in which the R bit was set by both peers, the PCC SHOULD set the P flag by default, "

7: "In case PCC cannot accept this, it would react as per the processing rules of unacceptable update in [RFC8231]."
P: "If the PCC cannot accept this, it would react as per the processing rules of unacceptable update in [RFC8231]."
C: The "it would react" is very unclear -- is this "it MUST"? "SHOULD"? Why might the PCC not accept this?

Like Warren, I find this document difficult to read, possibly due to my lack of knowledge of PCE, i.e., this ballot is more "no opinion" rather than "no objection".

Like for the other PCE draft in this telechat, I wonder why Dhruv Dhody is not explicitly cited as contributor and does not even appear in the acknowledgements section.