Re: [Pce] Gunter Van de Velde's No Objection on draft-ietf-pce-segment-routing-ipv6-22: (with COMMENT)

[Cheng Li <[e-mail]>]

Seems the email is cut due to some reasons ☹

I will update the draft to address Gunter's email. Please check @Gunter Van de Velde

Thanks,
Cheng



-----Original Message-----
From: Cheng Li <c.l=[e-mail]> 
Sent: Wednesday, April 3, 2024 12:00 PM
To: Dhruv Dhody <[e-mail]>; Gunter Van de Velde <[e-mail]>
Cc: The IESG <[e-mail]>; [e-mail]; [e-mail]; [e-mail]; [e-mail]
Subject: RE: Gunter Van de Velde's No Objection on draft-ietf-pce-segment-routing-ipv6-22: (with COMMENT)

Hi Dhruv, and Gunter, 

Thank you for your comments. Please see my reply inline, will update the draft accordingly soon.

Thanks,
Cheng


-----Original Message-----
From: Dhruv Dhody <[e-mail]>
Sent: Wednesday, April 3, 2024 11:41 AM
To: Gunter Van de Velde <[e-mail]>
Cc: The IESG <[e-mail]>; [e-mail]; [e-mail]; [e-mail]; [e-mail]
Subject: Re: Gunter Van de Velde's No Objection on draft-ietf-pce-segment-routing-ipv6-22: (with COMMENT)

Hi Gunter,

Thanks for a detailed review.

On Tue, Apr 2, 2024 at 10:49 PM Gunter Van de Velde via Datatracker < [e-mail]> wrote:

> Gunter Van de Velde has entered the following ballot position for
> draft-ietf-pce-segment-routing-ipv6-22: No Objection
>
> When responding, please keep the subject line intact and reply to all 
> email addresses included in the To and CC lines. (Feel free to cut 
> this introductory paragraph, however.)
>
>
> Please refer to
> https://www.ietf.org/about/groups/iesg/statements/handling-ballot-posi
> tions/ for more information about how to handle DISCUSS and COMMENT 
> positions.
>
>
> The document, along with other ballot positions, can be found here:
> https://datatracker.ietf.org/doc/draft-ietf-pce-segment-routing-ipv6/
>
>
>
> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
>
> Please find this review using a fresh pair of eyes upon the draft. 
> feel free to use or ignore these comments. Comments are ordered with 
> some first set of idnit typo's, followed with observations when 
> reading the document.
>
> **Idnits:**
>
> 349        Endpoint node as well as the tailend node also need to be
> considered
>
> I believe that the grammatically correct form is "tail-end," which 
> refers to the final part of something, such as a process, activity, or 
> physical object.
> Using a hyphen clarifies that the two words function together as a 
> single concept. Not sure if there is earlier art that uses the term 
> with the proposed spelling in the document?
>
>
Dhruv: I checked; authors - please change to tail-end!
[Cheng]Ack, no problem.


> 659        PCE.  As such,the flags MUST be set to zero and a (MSD-Type,MSD-
>
> s/such,the/such, the/
>
> 635        mechanisms, e.g routing protocols [RFC9352], then it ignores the
>
> s/e.g/e.g./
>
> 653        SRv6 MSD capabilties, the PCC MUST send a PCErr message with
> Error-
>
> s/capabilties/capabilities/
>
>
Dhruv: Ack for above!
[Cheng]Ack.



> **Observations when reading through the document:**
>
> 20         Segment Routing (SR) can be used to steer packets through an
> IPv6 or
> 21         MPLS network using the source routing paradigm.  SR enables any
> head-
> 22         end node to select any path without relying on a hop-by-hop
> signaling
> 23         technique (e.g., LDP or RSVP-TE).
>
> Proposed rewrite
> Segment Routing (SR) can be used to steer packets through a network 
> using the
> IPv6 or MPLS data plane, employing the source routing paradigm. SR 
> enables any head-end node to select any path without relying on 
> hop-by-hop signaling techniques (e.g., LDP or RSVP-TE).
>
>
Dhruv: Thanks for the rewrite, it reads better!
[Cheng] No problem


> 29         Since SR can be applied to both MPLS and IPv6 forwarding
> planes, a
> 30         PCE should be able to compute an SR Path for both MPLS and IPv6
> 31         forwarding planes.
>
> I suspect we are talking dataplane instead of forwarding plane? I see 
> the terms "forwarding plane" and "data plane" often used 
> interchangeably, but they do seem to have nuanced differences. The 
> forwarding plane deals with the logical decision-making process of 
> packet forwarding, the data plane deals with the physical 
> implementation of forwarding those packets based on those decisions.
> In addition the term dataplane is used later in this same abstract. 
> Maybe best to use single terminology (maybe dataplane) through the 
> document?
>
>
Dhruv: Looking at spring RFCs I see a mix of terms but when talking about SR instantiation as SR-MPLS and SRv6, the term data-plane is used and thus we should also use the same.
[Cheng]Ack



> 31         forwarding planes.  The PCEP extension and mechanisms to
> support SR-
> 32         MPLS have been defined.
>
> What about adding the reference to RFC5440?
>

Dhruv: I would avoid adding references in the abstract.
[Cheng]I agree with Dhruv of this


>
> 32         MPLS have been defined.  This document describes the extensions
> 33         required for SR support for the IPv6 data plane in the Path
> 34         Computation Element communication Protocol (PCEP).
>
> This text reads a bit odd. What about a readability rewrite:
> “This document outlines the necessary extensions to support Segment 
> Routing
> (SR) for the IPv6 data plane within the Path Computation Element 
> Communication Protocol (PCEP).”
>
>
Dhruv: Ack, with slight modification as the whole para can be read as -

"Since SR can be applied to both MPLS and IPv6 data-planes, a PCE should be able to compute an SR Path for both MPLS and IPv6 data-planes. The Path Computation Element communication Protocol (PCEP) extension and mechanisms to support SR-MPLS have been defined. This document outlines the necessary extensions to support SR for the IPv6 data-plane within PCEP."
[Cheng]Will update and double-check with Gunter.


> 126        When the SR architecture is applied to the MPLS forwarding
> plane, it
> 127        is called SR-MPLS.  When the SR architecture is applied to the
> IPv6
> 128        data plane, is is called SRv6 (Segment Routing over IPv6 data
> plane)
> 129        [RFC8754].
>
> See earlier comments. Data plane vs forwarding plane.
>
> 133        IGP SPT.  Such paths may be chosen by a suitable network
> planning
> 134        tool, or a PCE and provisioned on the ingress node.
>
> The correlation between PCE and suitable network planning tool is 
> unclear
[Cheng]Ack.