Re: [Pce] WGLC for draft-ietf-pce-lsp-extended-flags-02

Hi Aijun,

As a WG member...

On Thu, May 12, 2022 at 6:58 AM Aijun Wang <wangaijun@tsinghua.org.cn>
wrote:

> Hi, Dhruv and Quan:
> Is there any reason to define the extended flag in variable length?
>

The aim was to fix it once and not worry about running out of flags ever
again.
Moreover, there is a precedence of this technique in the context of PCE, so
the implementations already handle these cases well.

https://www.rfc-editor.org/rfc/rfc5088.html#section-4.5
https://www.rfc-editor.org/rfc/rfc5089.html#section-4.5

> Should it be more reasonable that just define one 32 bit extended flag and
> if necessary, define another extended flag TLV?
>

Yes, it can be done that way. Is it more reasonable? That is debatable...
Open to feedback from the WG.

> And, as I read section 3.2:
> https://www.ietf.org/archive/id/draft-ietf-pce-lsp-extended-flags-02.html#section-3.2
> “…. …
> If a PCEP speaker receives the LSP-EXTENDED-FLAG TLV of a length less than
> the one supported by the implementation, it will consider the bits beyond
> the length to be unset.
> … ….”
>
> Will the above  lead to misbehavior in some situations?
>
>
A (TLV L=8) ------ B (TLV L=4)
When A receives an LSP-EXTENDED-FLAG TLV with Length = 4, even though it
understands/supports more flags than 32, it considers that those other
flags are unset for B.
When B receives an LSP-EXTENDED-FLAG TLV with Length = 8, since B only
understands limited bits, it considers all the other ones as unassigned and
ignores them.

Note that this behavior is similar to how considering A supports 10 flags
and B supports 3 flags would be handled even though the L=4 for both.

What am I missing?

Anyway, I recommend the fixed length(then the length field is unnecessary)
> and clear description/usages of each bit of the flag.
>
>
This document creates the TLV and a registry. The actual bits and their
usage belong in other documents.

Thanks!
Dhruv (as a WG member)

> Aijun Wang
> China Telecom
>
> On May 11, 2022, at 21:28, Dhruv Dhody <dd@dhruvdhody.com> wrote:
>
> 
> Hi WG,
>
> This email starts a 2-weeks working group last call for
> draft-ietf-pce-lsp-extended-flags-02 [1].
>
> Please indicate your support or concern for this draft. If you are opposed
> to the progression of the draft to RFC, please articulate your concern. If
> you support it, please indicate that you have read the latest version and
> it is ready for publication in your opinion. As always, review comments and
> nits are most welcome.
>
> The WG LC will end on Wednesday 25th May 2022.
>
> A general reminder to the WG to be more vocal during the
> last-call/adoption and help us unclog our queues :)
>
> Thanks,
> Dhruv & Julien
>
> [1] https://datatracker.ietf.org/doc/draft-ietf-pce-lsp-extended-flags/
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