Re: [mpls] end of WGLC, RE: working group last call for draft-ietf-mpls-lsp-ping-reply-mode-simple-01

[t.petch <[e-mail]>]

---- Original Message -----
From: "Loa Andersson" <[e-mail]>
Sent: Wednesday, April 22, 2015 2:15 PM

> Tom,
>
> On 2015-04-20 00:07, Nobo Akiya wrote:
> >     <tp>
> >
> >     Yes but ... I think that it is a change of meaning.  Is is
enough just
> >     to ignore the TLV or should the whole PDU be discarded?  I find
it
> >     difficult to know but don't feel strongly about that choice so
will go
> >     with what you suggest.
> >
> >     </tp>
>
> So I don't misunderstand what you are saying. It seems to me like the
> comments made by Adrian and you actually requires a "change of
meaning",
> that is kind of essence of a "cooment", right?
>
> As for what to do with if the TLV is not recognized, it is
> intentionally requested from a space where it can be silently dropped
> (i.e. "ignored").
>
>     The new TLV Type value should be assigned from the range
>     (32768-49161) specified in [RFC4379] section 3 that allows the TLV
>     type to be silently dropped if not recognized.
>
>       Type   Meaning                            Reference
>       ----   -------                            ---------
>       TBD1   Reply Mode Order TLV               this document
>
> What is it that I miss?

Nothing serious.  My initial thought was to echo Adrian, that, at least
in this context, there should be an indication what to do if a MUST or
SHOULD was violated without just then having a clear sense of what it
should be instead.

The I-D did require (MUST) one entry in the TLV and wanted (SHOULD)
more.  Adding what to do if that did not happen I was seeing as
clarification.  I then read Nobo as proposing going a bit further saying
requires (MUST) one or more.  Which might lead to boxes taking a
simplistic approach and always putting in the new TLV with a single
entry and ignoring the traditional TLV.  Not a problem just a change
from what others might think that they have consented to.

On the question of what to do when the rules are violated, again I did
not initially think of what the action should be.  On reflection, I am
still unsure.  I understand that the Reply Mode Order TLV  is optional
and so can be ignored when not understood; that's fine.  But if it is
understood and can be seen to be defective, should the box with that
knowledge discard just that TLV and accept the remainder of the message?
Or should it argue that if this TLV is defective, then likely the rest
is as well and should be ignored?  I am unsure.

If there is scope for a breach of security, or taking a hit in
performance, then ignore is the right policy. If the requirement is to
get as much data as possible from a failing network, then use it is the
right policy.  As long as the I-D is clear, I am not too fussed which
way it goes.  I am content with the changes that Nobo has proposed.

Tom Petch

> /Loa
>
> --
>
>
> Loa Andersson                        email: [e-mail]
> Senior MPLS Expert                          [e-mail]
> Huawei Technologies (consultant)     phone: [phone]