Re: [Lsr] WG Last Call for draft-ietf-lsr-flex-algo

Les,

I think this is not very obvious as Tony is pointing out.

See RFC 8570 says:

      Type    Description
      ----------------------------------------------------
       33     Unidirectional Link Delay

       34     Min/Max Unidirectional Link Delay

That means that is someone implementing it reads text in this draft
literally (meaning Minimum value of Unidirectional Link Delay) it may pick
minimum value from ULD type 33 :)

If you want to be precise this draft may say minimum value of Min/Max
Unidirectional Link Delay (34) and be done.

That's all.

Cheers,
R.

On Tue, Aug 18, 2020 at 6:04 PM Les Ginsberg (ginsberg) <ginsberg=
40cisco.com@dmarc.ietf.org> wrote:

> Tony –
>
>
>
> As an author of both RFC 8570 and I-D.ietf-isis-te-app, I am not sure why
> you are confused – nor why you got misdirected to code point 33.
>
>
>
> RFC 8570 (and its predecessor RFC 7810) define:
>
>
>
> 34           Min/Max Unidirectional Link Delay
>
>
>
> This sub-TLV contains two values:
>
>
>
> “Min Delay:  This 24-bit field carries the minimum measured link delay
>
>       value (in microseconds) over a configurable interval, encoded as
>
>       an integer value.
>
>
>
>    Max Delay:  This 24-bit field carries the maximum measured link delay
>
>       value (in microseconds) over a configurable interval, encoded as
>
>       an integer value.”
>
>
>
> It seems clear to me that the flex-draft is referring to Min
> Unidirectional Link Delay in codepoint 34.
>
>
>
> I agree it is important to be unambiguous in specifications, but I think
> Peter has been very clear.
>
> Please explain how you managed to end up at code point 33??
>
>
>
>    Les
>
>
>
>
>
>
>
> *From:* Lsr <lsr-bounces@ietf.org> *On Behalf Of * tony.li@tony.li
> *Sent:* Tuesday, August 18, 2020 7:44 AM
> *To:* Peter Psenak (ppsenak) <ppsenak@cisco.com>
> *Cc:* lsr@ietf.org; lsr-ads@ietf.org; Christian Hopps <chopps@chopps.org>;
> Acee Lindem (acee) <acee@cisco.com>; draft-ietf-lsr-flex-algo.all@ietf.org
> *Subject:* Re: [Lsr] WG Last Call for draft-ietf-lsr-flex-algo
>
>
>
>
>
> Hi Peter,
>
>
>
>
>
> section 5.1 of the draft-ietf-lsr-flex-algo says:
>
>
> Min Unidirectional Link Delay as defined in [I-D.ietf-isis-te-app].
>
> We explicitly say "Min Unidirectional Link Delay", so this cannot be mixed
> with other delay values (max, average).
>
>
>
>
>
> The problem is that that does not exactly match “Unidirectional Link
> Delay” or “Min/Max Unidirectional Link Delay”, leading to the ambiguity.
> Without a clear match, you leave things open to people guessing. Now, it’s
> a metriic, so of course, you always want to take the min.  So type 33 seems
> like a better match.
>
>
>
>
>
> section 7.3. of ietf-isis-te-app says:
>
> Type   Description                          Encoding
>                                            Reference
> ---------------------------------------------------------
> 34      Min/Max Unidirectional Link Delay    RFC8570
>
>
>
>
>
> And it also says:
>
>
>
> 33      Unidirectional Link Delay            RFC8570 <https://tools.ietf.org/html/rfc8570>
>
>
>
>
>
> This does not help.
>
>
>
>
>
> So, IMHO what we have now is correct and sufficient, but I have no issue
> adding the text you proposed below.
>
>
>
>
>
> What you have now is ambiguous. We have a responsibility, as writers of
> specifications, to be precise and clear.  We are not there yet.
>
>
>
>
>
> BTW, before I posted 09 version of flex-algo draft, I asked if you were
> fine with just referencing ietf-isis-te-app in 5.1. I thought you were, as
> you did not indicate otherwise.
>
>
>
>
>
> My bad, I should have pressed the issue.
>
>
>
>
>
> Anyway, I consider this as a pure editorial issue and hopefully not
> something that would cause you to object the WG LC of the flex-algo draft.
>
>
>
>
>
> I’m sorry, I think that this is trivially resolved, but important
> clarification.
>
>
>
> You also have an author’s email that is bouncing, so at least one more
> spin is required.
>
>
>
> Sorry,
>
> Tony
>
>
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