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

Robert,

Thank you, exactly.

We just need a clarification of the document.  I don’t understand why this is such a big deal.

Tony

> On Aug 18, 2020, at 9:22 AM, Robert Raszuk <robert@raszuk.net> wrote:
> 
> 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 <mailto: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
> 
>  
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>  
> 
> From: Lsr <lsr-bounces@ietf.org <mailto:lsr-bounces@ietf.org>> On Behalf Of tony.li@tony.li <mailto:tony.li@tony.li>
> Sent: Tuesday, August 18, 2020 7:44 AM
> To: Peter Psenak (ppsenak) <ppsenak@cisco.com <mailto:ppsenak@cisco.com>>
> Cc: lsr@ietf.org <mailto:lsr@ietf.org>; lsr-ads@ietf.org <mailto:lsr-ads@ietf.org>; Christian Hopps <chopps@chopps.org <mailto:chopps@chopps.org>>; Acee Lindem (acee) <acee@cisco.com <mailto:acee@cisco.com>>; draft-ietf-lsr-flex-algo.all@ietf.org <mailto: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>
>  
> 
>  
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> This does not help.
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>  
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> 
> 
> 
> So, IMHO what we have now is correct and sufficient, but I have no issue adding the text you proposed below.
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>  
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>  
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> What you have now is ambiguous. We have a responsibility, as writers of specifications, to be precise and clear.  We are not there yet.
> 
>  
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> 
> 
> 
> 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.
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> 
> 
> 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.
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> I’m sorry, I think that this is trivially resolved, but important clarification.
> 
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> 
> You also have an author’s email that is bouncing, so at least one more spin is required.
> 
>  
> 
> Sorry,
> 
> Tony
> 
>  
> 
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