Re: [Gen-art] Review of draft-ietf-ccamp-flexible-grid-ospf-ext-07

Daniele Ceccarelli <> Mon, 06 February 2017 13:37 UTC

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From: Daniele Ceccarelli <>
To: Jari Arkko <>, Pete Resnick <>
Thread-Topic: [Gen-art] Review of draft-ietf-ccamp-flexible-grid-ospf-ext-07
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Date: Mon, 06 Feb 2017 13:36:46 +0000
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Subject: Re: [Gen-art] Review of draft-ietf-ccamp-flexible-grid-ospf-ext-07
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Hi Jari, Pete,

First of all thanks for the accurate review.

All the nits/editorial comments are correct and will be fixed.

Regarding the minor issue: 

> 4.1.1:
> The figure is a bit confusing: There might not exist a "Max Slot Width at Priority
> 7" if bit 7 is clear in the Priority field, correct?
> Perhaps it would be better to just show that as "..." or "Max Slot Width at
> Priority n". The thing is, it might only be a single value, followed by the
> padding, so having the second value in there might be misleading. (Perhaps
> similar constructs are used in other MPLS docs and people will understand. But
> it took me a while to figure it out.)

it was difficult to express in the figure the fact that only some of the priorities are advertised. As you said it could be one, two or any number up to 8. 
What about a single field (with ~ on the borders to indicate that it can have variable length) saying "Max Slot Width at Prio n" and then say that 16 bits are used for each prio and when an odd number of priorities is used the field is padded to line up with multiples of 32 bits?

> The discussion of Priority was very confusing for me. In the third sentence, do
> you mean, "A bit is set (1) corresponding to each priority represented in the
> sub-TLV, and clear (0) for each priority not represented in the sub-TLV"? I don't
> understand the MUST/MUST NOT as you had it. And I don't understand the
> last sentence at all. Are you trying to say, "The leftmost bit (priority level 0)
> MUST be set, and priority level 0 MUST be advertised in the sub-TLV."?
> Otherwise, I don't get it.

It means that if the priority field is set to e.g. 10010010 in the following you would find 4 fields indicating respectively: Max Slot Width at Priority 0, Max Slot Width at Priority 3, Max Slot Width at Priority 6 and since they are 3 a 16 bits padding to 32 bits. 
It also means that at least one priority must be advertised (i.e. priority 00000000 is not allowed).

> I don't understand the MAY in the last sentence. Does that mean that I MAY
> also set it to the highest possible nominal central frequency supported by the
> link? I don't understand what that sentence is trying to tell me.

An example is provided in section 4.1.2, where the available range goes from -2 to +8 but the range supported by the link goes from -9 to +11. The sentence means that even if not available it could be possible to indicate also n=-9 to indicate the starting point of the range supported by the link. 

  " In this example, it is assumed that the lowest nominal central
   frequency supported is n= -9 and the highest is n=11. Note they
   cannot be used as a nominal central frequency for setting up a LSP,
   but merely as the way to express the supported frequency range."

I'm ok with dropping the sentence.

Thank you

> -----Original Message-----
> From: Jari Arkko []
> Sent: lunedì 6 febbraio 2017 12:32
> To: Pete Resnick <>
> Cc:;;
> Subject: Re: [Gen-art] Review of draft-ietf-ccamp-flexible-grid-ospf-ext-07
> Thanks for your review, Pete. Authors, any comments?
> Jari