Re: [Lsr] AD Review of draft-ietf-isis-mpls-elc-10

Peter Psenak <ppsenak@cisco.com> Fri, 20 March 2020 12:58 UTC

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To: Alvaro Retana <aretana.ietf@gmail.com>, "draft-ietf-isis-mpls-elc@ietf.org" <draft-ietf-isis-mpls-elc@ietf.org>
Cc: "Acee Lindem (acee)" <acee@cisco.com>, "lsr@ietf.org" <lsr@ietf.org>, "lsr-chairs@ietf.org" <lsr-chairs@ietf.org>
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From: Peter Psenak <ppsenak@cisco.com>
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Date: Fri, 20 Mar 2020 13:58:00 +0100
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Subject: Re: [Lsr] AD Review of draft-ietf-isis-mpls-elc-10
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On 20/03/2020 11:59, Alvaro Retana wrote:
> On March 20, 2020 at 6:22:38 AM, Peter Psenak wrote:
> 
> 
> ...
>>> Besides the in-line comments, I want to point out here that this
>>> specification is incomplete. It needs to have (1) a formal description of
>>> the new MSD-Type (similar to §5/rfc8491), and (2) a discussion of the
>>> interaction with the BMI-MSD.
>>
>> sorry, I missed it.
>>
>> Entropy Readable Label Depth is defined in rfc8662.
>>
>> I have modified the text as foolows:
>>
>> "A new MSD-type [RFC8491], called ERLD-MSD is defined to
>> advertise the ERLD [RFC8662] of a given router. A MSD-Type code 2
>> has been assigned by IANA for EARLD-MSD."
>>
>> Would that be good enough?
> 
> Not quite.  According to rfc8662, when a new MSD is defined, the
> document MUST indicate the meaning of the absence of the MSD
> advertisement.  For example, it says this about the BMI-MSD: "The
> absence of BMI-MSD advertisements indicates only that the advertising
> node does not support advertisement of this capability."

ok, I  will add that.

> 
> 
> Also, I need you to talk about the interaction between ERLD-MSD and
> BMI-MSD.  If both are present, what should happen?  Should one take
> precedence, should both be ignored, can they coexist without issues???

how are BMI-MSD and EARLD-MSD related?

BMI-MSD signals the total number of MPLS labels that can be imposed.

EARLD-MSD - is defined as the number of labels a router can both:

    a.  Read in an MPLS packet received on its incoming interface(s)
        (starting from the top of the stack).

    b.  Use in its load-balancing function.

I don't really see why one would affect the other.

thanks,
Peter

> 
> 
> Thanks!
> 
> Alvaro.
> 
>