Re: [babel] proposed info model change

David Schinazi <dschinazi.ietf@gmail.com> Sat, 13 February 2021 21:53 UTC

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From: David Schinazi <dschinazi.ietf@gmail.com>
Date: Sat, 13 Feb 2021 13:53:08 -0800
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To: "STARK, BARBARA H" <bs7652@att.com>
Cc: Mahesh Jethanandani <mjethanandani@gmail.com>, =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= <toke=40toke.dk@dmarc.ietf.org>, "babel@ietf.org" <babel@ietf.org>
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Subject: Re: [babel] proposed info model change
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Ah I see, thanks for the explanation! I'm fine with the change then.

David

On Fri, Feb 12, 2021 at 6:43 AM STARK, BARBARA H <bs7652@att.com> wrote:

> Just to be clear ...
>
> An enabled Babel instance (that is sending and receiving Babel packets)
> already has a requirement for unique non-zero router-id. Where we were
> having a problem was with not-enabled Babel instances that weren’t actively
> running the protocol (had maybe just been installed). I think it was
> babeld that was just using a default of all zeroes until it was enabled;
> at which time it generated its unique router-id. With this not-enabled
> “zero” default, the possibility exists for multiple not-enabled Babel
> instances to be defaulted to zero, which would lead to YANG having a
> problem with having a unique router-id to identify them by.
>
>
>
> The fact that the Babel protocol forbids zero valued router-ids doesn’t
> mean not-enabled instances can’t have that as a default; and it doesn’t
> prevent there from being multiple not-enabled instances with a default
> value.
>
>
>
> TR-181 doesn’t have a problem with this, because it uses a unique key
> distinct from the router-id. The Babel protocol spec already has what it
> needs to make sure the router-id for enabled instances are unique (and the
> data/info model doesn’t need to be involved in policing this). So this
> really is just about making sure the language is suitable to ensure YANG
> can use this parameter as a unique key, without putting constraints on the
> protocol. If YANG were fine with a Babel instance that started with
> router-id zero and then changed to something else once the protocol started
> running, then zero wouldn’t be a problem if there is just a single instance
> with that zero value.
>
> Barbara
>
>
>
> *From:* Mahesh Jethanandani <mjethanandani@gmail.com>
> *Sent:* Thursday, February 11, 2021 11:56 PM
> *To:* David Schinazi <dschinazi.ietf@gmail.com>
> *Cc:* Toke Høiland-Jørgensen <toke=40toke.dk@dmarc.ietf.org>rg>; STARK,
> BARBARA H <bs7652@att.com>om>; babel@ietf.org
> *Subject:* Re: [babel] proposed info model change
>
>
>
> Hi David,
>
>
>
> On Feb 11, 2021, at 7:09 PM, David Schinazi <dschinazi.ietf@gmail.com>
> wrote:
>
>
>
> We banned all-zeroes and all-ones between draft-ietf-babel-rfc6126bis-00
> and draft-ietf-babel-rfc6126bis-01. If memory serves, the idea was to
> reserve them for future extensibility. Also, banning all-zeroes allows
> using that as a sentinel value in software.
>
>
>
> Adding the uniqueness requirement sounds good to me, but removing the ban
> on all-zeroes/all-ones could lead to problems. If the core protocol doesn't
> allow it, why should the informational model allow it?
>
>
>
> If the protocol banned it, that is a different question, and info model
> can reflect that. I just wanted to point out that it is not because of the
> data model.
>
>
>
> Cheers.
>
>
>
>
>
> David
>
>
>
> On Thu, Feb 11, 2021 at 2:00 PM Toke Høiland-Jørgensen <toke=
> 40toke.dk@dmarc.ietf.org> wrote:
>
> Mahesh Jethanandani <mjethanandani@gmail.com> writes:
>
> > Hi Toke,
> >
> > The rational has to do with what a data model like YANG does with
> > router-id. To it the router-id is a key, in the form of a string. That
> > string has to be unique. YANG does not prevent it being a string of
> > zeros or ones, provided that string is unique. Thus the dropping of
> > the "MUST NOT” and the addition of “MUST”.
>
> Right. I seem to recall there being some other reason why it shouldn't
> be 0, but can't find the discussion now, and looking at the code that
> doesn't seem to care. So no objection from me I guess :)
>
> -Toke
>
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> Mahesh Jethanandani
>
> mjethanandani@gmail.com
>
>
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