Re: [babel] proposed info model change

Juliusz Chroboczek <jch@irif.fr> Fri, 26 February 2021 19:27 UTC

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Date: Fri, 26 Feb 2021 20:26:54 +0100
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From: Juliusz Chroboczek <jch@irif.fr>
To: "STARK, BARBARA H" <bs7652@att.com>
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Subject: Re: [babel] proposed info model change
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> 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.

It's not an implementation problem, it's a protocol issue.

In the protocol, the router-id only appears on the wire when a router
redistributes (originates) a route.  If a router is not originating
routes, because it is only connected to transit networks, it does not need
a router-id.

So in this case, the information model would be imposing a slightly
stronger requirement on implementations than the core protocol: in order
to implement the information model, a router would need to draw a router-id
for itself even if it is only connected to transit networks.

I don't find this requirement too onerous, and I don't mind the
information model making it.

-- Juliusz