Re: [babel] Dummy source address [was: I-D Action: draft-ietf-babel-v4viav6-01.txt]

Oh that's a good point, I totally agree.
(1) or (4) both seem like the best outcome here.
I think I'm now leaning towards (4).

David

On Tue, Apr 13, 2021 at 3:50 PM Juliusz Chroboczek <jch@irif.fr> wrote:

> > a separate Babel dummy address
>
> I've been thinking about this all evening, and I think I now see what
> makes me uncomfortable.  (Dinner helped.)
>
> By the time the IPv4 module has decided it needs to send an ICMPv4 packet,
> it does not necessarily know whether the issue it's reporting is due to
> Babel or to some routing protocol.  In fact, there might not even be
> a well defined responsible protocol -- if a router running both Babel and
> BGP finds out that it has no route to a given destination, is the ICMPv4
> packet associated with Babel or BGP?
>
> Thus, any implementable procedure for sending ICMPv4 must be independent
> of any given routing protocol -- so it's not reasonable to have a Babel
> dummy address, distinct from a hypothetical BGP dummy address or an OSPF
> dummy address.  If we define a dummy address, that address must be common
> across all routing protocols.
>
> Not sure how to proceed:
>
>  1. reuse the 4rd dummy address, as David suggested, repurposing it
>     to be a generic dummy address?
>  2. write a new RFC defining a cross-protocol dummy address?
>  3. define a cross-protocol dummy address in this draft?
>  4. remain vague, as in the current text?
>  5. some other solution I'm missing?
>
> I'm not volunteering for (2), although I could perhaps be a co-author.
> (3) seems like exceeding the scope of this document.  (1) and (4) would be
> fine with me.
>
> -- Juliusz
>
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