Re: [Idr] AD Review of draft-ietf-idr-bgp-bestpath-selection-criteria-12

Alvaro Retana <> Mon, 04 May 2020 18:44 UTC

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From: Alvaro Retana <>
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Date: Mon, 4 May 2020 11:43:58 -0700
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To: "Rajiv Asati (rajiva)" <>, "" <>
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Subject: Re: [Idr] AD Review of draft-ietf-idr-bgp-bestpath-selection-criteria-12
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On May 4, 2020 at 2:10:14 PM, Rajiv Asati (rajiva) wrote:

[Explicitly adding draft-ietf-idr-tunnel-encaps to the distribution.]



> Thanks, Alvaro. While it would have been preferred to keep the (NH selection
> / verification) logic independent, it seems that there may perhaps be the
> following 2 means to solidify the logic -
> a- Tunnel Encapsulation Attribute (updating rfc5512)
> b- Cost Community
> It seems that (a) is somewhat more progressive than (b), and clearly conveys
> the encap preference that can be leveraged. Thoughts?
> If agreed, then section 3 could be updated to reflect something akin to the
> following -

As a matter of fact, §5 of draft-ietf-idr-tunnel-encaps lists

   *  The tunnel is specified in a TLV whose Tunnel Endpoint sub-TLV
      identifies an IP address that is reachable. a condition for the tunnel to be considered feasible.  In my
review of that document [1] I wrote this:

   [major] How is reachability determined?  Where (which table) should
   the address be looked up in?  In the sequence above, the destination
   address of P and the address of the endpoint may be resolvable in
   different tables...

   [BTW, please also take a look at
   draft-ietf-idr-bgp-bestpath-selection-criteria, which I think tries to
   define a related, if not the same, concept.]

I think this is a good time for you and the authors of
draft-ietf-idr-tunnel-encaps to talk.