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

["Rajiv Asati (rajiva)" <[e-mail]>]

Alvaro,

Well pointed. Back in Feb, when I went through the encap draft (recalling the machinery like in the below excerpt) and discussed with Acee, I also realized these two drafts being complementary in that NH verification regard.  

/
   If the Tunnel Endpoint sub-TLV contains an IPv4 or IPv6 address that
   is valid but not reachable,  
/

The question (of yours) we need to answer is what's in scope and what's not. For ex, what OAM protocol is used for reachability determination should be out of scope, but where this check is executed should be. Hoping that we have some active discussion on that.

Keyur, Srihari, Gunter, thoughts?

-- 
Cheers,
Rajiv  

-----Original Message-----
From: Alvaro Retana <[e-mail]>
Date: Monday, May 4, 2020 at 2:44 PM
To: Rajiv Asati <[e-mail]>, "[e-mail]" <[e-mail]>
Cc: Susan Hares <[e-mail]>, "[e-mail]" <[e-mail]>, "[e-mail]" <[e-mail]>, "[e-mail]" <[e-mail]>
Subject: Re: AD Review of draft-ietf-idr-bgp-bestpath-selection-criteria-12
Resent-From: <[e-mail]>
Resent-To: Rajiv Asati <[e-mail]>
Resent-Date: Monday, May 4, 2020 at 2:44 PM

    On May 4, 2020 at 2:10:14 PM, Rajiv Asati (rajiva) wrote:

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


    Rajiv:

    Hi!


    > 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.

    ...as 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.


    Thanks!

    Alvaro.


    [1] https://mailarchive.ietf.org/arch/msg/idr/S1nyz1sewA_Xqf63W_vz8c4L8Z0/