Re: [Idr] Can one Destination Address appear in both Tunnel Encap Attribute and in MP_REACH_NLRI ?

Robert Raszuk <robert@raszuk.net> Thu, 17 October 2019 08:25 UTC

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From: Robert Raszuk <robert@raszuk.net>
Date: Thu, 17 Oct 2019 10:25:13 +0200
Message-ID: <CAOj+MMHs91BoMpgrN2-qtMAgVtiUE_e2bm=BG=+xVnfU9-6Aaw@mail.gmail.com>
To: Srihari Sangli <ssangli@juniper.net>
Cc: Srihari Sangli <ssangli=40juniper.net@dmarc.ietf.org>, Linda Dunbar <linda.dunbar@futurewei.com>, "idr@ietf.org" <idr@ietf.org>, "draft-ietf-idr-tunnel-encaps@ietf.org" <draft-ietf-idr-tunnel-encaps@ietf.org>
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Subject: Re: [Idr] Can one Destination Address appear in both Tunnel Encap Attribute and in MP_REACH_NLRI ?
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Srihari,

Can you comment on the expected BGP next hop validation behaviour ?

Can you also comment on the next hop BGP is installing the prefixes to RIB
with ?

Is tunnel endpoint now the NH BGP is asking RIB to track ?

None of those seems to be described in section 5 of the draft. How do you
even know on sender side that all remote BGP speakers will honor tunnel
encapsulation attribute and will actually use end-point from its mandatory
TLV instead of NLRI next hop ?

Linda,

Perhaps for your use case much cleaner solution would be to just
use Encapsulation Extended Community as defined in RFC 5512 section 4.5
instead of tunnel attribute ?

Thx,
R.




On Thu, Oct 17, 2019 at 10:08 AM Srihari Sangli <ssangli@juniper.net>; wrote:

> Hi Robert,
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> My reading of Linda's point was a question regarding the case where for
> prefix A NLRI points to
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> next hop NH_1 but tunnel endpoint says go to NH_2.
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> Is such update still valid ?
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> Has tunnel encapsulation attribute power to "overrule" BGP next hop from
> MP_REACH ?
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> The draft in Section 5 explains this. If the update has a valid Tunnel
> Encapsulation attribute and if any of the tunnel(s) is considered to be
> feasible, then it MUST use the tunnel. That means in your example, such an
> update is valid and NH_2 should be used.
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> Hope this helps. Thanks.
>
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> srihariā€¦
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