Re: [Idr] I-D Action: draft-kaliraj-idr-multinexthop-attribute-01.txt

Robert Raszuk <robert@raszuk.net> Sat, 03 July 2021 19:46 UTC

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From: Robert Raszuk <robert@raszuk.net>
Date: Sat, 3 Jul 2021 21:45:56 +0200
Message-ID: <CAOj+MMHngcqSX-HrrbShPXHHUxLx7S4M+iuQhJ7_tsNrPkgKeg@mail.gmail.com>
To: Kaliraj Vairavakkalai <kaliraj@juniper.net>
Cc: Minto Jeyananth <minto@juniper.net>, "idr@ietf. org" <idr@ietf.org>
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Subject: Re: [Idr] I-D Action: draft-kaliraj-idr-multinexthop-attribute-01.txt
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Hi,

> KV2> EBGP is not discounted. One simple example where this can be useful
for EBGP
> is the inter-AS parallel-links case. Even when using one bgp-session
between loopbacks
> over the parallel-links, the MNH can be used to specify how the
load-balancing should
> happen on the parallel links.

And how would you detect liveness of all of those parallel links ? Static +
BFD ?

What's wrong with today's solution of using loopback for next hop +
disable-connected-check knob and point static routes to resolve such next
hop over parallel links ? Sure you can use more then one loopback here as
well and that loopback is only significant locally over EBGP boundary.


KV2> there are some scenarios where it could be. The PE sends the RD:Pfx
> with MNH(IngressIP1, IngressIP2) thus attracting traffic to the
> more-optimal ingress-Forwarding-elements. Avoiding intra-fabric hops. The
> mechanism was invented to solve such a scenario only.
>

IMO this use case is a pretty bad idea. When such interface IngressIP1 or
IP2 goes down you need to repair the encapsulation all the way in the edge
instead of just performing local repair to get to the same loopback in
milliseconds. It almost smells like some solution to fix platform
deficiency in deployments of BGP as an IGP.

Tx,R.