[c-nsp] LDPv6 Census Check

Saku Ytti saku at ytti.fi
Mon Jun 15 09:30:58 UTC 2020

On Mon, 15 Jun 2020 at 12:24, <adamv0025 at netconsultings.com> wrote:

> Yes this is where each node needs to have a label uniquely identifying every
> LSP passing through it.
> Saku,
> With IP header you don't need this,
> Consider this:
> PE1 to PE2 via 3 P-core nodes
> With ECMP in IP, then PE1 just needs single FEC the DST-IP of PE2, which
> will be load-shared across all 3 paths.
> Using MPLS If you need to uniquely identify each path you need 3 FECs (3
> LSPs one via each P core node), now imagine you have 100K possible paths
> across the fabric
>  -that's a lot of FECs on PE1 or any node in the fabric where each has to
> have a unique label for every possible unique path via the core that the
> particular node is part of.

Are we talking about specific implementations of fundamentals? It
sounds like we are talking about a specific case where IP next-hop is
unilist of N next-hops, and MPLS next-hop is a single item without
indirection? This is not a fundamental difference, this is
implementation detail.
There is no particular reason MPLS next-hop couldn't be unilist of N

I think people are too focused on thinking IP and MPLS have some
inherent magical property differences, they don't. We only care about
lookup cost (again IP can be made cheap with IPinIPinIP tunnels and
telling LSR devices all lookups are LEM host lookups) and we care
about key width. Rest is implementation detail.

Yes on typical case there are some biases in IP and MPLS, but these
can be rendered away leaving the fundamental differences. Briding the
gap from MPLS to IP is far smaller than bridging the gap from IP to
MPLS, there is so much added value which depends on MPLS tunnels.


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