[c-nsp] LDPv6 Census Check

Saku Ytti saku at ytti.fi
Fri Jun 12 15:26:04 UTC 2020

On Fri, 12 Jun 2020 at 18:16, David Sinn <dsinn at dsinn.com> wrote:

> I'm not sure what implementation you are saying doesn't exist. The Broadcom XGS line is all on-die. The two largest cloud providers are using them in their transport network (to the best of my understanding). So I'm not sure if your saying that no one is using small boxes like I'm describing or what. And it doesn't have to be MPLS over IP. That is one option, but IPIP is another.

I'm saying implementation which has off-chip and supports putting some
on-chip. So that you could have full table lookup for edge packets and
and fast exact lookup for others. Of course we do have platforms which
do have large LEM tables off-chip.

> Again, feel free to look at only one small aspect and say that it is completely better in all cases. MPLS is not better in wide ECMP cases, full stop. SR doesn't help that when you actually look at the problems at massive scale as I have done. You continually are on the trade-off spectrum of irrationally deep label stacks or enumeration of all of the possible paths through the network and burn all of your next-hop re-writes. At least if you want high-radiux, single chip systems. So this is not sentimentally around a protocol, it's the practical reality when you look at the problems at scale using commodity components. So if you want to optimize for costs and power (which is operational costs), MPLS is not where it is at.

I'm not sure why this deep label stack keeps popping, if we need
multiple levels of tunneling, we need it in IP too, and it's almost
more expensive in IP. Cases I can think of in SR, you'll only loop top
label or two, even if you might have 10 labels.
For every apples to apples cases MPLS tunnels are superior to IP
tunnels. If you want cheap very small FIB backbone, then all traffic
will need to be IP tunneled to egress, and you get all the MPLS
problems, and you get more overhead and larger keys (larger keys is
not a big deal).

Now if discussion is do we need tunnelling at all, the discussion is
very different.


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