[c-nsp] Rant: ASR1000 MPLS (not) load-balancing

Saku Ytti saku at ytti.fi
Thu Jan 2 10:19:40 EST 2020

On Thu, 2 Jan 2020 at 17:08, Robert Raszuk <robert at raszuk.net> wrote:

> But for me from the perspective of number of years passed by I think using MPLS transport is just a one big mistake.

Pistols at dawn, I drank the kool aid and it's good.

> MPLS for service demux is great, but I really see no advantages in using LDP or even concept of global labels for transport. IP transport be it IPv4 or IPv6 offers  much more advantages, native summarization UDP or flow label adds a lot of entropy while MPLS service label can still sit happy behind.

We need tunneling, that much is clear, what the tunnel bytes exactly
are, is not very interesting to me, as long as there are as few of
them as possible. Toy idea from some 6 years back

> If you need TE - it seems pretty trivial to do that with either IPv6 or IPv4 encapsulation too.

I see no upside. Exact match MPLS is on-chip LEM, which is cheap, this
is good, tunneling should be exact match LEM lookup. IP is LPM, it's
fundamentally more expensive. Not to mention too many bytes, so you
need more overspeed for given edge rate.
Minimum amount of excess bytes, LEM table lookup, these are
fundamental requirements for ideal tunneling mechanism, tunneling is
needed. If it's MPLS or what ever is not important, but IP is
blatantly worse.


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