> Töma Gavrichenkov > Sent: Friday, March 8, 2019 5:07 PM > > On Fri, Mar 8, 2019 at 7:48 PM Saku Ytti <s...@ytti.fi> wrote: > > Why do you think it would be expensive? It's cheaper than how ECMP is > > done for L3 keys, because you just read the flow label and not > > calculate any hash. > > The most honest answer would be: I have no idea. That's just what I've seen, > rather briefly though, as we weren't going to investigate that part at the > time. > > It's been a while since then, and maybe there was a mistake on our side (at > least within a perfectly academic context I must assume that there was, as > there was no peer review — we were not in academy after all!), but I'm still > inclined to, first, see the benchmarks of any proposed piece of hardware > that's promising you ECMP with flow labels, second, make any statements > about the latter. > We did this exact testing a while back on Juniper 2nd and 3rd gen PFEs. The results showed it doesn't matter a tiny bit whether you do 5-tuple hash or use flow label. So the bottom line is on modern NPUs it doesn't really matter.
adam