[j-nsp] LAG/ECMP hash performance

[adamv0025 at netconsultings.com]

> James Bensley
> Sent: Thursday, August 29, 2019 9:52 AM
> 
> In the worst case scenario (1), with 4 bytes of CRC output to represent an
> entire frame there is a large amount of hash collisions; Min size frame; 6
byte
> SRC, 6 byte DST, 2 byte EType, 46 byte payload == 2^480 possible Ethernet
> frames being mapped to 2^32 CRC values? 
>
Hmm isn't it more like 2^480 possible Ethernet frames being mapped to 2^32
CRC values which are then mapped to 2^6 buckets (assuming 64-way balancing
-not sure what's the value in Saku's setup).
All this time watching the thread I'm thinking if it's just coincidence that
in some cases no matter how good the hash value is the available buckets
skew the balancing. (and I guess that's why three are knobs to shift the
hash around.
 
adam