Finally someone decided to make IPv6 flow label useful. First they had to justify why they want to change it, and then modify the definition (way too much work for a field nobody ever used). Planned use is to enhance ECMP load balancing, both in native IPv6 environments (where using the flow label is faster than digging deep into variable-length IPv6 extension headers) and (even more importantly) in tunneled environments, where the flow label propagates the entropy from the tunnel payload into the envelope header.