Brian E Carpenter wrote on 06/12/2018 20:35:
But there's a preliminary question: how widely is the flow label set
by sending hosts? The answer is: widely, by modern o/s releases. But not
much, by legacy o/s releases.
more to the point, if you were going to implement a forwarding device,
do you depend solely on the flow label?
This gives end-user device control over the hashing path on a purely
discretionary basis. I.e. and end user can change the flow label and
consequently make their own decisions about which network path to use,
without affecting any other transmission characteristic of the network
flow, e.g. port numbers, IP addresses, etc.
Operationally, flow labels can cause grief. APNIC had a blog posting on
this a while back
https://blog.apnic.net/2018/01/11/ipv6-flow-label-misuse-hashing/
Most devices allow the operator to selectively use flow labels as an
entropy source for hashing.
Nick
