Brian E Carpenter wrote :
So, I'd say that the default behavior for a relayed packet should be "Assign 0", and "Assign a new flow label according to RFC3697" should be optional (just as the whole of RFC3697 is optional). And this is entirely independent of whether or not the incoming packet has a non-zero flow label.
This is IMU the right behavior I had essentially the same conclusion (see for example http://www.ietf.org/mail-archive/web/behave/current/msg03789.html). A slightly different wording could however, IMO, be preferable. "Assign 0" and "RFC3697" should be placed on an equal footing, no one being more "default" than the other: a source may have either behavior; a destination or an intermediate node may not assume any of the two behaviors in particular. Rémi