Jarno Rajahalme <[email protected]> writes: > These are two different things: flow labeling (which labels to > assign) and flow state establishment (how to treat specific > flows). My own reading has been that flow labeling mechanisms may be > stateful or stateless (for example, pseudo-random sequences were > mentioned explicitly), and that signaling mechanisms may be needed > to provide flow-specific treatment.
This is an important observation. I think we can allow for stateless use of the Flow Label while preserving the original definition for other types of usages. The original restrictions about not reusing Flow Label values had to do with stateful setup protocols. There was an assumption of sorts that there was agreement between the source of the traffic and the routers on what a particular Flow Label value meant and how the router was to assign resources. If an originating node reboots, and reuses a Flow Label value too soon, the routers may not have timed out their state and undesirable things might happen. We should preserve those semantics, not that I'm optimistic we will ever need to, but because we can easily enough. For stateless usages of the flow label, it really doesn't matter if a particular Flow Label value is reused too soon. It's in the stateful case that it matters. So just require that when the Flow Label is set to a value as part of a stateful flow usage, in *that* case, make sure we don't reuse Flow Label values too soon. That is, for the more complex case (stateful involving setup) it's still fine to required adherance to the original semantics. For the stateless use, we can relax the requirements. The only place where this gets potentially messy is if you have an originating node setting the Flow Label using stateful means, but is also originating packets with zero Flow Label values, and then some intermediate device changes those values from 0 to something else -- potentially colliding with the stateful value. But this is a bit of an edge case. We could require any node that uses stateful Flow Setup to set all Flow Labels properly, or at a minimum not to send out Flow Label values that are zero. Thomas -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
