Perry E. Metzger writes:
>
> Am I correct in saying that, at this point, the flow label is at most
> a way for intermediate routers to avoid layer violations, since a flow
> is immutable and is properly given as a <srcaddr,dstaddr,flownum> tuple?
Yes.
> One must ask what kind of layer violations this is intended to
> stop, and what the purpose of those layer violations is. Generally
> speaking, routers only reach in to the lower layers to determine how
> to differentiate traffic between two hosts for purposes of
> prioritization.
UDP ports in ESP encrypted payloads. Tunnels inside
tunnels inside tunnels inside tunnels. New protocols
which may not even have abstracted ports. New Protocols
period. TCAM widths that lose to Moore's Law.
Need I go on?
> If it is intended to stop routers looking at the different layers to
> prioritize traffic, it is a failure, since the flow label tells an
> intermediate router nothing it needs to know to prioritize traffic
> other than "this is flow #N". You can't decided "hmm, interactive
> traffic -- better bump that above bulk file transfer" based on the
> flow label. At best, you can use the flow label for doing something
> like penalizing flows with non-friendly flow control
> characteristics.
RSVP is your friend.
Mike
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