>Locking the value to end-to-end immutable adds value to the process
>because there is no other mechanism for an application to assure that
>every router along the path that chooses to may see its intent. All the
>current mechanisms allow random administrative policies to change the
>message from the origin, so why would an application writer bother
>setting a value that he has no way of knowing that it will reach the
>intended remote target?
What is wrong with a hop-by-hop option? Isn't that the "right"
mechanism for an IPv6 host to send a "message" that is processed
by all routers in the path?
>You are assuming that every router along the path is part of the same
>administrative system and would react consistently to the marking.
No I'm not assuming that all routers in the path will understand
the flow label. I am assuming, though, that the flow label will
only be _useful_ within an administrative system that has
a consistent (or at least compatible) understanding of its meaning.
>It is
>perfectly reasonable for my local administrative domain to have an
>interactive system to manage the values, then have some intermediate
>domain use a set of canned rules about src/dst/dscp/fl to achieve a
>specific service, and finally have a prior administrative arrangement
>with the remote domain to treat the packets consistently with the origin
>domain. If the intermediate domain is allowed to modify the bits there
>is no way for the remote domain to know the origin's intent.
I don't understand how these three systems can usefully interpret
the same bits in two different ways. If I am choosing a random
flow label value at the source (with an "interactive system" that
indicates its meaning out-of-band), why won't I just get random
behaviour from the intermediate domain in your example?
Could you give a practical example of when this would be useful?
>Again I agree, but the specific mechanism I would leave to a WG focused
>on signalling or other interactions that would manage state.
Then, why not leave the specification of flow label semantics and
rules to this same WG?
Margaret
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