Steve Blake wrote:
> I agree with your conclusion, but I disagree with the assumptions
> you are making about diffserv (for the sake of argument, say).
I assume you are talking about the WG not the protocol. :)
> RFC2475 was built on the assumption of bilateral agreements between
> peering providers, because that was the only model that had a hope
> of being deployed.
But bi-lat's don't necessarily require mutability of the TC field. That
was simply a concession to those who wanted knobs to make it more
difficult for the less skilled. Now we have a mechanism that only has
a hope of being deployed, but is operationally useless on a global
scale because it lacks any context.
> The Diffserv flow-label proposal is trying to
> invent an end-to-end, in-band QoS "signaling" mechanism to operate in
> parallel with the hop-by-hop DSCP "signaling".
Basically the hop-by-hop decisions have to be based on consistent
end-to-end semantics of a set of bits, but the TC field was allowed
to be randomized so it is currently useless for that purpose. This
is still fixable by locking down the PHBs and matching DSCPs, so
there is no need for taking additional header bits.
> The only additional
> in-band information that would be remotely useful for Diffserv would
> be a credit card account number.
Not if the proposed new end-to-end signaling is left as mutable. There
will be a never-ending series of requests for bits until it is accepted
that what is required is an end-to-end immutable set that the origin
node uses to identify its intent for the packets, (in or out of band).
The intervening networks will always make local decisions based on
those bits, so there is no need to rewrite them at every domain boundary.
All the TC field is used for now is an embedded MPLS type tag, so why is
it embedded? Shouldn't it be the end-to-end consistent set of bits and
let MPLS do the tagging it will undoubtedly do for TE purposes anyway?
Tony
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