[e2e] admission control vs congestion control

[Lisong Xu]

On 4/17/06, Fred Baker <fred at cisco.com> wrote:
> The usual reason given for avoiding admission models is that people
> don't want to build large amounts of state into the network. Having
> said that, network operators then build MPLS  or other circuit-switch
> infrastructures, and perhaps engineer those routes to maximize the
> traffic they can send over them or to maximize their ability to
> recover cleanly from failures. This involves a *lot* of state in the
> network, much more than bandwidth admission techniques call for.

I agree with you that "people don't want to build large amounts of
state into the network." But there are also admission control methods
that do not build any state into the network, such as probing-based
methods. Why these methods have not been widely accepted and
implemented? I guess the tcp friendliness is one of the reasons, are
there any other fundamental reasons?

Thanks
Lisong