[e2e] admission control vs congestion control

[Henning Schulzrinne]

- Delay until admission decision makes many such techniques unsuitable 
for applications where humans are waiting ("post-dial delay")
- Overhead of probing, particularly if the probe has to be repeated 
after a failure
- Guarantees tend to be weak, i.e., you may get a positive answer and 
still suffer packet loss, particularly if the number of flows is small 
and flows are bursty or on-off (such as voice) if the probe gets "lucky"

> 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