More thoughts on end-to-end

I was reading this paper (actually, the version at the top of that page) and noticed how my previous comments on the end-to-end principle seem to be justified in a paper touting the need for end-to-end congestion control and TCP friendliness. A major observation here is that with the Internet as large and diverse as it is (and this was written in 1999), we cannot simply trust that everyone on the network will play nice. A quote from the conclusions in the paper:

We have argued in this paper on the need for end-to-end congestion
control, and further, on the need for mechanisms in the
network to detect and restrict unresponsive or high-bandwidth
best-effort flows in times of congestion. Such mechanisms
would provide a incentive in support of end-to-end congestion
control for best-effort traffic.

A major portion of this paper recommends the use of network mechanisms to restrict non-compliant (TCP-unfriendly) traffic on the network, thus encouraging others to play fair. At the same time, it is also mentioned how providers could allow premium rates (amazing how this has all played out) that would follow different rules. My point is simply this: whether or not we intended to, we have already violated the end-to-end principle out of necessity. I'm not sure that's a bad thing, as long as we do it in a straightforward and fair way - yes, there will be added complexity in the network, but so long as we have something akin to a standard API for other layers to interact with, this could be a strength.