Re: So delay == proxy for throttling. Simple idea.
Kinda. CAIDA's been doing network analysis for years, but it's a wicked problem. Especially if you're on the outside looking in. And even more so if there's various shenanigans going on around peering disputes.
But it's a way to detect congestion. That doesn't necessarily mean throttling, ie trying to shove 15Gbps of traffic down a 10Gbps pipe isn't going to work. Behind that is the age-old problem of who pays to upgrade those links. In the paper, it seems to indicate a lot of the congestion's at YT's end.. And behind all that are the challenges with ISP's control over traffic routing vs say, Google's ability to detect congestion and direct sessions to servers & connections that may have spare capacity.
Then there's the real neutrality stuff. So technically, it makes sense to be able to prioritise real-time or time senstive sessions like voice or live video. All common in private MLPS VPNs, but key to the holy war around 'Net Neutrality.. Because the fear that if you start classifying traffic, you then start charging premiums for carrying it.. Which is also complicated by content providers obfusticating their session control protocols so ISPs couldn't act on them even if they wanted to/were allowed to.
But without an ability to manage congestion, the Internet will remain fundamentally best efforts.