Ask HN: How will ISP's enable network priority post NN?

I can't imagine it will be by IPv4 address. That seems too hard for cloud based solutions to jump on board and pay extra. If it is an IP header, couldn't one simply install an OS plugin that adds that header to every packet? If it is an HTTP header, couldn't one simply install a webserver plugin that adds that header to every request? Is it HTTP/S only and done via domain name inspection with transparent proxies? In which case couldn't we run the web on another port? Will it be a standard approach across all ISP's, or will each ISP do something different?