It would be really nice if the major CDNs had virtual machines small network operators with very expensive regional transport costs could spin up. Hit rate would be very low, of course, but the ability to grab some of these mass-market huge updates and serve them on the other end of the regional transport at essentially no extra cost would be great. I'm sure legal arrangements make that difficult, though. +1
I think primary reason is that many major CDN offload nodes implemented such way that they require significant amount of maintenance and support. And doesnt matter, small or big ISP - they will have problems, and when the company that installed this CDN node is huge, like Facebook or Google, to crank all the bureaucratic wheels to change silly power supply or HDD - it comes at a huge cost for them. Also add that small ISP often dont have 24/7 support shifts, less qualified for complex issues, more likely to have poor infrastructure (temperature/power/reliability), that means more support expenses. And they don’t give a damn that because of their "behemothness", they increase the digital inequality gap. When a large ISP or ISP cartel member enter some regional market, local providers will not be able to compete with him, since they cannot afford CDN nodes due traffic volume. Many of CDN also do questionable "BGP as signalling only" setups with proprietary TCP probing/loss, that often doesn't work reliably. Each of them is trying to reinvent the wheel, "this time not round, but dodecahedral". And when it fails, ISP will waste time of support, until it reach someone who understand issue. In most cases, this is a blackbox setup, and when problem happens ISP are endlessly trying to explain problem to outsourced support, who have very limited access as well, and responding like robot according to the his "support workflow", with zero feedback to common problems. Honestly, it's time to develop an open standard for caching content on open CDN nodes, which should be easy to use for both content providers and ISPs. For example, at one time existed a special hardcoded "retracker.local" server in many torrent clients, which optionally(if resolved on ISP, static entry in recursor) was used for the discovery of nearest seeders inside network of a local provider. http://retracker.local/ Maybe it is possible to make a similar scheme, if the content provider wants "open" CDN to work, it will set some alternative scheme cdn://content.provider.com/path/file or other kind of hint, with content validity/authenticity mechanism. After that, the browser will attempt to do CDN discovery, for example: "content.provider.com.reservedtld" and will push request through it. I'm sure someone will have a better idea how to do that. As a result, the installation of such "offloading node" will be just installing container/vm and, if the load is increased, increasing the number of servers/vm instances.