I think this is a problem with https. I remember intermittent connectivity as way better before Google forced the issue.
And yes I like https. But it comes with drawbacks. E.g. no isp caching.
Also I am very happy that it is not a thing and that ISPs cannot do that. When I go to a website I want to get the website from the webserver exactly as the server delivers it and not some other page that my ISP thinks is how the website should look.
Besides with global CDNs we have something very similar but better anyway. I don't get the site from the other side of the world but from the closest CDN server that does caching. The important difference is that the CDN server is authorized by the website to cache the page and the webmaster has control over what it does.
Transparent squid proxies were common back when most sites were on http. They let ISPs reduce the use of their limited upstream bandwidth, while also making sites load faster. The complexity and resource requirements were modest: install squid on a server, and configure the router to redirect (masquerade) all outgoing TCP port 80 connections to the port configured for squid on that server.
With bandwidth usage the diversity of the data retrived over the internet has also gone up. You can't just cache the few most popular websites and save most bandwidth. But bandwidth capacity has scaled a lot so you probably also do not need to.
You could have some hash check to prevent hijacking. The old method would be naive today.
There would be some privacy concerns I guess. But it could be opt-in on the site owners part. I think caching some videos and pictures would save a lot of power.
> Besides with global CDNs we have something very similar but better anyway.
Sure but they are some switches away.
But how do you know that the cached site is up to date? How does the ISP know that? What about dynamic content? What about consistency between different requests that are part of the same page load?
> Sure but they are some switches away.
My point is that this does not matter much. Usually, at least in non sparsely populated parts of the world with modern infrastructure, these switches are close and there is lots of bandwidth capacity.
I just don't think it makes sense for ISPs to save bandwidth on these links by building their own local data centers when they peer with a CDN data center anyway.
It would be interesting to know how much bandwidth would be saved by caching X gb of the most downloaded films, pictures and textfiles at a neighbourhood level.
In the 90s early 00s I think the share was way bigger than it would be now.