Wild idea:
A yum plugin that short-circuits any downloading where the expected
checksum of the data is known beforehand. It would first ask on the
local network for the file, providing:
* The baseurl or mirrorlist url.
* The path relative to the root of the repo.
* The name of the file.
* The expected checksum.
If no yum cache service is available on the network, no such service has
a suitable file or the request times out (a short timeout, 1 second
perhaps), the plugin would fall back to the baseurl or mirrors as usual.
That looks to me like an ad-hoc peer-to-peer network.
If you have a small network of machines and want to take advantage of
caching, share the files yum has cached locally to other Fedora network
nodes.
Sounds like a project for me, eh ?