detect lower level network attributes

[Antoine Martin]

Similar to #1860.
This could be done at both ends.

There might be some APIs we can use to get more feedback on the state of the connection: packet loss, retransmits, etc. Or even, the jitter itself directly?

Another option (not sure we want to go down that route):​icmp ping.

We could then plug the data into the heuristics to better tune the network layer for the actual connection state.