There are thousands of Tor relays. And so it's arguably impractical for each relay to maintain persistent connections with all of the others, even without padding traffic.
At the other extreme, a given relay would only connect with another when it received a cell that was addressed there. Is this how Tor currently works?
I gather that relays perform no explicit mixing. But, beyond padding to constant cell size, are there steps to obfuscate inter-relay traffic? For example, can obfsproxy be used between relays?
Is the cell structure of individual circuits obvious in inter-relay traffic? To what extent is it obscured through TCP mechanics?