The host *is* the edge of the network.
I'm sorry to have not mentioned that I consider the host nodes,
or the end nodes, are not edges but instead something attaching
on network edges. I consider the very last hub, or the access router
which the end nodes connected to as the 'network edge'.
So there's no network between me and another computer on the
same unswitched Ethernet?
For example the old 10Base2 ethernet links? Or a cross-link twisted-pairs?
I can say the full length of the 10Base2 link can be regarded as a (passive)
repeater hub.
I think 'network edge' is somewhat a arbitrary definition. Maybe I'm not
correct but I believe distinguishing 'network edge' from 'end node' may provide
some convenience for further discussion on the congestion control and avoidance
mechanism.