Those labels of network flows have been gaining currency in the industry.

Here's an example diagram:

http://www.theregister.co.uk/2011/08/15/xsigo_private_virtua...

Also see "north-south" and "east-west" in sub-heading "Changing traffic patterns":

http://en.wikipedia.org/wiki/Software-defined_networking#The...

Amazon's AWS presentations also sometimes mention network traffic inside the datacenter in terms of “east-west traffic” & “north-south”.

http://www.enterprisetech.com/2014/11/14/rare-peek-massive-s...