Network is a type of Communicate. Message is a type of Communicate. 
Difficult is etymologically related to Difficulty. Difficult is a different concept from Ease. Ease is a different concept from Hard. 
Network --IsA--> Communicate <--IsA-- Message 
Difficulty <--EtymologicallyRelatedTo-- Difficult <--DistinctFrom--> Ease <--DistinctFrom--> Hard 