One of my questions I had from the readings was whether or not a network had a centre and could we create our own network centres.  This question was answered in the unlecture (no a network does not have a centre).  My next question however is whether or not a network has a boundary.  Does it have a limit beyond which it can no longer be expanded, where it can no longer grow.  Is there a point where the network will link but into itself, becoming a loop?