[c-nsp] ospf design question

[Mark Kent]

With three routers in a point-to-point row:

[rtr1]<-->[rtr0]<-->[rtr2]

what are the principal differences between these
three ospf designs:

A) Three areas: area 0 in the middle, one ospf process/router.

B) It's all area 0, one ospf process/router.

C) No area 0.  The endpoints (rtr1, rtr2) have one
   ospf process each with one area defined, covering
   the interface between it and the neighbor.

   The internal router has two ospf processes 
   defined, each like above, with one area per
   process and "redist ospf <other-process>"

I note that despite the cisco ospf design guide
saying that there has to be a area 0, it seems that
is not true in practice (i.e., C works).

Thanks,
-mark