[ns] Dear Diffusion users

[Anas]

Hi i am trying to implement Directed diffusion in my WSN simulation and
i found twoo ways of defining diffusion 
the first is 
set opt(adhocRouting)   Directed_Diffusion
Which is used in the simple-diffusion example 
While in the test-suit-wireless-diffusion the routing was defined as
follows 
set opt(adhocRouting)   DIFFUSION/RATE 
set opt(adhocRouting)   DIFFUSION/PROB

so can any body tell me what is the difference