How many kinds of queue principles has ns supported?

[K Sun <ksun@essex.ac.uk>]

Hello,
      In Ns documents, I can not find how many kinds of queue 
principles ns has supported, although there is a lot description on how 
to develop a new simulation of queue principle. 
     Sometimes, I feel there are some details about how to develop 
simulation program of ns in ns notes, but I did not find what have been 
realized in ns.
     I really hope to get more materials of describing ns itself and 
hope to get an answer of my question above as soon as possible.

     Thanks,

     Sun Kai