CoA server conception

[Yuriy Ivkin]

Greetings!

  I am trying to understand the conception of coa server. What 
functionality does it brings ? Is it a some kind of proxy ?

For example, I have a NAS server with configured coa port. I can send a 
disconnect request directly into it. If I configure a coa server on a 
freeradius server, will I be able to send a disconnect request to the 
freeradius instead and that is all?

Thanks in advance for your answers!

-- 
Best regards,
Yuriy Ivkin