what is a controller & service module ?
and what is the functional difference between them ?
in a WAN router a controller controls an hardware resource like an E1/T1 or DS3 by controlling all OSI Layer1 parameters like clock (internal|line) line code used, the way that the link is used (for E1/T1 how the DS0 are used).
The configuration of the controller object generates logical interfaces that are in the case of E1/T1 groups of DS0 timeslots.
In a WAN router you can find network modules that are daughter cards that you can insert into the router. The level of modularity and flexibility is high because this network modules can host submodules like WICs VWICs and son
network modules, WAN modules, etherswitch modules under
The term service modules is used instead for multilayer switches modules like CSM, FWSM, NAM..
Hope to help