Is there a DETAILED packet processing flow chart for IOS (specially the ISR platform)?
packet comes to input interface -->
decision branches (depending on processing modes, route, inspection processes, session, policy lookup, nat, buffering, etc) -->
packet goes out output interface--->
This is general process order for all IOS software based router; ISR is in that category. For routers like 7600s, ASRs and Catalyst switches, they might not follow same order, because those are hardware based devices. Totally different animal.