- does group communication use skb? (I'm assuming it does) - does routing use skb? (I'm assuming it does) - does process management use skb? - does communication need synchronisation? - does process management need synchronisation? - is synchronisation inherently related to processes (eg for blocking, waiting or notifying) or is it independent of the concepts of processes and threads and can it all be done through communication - communication and process management use each other (eg for blocking, getting notified of messages arriving, etc.) - does skb use process management? - does skb use communication? - does the base functionality use communication - where does tracing/debugging fit in in a level diagram? - do device management and device drivers use protection (prinipals) - do device management and device drivers use resource management and accounting?