[p_l]

The degree of automation varies - I'm not in avionics industry so I can't give exact data. However if you read through things like AFDX standard (what's published of it) and ARINC-653 and the like, there's enough to get the gist of it.

For example, AFDX ensures no congestion by statically assigned timeslots, effectively using Ethernet in a sort-of TDMA setup, coupled by special switches that effectively implement virtual circuits based on, again precomputed, mapping loaded into them (at least the standard implies there's no MAC-learning supposed to happen). This allows you to develop and do basic test with any random Ethernet switch before needing a proper AFDX one for more thorough testing, as the application-level protocol is essentially UDP over IP. However you need to consider a whole AFDX network segment when assigning the timeslots and virtual channels, and that's where tools come in :)