swh - Arinc 629 is B777 (and A330/340)? and yes it's linked to a standard TCP/IP network (this is where the "hacker" is), but it's one way communication.
Those buses are normally segregated/partitioned according to their function, and gateways/bridges connect different partitions.
which is why all stories about "hacking" of aircraft so far have been fictitious. Each path on the gateway must be programmed.
My summary of a/c hacking stories so far is this: There is a wire from the headphone socket on seat 29C which is connected to [insert something here] which again is connected to a wire via [insert box here], and through various other devices, I have now, very ingeniously, traced physical wires/"connections" from the headphone socket to the FMS. They're physically connected, it must mean something can be hacked, because it's computers! Yet if I plug my [insert evil hacking tool here] into the headphone socket I have no control over the FMS, despite the "physical connection".