EtherCAT is realtime Ethernet based protocol for industrial control and automation. It is fast, it can be done using your laptop RJ45 port, it is established standard - it is great. It is especially well adapted for motion control applications. Hard real time features like Distributed Clocks make for guaranteed synchronization in nanosecond precision range. You can get equipment from array of vendors, and open source controllers (IgH, SOEM) for free - there is even LinuxCNC integration available. But so far there was not much open source EtherCAT devices. Particularly I found no open source EtherCAT servodrive. We cannot leave it like that.