Performance

Custom Ethernet protocols from office technology rely on user data being sent as individual packets to each device, embedded in a defined framework made from protocol overheads.

The overhead in data traffic is disproportionately high in small user data packets such as simple setpoint targets. For example, if status data of 4 bytes per device for 20 devices were sent individually, that would take up 1,680 bytes = 20*84 bytes altogether (smallest packet size with Ethernet: 64 bytes). However, only 80 bytes would be used productively for the application - that’s approximately. 5% of the bandwidth, even during low-peak cycle times.

In Sercos telegrams, however, up to 1,494 bytes of all device user data is packed together with an additional 44 bytes of overhead. With packets that are a maximum size of 1,538 bytes, the bandwidth available for productive data increases to up to 97%.