When two units talk to each other, they need to agree on their communication speed.
Wired Ethernet currently has three commonly used connection speeds:
- 10 Mbps/half or full duplex
- 100 Mbps/half or full duplex
- 1 Gbps/full duplex
The higher the speed, the more data can be transmitted between the two units in the same time interval. Therefore, higher speeds also require more powerful equipment to process the larger data loads. 10/100 Mbps is the most common speed for small- and medium-sized products because they do not need to transmit large amounts of data.
When you are going to connect two units, you must find a speed that both units can use. The Ethernet standard offers “auto-negotiation”, which automatically finds the fastest common speed that the two units can use to communicate. However, not all units support “auto-negotiation”, and in these cases you must set the speed manually on the devices. Furthermore, in some situations, the length or quality of the cable can interfere with the “auto-negotiation” function and the connection speeds must be set manually.
If the communication to/from your unit is unstable or not working at all, then the “auto-negotiation” function is either not available or has failed. You then have to set the connection speed manually in the configuration software of the unit.