Rockwell Automation 22-COMM-E EtherNet/IP Adapter - Manual (Page 158)

G-8 Glossary
T
TCP (Transmission Control Protocol)
EtherNet/IP uses this protocol to transfer Explicit Messaging packets
using IP. TCP guarantees delivery of data through the use of retries.
U
UDP (User Datagram Protocol)
EtherNet/IP uses this protocol to transfer I/O packets using IP. UDP
provides a simple, but fast capability to send I/O messaging packets
between devices. This protocol ensures that adapters transmit the most
recent data because it does not use acknowledgements or retries.
Z
Zero Data
When communications are disrupted (for example, a cable is
disconnected), the adapter and drive can respond with zero data. Zero
data results in the drive receiving zero as values for Logic Command and
Reference data. If the drive was running and using the Reference from
the adapter, it will stay running but at zero Reference.