Specifications

IEEE 802.3 Ethernet Communication
ADDvantage-32 PLUS
8-27
8.9 TRANSMISSION CONCEPTS
Most Ethernet communications use either the UDP or TCP formats as follows in 8.9.1 and
8.9.2.
The Requests for Comments (RFC) document series referenced below is a set of technical and
organizational notes about the Internet (originally the ARPANET), beginning in 1969. Memos
in the RFC series discuss many aspects of computer networking, including protocols,
procedures, programs, and concepts.
8.9.1 User Datagram Protocol (UDP)
UDP is a standard protocol described by RFC 768, “User Datagram Protocol”. UDP is an
application interface to IP. It adds no reliability, flow-control, or error recovery to IP. It simply
serves as a multiplexer/demultiplexer for sending and receiving datagrams, using ports to direct
the datagrams, as shown in the following diagram.
Figure 8.9.1 UDP - Demultiplexing based on ports
UDP provides a mechanism for one application to send a datagram to another. The UDP layer
can be regarded as being extremely thin and consequently has low overheads, but it requires
the application to take responsibility for error recovery and so on.
This format is used by the GE-Fanuc Ethernet Global Data (EGD) and Allen-Bradley Implicit
Messaging.