Rockwell Automation 1756-NEX Nexus Module - Manual (Page 28)

3-2 About the NeXUS Network
Publication 1756-UM524B-EN-P - December 2008
Supported Services
The ADP protocol provides to application programs 2 means of message transmission:
peer-to-peer and multicast. Because the peer-to-peer message transfer requires a
connection-oriented service as an underlayer, it uses the TCP protocol.
Since multicast transmission is connectionless, multicast messages are sent and received
using the UDP protocol. As with any connectionless service, delivery and sequence of
messages is not guaranteed. Nor is there a flow control mechanism.
OSI Layer NeXUS Network Protocol Comments
Layer 7 - Application NEXUS or ADP See the latest copy of the following
ADP specification, available at
http://www.mstc.or.jp/jop/misc/spec-e
.html:
Manufacturing Science and
Technology Center, Japan FA Open
Systems Promotion Group,
Distributed Manufacturing
Architecture Committee,
“Specifications for Autonomous
Decentralized Protocol”, R. 3.0,
MSTC/JOP (September 30, 1999).
Layer 6 - Presentation Not implemented
Layer 5 - Session Not implemented
Layer 4 - Transport UDP and TCP Most ADP messages are transferred
using the UDP protocol; some are
transferred using the TCP protocol
Layer 3 - Network IP
Layer 2 - Data Link IEEE/802.3 - Ethernet
Layer 1 - Physical IEEE/802.3 - Ethernet
Physical Medium IEEE/802.3 - Ethernet
TIP
The 1756-CLX/C module supports multicast transmission services
only.