Rockwell Automation Ethernet Design Considerations Reference Manual - Manual (Page 62)

62 Rockwell Automation Publication ENET-RM002C-EN-P - May 2013
Chapter 4 EtherNet/IP Protocol
TCP Connections
TCP connections are used for all EtherNet/IP communication and are
established before one device on the network transmits data to one or more
devices on the network. EtherNet/IP communication modules use one TCP
connection for each IP address to which the module is connected.
TCP connections are automatically established before CIP connections because
you can establish CIP connections only over a TCP connection. A single TCP
connection supports multiple CIP connections.
CIP Connections
CIP connections are automatically established over a TCP connection and
transfer data from one device on the EtherNet/IP network to another. The
following are examples of CIP connections:
• Logix5000 controller message transfer to Logix5000 controller
• I/O or produced tag
• Program upload
• RSLinx DDE/OPC client
• PanelView polling of a Logix5000 controller
There are different CIP connections.
IMPORTANT EtherNet/IP communication modules also have web servers that use TCP
connections for non-CIP traffic, such as HTTP. However, TCP connections used
for non-CIP traffic do not count against the limits listed above.
Table 9 - CIP Connections
CIP Connection Description
Bridged A bridged connection is a connection that passes through the EtherNet/IP communication
module. The end point of the connection is a module other than the EtherNet/IP
communication module.
EXAMPLE: An explicit connection from a controller through a 1756-EN2T module to another
controller.
End-node An end-node connection is a connection whose end point is the EtherNet/IP communication
module itself.
EXAMPLE: An explicit connection from RSLinx software to the EtherNet/IP communication
module to set the module's IP address.
Rack-optimized A rack-optimized connections is an implicit message connection to a rack or assembly object
in the EtherNet/IP communication module. Data from selected I/O modules is collected and
produced on one connection (the rack-optimized connection) rather than on a separate
direct connection for each module.
This CIP connection is available with only digital I/O modules.
Direct An implicit message connection from a controller to an specific I/O module (as opposed to a
rack-optimized connection).
This CIP connection is available with analog and digital I/O modules.