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Network System Definitions Appendix C
FL-net IP Address
IP addresses (INET addresses) are used to distinguish each communications device from multiple communi-
cations devices connected to the Ethernet. Therefore, a unique IP address must be set for each communica-
tions device connected to the Ethernet. An IP address is comprised of a network address indicating the
network to which the communications device is connected, and the host address for the communications
device. The networks are classified as class A, B, or C, depending on the network size (classes D and E are
also supported for other specific purposes).
Note The parts shown in gray indicate the section of the IP address corresponding to the network and node
addresses.
The IP addresses for communications devices connected to the same network will all have the same network
address; each device will have a unique host address. The default FL-net IP address is 192.168.250.N (N:
Node number between 1 and 254). It is recommended to use class C address, with the host address in the
lower byte matching the FL-net protocol node number.
FL-net Subnet Mask
The FL-net subnet mask is always 255.255.255.0. Set the subnet mask to 255.255.255.0 in the FL-net Unit
Setup (CPU Bus Unit Setup Area) using the FL-net Unit Support Software. This format is the same as that for
the network address and host address used in class C.
TCP/IP and UDP/IP Communications Protocol
The main protocols used by Ethernet are TCP, UDP, and IP. IP is located in the network layer of the communi-
cations protocol, and controls the flow of communications data. TCP and UDP are located in the transport layer
and both use IP as the network layer, but the service provided is significantly different. TCP provides a reliable
delivery service that does not recognize delineation in the data for the upper layer. UDP, however, functions by
transferring data packets from IP (datagrams) to the upper layer without modification, and without confirming
whether the data has reached the destination. Data processing, such as reception confirmation and resending,
is performed in the upper layer. UDP does not have the reliability of TCP, but can deliver communications ser-
vices with small overhead.
FL-net uses UDP because TCP’s elaborate data confirmation and resending procedures are redundant in an
FL-net system. High-speed data exchange is enabled by replacing these procedures with procedures for con-
trolling the right to transmit using tokens and performing multiple frame division/synthesis in the upper FL-net
protocol layer.
0 to 127 xxx.xxx.xxx.xxx Xxx.xxx.xxx.xxx
128 to 191 xxx.xxx.xxx.xxx Xxx.xxx.xxx.xxx
192 to 223 xxx.xxx.xxx.xxx Xxx.xxx.xxx.xxx
Host address
Network address First octet
Class
A
B
C
1 0 X
2
0
2
7
2
8
2
2
7
2
3
0
2
2
9
2
2
8
Network address
Host address
Fixed