Chapter 15: Appendix

[5] FL-net sub net mask

The sub net mask on an FL-net is always "255.255.255.0." The user does not need to set this sub net value.

This value is identical to the original network address section and the device address section of the class C.

[6] TCP/IP, UDP/IP protocols

TCP, UDP, and IP are major protocols used on Ethernet networks.

The IP is located in the network layer of communication protocols and controls the flow of communication data.

The TCP and UDP are located in the transport layer. Both use the IP as a network layer. However, there is not much difference between these protocols in their details.

The TCP provides reliable service that does not care about the partition of data in the upper layer. On the other hand, the UDP transfers groups of data (data diagram) from the IP to the upper layer without any modification. It pays no attention to whether or not the data arrives nor does it care what the destination is. Confirmation of the data being received and re-sending the data is the job of the upper layer.

Although the UDP is not reliable, compared with the TCP, its advantage is that it has a small communication overhead.

The FL-net uses the UDP. This is because the TCP's data confirmation and re-sending procedures make it difficult to meet the FL-net goals. By omitting this procedure, the FL-net protocol layer controls data transmission correctly using tokens. And it divides and recombines multiple frames, so that it can provide high speed data exchange.

[7] FL-net port number

In order to offer service from the FL-net protocol layer, that is the upper position of the transport layer, the following port numbers are already specified. However, the user does not need to set the parameters for these port numbers.

FL-net port number

 

Name

Port number

1

Port number for cyclic transfer

55000 (fixed)

 

 

 

2

Port number for message communication

55001 (fixed)

 

 

 

3

Port number for a participation request frame

55002 (fixed)

 

 

 

4

Port number for sending data

55003 (fixed)

 

 

 

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