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FINS/UDP Method
Section 8-2
8-2
FINS/UDP Method
8-2-1
Overview
FINS/UDP Features
The FINS/UDP method is a FINS communications method that uses the UDP/
IP protocol. UDP/IP is a connectionless communications protocol. When a
message is sent from one node to another, the two nodes have an equal rela-
tionship and there is no clear connection. If using TCP is like making a tele-
phone call, then UDP is more like delivering a memo by hand. Although the
UDP protocol is fast, data communications are less reliable than with TCP.
In particular, when sending large amounts of data involving significant routing,
the user must program measures, such as retries, into applications in order to
improve reliability.
The FINS/UDP method has the following features:
• Because FINS/UDP is a connectionless protocol, there is no limit to the
number of corrections.
• FINS/UDP can be used for broadcasting.
• When data is sent via an IP network with multiple layers (such as the
Internet), communications reliability drops.
FINS/UDP Frame Format
The following diagram shows the structure of a UDP packet used for sending
and receiving data on an Ethernet network.
As the diagram shows, a nested structure is used with the FINS/UDP method,
i.e., Ethernet Ver. 2, IP frame, UDP frame, and FINS frame. A UDP data sec-
tion (FINS frame) that exceeds 1,472 bytes is split into packets for transmis-
sion. The split UDP data is then joined automatically at the UDP/IP protocol
layer. There is normally no need to pay attention at the application layer to this
split, but it may not be possible to send 1,472-byte UDP packets over an IP
network with multiple layers. When using the FINS communications service in
a system such as this, select the FINS/TCP method.
Node
Node
Data transmission 1
Data transmission 2
Data transmission 3
Data is sent in one direction, with no
confirmation of whether the data was
received. Because there are few procedures
involved, data can be sent at high speed but
with less reliability than with TCP.
Ethernet Ver. 2
IP
UDP
FINS frame
FCS
UDP packet
Содержание CJ2H-CPU6 - REV 02-2010
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Страница 38: ...12 Network Configurator Overview Section 1 5...
Страница 58: ...32 Selecting the Network Devices Section 2 3...
Страница 116: ...90 Auxiliary Area Data Section 4 5...
Страница 222: ...196 Message Communications Errors Section 7 6...
Страница 364: ...338 Using the Backup Tool Section 13 3...
Страница 402: ...376 CS CJ series Ethernet Unit Function Comparison Appendix A...
Страница 404: ...378 Ethernet Network Parameters Appendix B...
Страница 406: ...380 TCP Status Transitions Appendix C...
Страница 452: ...426 Precautions for Using Windows XP Vista or Windows 7 Appendix G...
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