Tcp (Transmission Control Protocol); Udp (User Datagram Protocol) - WAGO -I/O-SYSTEM 750 Manual

214 Fieldbus Communication
physically receives every packet. The resolution of IP address to Ethernet
address is solved by the use of algorithms, IP multicast addresses are embedded
in Ethernet multicast addresses.
12.1.1.2

TCP (Transmission Control Protocol)

As the layer above the Internet protocol, TCP (Transmission Control Protocol)
guarantees the secure transport of data through the network.
TCP enables two subscribers to establish a connection for the duration of the
data transmission. Communication takes place in full-duplex mode (i.e.,
transmission between two subscribers in both directions simultaneously).
TCP provides the transmitted message with a 16-bit checksum and each data
packet with a sequence number.
The receiver checks that the packet has been correctly received on the basis of
the checksum and then sets off the sequence number. The result is known as the
acknowledgement number and is returned with the next self-sent packet as an
acknowledgement.
This ensures that the lost TCP packets are detected and resent, if necessary, in
the correct sequence.
TCP Data Packet
The packet header of a TCP data packet is comprised of at least 20 bytes and
contains, among others, the application port number of the transmitter and the
receiver, the sequence number and the acknowledgement number.
The resulting TCP packet is used in the data unit area of an IP packet to create a
TCP/IP packet.
TCP Port Numbers
TCP can, in addition to the IP address (network and subscriber address),
respond to a specific application (service) on the addressed subscriber. For this
the applications located on a subscriber, such as a web server, FTP server and
others are addressed via different port numbers. Well-known applications are
assigned fixed ports to which each application can refer when a connection is
built up
(Examples: Telnet Port number: 23, http Port number: 80).
A complete list of "standardized services" is contained in the RFC 1700 (1994)
specifications.
12.1.1.3

UDP (User Datagram Protocol)

The UDP protocol, like the TCP protocol, is responsible for the transport of data.
Unlike the TCP protocol, UDP is not connection-orientated; meaning that there
are no control mechanisms for the data exchange between transmitter and
receiver. The advantage of this protocol is the efficiency of the transmitted data
and the resulting higher processing speed.
Manual
1.5.0
750-882 Media Redundancy ETHERNET Controller
WAGO-I/O-SYSTEM 750