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7.3 Transport Protocol Mappings ToC Previous Next

7.3.3 OPC UA Ethernet ToC Previous Next

OPC UA Ethernet is a simple Ethernet based protocol using EtherType 0xB62C that is used to transport UADP NetworkMessages as payload of the Ethernet II frame without IP or UDP headers.

The syntax of the Ethernet transporting protocol URL used in the Address parameter defined in 6.2.7.3 has the following form:

opc.eth://<host>[:<VID>[.PCP]]

The host is a MAC address, an IP address or a registered name like a hostname. The format of a MAC address is six groups of hexadecimal digits, separated by hyphens (e.g. 01-23-45-67-89-ab). A system may also accept hostnames and/or IP addresses if it provides means to resolve it to a MAC address (e.g. DNS and Reverse-ARP).

The VID is the VLAN ID as number.

The PCP is the Priority Code Point as one digit number. This optional parameter is typically configured as part of the QoS settings on the network interface and not of the address.

The transport of a UADP NetworkMessage in an Ethernet II frame is defined in Table 162.

Table 162 – UADP message transported over Ethernet

Name Description
Frame Header The frame header with an EtherType of 0xB62C.
UADP NetworkMessage The UADP NetworkMessage is sent as Ethernet payload.
Frame Footer The frame footer.

For OPC UA Ethernet the MaxNetworkMessageSize and the DiscoveryMaxMessageSize plus additional headers shall be limited to an Ethernet frame size of 1522 Byte.

Note: The MaxNetworkMessageSize is typically 1500 Byte since the additional headers have a size of 22 Byte and it consists of 6 Byte destination address, 6 Byte source address, 2 Byte EtherType, 4 Byte frame check sequence and optionally 4 Byte VLAN tag. This is based on Q-tagged frames defined in IEEE Std 802.3-2018.

The IANA registered OPC UA EtherType for UADP communication is 0xB62C.

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