6.4.1 Datagram Transport Protocol

6.4.1.1 Quality of service parameters

6.4.1.1.1 QosCategory and DatagramQos

The QosDataTypes defined in the following chapters are used in the DatagramQos parameter in different datagram specific transport protocol mapping settings.

The DatagramQos contains an array of QosDataTypes. The array is null or empty if no QoS related parameters are set.

The DatagramQos parameter is always combined with a QosCategory parameter. Depending on the content of the QosCategory String, different elements need to be present within the DatagramQos array.

The specific processing of the QosCategory and DatagramQos content is described in 5.4.6.4.

Standard QosCategory values are defined in Table 118.

6.4.1.1.2 QosDataType structure

This Structure DataType is an abstract base type for Structures with QoS related parameters. The QosDataType is formally defined in Table 119.

The QosDataType Structure representation in the AddressSpace is defined in Table 120.

6.4.1.1.3 TransmitQosDataType

This Structure DataType is an abstract base type for Structures with transmit QoS related parameters. The TransmitQosDataType is formally defined in Table 121.

The TransmitQosDataType Structure representation in the AddressSpace is defined in Table 122.

6.4.1.1.4 TransmitQosPriorityDataType

6.4.1.1.4.1 PriorityLabel

The PriorityLabel with DataType String specifies the priority of the according sender. The network stack will use the PriorityLabel to look up the priority settings for the transport protocol headers.

The priority labels defined by OPC UA should have the following form:

opc.qos.lbl://<label>

Example values are “opc.qos.lbl://low” or “opc.qos.lbl://high”. The mapping is described in 5.4.6.4.

Note: This version does not define concrete labels. The engineering process needs to provide them and also build up the PriorityMappingTable in OPC 10000-22 accordingly.

6.4.1.1.4.2 TransmitQosPriorityDataType structure

This Structure DataType is used to represent the priority lable specific transmit QoS parameters. It is a subtype of the TransmitQosDataType defined in 6.4.1.1.3.

The TransmitQosPriorityDataType is formally defined in Table 123.

Its representation in the AddressSpace is defined in Table 124.

6.4.1.1.5 ReceiveQosDataType

This Structure DataType is an abstract base type for Structures with receive QoS related parameters. The ReceiveQosDataType is formally defined in Table 125.

The ReceiveQosDataType Structure representation in the AddressSpace is defined in Table 126.

6.4.1.1.6 ReceiveQosPriorityDataType

6.4.1.1.6.1 PriorityLabel

The PriorityLabel with DataType String specifies the priority of the according sender.

Futher details are defined in 6.4.1.1.4.1.

6.4.1.1.6.2 ReceiveQosPriorityDataType structure

This Structure DataType is used to represent the priority lable specific receive QoS parameters. It is a subtype of the ReceiveQosDataType defined in 6.4.1.1.5.

The ReceiveQosPriorityDataType is formally defined in Table 127.

Its representation in the AddressSpace is defined in Table 128.

6.4.1.2 Datagram PubSubConnection

6.4.1.2.1 DiscoveryAddress

The DiscoveryAddress parameter contains the network address information used for the discovery probe and announcement messages. The different Structure DataTypes used to represent the Address are defined in 6.2.7.5.3.

6.4.1.2.2 DatagramConnectionTransportDataType structure

This Structure DataType is used to represent the datagram specific transport mapping parameters for PubSubConnections. It is a subtype of the ConnectionTransportDataType defined in 6.2.7.5.2.

The DatagramConnectionTransportDataType is formally defined in Table 129.

Its representation in the AddressSpace is defined in Table 130.

6.4.1.2.3 DiscoveryAnnounceRate

The DiscoveryAnnounceRate with DataType UInt32 defines the interval in seconds used for cyclic sending of discovery announcement messages related to this connection.

The default value is 0 and defines that discovery announcement messages are only sent as response to discovery probe messages.

6.4.1.2.4 DiscoveryMaxMessageSize

The DiscoveryMaxMessageSize with DataType UInt32 indicates the maximum size in bytes for NetworkMessages created for discovery. It refers to the size of the complete NetworkMessage including padding and signature without any additional headers added by the transport protocol mapping. If the size of a NetworkMessage exceeds the DiscoveryMaxMessageSize, the behaviour depends on the message mapping.

The default value is 0 and defines that the default size for the transport protocol ist used. The default size is defined for the transport protocol mappings in 7.3.

NOTE The value for the DiscoveryMaxMessageSize should be configured in a way that ensures that NetworkMessages together with additional headers added by the transport protocol are still smaller than or equal than the transport protocol MTU.

6.4.1.2.5 QosCategory

Selects the general category of QoS the PubSubConnection requires. Further details are defined in 6.4.1.1.1.

The parameter shall be null or empty if no QoS related parameters are set.

6.4.1.2.6 DatagramQos

The DatagramQos parameter contains QoS related parameters for the PubSubConnection as array of QosDataType Structures. The abstract DataType is defined in 6.4.1.1.2. The concrete subtypes are used to represent different QoS settings for transmit and receive that can be combined in the array.

The array shall not contain multiple instances of a concrete subtype e.g. transmit PriorityLabel entry.

The parameter shall be null or empty if no QoS related parameters are set.

6.4.1.2.7 DatagramConnectionTransport2DataType structure

This Structure DataType is used to represent the datagram specific transport mapping parameters for a PubSubConnection.

It is a subtype of the DatagramConnectionTransportDataType defined in 6.4.1.2.2.

The DatagramConnectionTransport2DataType is formally defined in Table 131.

Its representation in the AddressSpace is defined in Table 132.

6.4.1.3 Datagram WriterGroup

6.4.1.3.1 MessageRepeatCount

The MessageRepeatCount with DataType Byte defines how many times every NetworkMessage is repeated. The default value is 0 and disables the repeating.

6.4.1.3.2 MessageRepeatDelay

The MessageRepeatDelay with DataType Duration defines the time between NetworkMessage repeats in milliseconds. The parameter shall be ignored if the parameter MessageRepeatCount is set to 0.

6.4.1.3.3 DatagramWriterGroupTransportDataType structure

This Structure DataType is used to represent the datagram specific transport mapping parameters for WriterGroups. It is a subtype of the WriterGroupTransportDataType defined in 6.2.6.7.2.

The DatagramWriterGroupTransportDataType is formally defined in Table 133.

Its representation in the AddressSpace is defined in Table 134.

6.4.1.3.4 Address

The Address parameter contains the network address information for the communication middleware related to the WriterGroup. The different Structure DataTypes used to represent the Address are defined in 6.2.7.5.3.

The parameter shall be null if an address is not set at this level. If the parameter is set, it overwrites the Address on the PubSubConnection.

6.4.1.3.5 QosCategory

Selects the general category of QoS the WriterGroup requires. Further details are defined in 6.4.1.1.1.

The parameter shall be null or empty if no QoS related parameters are set.

6.4.1.3.6 DatagramQos

The DatagramQos parameter contains QoS related parameters for the WriterGroup as array of TransmitQosDataType Structures. The abstract TransmitQosDataType is defined in 6.4.1.1.3. The concrete subtypes are used to represent different QoS settings that can be combined in the array.

The array shall not contain multiple instances of a concrete subtype e.g. transmit PriorityLabel entry.

The parameter shall be null or empty if no QoS related parameters are set.

6.4.1.3.7 DiscoveryAnnounceRate

The DiscoveryAnnounceRate with DataType UInt32 defines the interval in seconds used for cyclic sending of discovery announcement messages related to the WriterGroup.

The default value is 0 and defines that discovery announcement messages are only sent as response to discovery probe messages.

6.4.1.3.8 Topic

The Topic parameter with DataType String contains the unique name of the data stream produced by the WriterGroup within a Message Oriented Middleware.

A unique default name can be created by combining the PublisherId with the WriterGroupId using ‘.’ As separator.

6.4.1.3.9 DatagramWriterGroupTransport2DataType structure

This Structure DataType is used to represent the datagram specific transport mapping parameters for WriterGroups. It is a subtype of the DatagramWriterGroupTransportDataType defined in 6.4.1.3.3.

The DatagramWriterGroupTransportDataType is formally defined in Table 135.

Its representation in the AddressSpace is defined in Table 136.

6.4.1.4 Datagram ReaderGroup parameters

There are no datagram-specific transport mapping parameters defined for the ReaderGroup.

6.4.1.5 Datagram DataSetWriter parameters

There are no datagram-specific transport mapping parameters defined for the DataSetWriter.

6.4.1.6 Datagram DataSetReader

6.4.1.6.1 Address

The Address parameter contains the network address information for the communication middleware related to the DataSetReader. The different Structure DataTypes used to represent the Address are defined in 6.2.7.5.3.

The parameter shall be null if an address is not set at this level. If the parameter is set, it overwrites the Address on the PubSubConnection.

6.4.1.6.2 QosCategory

Selects the general categorty of QoS the DataSetReader requires. Further details are defined in 6.4.1.1.1.

The parameter shall be null or empty if no QoS related parameters are set.

6.4.1.6.3 DatagramQos

The DatagramQos parameter contains the QoS related parameters for the DataSetReader as array of ReceiveQosDataType Structures. The abstract ReceiveQosDataType is defined in 6.4.1.1.5. The concrete subtypes are used to represent different QoS settings that can be combined in the array.

The array shall not contain multiple instances of a concrete subtype e.g. receive PriorityLabel entry.

The parameter shall be null or empty if no QoS related parameters are set.

6.4.1.6.4 Topic

The Topic parameter with DataType String contains the unique name of the data stream from the Publisher that contains the DataSetMessages of interest for the DataSetReader. The Topic is defined by the Publisher.

6.4.1.6.5 DatagramDataSetReaderTransportDataType structure

This Structure DataType is used to represent the datagram transport mapping parameters for DataSetReaders. It is a subtype of the DataSetReaderTransportDataType defined in 6.2.9.13.2.

The DatagramDataSetReaderTransportDataType is formally defined in Table 137.

Its representation in the AddressSpace is defined in Table 138.

6.4.1.7 DTLS PubSubConnection parameters

6.4.1.7.1 ClientCipherSuite

The parameter ClientCipherSuite defines the DTLS 1.3 cipher suite that is used for data security of the PubSub communication. Supported cipher suites are described in Part 7. This is the cipher suite sent from the client-side in the DTLS handshake.

Note that the cipher suite describes the data encryption and data authenticity algorithms used. Key agreement and certificate signature algorithms are designated via the OPC UA Client Server Security Policy.

The client cipher suite is configured at the PubSubConnection level. This parameter denotes the single cipher suite that the DTLS client will offer in the DTLS handshake. This cipher suite must match a cipher suite entry configured in ServerCipherSuites for the server side of the DTLS handshake. If this variable is not configured (e.g. set to the null string) then for a given PubSubConnection the device is meant to act as a server.

6.4.1.7.2 ServerCipherSuites

The parameter ServerCipherSuites defines the DTLS 1.3 cipher suite(s) that are used for data security of the PubSub communication. Supported cipher suites are described in OPC 10000-7. This is a list of cipher suites that the server will accept if offered by a client. In DTLS PubSub a client will only offer one cipher suite. The server will then either accept that one cipher suite as it is listed in ServerCipherSuites or reject it if it is not included in ServerCipherSuites.

Note that the cipher suite describes the data encryption and data authenticity algorithms used. Key agreement and certificate signature algorithms are designated via the OPC UA Client Server Security Policy.

6.4.1.7.3 ZeroRTT

The ZeroRTT parameter is a DataType Boolean. This parameter describes whether or not the zero round-trip-time feature of DTLS 1.3 is enabled. If this parameter is not set then it defaults to False. Note that using the Zero Round-Trip-Time feature has implications for security, as PubSub data will be sent before full authentication occurs. It is the responsibility of the user to decide whether or not this is acceptable.

6.4.1.7.4 CertificateGroupId

The CertificateGroupId parameter is the NodeId of the CertificateGroup used for the DTLS Tranpsort. This includes the Certificate and TrustList that are to be used for establishing DTLS sessions. Note that the CertificateGroup used for DTLS may be restricted via profile, see Part 7 for more information on the profiles support DTLS.

6.4.1.7.5 VerifyClientCertificate

The VerifyClientCertificate parameter is a DataType Boolean. This parameter describes whether or not the client certificate will be requested and verified by the server as part of the DTLS handshake. If this parameter is not set then it defaults to True.

6.4.1.7.6 DtlsPubSubConnectionDataType

This Structure DataType is used to represent additional DTLS specific datagram transport mapping parameters for PubSubConnections.

The DtlsPubSubConnectionDataType is formally defined in Table 139.

Its representation in the AddressSpace is defined in Table 140.