6 PubSub Communication Parameters ToC Previous Next

6.2 Common Configuration Parameters ToC Previous Next

6.2.4 Shared PubSubGroup Parameters ToC Previous Next General ToC

The parameters are shared between WriterGroup and ReaderGroup.

The parameters are related to PubSub NetworkMessage security. See 5.4.3 for an introduction of PubSub security and 8 for the definition of the PubSub Security Key Service. SecurityMode ToC

The SecurityMode indicates the level of security applied to the NetworkMessages published by a WriterGroup or received by a ReaderGroup. The MessageSecurityMode DataType is defined in OPC 10000-4. SecurityGroupId ToC

The SecurityGroupId with DataType String is the identifier for a SecurityGroup in the Security Key Server. It is unique within a SKS.

The parameter is null if the SecurityMode is NONE_1.

If the SecurityMode is not NONE_1 the SecurityGroupId identifies the SecurityGroup. The SecurityGroup defines the SecurityPolicy and the security keys used for the NetworkMessage security. The PubSubGroup defines the SecurityMode for the NetworkMessages sent by the group. SecurityKeyServices ToC

SecurityKeyServices is an array of the DataType EndpointDescription and defines one or more Security Key Servers (SKS) that manage the security keys for the SecurityGroup assigned to the PubSubGroup. The EndpointDescription DataType is defined in OPC 10000-4.

The parameter is null if the SecurityMode is NONE_1.

Each element in the array is an Endpoint for an SKS that can supply the security keys for the SecurityGroupId. Multiple Endpoints exist because an SKS may support multiple transport profiles and/or may have multiple redundant instances. The UserTokenPolicies in each Endpoint specify what user credentials are required. OPC 10000-4 describes UserTokenPolicies in more detail. MaxNetworkMessageSize ToC

The MaxNetworkMessageSize with DataType UInt32 indicates the maximum size in bytes for NetworkMessages created by the WriterGroup. 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 MaxNetworkMessageSize, the behaviour depends on the message mapping.

The transport protocol mappings defined in 7.3 may define restrictions for the maximum value of this parameter.

Note 1: The value for the MaxNetworkMessageSize should be configured in a way that ensures that NetworkMessages together with additional headers added by the transport protocol are still smaller or equal than the transport protocol MTU. GroupProperties ToC

The GroupProperties parameter is an array of DataType KeyValuePair that specifies additional properties for the configured group. The KeyValuePair DataType is defined in OPC 10000-5 and consists of a QualifiedName and a value of BaseDataType.

The mapping of the name and value to concrete functionality may be defined by transport protocol mappings, future versions of this specification or vendor specific extensions. PubSubGroup Structure ToC Model

This Structure DataType is an abstract base type for PubSubGroups. The PubSubGroupDataType is formally defined in Table 20.

Table 20 – PubSubGroupDataType Structure

Name Type Description
PubSubGroupDataType Structure  
   name String The name of the PubSubGroup.
   enabled Boolean The enabled state of the PubSubGroup.
   securityMode MessageSecurityMode Defined in
   securityGroupId String Defined in
   securityKeyServices EndpointDescription[] Defined in
   maxNetworkMessageSize UInt32 Defined in
   groupProperties KeyValuePair[] Defined in

The PubSubGroupDataType Structure representation in the AddressSpace is defined in Table 21.

Table 21 – PubSubGroupDataType Definition

Attributes Value      
BrowseName PubSubGroupDataType      
IsAbstract True      
References NodeClass BrowseName IsAbstract Description
Subtype of Structure defined in OPC 10000-5.        
HasSubtype DataType WriterGroupDataType FALSE Defined in
HasSubtype DataType ReaderGroupDataType FALSE Defined in

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