The PubSubKeyPushTargetType is formally defined in Table 181.

An instance of this ObjectTypeincludes all information required to establish a secure connection to the Serverthat is the target of a push operation as described in 5.4.4.3. If any of the connection information changes, the PubSubKeyPushTargetmust be removed and a new PubSubKeyPushTargetwith updated connection information must be added.

Table 181– PubSubKeyPushTargetType definition

Attribute	Value
BrowseName	PubSubKeyPushTargetType
IsAbstract	False
References	NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
Subtype of BaseObjectType defined in OPC 10000-5.
HasPushed SecurityGroup	Object	<SecurityGroupName>		SecurityGroupType	Optional‌Placeholder
HasProperty	Variable	ApplicationUri	String	PropertyType	Mandatory
HasProperty	Variable	EndpointUrl	String	PropertyType	Mandatory
HasProperty	Variable	SecurityPolicyUri	String	PropertyType	Mandatory
HasProperty	Variable	UserTokenType	UserTokenPolicy	PropertyType	Mandatory
HasProperty	Variable	RequestedKeyCount	UInt16	PropertyType	Mandatory
HasProperty	Variable	RetryInterval	Duration	PropertyType	Mandatory
HasProperty	Variable	LastPushExecutionTime	DateTime	PropertyType	Mandatory
HasProperty	Variable	LastPushErrorTime	DateTime	PropertyType	Mandatory
HasComponent	Method	ConnectSecurityGroups	Defined in 8.6.3		Mandatory
HasComponent	Method	DisconnectSecurityGroups	Defined in 8.6.4		Mandatory
HasComponent	Method	TriggerKeyUpdate	Defined in 8.6.5		Mandatory
Conformance Units
PubSub Model SKS Push

The Property ApplicationUriis the ApplicationUriof the Serverthat is the target of a push. The push operation shall fail if the ApplicationUriof the connected target Server does not match this parameter.

The Property EndpointUrlis the URL of the Endpointof the Serverthat is the target of a push.

The Property SecurityPolicyUriis a Stringthat contains the security policy the SKS shall use to establish a SecureChannelto the PubSubKeyPushTarget. The MessageSecurityModeshall always be SignAndEncrypt.

The Property UserTokenTypecontains the type of user toke to be used for the connection to the PubSubKeyPushTarget. The default is Anonymousand authorization is accomplished in this case with the application identity of the SKS.

The Property RequestedKeyCountis the number of keys that are to be pushed on each update. The minimum setting for this is three.

The Property RetryIntervaldefines the interval the SKSshall use to retry pushing keys after an error appeared.

The Property LastPushExecutionTimeindicates the time the last push operation was executed successfully on the PubSubKeyPushTarget. A null DateTimevalue indicates that no successful push was executed.

The Property LastPushErrorTimeindicates the last time a push operation failed on the PubSubKeyPushTarget. A null DateTimevalue indicates that no error has occurred.

The first push is started at the time a SecurityGroupis assigned to the PubSubKeyPushTarget. The assignment is done with the Method ConnectSecurityGroupsor with a successful update of the PubSubKeyPushTargetswith PubSubConfigurationType CloseAndUpdate. The sequence for push is described in 5.4.4.3.

In a period of half the KeyLifetimeof a SecurityGroup, the SKS shall open a secure communication to each related PubSubKeyPushTargetsand shall call SetSecurityKeysto push the security keys for a SecurityGroupinto a Publisheror Subscriber. The SKS shall push the previous security key, the current key, and at least one future key to bridge longer unavailability time of the SKS. If it is not possible to push security keys to a PubSubKeyPushTargetdue to errors in establishing the communication or due to errors returned from the SetSecurityKeys Method call, the SKS shall retry pushing the security keys in a period of RetryInterval. If multiple future security keys are pushed, it is up to the SKS to define when security keys are pushed, but at a minimum it shall be at the half KeyLifetimeof the current key when only one future key is remaining.

Since the SKS is unaware of the state of a PubSubKeyPushTarget, it is recommended for a PubSubKeyPushTargetto persist security keys. This allows the PubSubKeyPushTargetto continue secured PubSub communication after a power cycle, as long as the outage time is smaller than the time covered with currentKey and FutureKeys. If keys are not persisted, it may take up to half the KeyLifetimeto get the first set of security keys. The PubSubKeyPushTargetspersisting security keys shall have an understanding of time (either synchronized or battery backup) allowing them to determine whether the current key is still valid to use, or whether to use a future keyfollowing a power interruption.

This Methodconnects instances of SecurityGroupType to thisPubSubKeyPushTarget. This indicates that the SKSshall use the push model to distribute the keys of the SecurityGroupto the PubSubKeyPushTarget.

The SKS shall push keys following this assignment. If an assignment does already exist, the entry is ignored.

If the assignment for a SecurityGroupalready exists, a Good_EntryReplaced should be returned for that SecurityGroupand a new push of the existing keys shall be triggered to the push target.

The Clientshall be authorized to modify the configuration for the SKSfunctionality and shall use at least a signed communication channel when invoking this Methodon the Server.

Signature

ConnectSecurityGroups(

[in]NodeId[] SecurityGroupIds,

[out]StatusCode[]ConnectResults

);

Argument	Description
SecurityGroupIds	The NodeIdsof the SecurityGroupsto connect to the PushTarget.
ConnectResults	The result codes for the SecurityGroups to connect.

Method Result Codes

ResultCode	Description
Bad_UserAccessDenied	The Sessionuser is not allowed to connect SecurityGroupsto the push target.
Bad_SecurityModeInsufficient	The communication channel is not using signing.

Operation Result Codes

ResultCode	Description
Good_EntryReplaced	The PushTarget was already assigned to the SecurityGroup, a new push was triggered
Bad_NodeIdUnknown	A SecurityGroupNodeIdis unknown.
Bad_NodeIdInvalid	A SecurityGroupNodeIdis not a NodeIdof a SecurityGroupType Object.

Table 182specifies the AddressSpacerepresentation for the ConnectSecurityGroups Method.

Table 182– ConnectSecurityGroups Method AddressSpace definition

Attribute	Value
BrowseName	ConnectSecurityGroups
References	NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
HasProperty	Variable	InputArguments	Argument[]	PropertyType	Mandatory
HasProperty	Variable	OutputArguments	Argument[]	PropertyType	Mandatory
ConformanceUnits
PubSub Model SKS Push

This Methoddisconnects instances of SecurityGroupTypefrom thisPubSubKeyPushTarget. This indicates that the SKSshall stop using the push model to distribute the keys of those SecurityGroupsto the PubSubKeyPushTarget.

The Clientshall be authorized to modify the configuration for the SKSfunctionality and shall use at least a signed communication channel when invoking this Methodon the Server.

Signature

DisconnectSecurityGroups(

[in]NodeId[] SecurityGroupIds,

[out]StatusCode[]DisconnectResults

);

Argument	Description
SecurityGroupIds	The NodeIdsof the SecurityGroups to disconnect.
DisconnectResults	The result codes for the SecurityGroups to disconnect.

Method Result Codes

ResultCode	Description
Bad_UserAccessDenied	The Sessionuser is not allowed to disconnet SecurityGroupsfrom the push target.
Bad_SecurityModeInsufficient	The communication channel is not using signing.

Operation Result Codes

ResultCode	Description
Bad_NodeIdUnknown	A SecurityGroupNodeIdis unknown.
Bad_NodeIdInvalid	A SecurityGroupNodeIdis not a NodeIdof a SecurityGroupType Object.

Table 183specifies the AddressSpacerepresentation for the DisconnectSecurityGroups Method.

Table 183– DisconnectSecurityGroups Method AddressSpace definition

Attribute	Value
BrowseName	DisconnectSecurityGroups
References	NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
HasProperty	Variable	InputArguments	Argument[]	PropertyType	Mandatory
HasProperty	Variable	OutputArguments	Argument[]	PropertyType	Mandatory
ConformanceUnits
PubSub Model SKS Push

This Methodtriggers a key update of all SecurityGroupsrelated to the PubSubKeyPushTarget. The SKS shall push the new set of keys for all related SecurityGroups, even if not currently scheduled.

The Clientshall be authorized to modify the configuration for the SKSfunctionality and shall use at least a signed communication channel when invoking this Methodon the Server.

Signature

TriggerKeyUpdate();

Method Result Codes

ResultCode	Description
Bad_UserAccessDenied	The Sessionuser is not allowed to trigger a key update on this push target.
Bad_SecurityModeInsufficient	The communication channel is not using signing.

The HasPushedSecurityGroup ReferenceTypeis a concrete ReferenceTypethat can be used directly. It is a subtype of the HierarchicalReferences ReferenceType.

The SourceNodeof Referencesof this type shall be an Objectof ObjectType PubSubKeyPushTargetType or an ObjectTypethat is a subtype of PubSubKeyPushTargetType defined in 8.6.1.

The TargetNodeof this ReferenceType shall be an Objectof the ObjectType SecurityGroupTypedefined in 8.4.1.

Serversshall provide the inverse Referencethat relates a SecurityGroup Objectback to a PubSubKeyPushTargetType Object.

The representation of the HasPushedSecurityGroup ReferenceTypein the AddressSpaceis specified in Table 184.

Table 184– HasPushedSecurityGroupReferenceType

Attributes	Value
BrowseName	HasPushedSecurityGroup
InverseName	HasPushTarget
Symmetric	False
IsAbstract	False
References	NodeClass	BrowseName	Comment
Subtype of HierarchicalReferences defined in OPC 10000-5.
Conformance Units
PubSub Model SKS Push

Table 185specifies the AddressSpacerepresentation for the TriggerKeyUpdate Method.

Table 185– TriggerKeyUpdate Method AddressSpace definition

Attribute	Value
BrowseName	TriggerKeyUpdate
ConformanceUnits
PubSub Model SKS Push