Specifies the wire-protocol-related attributes for the com.rti.dds.domain.DomainParticipant. More...
Public Attributes | |
| int | participant_id |
| A value used to distinguish among different participants belonging to the same domain on the same host. More... | |
| RtpsWellKnownPorts_t | rtps_well_known_ports |
| Configures the RTPS well-known port mappings. More... | |
| int | rtps_host_id |
| The RTPS Host ID of the domain participant. More... | |
| int | rtps_app_id |
| The RTPS App ID of the domain participant. More... | |
| int | rtps_instance_id |
| The RTPS Instance ID of the com.rti.dds.domain.DomainParticipant. More... | |
| int | rtps_reserved_port_mask |
| Specifies which well-known ports to reserve when enabling the participant. More... | |
| WireProtocolQosPolicyAutoKind | rtps_auto_id_kind = WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_UUID |
| Kind of auto mechanism used to calculate the GUID prefix. More... | |
| boolean | compute_crc |
| Adds RTPS CRC submessage to every message when this field is set to com.rti.dds.infrastructure.true. More... | |
| boolean | check_crc |
| Checks if the received RTPS message is valid by comparing the computed CRC with the received RTPS CRC submessage when this field is set to com.rti.dds.infrastructure.true. More... | |
 Public Attributes inherited from QosPolicy | |
| final QosPolicyId_t | id |
| The ID of this QoS policy. More... | |
| final String | policy_name |
| The name of this QoS policy. More... | |
Static Public Attributes | |
| static final int | RTPS_AUTO_ID = 0 |
| Indicates that RTI Connext should choose an appropriate host, app, instance or object ID automatically. More... | |
Detailed Description
Specifies the wire-protocol-related attributes for the com.rti.dds.domain.DomainParticipant.
- Properties:
- RxO = N/A
Changeable = NO
Usage
This QoS policy configures some participant-wide properties of the DDS Real-Time Publish Subscribe (RTPS) on-the-wire protocol. (com.rti.dds.infrastructure.DataWriterProtocolQosPolicy and com.rti.dds.infrastructure.DataReaderProtocolQosPolicy configure RTPS and reliability properties on a per com.rti.dds.publication.DataWriter or com.rti.dds.subscription.DataReader basis.)
NOTE: The default QoS policies returned by RTI Connext contain the correctly initialized wire protocol attributes. The defaults are not normally expected to be modified, but are available to the advanced user customizing the implementation behavior.
The default values should not be modified without an understanding of the underlying Real-Time Publish Subscribe (RTPS) wire protocol.
In order for the discovery process to work correctly, each com.rti.dds.domain.DomainParticipant must have a unique identifier. This QoS policy specifies how that identifier should be generated.
RTPS defines a 96-bit prefix to this identifier; each com.rti.dds.domain.DomainParticipant must have a unique value for this prefix relative to all other participants in its domain.
If an application dies unexpectedly and is restarted, the IDs used by the new instance of DomainParticipants should be different than the ones used by the previous instances. A change in these values allows other DomainParticipants to know that they are communicating with a new instance of an application, and not the previous instance.
For legacy reasons, RTI Connext divides the 96-bit prefix into three integers:
- The first integer is called host ID. The original purpose of this integer was to contain the identity of the machine on which the DomainParticipant is executing.
- The second integer is called an application ID. The original purpose of this integer was to contain a value that identifies the process or task in which the DomainParticipant is contained.
- The third integer is called instance ID. The original purpose was to contain a value that uniquely identifies a DomainParticipant within a task or process.
The com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_auto_id_kind field can be used to configure the algorithm that RTI Connext uses to populate the 96-bit prefix. Then you can optionally overwrite specific parts of the 96-bit prefix by explicitly configuring the com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_host_id (first integer), com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_app_id (second integer), and com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_instance_id (third integer).
The com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_auto_id_kind field supports three different prefix generation algorithms:
-
In the default and most common scenario, com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_auto_id_kind is set to com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_UUID. As the name suggests, this mechanism uses a unique, randomly generated UUID to fill the rtps_host_id, rtps_app_id, or rtps_instance_id fields. The first two bytes of the rtps_host_id are replaced with the RTI vendor ID (0x0101).
-
(Legacy) When rtps_auto_id_kind is set to com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_IP, the 96-bit prefix is generated as follows:
- rtps_host_id: The 32-bit value of the IPv4 of the first up and running interface of the host machine is assigned. If the host does not have an IPv4 address, the host-id will be automatically set to 0x7F000001.
- rtps_app_id: The process (or task) ID is assigned.
- rtps_instance_id: A counter is assigned that is incremented per new participant within a process.
-
(Legacy) When rtps_auto_id_kind is set to com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_MAC, the 96-bit prefix is generated as follows:
- rtps_host_id: The first 32 bits of the MAC address of the first up and running interface of the host machine are assigned.
- rtps_app_id: The last 32 bits of the MAC address of the first up and running interface of the host machine are assigned.
- rtps_instance_id: This field is split into two different parts. The process (or task) ID is assigned to the first 24 bits. A counter is assigned to the last 8 bits. This counter is incremented per new participant.
DDS_RTPS_AUTO_ID_FROM_IP is not a good algorithm to guarantee prefix uniqueness, because the process ID can be recycled by the OSs.
Some examples are provided to clarify the behavior of this QoSPolicy in case you want to change the default behavior with com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_MAC.
First, get the participant QoS from the DomainParticipantFactory:
Second, change the com.rti.dds.infrastructure.WireProtocolQosPolicy using one of the options shown below.
Third, create the com.rti.dds.domain.DomainParticipant as usual, using the modified QoS structure instead of the default one.
Option 1: Use com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_MAC to explicitly set just the application/task identifier portion of the rtps_instance_id field.
Option 2: Handle only the per participant counter and let RTI Connext handle the application/task identifier:
Option 3: Handle the entire rtps_instance_id field yourself:
NOTE: If you are using com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_MAC as rtps_auto_id_kind and you decide to manually handle the rtps_instance_id field, you must ensure that both parts are non-zero (otherwise RTI Connext will take responsibility for them). RTI recommends that you always specify the two parts separately in order to avoid errors.
Option 4: Let RTI Connext handle the entire rtps_instance_id field:
NOTE: If you are using com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_MAC as rtps_auto_id_kind and you decide to manually handle the rtps_instance_id field, you must ensure that both parts are non-zero (otherwise RTI Connext will take responsibility for them). RTI recommends that you always specify the two parts separately in order to clearly show the difference.
Member Data Documentation
◆ RTPS_AUTO_ID
|
static |
Indicates that RTI Connext should choose an appropriate host, app, instance or object ID automatically.
If this special value is assigned to com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_host_id, com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_app_id, com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_instance_id, com.rti.dds.infrastructure.DataWriterProtocolQosPolicy.rtps_object_id or com.rti.dds.infrastructure.DataReaderProtocolQosPolicy.rtps_object_id RTI Connext will assign the ID automatically.
The actual ID value is chosen when the QoS is set: the QoS returned from com.rti.dds.domain.DomainParticipant.get_qos, com.rti.dds.publication.DataWriter.get_qos or com.rti.dds.subscription.DataReader.get_qos will never have this value.
◆ participant_id
| int participant_id |
A value used to distinguish among different participants belonging to the same domain on the same host.
Determines the unicast port on which meta-traffic is received. Also defines the default unicast port for receiving user-traffic for DataReaders and DataWriters (can be overridden by the com.rti.dds.subscription.DataReaderQos.unicast or com.rti.dds.publication.DataWriterQos.unicast).
For more information on port mapping, please refer to com.rti.dds.infrastructure.RtpsWellKnownPorts_t.
Each com.rti.dds.domain.DomainParticipant in the same domain and running on the same host, must have a unique participant_id. The participants may be in the same address space or in distinct address spaces.
A negative number (-1) means that RTI Connext will automatically resolve the participant ID as follows.
- RTI Connext will pick the smallest participant ID based on the unicast ports available on the transports enabled for discovery.
- RTI Connext will attempt to resolve an automatic port index either when a DomainPartcipant is enabled, or when a DataReader or DataWriter is created. Therefore, all the transports enabled for discovery must have been registered by this time. Otherwise, the discovery transports registered after resolving the automatic port index may produce port conflicts when the DomainPartcipant is enabled.
[default] -1 [automatic], i.e. RTI Connext will automatically pick the participant_id, as described above.
[range] [>= 0], or -1, and does not violate guidelines stated in com.rti.dds.infrastructure.RtpsWellKnownPorts_t.
◆ rtps_well_known_ports
| RtpsWellKnownPorts_t rtps_well_known_ports |
Configures the RTPS well-known port mappings.
Determines the well-known multicast and unicast port mappings for discovery (meta) traffic and user traffic.
[default] com.rti.dds.infrastructure.RtpsWellKnownPorts_t.INTEROPERABLE_RTPS_WELL_KNOWN_PORTS
◆ rtps_host_id
| int rtps_host_id |
The RTPS Host ID of the domain participant.
A specific host ID that is unique in the domain.
[default] com.rti.dds.infrastructure.WireProtocolQosPolicy.RTPS_AUTO_ID. The default value is interpreted as follows:
If com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_auto_id_kind is equal to com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_IP, the value will be interpreted as the IPv4 address of the first up and running interface of the host machine.
If com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_auto_id_kind is equal to com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_MAC, the value will be interpreted as the first 32 bits of the MAC address assigned to the first up and running interface of the host machine.
If com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_auto_id_kind is equal to com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_UUID, the value will be the first 32 bits of the GUID prefix assigned by the UUID algorithm.
[range] [0,0xffffffff]
◆ rtps_app_id
| int rtps_app_id |
The RTPS App ID of the domain participant.
A participant specific ID that, together with the rtps_instance_id, is unique within the scope of the rtps_host_id.
If a participant dies and is restarted, it is recommended that it be given an app ID that is distinct from the previous one so that other participants in the domain can distinguish between them.
[default] com.rti.dds.infrastructure.WireProtocolQosPolicy.RTPS_AUTO_ID. The default value is interpreted as follows:
If com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_auto_id_kind is equal to com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_IP the value will be the process (or task) ID.
If com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_auto_id_kind is equal to com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_MAC the value will be the last 32 bits of the MAC address assigned to the first up and running interface of the host machine.
If com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_auto_id_kind is equal to com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_UUID, the value will be the middle 32 bits of the GUID prefix assigned by the UUID algorithm.
[range] [0,0xffffffff]
◆ rtps_instance_id
| int rtps_instance_id |
The RTPS Instance ID of the com.rti.dds.domain.DomainParticipant.
This is an instance-specific ID of a participant that, together with the rtps_app_id, is unique within the scope of the rtps_host_id.
If a participant dies and is restarted, it is recommended that it be given an instance ID that is distinct from the previous one so that other participants in the domain can distinguish between them.
[default] com.rti.dds.infrastructure.WireProtocolQosPolicy.RTPS_AUTO_ID. The default value is interpreted as follows:
If com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_auto_id_kind is equal to com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_IP, a counter is assigned that is incremented per new participant. For VxWorks-653, the first 8 bits are assigned to the partition id for the application.
If com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_auto_id_kind is equal to com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_MAC, the first 24 bits are assigned to the application/task identifier and the last 8 bits are assigned to a counter that is incremented per new paricipant.
If com.rti.dds.infrastructure.WireProtocolQosPolicy.rtps_auto_id_kind is equal to com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_UUID, the value will be the last 32 bits of the GUID prefix assigned by the UUID algorithm.
[range] [0,0xffffffff] NOTE: If you use com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_MAC as rtps_auto_id_kind and you decide to manually handle the rtps_instance_id field, you must ensure that both the two parts are non-zero, otherwise the middleware will take responsibility for them. We recommend that you always specify the two parts separately in order to avoid errors. (examples)
◆ rtps_reserved_port_mask
| int rtps_reserved_port_mask |
Specifies which well-known ports to reserve when enabling the participant.
Specifies which of the well-known multicast and unicast ports will be reserved when the DomainParticipant is enabled. Failure to allocate a port that is computed based on the com.rti.dds.infrastructure.RtpsWellKnownPorts_t will be detected at this time, and the enable operation will fail.
[default] com.rti.dds.infrastructure.RtpsReservedPortKind.MASK_DEFAULT
◆ rtps_auto_id_kind
| WireProtocolQosPolicyAutoKind rtps_auto_id_kind = WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_UUID |
Kind of auto mechanism used to calculate the GUID prefix.
[default] com.rti.dds.infrastructure.WireProtocolQosPolicyAutoKind.RTPS_AUTO_ID_FROM_UUID
◆ compute_crc
| boolean compute_crc |
Adds RTPS CRC submessage to every message when this field is set to com.rti.dds.infrastructure.true.
The computed CRC covers the entire RTPS message excluding the RTPS header.
[default] com.rti.dds.infrastructure.false
◆ check_crc
| boolean check_crc |
Checks if the received RTPS message is valid by comparing the computed CRC with the received RTPS CRC submessage when this field is set to com.rti.dds.infrastructure.true.
com.rti.dds.infrastructure.WireProtocolQosPolicy.compute_crc must be enabled at the publishing application for validating the message at the subscribing application.
[default] com.rti.dds.infrastructure.false