DDS_RtpsReliableReaderProtocol_t Struct Reference

Qos related to reliable reader protocol defined in RTPS. More...

Data Fields
struct DDS_Duration_t	min_heartbeat_response_delay
	The minimum delay to respond to a heartbeat.
struct DDS_Duration_t	max_heartbeat_response_delay
	The maximum delay to respond to a heartbeat.
struct DDS_Duration_t	heartbeat_suppression_duration
	The duration a reader ignores consecutively received heartbeats.
struct DDS_Duration_t	nack_period
	The period at which to send NACKs.
DDS_Long	receive_window_size
	The number of received out-of-order samples a reader can keep at a time.
struct DDS_Duration_t	round_trip_time
	The duration from sending a NACK to receiving a repair of a sample.
struct DDS_Duration_t	app_ack_period
	The period at which application-level acknowledgment messages are sent.
struct DDS_Duration_t	min_app_ack_response_keep_duration
	Minimum duration for which application-level acknowledgment response data is kept.
DDS_Long	samples_per_app_ack
	The minimum number of samples acknowledged by one application-level acknowledgment message.

Detailed Description

Qos related to reliable reader protocol defined in RTPS.

It is used to config reliable reader according to RTPS protocol.

Properties:

RxO = N/A
Changeable = NO

QoS:

DDS_DataReaderProtocolQosPolicy DDS_DiscoveryConfigQosPolicy

Field Documentation

struct DDS_Duration_t DDS_RtpsReliableReaderProtocol_t::min_heartbeat_response_delay

The minimum delay to respond to a heartbeat.

When a reliable reader receives a heartbeat from a remote writer and finds out that it needs to send back an ACK/NACK message, the reader can choose to delay a while. This sets the value of the minimum delay.

[default] 0 seconds

[range] [0, 1 year], <= max_heartbeat_response_delay

struct DDS_Duration_t DDS_RtpsReliableReaderProtocol_t::max_heartbeat_response_delay

The maximum delay to respond to a heartbeat.

When a reliable reader receives a heartbeat from a remote writer and finds out that it needs to send back an ACK/NACK message, the reader can choose to delay a while. This sets the value of maximum delay.

[default] The default value depends on the container policy:

• For DDS_DataReaderProtocolQosPolicy::rtps_reliable_reader: 0.5 seconds
  
• For DDS_DiscoveryConfigQosPolicy::publication_reader: 0 seconds
  
• For DDS_DiscoveryConfigQosPolicy::subscription_reader: 0 seconds
  
• For DDS_DiscoveryConfigQosPolicy::participant_message_reader: 0 seconds
  

[range] [0, 1 year], >= min_heartbeat_response_delay

struct DDS_Duration_t DDS_RtpsReliableReaderProtocol_t::heartbeat_suppression_duration

The duration a reader ignores consecutively received heartbeats.

When a reliable reader receives consecutive heartbeats within a short duration that will trigger redundant NACKs, the reader may ignore the latter heartbeat(s). This sets the duration during which additionally received heartbeats are suppressed.

[default] 0.0625 seconds

[range] [0, 1 year],

struct DDS_Duration_t DDS_RtpsReliableReaderProtocol_t::nack_period

The period at which to send NACKs.

A reliable reader will send periodic NACKs at this rate when it first matches with a reliable writer. The reader will stop sending NACKs when it has received all available historical data from the writer.

[default] 5 seconds

[range] [1 nanosec, 1 year]

DDS_Long DDS_RtpsReliableReaderProtocol_t::receive_window_size

The number of received out-of-order samples a reader can keep at a time.

A reliable reader stores the out-of-order samples it receives until it can present them to the application in-order. The receive window is the maximum number of out-of-order samples that a reliable reader keeps at a given time. When the receive window is full, subsequently received out-of-order samples are dropped.

[default] 256

[range] [>= 1]

struct DDS_Duration_t DDS_RtpsReliableReaderProtocol_t::round_trip_time

The duration from sending a NACK to receiving a repair of a sample.

This round-trip time is an estimate of the time starting from when the reader sends a NACK for a specific sample to when it receives that sample. For each sample, the reader will not send a subsequent NACK for it until the round-trip time has passed, thus preventing inefficient redundant requests.

[default] 0 seconds

[range] [0 nanosec, 1 year]

struct DDS_Duration_t DDS_RtpsReliableReaderProtocol_t::app_ack_period

The period at which application-level acknowledgment messages are sent.

A DDS_DataReader sends application-level acknowledgment messages to a DDS_DataWriter at this periodic rate, and will continue sending until it receives a message from the DDS_DataWriter that it has received and processed the acknowledgment and an AppAckConfirmation has been received by the DDS_DataReader. Note: application-level acknowledgment messages can also be sent non-periodically, as determined by DDS_RtpsReliableReaderProtocol_t::samples_per_app_ack.

[default] 5 seconds

[range] [1 nanosec, 1 year]

struct DDS_Duration_t DDS_RtpsReliableReaderProtocol_t::min_app_ack_response_keep_duration

Minimum duration for which application-level acknowledgment response data is kept.

The user-specified response data of an explicit application-level acknowledgment (called by DDS_DataReader_acknowledge_sample or DDS_DataReader_acknowledge_all) is cached by the DDS_DataReader for the purpose of reliably resending the data with the acknowledgment message. After this duration has passed from the time of the first acknowledgment, the response data is dropped from the cache and will not be resent with future acknowledgments for the corresponding sample(s).

[default] 0 sec

[range] [0 sec, 1 year]

DDS_Long DDS_RtpsReliableReaderProtocol_t::samples_per_app_ack

The minimum number of samples acknowledged by one application-level acknowledgment message.

This setting applies only when DDS_ReliabilityQosPolicy::acknowledgment_kind = DDS_APPLICATION_EXPLICIT_ACKNOWLEDGMENT_MODE or DDS_APPLICATION_AUTO_ACKNOWLEDGMENT_MODE

A DDS_DataReader will immediately send an application-level acknowledgment message when it has at least this many samples that have been acknowledged. It will not send an acknowledgment message until it has at least this many samples pending acknowledgment.

For example, calling DDS_DataReader_acknowledge_sample this many times consecutively will trigger the sending of an acknowledgment message. Calling DDS_DataReader_acknowledge_all may trigger the sending of an acknowledgment message, if at least this many samples are being acknowledged at once.

This is independent of the DDS_RtpsReliableReaderProtocol_t::app_ack_period, where a DDS_DataReader will send acknowledgement messages at the periodic rate regardless.

When this is set to DDS_LENGTH_UNLIMITED, then acknowledgement messages are sent only periodically, at the rate set by DDS_RtpsReliableReaderProtocol_t::app_ack_period.

[default] 1

[range] [1, 1000000], or DDS_LENGTH_UNLIMITED