TransportMulticastMappingQosPolicy Class Reference

Specifies the multicast address on which a com.rti.dds.subscription.DataReader wants to receive its data. It can also specify a port number as well as a subset of the available (at the com.rti.dds.domain.DomainParticipant level) transports with which to receive the multicast data. More...

Inheritance diagram for TransportMulticastMappingQosPolicy:

Public Attributes
final TransportMulticastMappingSeq	value
	A sequence of multicast communications settings.
Public Attributes inherited from QosPolicy
final QosPolicyId_t	id
	The ID of this QoS policy.
final String	policy_name
	The name of this QoS policy.

Additional Inherited Members
Public Member Functions inherited from Struct
abstract boolean	equals (Object obj)
abstract int	hashCode ()
String	toString ()
Protected Member Functions inherited from Struct
	Struct ()
abstract void	pull_from_nativeI (long native_status)
abstract void	push_to_nativeI (long native_status)

Detailed Description

Specifies the multicast address on which a com.rti.dds.subscription.DataReader wants to receive its data. It can also specify a port number as well as a subset of the available (at the com.rti.dds.domain.DomainParticipant level) transports with which to receive the multicast data.

By default, a com.rti.dds.publication.DataWriter will send individually addressed packets for each com.rti.dds.subscription.DataReader that subscribes to the topic of the DataWriter – this is known as unicast delivery. Thus, as many copies of the data will be sent over the network as there are DataReaders for the data. The network bandwidth used by a DataWriter will thus increase linearly with the number of DataReaders.

Multicast addressing (on UDP/IP transports) allows multiple DataReaders to receive the same network packet. By using multicast, a com.rti.dds.publication.DataWriter can send a single network packet that is received by all subscribing applications. Thus the network bandwidth usage will be constant, independent of the number of DataReaders.

Coordinating the multicast address specified by DataReaders can help optimize network bandwidth usage in systems where there are multiple DataReaders for the same com.rti.dds.topic.Topic.

Entity:

com.rti.dds.subscription.DataReader

Properties:

RxO = N/A
Changeable = NO

Member Data Documentation

final TransportMulticastMappingSeq value

A sequence of multicast communications settings.

An empty sequence means that multicast is not used by the entity.

The RTPS wire protocol currently limits the maximum number of multicast locators to four.

[default] Empty sequence.