TransportMulticastMappingQosPolicy Class Reference
[TRANSPORT_MULTICAST]

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:

List of all members.

Public Attributes
final TransportMulticastMappingSeq	value
	A sequence of multicast communications settings.

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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

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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.