Yes it is. An example of how to select the reliable QoS for your data is shown in the Tutorial example that comes with the Community Edition. The Chatter app for example sends its chat messages as reliable data. On the wire, they will be distributed by means of a reliable multicast protocol using UDP.
Hope this helps, Reinier
posted on Monday, April 12, 2010 - 06:12 am
What is the multicast group in the context of DDS? Is it the list of subscribers listening on one particular Topic?
Also, if we are making use of TCP connection do we still need to enable reliable QoS since TCP is inherently a reliable transport mechanism. Also would multicasting be possible using TCP?
In case you are interested, OpenDDS supports a reliable multicast transport as well. I have attempted to answer your specific questions below:
> What is the multicast group in the context of DDS? Is it the list of subscribers listening on one particular Topic?
In OpenDDS, multicast groups may be configured by the user on a per-transport basis. Currently, multicast groups more or less correspond with a domain; there is no arbitrary restriction on the number of topics used.
That said, if you wish to segregate your traffic further, you may do so by creating multiple transports and attaching to a set of publishers and subscribers to a particular topic.
One different to mention is transport reliability is configured at the transport rather than through the ReliabilityQosPolicy. This permits OpenDDS to multiplex reliable and best-effort samples across the same link which can significantly increase performance.
> Also would multicasting be possible using TCP?
Unfortunately, no. IP multicast is a many-to-one routing topology; it is connectionless. UDP/IP is probably the most common protocol which is used in conjunction with multicast.