What is Multicasting?

Grid Version: 11.2
OS : AIX 6.1
I come across articles on RAC on AIX where the term Multicasting is frequently referenced. (For eg: thread like below)
NICs for Private Interconnect redundancy
When I googled it , i found articles like below which hasn't got anything to do with RAC networking at all
http://en.wikipedia.org/wiki/Multicast
Any idea what Multicasting is and how it is related to RAC?

Hi,
IP multicast is a technique for one-to-many communication over an IP infrastructure in a network. It scales to a larger receiver population by not requiring prior knowledge of who or how many receivers there are. Multicast uses network infrastructure efficiently by requiring the source to send a packet only once, even if it needs to be delivered to a large number of receivers. The nodes in the network take care of replicating the packet to reach multiple receivers only when necessary.
The most common transport layer protocol to use multicast addressing is User Datagram Protocol (UDP). By its nature, UDP is not reliable—messages may be lost or delivered out of order. Reliable multicast protocols such as Pragmatic General Multicast (PGM) have been developed to add loss detection and retransmission on top of IP multicast.
The multicast addresses are in the range 224.0.0.0 through 239.255.255.255. The range of addresses between 224.0.0.0 and 224.0.0.255, inclusive, is reserved for the use of routing protocols and other low-level topology discovery or maintenance protocols, such as gateway discovery and group membership reporting. Multicast routers should not forward
any multicast datagram with destination addresses in this range, regardless of its TTL.
http://www.iana.org/assignments/multicast-addresses/multicast-addresses.xml
Oracle Grid Infrastructure 11.2.0.2 introduces a new feature called "Redundant Interconnect Usage", which provides an Oracle internal mechanism to make use of physically redundant network interfaces for the Oracle (private) interconnect.
As part of this new feature, multicast based communication on the private interconnect is utilized to establish communication with peers in the cluster on each startup of the stack on a node.
Once the connection with the peers in the cluster has been established, the communication is switched back to unicast. Per default, the 230.0.1.0 address (port 42424) on the private interconnect network is used for multicasting. Another IP can be enabled using the patch mentioned below, if it is determined that using the 230.0.1.0 IP causes the multicast communication to fail. Multicasting on either of these IPs and the respective port must, however, be enabled and functioning across the network and on each node meant to be part of the cluster. If multicasting is not enabled as required, nodes will fail to join the cluster with the symptoms discussed.
Regards,
Levi Pereira
Edited by: Levi Pereira on May 31, 2012 2:20 PM

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IN addition to what is mentioned here.
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Video Conferencing in internet

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Please help! Thank you in advance!

it appears you posted an identical message in two threads. i've responded in the other thread:
http://forums.adobe.com/message/3701380#3701380

Copper multicasting - what is actually going on

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What To Expect With MDT 2013 Multicast from WDS 2008 R2?

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What should the multicast rate be set at?

what should the multicast rate be set at in the wireless options box?
mine was set at the default of 6 Mbps but could be set higher: 9, 12, 18 & 24Mbps.
Any care to explain what it does?
Regards Simon

That sets the minimum date rate which is valid for a connection. If a connection can't maintain that rate, the connection will drop.
A side effect of setting it higher is that your usable range will decrease. You will need to be closer to the base station to maintain a higher data rate.

What is Multicasting?

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