This condition eventually creates a source-based multicast distribution tree.

In this case, the router closest to the receiverhost receives a multicast PIM join message from the receiver device requesting multicast for a specific group.

The RP then sends join messages upstream toward the source host.PIM.

So when a host leaves a multicast group its sends out a leave group message at 224.0.0.2(All routers).

If no IGMP report is received within 3 seconds then that particular group will timeout.

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Therefore, if a host (a process in a host) wants to receive a multicast message sent to a particular group, it needs to somehow listens to all messages sent to that particular group.

It describes the multicast protocols such as DVMRP, MOSPF, and PIM as well as the algorithms used in these protocols such as RPM and CBT.

The Multicast Backbone (MBone) is also investigated in this paper.

Although, this can be done by sending different unicast (point-to-point) messages to each of the destination hosts, there are many reasons which make having the multicasting capability desirable.

There are many applications like stock ticker applications which are required to transmit packets to hundreds of stations.

The packets sent to these stations share a group of links on their paths to their destinations.

Since multicasting requires the transmission of only a single packet by the source and replicates this packet only if it is necessary (at forks of the multicast delivery tree), multicast transmission can conserve the so much needed network bandwidth.

Another place where multicasting can be very helpful is in resource discovery.

There are many applications in which a host needs to find out whether a certain type of service is available or not.

Using multicast messages and sending the query to those hosts which are potentially capable of providing this service would be of great help.

Although some applications use multicast messages to transmit a packet to a group of hosts residing on the same network, there is no reason to impose this limitation.

Discovering the local domain-name server is where multicast messages need to be forwarded on remote networks if there is less than one server per network.

The scope of multicast packets can be limited by using the time-to-live (TTL) field of these packets.

Another important feature of multicasting is its support for datacasting applications.

The audio and video signals are captured, compresses and transmitted to a group of receiving stations.

Instead of using a set of point-to-point connections between the participating nodes, multicasting can be used for distribution of the multimedia data to the receivers.

In real world stations may join or leave an audio-cast or a video-cast at any time.

The flexibility in joining and leaving a group provided by multicasting can make the variable membership much easier to handle.

By definition a multicast message is sent from a source to a group of destination hosts.

In IP multicasting, multicast groups have an ID called multicast group ID.

Whenever a multicast message is sent out, a multicast group ID specifies the destination group.

These group IDs are essentially a set of IP addresses called Class D.

Multicast Group