Multicast applications - Minimalist Internet Multicast Service Model

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Multicast aplications:
- Internet radio broadcast,
- Ttelevision broadcast,
- Video conferencing,
- Stock market tickers,
- Slide presentations,
- File transfers to multiple locations,
- Dynamic web page updates,
- Online gaming,
- News feeds,
- Chatrooms, and more.

There are three general categories of multicast
applications:

One-to-Many (1toM): A single host sending to two or more (n)
receivers

Many-to-Many (MtoM): Any number of hosts sending to the same
multicast group address, as well as receiving from it

Many-to-One (Mto1): Any number of receivers sending data back to a
(source) sender via unicast or multicast

IP Multicast is a technique for many-to-many communication over an IP infrastructure. It scales to a larger receiver population by not requiring prior knowledge of who or how many receivers there are. Multicast utilizes 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 IP Multicast model requires a great deal more state inside the network than the IP unicast model of best-effort delivery does, and this has been the cause of some criticism. Also, no mechanism has yet been demonstrated, that would allow the IP Multicast model to scale to millions of senders and millions of multicast groups and, thus, it is not yet possible to make fully-general multicast applications practical in the commercial Internet.

As of 2006, most efforts at scaling multicast up to large networks have concentrated on the simpler case of single-source multicast, which seems to be more computationally tractable.

For both these reasons, and also reasons of economics, IP Multicast is not in general use in the commercial Internet.

Other multicast technologies not based on IP Multicast are more widely used. These include Internet Relay Chat (IRC) and PSYC, which are more pragmatic and scale better for large numbers of small groups. IRC implements a spanning tree across its overlay network whereas PSYC uses custom multicast strategies per conference. Also some Peer-to-peer technologies employ the multicast concept when distributing content to multiple recipients.

IP Multicast is however, widely deployed in Enterprises, Commercial Stock Exchanges and Multimedia content delivery networks, where it is used for efficiently utilizing the networks resources for one to many or many to many communication. For example, a common Enterprise use of IP Multicast is for IP TV applications like distance learning or televising company meetings. In stock exchanges it is used for distributing stock trading data. In content delivery networks it is used to provide commercial television to a set of subscribers over IP infrastructure.

More info below.

1 One-to-Many Applications

One-to-Many (1toM) applications have a single sender, and multiple
simultaneous receivers.

When people think of multicast, they most often think of broadcast-
based multimedia applications: television (video) and radio (audio).
This is a reasonable analogy and indeed these are significant
multicast applications, but these are far from the extent ...