The NIIF Program introduced IP multicast service in the HBONE network with the aim of supporting new applications and their localization in 2002.

In the following part we give a brief introduction of the IP multicast technology and the related most important freeware applications.

What is multicast?

The IP multicast technology is to provide the infrastructural background of group communication providing the efficient and economical utilization of the network resources. Apart from giving advantages to network operators and Internet providers it also provides new applications to users.

So the multicast technology provides communication and data transfer in user-created groups. One Multicast Group can have arbitrary number of users (Group Members) no matter where they are on the Internet. Users can optionally create their own groups and they can join or leave existing groups. When a Group Member wants to communicate with the other Group Members then they send the data to the address of the group and every member gets it.

We compared the traditional IP based data stream (Unicast, left side) and the multicast (right side) technology on the following diagram. A multimedia content (e.g. web TV) transfer, so called streaming server can be seen on both diagrams and also three monitors that symbolize the content demanding users. In a traditional case the users connect to the streaming server which sends completely separated streams to every user. This is shown by the red arrows. The diagram shows the disadvantage of the traditional unicast technology: there is the same data stream on different parts of the network. This configuration uses the network resources (nodes, bandwidth) unnecessarily and loads the streaming servers heavily.

However, multicast technology distributes the announced streams without redundancy to the Group Members as it is shown on the right diagram above. We can see that the distribution of the data streams is not processed by the server but it is shared by the network nodes. So the streaming server sends only one stream that gets to arbitrary users through joining the group of the streaming server which provides the optimal utilization of the network resources and media servers.

Multicast groups

Multicast groups can be identified by special network addresses, which come from in case of IPv4 the territory between 224.0.0.0 - 239.255.255.255 network addresses. One multicast group has only one group address which represents all members of the group and the data sent to this group address gets to the other members of the group.

It is very important that multicast groups are created and ceased dynamically and users also dynamically by request can join or leave groups. Certain contents of group addresses are usually announced on the Internet which can happen in many ways, e.g. through a webpage or a special protocol (SDP).

Multicast applicatios

The multicast technology makes possible the use of the following effective abd simple applications:

  • Video conferences
  • Live broadcasting
  • Web TV, web radio
  • Video-on-demand
  • E-learning
  • Whiteboard data change

Software

In the following we specify what kind of software is needed to use the services offered by the IP multicast.

Operating systems:

The widespread operating systems that are used nowadays contain the necessary drivers for the multicast technology:

  • Linux
  • FreeBSD, NetBSD, OpenBSD
  • Solaris
  • Windows 95 – limited availability
  • Windows 98/ME
  • Windows NT
  • Windows 2000/XP
  • etc.

Applications

In the following part we introduce briefly the most important multicast applications and give their internet address.

MBone tools:

The most important group of multicast applications is formed by the so called MBone tools. Their main advantage that they run on every operating system (Solaris, SunOS, Irix, Linux, FreeBSD, Windows), moreover they mostly contain IPv6 support.

Several conferences and audio and video programs are broadcasted on MBone(“Multicast Internet”).

The MBone tools were developed by the UCL Network and Multimedia Research Group and they can be downloaded free from the following address:

http://www-mice.cs.ucl.ac.uk/multimedia/software/