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Multicast service

The NIIF 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/

The MBone tool package contains many small programs. In the following we are going to introduce the most important ones:

Session Directory Tool (SDR)

SDR can be used to join multicast groups or create your own ones. The program can display the multicast groups available from that network and announce the groups created by the user on the Internet. By clicking on the displayed multicast group SDR automatically starts the MBone tool (e.g.. RAT, VIC, WB, etc.) that is relevant to the content announced by the given multicast. You can find the list of the announced broadcasts here.

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

Robust Audio Tool (RAT)

It enables us to take part in multicast audio conferences and we can create audio streams with it.

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

Videoconferencing Tool (VIC)

With the help of the VIC and a webcam we can take part in video conferences. If we do not have a camera we can still take a look in some public conferences or watch multicast broadcasts.

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

Whiteboard Tool (WB)

With the help of the WB we can communicate through drawings across the network

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

MPEG4IP:

Toos for creating and streaming MPEG4 content. We can broadcast MPEG4 content from a disk or live. The freely downloadable multiplatform Darwin Streaming Server, which was developed by Apple, can be used with MPEG4IP.

Download: http://mpeg4ip.sourceforge.net/

VideoLAN:

A multiplatform streaming software that enables DVD, DivX, VCD, MPEG1 és MPEG2 video and live broadcasts. Supported platforms: Linux, Windows, Mac OS X, BeOS, BSD, Solaris, QNX, iPaq. It has IPv6 support!

Download: http://www.videolan.org/

Cisco IPTV:

Streaming server software for MPEG, Windows Media, AVI, MP3 or live broadcasts by Cisco Systems. The demo version can be ordered by post.

Info: http://www.cisco.com/warp/public/cc/pd/mxsv/iptv3400/index.shtml

Related pages

• For more information on IP multicast technology the GÉANT network multicast page can be a good starting point
• : http://www.dante.net/nep/GEANT-MULTICAST/

• Multicast in Wikipedia

Troubleshooting

The HBone multicast service is on test run right now so it is possible that in some network segments the service is down or not working properly. If you experience problems and it is not in the network tools of the local institution but in the HBONE tools then submit the problem to the net-admin@niif.hu e-mail address.