The Conference Multiplexing and Management Centre
Where possible, the MICE partners and the Internet community are
providing multimedia services by applications that multicast directly
to all sites in the conference, with no centralised conference control
or multiplexing centre. This is very desirable to achieve good scaling
properties, but there are many reasons why many multi-point
conferences will require a centralised Conference Management and
Multiplexing Centre (CMMC). These reasons include:
- the mechanism for allowing communities to come in from different
networks (e.g. EUROPANET, UK-US Pipe, EBONE and ISDN)
- a way to relay between different protocol and coding standards
- the incorporation of stations with reduced facilities (e.g. Basic
Rate ISDN), video workstations without hardware Codecs, in higher
quality and hence data rate conferences
- a centre for multiplexing video and voice
- a centre for conference reservation, resource control and
management
- a centre for ensuring multicast of the shared workspace data, and
possibly the voice, to all conferees
- a centre of expertise - remote users only need to know how to
connect to the CMMC, and not how to interwork with (possibly
incompatible) remote sites - the CMMC hides this extra functionality
The MICE philosophy is not that all video and audio streams should
be forwarded through the CMMC, as this would negate many of the
benefits of multicast and distributed conferencing applications. Only
streams that actually require functional modification in the CMMC are
routed directly through it.
The above figure shows a typical conference configuration. The
three workstation simple multicast their video streams directly, and
display the results in windows on the workstation screens. However,
the three conference rooms using hardware codecs cannot display more
than one stream at a time, and so require the multiplexing facilities
of the CMMC. The CMMC also allows these conference rooms to interwork
at greater frame rates and quality than the workstations can manage,
whilst also remixing this video down to lower rates to be multicast to
the workstation based sites. The CMMC also provides a bridge onto the
ISDN network to allow sites without good internet connectivity to
participate. Clearly any ISDN based conference has severe scaling
limitations, but in this manner, a number of ISDN sites can be
incorporated into conferences that do scale gracefully.
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