Multimedia
Conferencing Over IP
In the IP environment, many
obstacles stand in the way
A
lthough videoconferencing has very successfully taken off over ISDN lines
particularly in certain vertical markets such as finance the time, trouble
and investment required to install and use it have been amongst the factors
that have restricted its widespread adoption. In particular, the need to install ISDN
of establishing a video
lines for H.320 videoconferencing often three lines were used, to provide six
connection.
channels for 384 Kbits/sec connections was a major inhibitor, and severely curbed
flexibility.
By Andrew Ward
By contrast, the Internet provides almost universal IP connectivity, and should make
it easy to connect virtually any two conferencing endpoints. It also removes the fixed
bandwidth limitation of ISDN lines. However, this and other advantages of IP are
only gradually having an impact, and according to Conferencing Markets &
Strategies 2001 October 2001" by Wainhouse Research, it won't be until the end of
2003 that IP calls will represent 50% of all videoconferencing calls made.
Slow Growth
This slow growth can be partly attributed to the technical issues surrounding
multimedia conferencing over IP. Anyone attempting to establish a video connec
tion across the Internet even between just two endpoints, never mind a large scale
conference may have encountered one or several of the numerous difficulties that
can attend such an endeavour. Although the H.323 standard for multimedia calls
over IP networks is now generally accepted, that doesn't solve all the problems.
Fortunately, academics and equipment vendors have been working to overcome
the remaining issues, and with judicious choice of hardware and software systems,
they can all be avoided.
Network Compatibility
The first and most obvious point is that for some organisations, it will be economi
cally undesirable to move to IP overnight, owing to an existing investment in ISDN
endpoint equipment. Also, some locations may not yet be served by high bandwidth
IP connections and are therefore restricted to ISDN. And if a videoconference is held
that includes external participants, then clearly the organisation has no control over
what technologies they may want or need to use, and so once again ISDN may enter
the picture.
This problem is solved by the availability of videoconferencing servers, also known
as multipoint conference (or control) units, that provide support for both network
types. Sometimes this is accomplished via plug in cards, and in some cases existing
ISDN videoconferencing servers can be upgraded to include IP interfaces simply by
the addition of new connection cards. Over time, as endpoints switch technologies
most endpoints today have dual network capabilities, in fact ISDN cards can be
removed to make way for further IP adapters. An alternative solution is to use an
ISDN to H.323 conversion gateway that can convert multimedia data between the
two networks and standards.
IP Addressing
IP addressing probably provides the biggest challenge to anyone attempting to link
two or more users. To make a connection between two endpoints means knowing
both IP addresses. However, in many cases an IP address will be inaccessible
Issue 138:January 2002
PC Network Advisor
File: T1848.1
page 11
Tutorial:Internet
www.pcnetworkadvisor.com
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