H.325
is a new multimedia communication system currently under development
in the ITU-T SG16. It aims to revolutionize the way in which users
will be able to communicate, bringing together a number of real-time
communication technologies that might be employed on multiple physical
devices.
H.323
is the dominant protocol for IP videoconferencing on the market.
Many products from many vendors interoperate to form complex systems for
education and industry. H.323 interoperates particulary well with H.320
and VoIP applications, so that a single
infrastructure can support voice and video both on the IP network
and PSTN.
H.320
H.320
supports videoconferencing over ISDN. This protocol has a long
and successful history. Sometimes considered a "legacy" protocol,
private industry still relies heavily on this protocol, and it provides
an important bridge to the
PSTN.
The IETF's Session Initiation Protocol
for IP is finding applications in videoconferencing, especially in the
software desktop endpoint with integrated instant messaging space.
Internetworking products between H.323 and SIP are starting to appear on
the market.
H.248, also referred to as Megaco, is the industry standard
media gateway control protocol, allowing a media gateway controller to
control all aspects of media flow on a gateway device.
MGCP, or Media Gateway Control Protocol, is similar in
function to H.248, but is simpler and more narrowly focused on
enabling a softswitch to control PSTN gateway devices.
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XMPP
The Extensible Messaging and Presence Protocol (XMPP) is
the IETF standard for instant messaging. It is based on XML
and widely supported in the industry, largely thanks to its early
introduction as an enterprise solution and work to make the platform
completely open.
H.239
H.239
allows multiple video streams to be transmitted in a single
session. This is commonly used for applications where it is desired
to display a picture of a presenter, as well as a shot of a
classroom, or computer display.
H.321
H.321
provides support for videoconferencing over ATM. A number of
successful systems have been built upon this technology, though the
general scarce deployment of ATM limits the overall reach of these systems.
H.324
provides support for low bandwidth videoconferencing over PSTN.
This protocol enjoys success particularly in Asian mobile markets,
as it has been chosen as the protocol of choice for 3G mobile video
communications.
H.350
provides directory services for a variety of conferencing
protocols including H.323, SIP, H.320 and non-standard protocols. It
makes it easy to find and dial users, support identity
management to allow for high scalability in deployments,
and store call handling preferences. You can
try out a sample directory search at the
ViDeNet Directory of Directories
portal. A brochure on H.350 is available for
vendors and
universities.
T.120
is a data collaboration conferencing standard often used
in conjunction with videoconferencing protocols to provide
application sharing, electronic whiteboarding, file transfer,
text chat, and other data services.
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