[h323plus] [Openh323-devel] help in creating WhiteBoard application using Opal

Paul E. Jones paulej at packetizer.com
Tue Oct 30 02:21:09 EDT 2007

Simon, Vishak,

If there was interest to address the NAT/FW issues in T.120, it would
certainly be possible.  We would need to change the T.123 layer (transport
specification) to enable, for example, transport via UDP, DTLS, or similar.
The other alternative would be to employ TCP relay servers in public
networks, which I suspect would not be preferred.  The problem is that
applications like app sharing can consume a lot of bandwidth, all of which
would be flowing through that box.

In any case, the biggest problem T.120 faced, in my opinion, was not
firewalls, but simply the business model.  T.120 requires installation of
software on the PC to provide functionality that one can do with a web
browser.  For whatever reason, people preferred not to have to install
software.  However, that mentality is now changing since folks are
installing software for voice, anyway.

The other hurdle was that Microsoft released NetMeeting, which used T.120.
It was extremely hard for any company to justify creating a product in that
market space when Microsoft was giving it away for free.  Now that MS is no
longer giving it away for free with Vista, perhaps it opens the door of
opportunity again?


> -----Original Message-----
> From: h323plus-bounces at lists.packetizer.com [mailto:h323plus-
> bounces at lists.packetizer.com] On Behalf Of Simon Horne
> Sent: Tuesday, October 30, 2007 12:49 AM
> To: Discussion on enhancements and development issues with the OpenH323
> library
> Cc: H323plus
> Subject: Re: [h323plus] [Openh323-devel] help in creating WhiteBoard
> application using Opal
> FYI opal is now opalVoIP and openH323 is continuing on as H323plus.
> OpenH323
> (the project "in general" is no longer being actively developed.
> T.120 support in Opal is at the same level it as it is in OpenH323 very
> very
> basic.
> There is a project on sourceforge which has been abandoned for many
> many
> years based on OpenH323.
> http://sourceforge.net/projects/opent120/
> T.120 development in general has pretty much stopped for various
> reasons
> including NAT issues. It uses TCP and you cannot easily use STUN,
> H.460.18/19 or emerging NAT technologies like P2Pnat to traverse NATs.
> That does not mean T.120 development has ceased.
> In h323plus www.h323plus.org we have added H.239 support or extended
> video
> to perform the same operation as T.120 app/whiteboarding would perform
> except over UDP so it can traverse NATs. It utilises the existing video
> plugin codecs to create a secondary video channel for the purpose of
> App
> Sharing. This work is continuing with the addition of app sharing
> controls
> such as H.249 collaberaton controls (remote userinputs, mouse movements
> and
> keystrokes).
> T.124 or Generic conference controls has also been resurrected and is
> being
> tunnelled through H.245 to perform "next generation" remote MCU control
> functionality such as Inviting and ejecting participants, Floor and
> chair
> controls and eventually the ability to introduce H.239 apps directly
> into
> conferences as presentations.
> If anyone would like to participate and/or contribute to this work then
> please let me know.
> Simon
>  -----Original Message-----
> From: openh323-devel-bounces at lists.sourceforge.net
> [mailto:openh323-devel-bounces at lists.sourceforge.net]On Behalf Of
> Vishak V.
> Kurup
> Sent: Monday, 29 October 2007 3:08 PM
> To: openh323-devel at lists.sourceforge.net
> Subject: [Openh323-devel] help in creating WhiteBoard application using
> Opal
> Hi,
>             I am Vishak. I want to develop a white board application
> for
> linux using gtk. I heard that whiteboard applications use T.120
> protocol.
> T.120 protocol is in the stack of Opal. So can any one please tell me
> how
> create a whiteboard application.
>  Regards

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