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?
Paul
-----Original Message----- From: h323plus-bounces@lists.packetizer.com [mailto:h323plus- bounces@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@lists.sourceforge.net [mailto:openh323-devel-bounces@lists.sourceforge.net]On Behalf Of Vishak V. Kurup Sent: Monday, 29 October 2007 3:08 PM To: openh323-devel@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