Subject: ISDN, Mbone gateway

From: Soghra Zamani <[email-masked]>
Date: Fri, 07 Feb 1997 10:11:53 +0000 (GMT)

Hello,

We are planning to set up an ISDN based video conferencing system. This
will be a self contained system, but we would like to be able to feed the
audio and video from the system to the MBONE. For this it seems that 
we need a UNIX system. Do you have any recommendations for the UNIX
system? We have a mild prefences for SUN equipment, and if you could 
recommend a particular system as being suitably powerful that would be
very helpful. What other peripherals do we need? Is there a particular
kind of video capture card that we need, and again specific
recommendations would be very gratfully received.

Thanks in advance,

Soghra

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From: Peter Hoermann <[email-masked]>
Date: Tue, 11 Feb 1997 13:12:04 +0100

Hi,

we at the GMD in Darmstadt, Germany, are working on a gateway between
ISDN and Mbone, too, and thus I'd like to give a comment to this topic,
too.

If I'd taken the answers to Soghra's question not absolutely wrong,
concerning the topic 'ISDN, Mbone gateway' appeared two basic
suggestions:

a) how to connect two Sun boxes over ISDN (Gilles Dauphin, Peter Parnes)
b) D/A converting of incoming audio and video signals -> analog signals
on the one side out, on the other side in -> A/D converting (Craig
Tenney).

Hm, as far as I know the main thing a gateway does is protocol
conversion. In case a) you simply connect the boxes - what about the
rest (ISDN/H.320 feed on the one side vs. Mbone feed on the other) ?
Case b) seems a better solution but still you got problems:
- the quality of the audio and video isn't getting any better if you
convert it to and fro (A/D, D/A) (or do you have more positive
experiences ?)
- videoconferencing is more than just audio and video; what about
whiteboard, shared workspace ?

In any case - no protocol conversion.

To be true, our approach is not yet decided, too:

on the one hand we're thinking about using a commercial (hard- or
software) gateway for the conversion from H.320 to H.323 and vice versa
(there are already some existing solutions from RADVision, PictureTel
and others). Our part in this case would be the converting from H.323 to
Mbone feed (and back). This is based on suggestions of the MICE/MERCI
project (see for example
http://www-mice.cs.ucl.ac.uk/mice/merci/deliverables/d10.1/d10.1.html,
chapter 7). The main argument against this approach: the offered
H.323/H.320 gateways are too expensive (some several thousand $$) for
just doing experiments.

On the other hand there would be a solution that does all the conversion
directly from Mbone feed to ISDN/H.320. One advantage over the
MICE/MERCI approach ('two step gateway') is that you don't loose time
converting twice (especially if you're using a software H.320/H.323
gateway), but that - off course - means more work.

Anyway, 'this is trickier than it looks' ('The 7th Guest', Microscope
Puzzle); I would be very thankful, too, for further comments on this
topic.

Regards

Peter

|--------------------------------------------------------------------------------------|
|Peter Hoermann                         EMail      :
[email-masked]             |
|                                       Homepage   :
http://www.darmstadt.gmd.de/~peha |
| GMD -                                              (don't expect too
much !)         |
| German National Research
Center                                                      |
| for Information Technology            Address    : GMD -
TKT                         |
| Institute for                                      Rheinstrasse
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| TeleCooperationTechnology                          D-64295 Darmstadt,
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|--------------------------------------------------------------------------------------|

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From: Peter Hoermann <[email-masked]>
Date: Thu, 13 Feb 1997 13:32:26 +0100

Hello Henning,

> ... at the end, there seems little justification for running the H.320
> stuff instead of IP-based tools over PPP. (Might be marginally useful
> for PictureTel boxes and the like, though.)

and that's why ! We are thinking about integrating users of H.320 based
videoconferencing systems (their users in most cases commercial
companies, that sunk plenty of bucks into MCUs and the like, i.e. had
lots of investment for their vc infrastructure) into Mbone conferences
(i.e. usually of the scientific area).
In the farer future, off course, there will be no more dividing into
those who have the (guaranteed) bandwidth and secure unicast (TelCos and
commercial users) and those without (guaranteed) bandwidth, but (yet
relatively unsecure) multicast (Mbone community).

Peter