<br><font size=2 face="sans-serif">Hi all,<br>
</font>
<br><font size=2 face="sans-serif">We are assessing the feasibility of
constructing AG Nodes at four sites so that they can connect together.
We shall use the conventional letters S, F, M and L to denote
the locations. Our major concern is network bandwidth and the goal of this
question is to understand whether, given the available network bandwidth,
a good quality inter-site communication is possible. We would also
like to understand what are the project constraints deriving from the available
bandwidth constraint. Following is a brief description of network links:</font>
<br><font size=2 face="sans-serif">Network Links</font>
<br><font size=2 face="sans-serif">Location "S" - Location "F":
2x155Mbps, present utilization 30%; </font>
<br><font size=2 face="sans-serif">Location "S" - Location "M":
4 Mbps Committed Information Rate [12 Mbps theoretical],
present utilization 50% </font>
<br><font size=2 face="sans-serif">Location "F" - Location "M":
4 Mbps Committed Information Rate [12 Mbps theoretical],
present utilization 50% </font>
<br><font size=2 face="sans-serif">Location "S" - Location "L":
4 Mbps Committed Information Rate [6 Mbps theoretical]
on a IMA connection [4 ATM lines] and 2 Mbps on a permanent dedicated connection;
both the two lines are at present utilized only for small FTP download
traffic, but we expect a 50% utilization rate in the future.</font>
<br>
<br><font size=2 face="sans-serif">We have not finalized the Access Grid
node configurations, but we would like to have in each node four cameras,
unless network bandwidth constraints forces us to reduce this figure. We
also do not know have at present any use case scenario, however, we may
assume that the most typical usage will be a two-site video conference.
</font>
<br>
<br><font size=2 face="sans-serif">Given that high quality video and audio
are required in order to make the Access Grid really useful, we need to
understand:</font>
<br>
<br><font size=2 face="sans-serif">Questions</font>
<br><font size=2 face="sans-serif">1. whether we are forced to limit
the project to sites "S" and "F" having a large bandwidth
direct connection or we can hold our original goal of connecting all the
four sites</font>
<br><font size=2 face="sans-serif">2. whether we can hold our goal of having
four video streams or we should instead assume that in each video conference
involving locations "M" and/or "L" only one video stream
can be used</font>
<br><font size=2 face="sans-serif">3. whether we should add a mixer, in
the sense of RFC 1889, acting as gateway towards locations "M"
and "L"</font>
<br><font size=2 face="sans-serif">4. whether we can afford having a multiple-site
video conference or we are restricted to two-site video conferences. </font>
<br><font size=2 face="sans-serif">5. whether Gary Refka's figures (see
Building an Access Grid Node), namely 256 Kbps per camera/site and
128 Kbps per site, are adequate/required for a high quality communication
or not. If we base our analysis on these figures, 2,256 Kbps should
be required/adequate for a four-cameras-per-site video conference</font>
<br><font size=2 face="sans-serif"> </font>
<br>
<br><font size=2 face="sans-serif">Thank you in advance to everybody helping
us to figure out how to cope with this issue.</font>
<br>
<br><font size=2 face="sans-serif">Best regards</font>
<br>
<br><font size=2 face="sans-serif">Bronek Carr</font>