This documentation is a revised edition of the
MICE documentation of
National Support Centre London
Revision by Jens Elkner (elkner@irb.cs.uni-magdeburg.de).
User Guide to sd
The Session Directory tool (sd) from Lawrence Berekeley Laboratories
(LBL) is the basic and most effective way of starting or joining a
multicast session. If can be used to start sessions on your local
machine, your local net or across the whole of the MBONE. Therefore
exercise great care. The "ttl" ("time to live",
which limits the scope of your session packets) should be set
according to your needs since it determines how far your transmission
will carry. Always start your experiments with a ttl of 1. You can
then increase it to 16 which will keep the session traffic in your site.
Browsing the MBONE
The standard use of sd is to browse the MBONE events which have been
entered after an announcement has gone to rem-conf@es.net.
The tool might look like this
Here you could select a session with the mouse (usually left button)
and then open the session. The figure shows that the 2nd Int. WWW
Conf. (Chicago) has been selected. In the lower window there is
further information on that session, including a WWW page for the
"agenda".
Some sessions will only have one medium (e.g. vat) and some will
have three, audio, video and shared drawing space. If you are limited,
the
wb
sessions are the easiest to multicast, in the sense that less data is
transferred, followed by audio (vat) and finally video (nv, ivs or vic).
Starting your own session
To start your own session in sd, follow these steps. Here we assume
that audio, video and shared drawing space will be needed.
- Click on "New" to create an entry in "sd"
- You must type some information into both the
"Name" and "Description" areas.
- Choose all three media: video, audio and wb (the whiteboard).
- In the video selection, choose either nv or ivs. To do this,
pull down a sub-menu (pull down from "Video")
- Note that nv is the default for video and dvi4 is the default
audio compression for vat.
- Choose a ttl of 16 to test the entry, and then edit the entry
again to make the entry global (to 47, 63 or 127). You must use "Edit"
on the same machine that you used to create the original entry.
- Each call to "New" creates a new, semi-random, Class D address
which is used for all the tools in the session. Sd also assigns port
and id numbers. If you wish to select your own addresses or ports,
you simply over-write those assigned by wb. This is not recommended,
however, since sd uses a sophisticated algorithm to reduce the likelihood
of address clashes.
- The sd entry should be tested on a remote machine, and all the tools
started from sd.
- To load a large PostScript file from a standard sd entry, start
wb
with the command beginning wb -P nnn followed by all the
other arguments (the multicast address and so on). The value of
nnn is the maximum size, in bytes, of any single PostScript
file to be displayed, and should be set accordingly. Invoking
wb -P 100000 -C 'Test WB' -t 16 224.2.87.45/37654
will allow you to load files of up to 100K to a wb at address
224.2.87.45 and port 37654.
For example,
This shows a "A MICE Seminar" in the "Name" field and "Jo Smith on
RSVP" in the "Description" field. Internally, the information seen
above is stored in the file $HOME/.sd_cache as follows:
s=A MICE seminar
i=Jo Smith on RSVP
o=gjoly@muridae.cs.ucl.ac.uk
c=224.2.160.221 1 2868982096 2869007296
m=audio 43021 50164
a=vt
m=video 46617 3831
m=whiteboard 50572 59942
The multicast address for all tools is 224.2.160.221, and nv will be
used, since this is the default video format. On audio, "vt" was
chosen rather than the default.
Finally, you may wish to alter the behaviour of a tool started from
sd. Here is an example of $HOME/.sd.tcl
that will allow you to start some tools with non-standards arguments.