[AG-TECH] TTL - Multicast

Allan Spale aspale at evl.uic.edu
Thu Mar 14 15:18:31 CST 2002

If I am familiar with what you are talking about, EVL actually is running
our AG nodelet with scripts (because it is a single Windows 2000 computer
with one camera and mic with no ability to use _rm-eventlistener).  So,
from the command line, the script issues a -B 1000 in order that the
bandwidth slider can be set to no more than 1000 kbps.  This option
resolved the same problem (256 kbps limit).  I am almost certain the
command line also includes -t 127 (for the ttl).  This seems to work ok,
and we can get bandwidth above 256 kbps.

I am checking e-mail from home today, so I cannot verify this or check the
command line, but other people might be able to verify that this does

Good luck.


On Thu, 14 Mar 2002, Nolan, Kevin [NCSUS] wrote:

> Actually, our problem is with the vic in windows.  We are using windows 2000
> machines as capture computers.  In linux the -B option works fine.
> According to the vic-userguide...
> -B
> 	Set the maximum value of the bandwidth slider to a user-specified
> number of kbit/s.  This value is limited to 256 kbit/s if the conference
> address is a multicast address and the TTL in use is greater than 64 (ie,
> the traffic will leave your multicast region).
> So in the windows vic the above is true, but in the linux vic this must have
> changed in the code.  It doesn't matter what we set the bandwidth to in
> windows...if the TTL is 127, it behaves as the guide suggests above.
> We'd like to be able to have a TTL of 127 and a bandwidth value of much more
> than 256 kbit/s on our windows capture machines.
> -----Original Message-----
> From: Robert Olson [mailto:olson at mcs.anl.gov] 
> Sent: Thursday, March 14, 2002 1:45 PM
> To: Nolan, Kevin [NCSUS]; 'ag-tech at mcs.anl.gov'
> Subject: Re: [AG-TECH] TTL - Multicast
> At 12:01 PM 3/14/2002 -0500, Nolan, Kevin [NCSUS] wrote:
> >The problem we're seeing with both VIC and Rat is that as the TTL value 
> >gets increased, the amount of data being transmitted is decreased as a way 
> >to alleviate network congestion.  The problem with this is that our remote 
> >sites generally connect via high-bandwidth links, and the associated lower 
> >frame rates are unacceptable for real-time communication between 
> >sites.  Is there any way that we can change these values, or does the 
> >source code have to be modified?
> the AG software passes a max-bandwidth option to vic that overrides the 
> default:
>          vic -t 127 -B 10000 ip/port
> What is rat doing with ttl? is it refusing to let you set the higher-rate 
> encodings? I don't think I have any particular settings to make rat work 
> properly.
> --bob

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