[AG-TECH] TTL - Multicast

Nolan, Kevin [NCSUS] knolan at ncsus.jnj.com
Thu Mar 14 13:35:08 CST 2002

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...

	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 

         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 

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