Is it possible to do dynamically throttled UPDcast transmission? We need
to throttle the data flow to a Logic Innovations IP encapsulator (with
LI's documentation attached with their permission).
The udpcast mutlticast address is considered a single route to the IPE.
The IPE sends out flow-control messages (described in document) that
shows how many bytes are available for traffic for each route every 100
milliseconds in a multicastand comes from a user specified multicast of
its own. Attached is the LI document, again with the manufactures
permission. Also, you can contact Theo Aukerman, taukerman(a)logici.com
for any additional info.
I'm asking these questions because IF this is possible, then this would
be an almost complete framework for an open source Data-casting network,
and can be used for over the air data-broadcasting from any DTV
transmitter or any other system with null packets. I currently work as
an engineer for a TV station that does data transmission, but would like
to move to an open source model.
Please confirm my guess (or explain how to implement it).
I need a "sender-timeout", a period of time while sender waits for receivers
to connect, and if none are connected - sender exits without transmission.
The only way to implement this is shell/perl/... script, which starts
udp-sender with --min-receivers option and monitors its stderr. If no
"Starting transfer" is found during specified period of time - it kills
http://udpcast.linux.lu/cmd.html states that --nosync is the default
when writing to a file or a pipe, but this does not appear to be the
case; I verified with strace that udp-receiver open()s its output
file with O_SYNC unless you specify --nosync.
We've used UDPcast for some time at my university to get computer labs ready for student use. It's always worked seamlessly for us.
Until now we've only used it to image Dell machines. Because Mac keeps getting more popular on our campus, this year we're filling up one lab with iMacs so they can dual boot and students can use whichever they want.
We set up and configured one of the iMacs and then used the same switch we usually use to connect it to the others so we could UDPcast. Unfortunately, it doesn't work -- we get to the point where the sender says it's sending, and the receivers say they're receiving, but nothing is happening. We've since tried one-to-one, specifying different IP addresses and subnet masks, things like that, but to no avail.
We're using the most recent version of UDPcast. It seems to be using the correct ethernet driver and finding the correct HD.
Has anyone else used UDPcast with Apple hardware? If so, is there anything we should be doing differently?
Stephen H. Foerster
Director, E-Learning Services