On Monday 12 May 2003 11:02, Gianni Minetti wrote:

Hi.

I'm evaluating the feasibility to use udp-cast as a reliable multicast file transfert protocol over a satellite link in order to distribute spooled db's differences.

Udpcast supports FEC (forward error correction) mode, which should make it suitable for monodirectional (or high latency) communication.

The way it works is that for n data packets, k "error correction" are computed, and also transmitted. The protocol can then compute all data packets using _any_ n packets (for instance n-3 data packets and 3 error correction packets). Thus, no acknowlegments are needed.

Just start the sender with the --fec and --async options.

Do you know any application of udp-cast over satellite links?

For the moment, I don't know any application. At work, we use a mtftp based protocol; the main reason for that is because this application was already in use before udpcast existed.

Are there any statistic model that better describe the reliability of udp-cast? What about udp-cast and the emerging pgm protocol (aka Tibco).

With FEC, you can tune udpcast for whatever reliability you need (just increase number of redundant packets per slice, or decrease number of data packets). If you expect packet losse to come in bursts, you may use interleaving.

Thanks a lot in advance for your interest and answers,

GM

Regards,

Alain