[Udpcast] Optimum setting for zero packet loss

Markus mbillerwell at gmail.com
Sun Feb 7 04:14:19 CET 2010

Hi Everyone,


I have a requirement to send large tar packets in half duplex (one way only
communication). I'm trying to determine what is the best values and to use
in udp-sender and udp-receiver.


My setup is, one server connected to another across a single 1Gb fibre link
(no return path). The tar packets are sometimes very large, in the Gb's and
I can't have any loss. 



My first setting were:-


On the sending server:-


udp-sender  --async  --log /tmp/log  --fec 8x6/64 --max-bitrate 100m
--autostart 1 --mcast-data-addr --interface eth0 -f
/root/send`date +%y%m%d%H%M`.tar 

There is a crontab to run this udp-sender line every 10 minutes to keep
sending new packets.


On the receiving server:-


udp-receiver  --interface eth0 --file /root/send`date +%y%m%d%H%M`.tar

There is a crontab to run a script checking if udp-receiver is running and
if not restarts it so it's ready for the next packet.



I initially started the -max-bitrate at 1000m and it actually successfully
got a tar packet across but after repetitive testing found it was dropping
packets halfway through the transfer. So I continued to decrease the
-max-bitrate. It got progressively better until I got to a bitrate of 100m.
Then I found that the receiving server would start to receive the packet
then dropped it straight away leaving a 0 byte size packet or occasionally a
very small file (e.g 8Mb), which from observation I found it was dropping it
almost instantly.


I currently have a test running over the weekend with a couple of changed
settings in the udp-sender:-


udp-sender  --async  --log /tmp/log  --fec 8x8/128 --max-bitrate 100m
--autostart 3 --mcast-data-addr --interface eth0 -f
/root/send`date +%y%m%d%H%M`.tar 


I increased the fec in hope that it would improve the transfer speed and
increased the autostart hoping it would help in not dropping out at the
beginning of a reception.


Could you please let me know your thoughts? 

Also if there are any things you think I should add or change in the
udp-sender or udp-receiver to improve the reliability and transfer speed.
For my requirements I really need to have a fasted transfer rate (and
thought I'd get better than 100Mb on a 1Gb link) and I certainly can't go
any slowed. I also require a zero loss performance.








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