[Udpcast] UDPcast performance on high speed networks?

Felix Rauch rauch at inf.ethz.ch
Tue Dec 17 15:56:00 CET 2002

Dear list members,

I'm interested in the best case performance of UDPcast on fast
networks like Fast Ethernet or Gigabit Ethernet. So far my results are
not so good, but maybe I'm doing something wrong and maybe somebody
can give me any hints.

For Fast Ethernet, I get the following performance (without disk

Clients Performance [MB/s]   re-xmits
1       11.8                 12
2        0.89                142290
4        0.93                103320
8        1.0                 ?

So, while I get wire speed with only one client and server, I only get
about 10% of the best performance for more than 1 client. Am I missing
something? Are the high re-xmit-numbers normal or do they point to a
problem? The commands I use are as follows:

node01:~/src/udpcast> ./udp-sender --file /dev/zero --full-duplex
node02:~/src/udpcast> ./udp-receiver --file /dev/null

On Gigabit Ethernet the performance seems even worse, I can barely
transmit any data. Here's what happens on the sender during 1 minute:

node01:~/src/udpcast> time ./udp-sender --file /dev/zero --full-duplex --interface eth1 --log /tmp/udpcast.log
Udp-sender 2001-12-31
Using mcast address
UDP sender for /dev/zero at on eth1
Broadcasting control to
New connection from  (#0) 00000019
Ready. Press any key to start sending data.

Starting transfer: 00000019
bytes=        163 072 re-xmits=000000 (  0.0%) slice=0112                 -   0
Received retransmittal request for 1 from 0:
Retransmitting 1.41
Retransmitting 1.42
Retransmitting 1.43
Retransmitting 1.90
0.000u 0.000s 1:06.53 0.0%mits=00+0k 0+0io 138pf+0we=0112                 -   0

And on the receiver:
node02:~/src/udpcast> time ./udp-receiver --file /dev/null --interface eth1 --log /tmp/udpcast.log
Udp-receiver 2001-12-31
UDP receiver for /dev/null at on eth1
received message, cap=00000019
Connected as #0 to
Listening to multicast on
Press any key to start receiving data!
bytes=        326 144  (  0.29 Mbps)
Cancelled by user
0.000u 0.020s 1:15.49 0.0%      0+0k 0+0io 140pf+0w

Any ideas?

Felix Rauch                      | Email: rauch at inf.ethz.ch
Institute for Computer Systems   | Homepage: http://www.cs.inf.ethz.ch/~rauch/
ETH Zentrum / RZ H18             | Phone: +41 1 632 7489
CH - 8092 Zuerich / Switzerland  | Fax:   +41 1 632 1307

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