On 7/20/07, Gerrit Renker <gerrit@xxxxxxxxxxxxxx> wrote:
Quoting Patrick: | Hi, | | Quick question on iperf and kernel 2.6.22 (official and exp DCCP tree). | I use 2 computers + 1 netembox in between | Here are iperf cmd lines I use : | on dccpServer : # iperf -s -Xdccp -l1424 | on dccpClient : # iperf -c dccpServer -Xdccp -l1424 -t30 This iperf variant only sends at full/maximum speed, i.e. it will try aggressively to stuff your link, until it is forced to slow down by the kernel. This generates a lot of other problems - such as increase in delay, queue overflow etc.
I still think that DCCP CCID3 should respond gracefully in this circumstance, not collapse. We have congestion control and we shouldn't go down to virtually nothing. TCP works fine, older versions of DCCP work fine. I've got to research what is going on for sure though. Might be time to use dccp_probe as well and work out what's going on? Are others aware of dccp_probe? - this is quite useful for looking at problems like this.
I haven't done bandwidth tests during the last days, but if you are doing such tests can you please compare with the constant-bitrate variant of iperf: * use original source http://www.erg.abdn.ac.uk/users/gerrit/dccp/apps/iperf/zip/iperf-2.0.2.tar.gz * only needs patch #1 from http://www.erg.abdn.ac.uk/users/gerrit/dccp/apps/iperf/patches/ * then try iteratively with the -b switch to increase the bandwidth, i.e. iperf -c dccpServer -l1424 -d -b1m # 1Mbps CBR DCCP iperf -c dccpServer -l1424 -d -b5m # 5Mbps iperf -c dccpServer -l1424 -d -b10m # 10Mbps
I will try these out - going to play with iperf for a bit now... Ian -- Web: http://wand.net.nz/~iam4/ Blog: http://iansblog.jandi.co.nz WAND Network Research Group - To unsubscribe from this list: send the line "unsubscribe dccp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
