James Carlson wrote, on 11-01-10 15:38: > Is there any chance you could make the raw tcpdump files (rather than > the decoded text output) available? It's much harder to debug things > when information has been subtracted. > > Based on what little is available here, I'm seeing what seems to be an > RTT that jumps around a lot, from a few milliseconds on up to 150 > milliseconds, and causing TCP to misbehave. It's likely that this is a > kernel issue that needs to be investigated. I created an new tcpdump of the issue and attached it in the mail. http://filebin.ca/zmmnws/tcpdump01.tar.gz I changed the sammy servers pppoe connection to an normal eth5 interface to an ciso router that is providing a 50/50mbit fiber interface. So the upload speed of the sammy server should be very high. But is only 30KB when uploading to my mobile umts systems. When uploading form an other server to the umts systems the upload speed is the max of that server (100kB) so the umts systems should not be the problem here. We opened the tcmpdumps with wireshark and did an analyse > export info and it showed a lot of "TCP Fast retransmissions" compared to the the other tcmpdump of the good download from the ashley server. I also tried the below kernels, but it did not change anything. linux-image-686 | 2.6.30 linux-image-686 | 2.6.31 linux-image-686 | 2.6.32 linux-image-amd64 | 2.6.30 linux-image-amd64 | 2.6.32 If anybody can have a look at the tcp dumps or maybe have other suggestion to get more debug info? Best regards, Jelle
------------------------------------------------------------------------ # this document describes my issue with a way to slow transfer speed # between my sammy server with pppoe g.shdsl and an alix05 server with # ppp hsdpa umts ------------------------------------------------------------------------ # two download tests, demonstrating that the alix05 server can download # with 250KB/s (umts hsdpa 3g) alix05:~# wget -cr http://ftp.nl.debian.org/debian/ls-lR.gz FINISHED --2010-01-15 13:43:41-- Downloaded: 1 files, 6.5M in 39s (168 KB/s) FINISHED --2010-01-15 13:44:54-- Downloaded: 1 files, 6.5M in 46s (143 KB/s) # one upload test to the sammy server, demonstrating that the alix05 # server can upload with 60KB/s and that the sammy server can download # with at least 60KB's (umts hsdpa 3g) alix05:~# scp ftp.nl.debian.org/debian/ls-lR.gz root@xxxxxxxxxxxxxxxxxx:/root/ 100% 6607KB 61.2KB/s 01:48 # one upload from the sammy server to the ashley server, demonstrating # that the sammy server can upload with 274KB/s. (g.shdsl) sammy:~# scp /root/ls-lR.gz root@xxxxxxxxxxxxx:/root/ 100% 6608KB 1.3MB/s 00:05 ### THIS IS THE ISSUE, THE DOWNLOAD SPEED OF 17KB/s IS WAY TO LOW ### # one download from sammy server to alix05 server that is going to slow alix05:~# scp root@xxxxxxxxxxxxxxxxxx:/root/ls-lR.gz ls-lR.gz 100% 6578KB 17.4KB/s 06:19 # control test, downloading from the ashley server to demonstrate that # the alix05 is capable of download at least with 97KB/s with scp alix05:~# scp root@xxxxxxxxxxxxx:/root/ls-lR.gz ls-lR.gz 100% 6608KB 88.1KB/s 01:15 ------------------------------------------------------------------------ root@ashley:~# tcpdump port 22 and host 62.140.137.47 -i eth1 -w tcpdump-raw-ashley-eth1.txt from alix05:~# scp root@xxxxxxxxxxxxx:/root/ls-lR.gz ls-lR.gz 100% 6608KB 89.3KB/s 01:14 ------------------------------------------------------------------------ sammy:~# tcpdump port 22 and host 62.140.137.47 -i eth5 -w tcpdump-raw-sammy-eth5.txt from alix05:~# scp root@xxxxxxxxxxxxxxxxxx:/root/ls-lR.gz ls-lR.g 100% 6608KB 24.5KB/s 04:30 ------------------------------------------------------------------------ # othertests: # scp root@xxxxxxxxxxx:/root/ls-lR.gz ls-lR.g ------------------------------------------------------------------------ mv /root/tcpdump-ashley-eth1.txt /home/jelle/tcpdump-raw-ashley-eth1.txt chown jelle:jelle /home/jelle/tcpdump-raw-ashley-eth1.txt chmod 644 /home/jelle/tcpdump-raw-ashley-eth1.txt scp --verbose /root/tcpdump-raw-sammy-eth5.txt root@xxxxxxxxxxxxx:/root/ # on ashley mv /root/tcpdump-raw-sammy-eth5.txt /home/jelle/tcpdump-raw-sammy-eth5.txt chown jelle:jelle /home/jelle/tcpdump-raw-sammy-eth5.txt chmod 644 /home/jelle/tcpdump-raw-sammy-eth5.txt ------------------------------------------------------------------------
