scp packet loss, https fine?

metalfan · 2008-11-14 08:51:29

Hi,

got some mysterious network problems, a connection between two archlinux machienes over several switches keeps loosing packets or at least wireshark says:

TCP Previous Segment lost
TCP Retransmission

but only if i use scp, no errors with https
datar ates are ~6mybte/s for scp and 11,5mbyte/s for https
both systems loads are below 0.5

any idea what that could be?

cactus · 2008-11-14 16:49:28

does ifconfig output show any errors, dropped, overruns, or collisions?

metalfan · 2008-11-20 17:01:08

no, ifconfig output looks fine.
its probably a switch somewhere along the path.

Bebo · 2008-11-20 17:08:24

Is it the infamous TCP window scaling problem? If you haven't tried it already, issue

echo 0 > /proc/sys/net/ipv4/tcp_window_scaling

and see if it gets any better. Alternatively, add the line

net.ipv4.tcp_window_scaling = 0

to the file /etc/sysctl.conf and issue sysctl -p

metalfan · 2008-11-22 10:32:37

ah, didnt know about that. but didnt help.

RedShift · 2008-11-23 17:41:42

Is the MTU for all networked devices set correctly? Have you checked ifconfig's output for errors on both sides?

metalfan · 2008-11-23 17:56:55

Yes, no errors on both sides.
havent played around with the MTU. ifconfig reports MTU as 1500

RedShift · 2008-11-24 22:49:59

Can you post a full dump? (.pcap file). Please make sure it only contains your scp traffic and no other traffic.

Arch Linux

#1 2008-11-14 08:51:29

scp packet loss, https fine?

#2 2008-11-14 16:49:28

Re: scp packet loss, https fine?

#3 2008-11-20 17:01:08

Re: scp packet loss, https fine?

#4 2008-11-20 17:08:24

Re: scp packet loss, https fine?

#5 2008-11-22 10:32:37

Re: scp packet loss, https fine?

#6 2008-11-23 17:41:42

Re: scp packet loss, https fine?

#7 2008-11-23 17:56:55

Re: scp packet loss, https fine?

#8 2008-11-24 22:49:59

Re: scp packet loss, https fine?

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