Arch Linux

metalfan

Member

Registered: 2007-11-22

Posts: 99

scp packet loss, https fine?

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

Taco Eater

From: t͈̫̹ͨa͖͕͎̱͈ͨ͆ć̥̖̝o̫̫̼s͈̭̱̞͍̃!̰

Registered: 2004-05-25

Posts: 4,622

Website

Re: scp packet loss, https fine?

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

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metalfan

Member

Registered: 2007-11-22

Posts: 99

Re: scp packet loss, https fine?

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

Bebo

Member

From: Göteborg, Sweden

Registered: 2006-06-07

Posts: 207

Re: scp packet loss, https fine?

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

Member

Registered: 2007-11-22

Posts: 99

Re: scp packet loss, https fine?

ah, didnt know about that. but didnt help.

RedShift

Member

From: Belgium

Registered: 2004-07-16

Posts: 230

Re: scp packet loss, https fine?

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

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metalfan

Member

Registered: 2007-11-22

Posts: 99

Re: scp packet loss, https fine?

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

RedShift

Member

From: Belgium

Registered: 2004-07-16

Posts: 230

Re: scp packet loss, https fine?

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

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