sending a large file with SCP to a certain server stalls at exactly 2112 kB

ubuntu ssh scp
Attila Szeremi picture Attila Szeremi · Aug 16, 2012 · Viewed 38k times · Source

There is a certain ubuntu 10.04 server where if I ssh a file onto it from any server that is outside the office where this server is (meaning any of use scp-ing onto this server through LAN from within this server always works for some reason), then scp-ing fails for any file over 2112 kB in size, and is stuck at 2112 kB. So

scp -vvv /home/attila-szeremi/aszeremi.tar.gz  [email protected]:~/aszeremi.tar.gz

shows something like 1% 2112KB 909.2KB/s - stalled - dynamically at the end, where the KB/s becomes lower and lower.

Does anyone know what may be causing this and how I can fix it?

What I have tried so far:

  • Limiting the speed with scp -l 2000. It just made the file sending slower, and at 2112 kB it got stuck again.
  • Enabling compresison with -C. It was still stalled at the same size.

Answer

dav.garcia picture dav.garcia · Nov 19, 2012

The only way I managed to get rid of this problem was by disabling TCP SACK:

$ sudo sysctl -w net.ipv4.tcp_sack=0

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