0

My ssh secure shell always freeze when I try to download file >100KB using SSH Secure File Transfer. Even if the download manage to start, the download speed is less than 1kb/s. But upload of large file (>100KB) is OK. Small file transfer is ok too.

I tried 

reboot

and 

/etc/init.d/networking restart

still the same.

I used speedtest_cli.py and get a transfer speed Download 780MBit/s. Upload 176.60Mbit/s which actually looks good.

I use netstat and see the Sent-Q is 208 for the SSH, I don't know if this affect the speed (means the Queue is stuck somewhere)? But this number is not big anyway.

I tried WinSCP. The same result.

Any ideas about the problem would be greated appreciated.

Tianyun Ling
  • 101
  • 1
  • How do you download? Using scp? – davidbaumann Dec 08 '15 at 20:01
  • I use Secure File Transfer – Tianyun Ling Dec 08 '15 at 20:02
  • That could easily have been caused by somebody configuring a firewall to drop legitimate traffic. Often when a firewall is configured by somebody who don't know what they are doing it will drop ICMP packets which are required for correct operation of the network. I would first try changing `advmss` on the default route to 1220 on both ends of the connection. If that is not an option, I would try reducing the MTU of the network interface at one end of the connection from 1500 to 1400. – kasperd Dec 08 '15 at 20:52
  • Do a tcpdump and wireshark. Sounds like an pmtu issue. If it's an mtu issue you should see that the connection is fine until a large packet is transmitted and then the large packet is retransmitted until the connection resets. – Nath Dec 09 '15 at 11:27

0 Answers0