[scponly] Transmission times

[Paul Hyder]

There are two likely problems:
	1. encryption speed for your selected/default ssh/scp cypher
	2. If this is a long distance transfer (long round trip time)
	   then ssh has an rather bad hard coded internal TCP window.

For #1 check your cpu load on the scponly server.  See other postings
for info on cypher selection.  Problem #2 can slow down transfers with
latency greater than about 5ms.  You should be able to hit this ftp data
rate with a combination of a tuned host and tuned ssh.  How fast is the
link?  What hardware/OS?
    Paul Hyder
    NOAA Earth System Research Laboratory, Global Systems Division
    Boulder, CO

BTW: If you are in a supported environment and able to compile ssh
from source code the patches from PSC.edu might be of interest.
( http://www.psc.edu/networking/projects/hpn-ssh/ )

Lou Piccoli wrote:
> I know that this question has probably been asked many times before but
> I am new to the list and need the info quickly if possible, so thanks
> for putting up with me in advance :)
> 
> Since moving to scponly from ftp, transmission times for the same amount
> of data has tripled at best. Can anyone tell me why the increase in time
> to transmit, is it because of the packet confirmations being done, are
> they being done?
> 
> Example:
> to ftp 75 100Mb files it took  20hrs
> 
> to scp 75 100Mb files it takes 70+
> 
> Can someone tell me what causes?
> 
> Thanks
> Lou
> 
> 
> 
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