ssh ports

[blu at vl.com (Tom Metro)]

John Boland wrote:
> in transferring a 500K file, there might be 4 or 5 retransmit.  the
> capture shows the stall: packets are moving along and then stop for a
> couple of minutes and just resume.

This sounds more like you have an underlying network problem, unrelated 
to SSH.

And this may or may not be of relevance to your problem:

http://www.onlamp.com/pub/a/onlamp/2005/11/17/tcp_tuning.html?page=2

   A Warning on the scp Program

   A common tool for copying files across the internet is scp.
   Unfortunately, TCP tuning does not help with scp throughput, because
   scp uses OpenSSL, which uses statically defined internal flow control
   buffers. These buffers act as a bottleneck on network throughput,
   especially on long-delay, high-bandwidth network links. The Pittsburgh
   Supercomputing Center's High Performance SSH/SCP page explains this in
   more detail and also has a patch for OpenSSL to fix this problem.


> ...on the target host, there are several rx_fcs_errors during the transfer.

What is an rx_fcs_errors error? Receive frame check sum error?

I found where it is declared in the source:
http://lxr.free-electrons.com/ident?i=rx_fcs_errors

but not surprisingly the data structures aren't documented.


> that's why i was asking about another port for return
> communication.

If a second port was a requirement, it wouldn't have worked at all.

If you were seeing a stall before the transfer was initiated, I'd 
suggest looking into things like SSH or TCP wrapper settings that cause 
a PTR lookup on the client IP, or an IDENT query, either of which might 
be failing and timing out.

  -Tom

-- 
Tom Metro
Venture Logic, Newton, MA, USA
"Enterprise solutions through open source."
Professional Profile: http://tmetro.venturelogic.com/

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