From: Alex Stade (alex@trdlnk.com)
Date: Mon Oct 06 2003 - 14:41:27 EDT
I opened a case with Sun support and their analysis is consistent with what
many of you have said. Here's their version;
> Hi Alexander,
> I took a look into the putty pscp client and its performance with solaris
> and linux systems. Bellow you will find my results, analilsis and
> recomendations for similar testing if you would like to look into the issue
> further over the weekend.
>
> pscp appears to interpret 1.99 as being non 2.0 compliant, but 1.99
> actually means 2.0 and 1.0 backward compatible. The default in linux is to
> support 2&1, in Solaris we only support 2 by default. So pscp contacts
> solaris with ssh version 2 and uses the sftp protocol, while it contacts
> linux with ssh version 1 and uses the scp protocol.
>
> pscp -2 <linux_host>:/file ./file is one quarter the speed as well. So
> this would appear to be a result either of the clients cipher
> implementations for ssh version 2, their recent change to using sftp when
> communicating with a version 2 server or some combination.
>
> Changing the sshd_config to list "Protocols 2" on the linux host brings the
> difference for pscp to solaris vs linux down to about 1:2 speed. This speed
> difference can be explained by default tuning differences between linux and
> solaris (tcp max mss, different cipher order etc. and may just be a result
> of my test environment) The algorithms could be changed in the sshd_config
> for each of the servers since pscp lacks a cipher flag and does not report
> which it uses for 2.0. It does report it uses blowfish for 1.0 which is
> likely faster than any 2.0 algorithm.
>
> sftp transfers between the solaris and linux box are on par with pscp in
> protocol 1 against linux. I did not test enabling version 1 compatibility
> on solaris since this is against our security recomendations but I would
> expect it to increase the speed between pscp and solaris to the same extent
> disabling it on linux decreased speed.
>
> Since these windows implementations lack server sides they can not be
> tested against themselves. I would conjecture that all of the clients
> tested either use putty as a backend or are heavily derived from it and
> probably include the 1.99 (2 & 1 compatibility) bug and many also follow
> putty's lead in converting scp commands to sftp requests against version 2
> servers.
>
> If you would like to test on your own, scp's -v option shows negotiations,
> pscp's -v is more limited but shows the ssh version selected. Killing and
> manually starting a single /usr/lib/sshd with "-d -d -d" allows you to see
> the full negotiation from either server's perspective.
>
> Perhaps a free client based on openssh such as the cygwin based one at
> http://lexa.mckenna.edu/sshwindows would perform better. (I have no
> personal experience with it or Cygwin and do not no how much of a
> performance penalty Cygwin is, but it could be tested against itself and is
> likely to behave similarly to unix openssh implementations.)
Once again, thanks for your time.
-Alex
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