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Re: Network Slowdowns?

From: Oliver Fromme <check+j70hk000rs05jd2r@xxxxxxxxxx>
Date: 12 Oct 2006 07:50:53 GMT

Matthew Dillon wrote:
 > [...]
 >    CPU overhead is a different beast entirely.   SSH has a lot of encryption
 >    and decryption overhead... my transfers over localhost top out at
 >    21.8 MBytes/sec on my test box.

The good old ssh1 package had a "-c none" option which
disabled encryption entirely.

Unfortunately the OpenSSH folks removed it for "security
reasons".  I have a patch that applies to FreeBSD's contrib
version of openssh; I think it should be usable on DF, too
(but I haven't tried).  The patch is very simple.


It is useful in cases where the underlying transport already
does encryption anyway (e.g. over IPSEC, an OpenVPN tunnel
or whatever), or if you trust the network (e.g. your home
LAN, of if it's a direct link between two boxes).  It makes
a hell of a difference if at least one of the two machines
has a slow CPU (or has a fast CPU but is loaded with other
processes), and you're scp'ing large amounts of data.
Of course you could use rcp, ftp or whatever, but the nice
thing with "scp -c none" is that you can still benefit from
all the other features of ssh, such as authentication via
the authorized_keys file, shortcuts via .ssh/config, easy
tunneling of X11 and other connections etc.

Best regards

Oliver Fromme,  secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd

Any opinions expressed in this message may be personal to the author
and may not necessarily reflect the opinions of secnetix in any way.

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