freebsd security - Jan 2016 - HPN and None options in OpenSSH

Julian Elischer <julian at freebsd.org> writes:
> what is the internal window size in the new ssh?
64 kB.

DES
-- 
Dag-Erling Sm?rgrav - des at des.no

On Sat, Jan 23, 2016 at 7:55 AM, Dag-Erling Sm?rgrav <des at des.no>
wrote:
> Julian Elischer <julian at freebsd.org> writes:
> > what is the internal window size in the new ssh?
>
> 64 kB.
>
> DES
> --
> Dag-Erling Sm?rgrav - des at des.no

Are you sure of this? I have not looked at the code, but my former
colleagues at the high performance research network ESnet claim at
http://fasterdata.es.net/data-transfer-tools/say-no-to-scp/  that the
internal buffers and effective window size have recently been increased
from 64KB to 1MB an allow for transfer rates of up to 140 Mbps over a link
with 53 ms. latency. With the HPN patches, they report 1.2 Gbps, making HPN
patches still significant over high latency paths.

That said, scp still performed poorly when compared to other technologies
(i.e. GridFTP) for bulk data transfer over high-latency high-bandwidth
links. (ESnet provides links of up to 400 Gbps between the US and Europe as
well as within the US, so this sort of thing is quite important to them.)
--
Kevin Oberman, Part time kid herder and retired Network Engineer
E-mail: rkoberman at gmail.com
PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683

Kevin Oberman <rkoberman at gmail.com> writes:
> Dag-Erling Sm?rgrav <des at des.no> writes:
> > Julian Elischer <julian at freebsd.org> writes:
> > > what is the internal window size in the new ssh?
> > 64 kB.
> Are you sure of this?
Sorry, I was thinking of 6.6 (in stable/10).  The buffer code in 7.1
supports dynamically-sized buffers with a hard limit of 128 MB.  The
default window size for client sessions is 2 MB, or 1 MB if associated
with a tty.  I'm not sure what the maximum size is.  Note that scp, sftp
etc. count as client sessions.  X11 and agent forwarding use different
(smaller) windows which improve latency at the cost of throughput.
> [...] scp still performed poorly when compared to other technologies
scp is a horrible protocol, use sftp or (preferably) rsync over ssh.

DES
-- 
Dag-Erling Sm?rgrav - des at des.no