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Subject: Re: OpenSSH HPN
To: =?UTF-8?Q?Dag-Erling_Sm=c3=b8rgrav?= <des@des.no>,
 Bob Bishop <rb@gid.co.uk>
References: <86io5a9ome.fsf@desk.des.no>
 <261DDEE0-B792-4715-A8EF-27E491122BD2@gid.co.uk> <861tby9k9s.fsf@desk.des.no>
Cc: freebsd-security@freebsd.org, freebsd-current@freebsd.org
From: Julian Elischer <julian@freebsd.org>
Message-ID: <56432770.7030600@freebsd.org>
Date: Wed, 11 Nov 2015 19:33:04 +0800
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On 11/10/15 7:16 PM, Dag-Erling Smørgrav wrote:
> Bob Bishop <rb@gid.co.uk> writes:
>> Is removing HPN going to impact the performance of tunnelled X
>> connexions?

yes if your rtt is greater than about 85 mSec
I don't know he details but I noticed a big difference.
I had thought X wouldn't show much difference but in fact it did.
At work we had to add HPN to get anything like acceptable performance
on various tunnels our appliance uses.
> I don't think so.  It mostly affects the performance of long
> unidirectional streams (file transfers) whereas the X protocol, as far
> as I know, is a bidirectional exchange of relatively short messages.  It
> may make a difference for applications that transfer large textures...
> I don't really know enough about the X protocol to say for certain, but
> I am typing this in Emacs over a non-HPN SSH connection, and I regularly
> tunnel Firefox between the same two machines (RHEL 7 desktop at work and
> FreeBSD 10 desktop at home).
>
> DES