SSH Compression

Jeff jeff at
Wed Aug 31 05:47:43 UTC 2011

Hi David,

Yes I noticed the echo in here. ;-)

Actually I found the answer I was looking for. The parameter  
NETWORK_COMPRESSION = True does the trick.

It's disabled by default according to

            boolean, default False

            Enables compression of the SSH traffic over the network.  
Note that
            while this will reduce your network traffic, it will  
increase your
            cpu load.

I've yet to test it with more than half a dozen terminals, but from  
what I can tell so far it is a well worthwhile trade. You should try  
it. :)



P.S. Hey Jonathan, how's Canada? Hope you don't mind but I thought I'd  
CC you in to solicit your comment if possible.

On 31 Aug 2011, at 12:04 AM, David Groos wrote:

> Hi Jeff,
> I'm thinking I hadn't understood what you were asking for--NX is an  
> application to do remote access, like tight-vnc.  Sounds like you  
> want to compress the video as it gets sent over the network as part  
> of the normal LTSP thin client process.  Yes?
> Compression is part and parcel of the LTSP thin client system, I  
> think.  For questions like you are asking, I would recommend that  
> you jump on some irc application like pidgin internet messenger and  
> go to the #ltsp room and ask your question on line.  It is much more  
> active than the #edubuntu room and it seems that most all of my  
> questions seem to be about ltsp :-)  This list server has been kinda  
> thin on answers lately.
> Good luck on tracking down some satisfaction.
> David
> On Aug 29, 2011, at 5:10 AM, Jeff wrote:
>> Thanks for the input, David.
>> Still getting my head around *NX. Can the client work from the thin- 
>> clients without loading a windowing system?
>> In the meantime, I found this article 
>>  about compression.
>> Looking around the configuration files I don't see any compression  
>> enabled in /var/lib/tftpboot/ltsp/i386/lts.conf so I've added:
>> ## SSH compression between LTSP client and server
>> remotely, but haven't been onsite to test it yet.
>> /var/lib/tftpboot/ltsp/i386/config-2.6.38-8-generic has several  
>> compression parameters, but nothing explicitly about SSH from what  
>> I can see.
>> Will post an update when I've had a chance to test.
>> Cheers,
>> Jeff
>> On 24 Aug 2011, at 3:24 PM, David Groos wrote:
>>> Hey Jeff, Sounds like you are looking for good gui remote access  
>>> over ssh? I use FreeNX as the server and use NoMachine's client  
>>> and now also use OpenNX since it works well with lion-10.7.  The  
>>> access over broadband internet is just like sitting at the  
>>> computer--works great to manage remote servers running Edubuntu/ 
>>> ltsp.  I hear it is even a decent experience over dial-up.  So,  
>>> while I don't know what the compression is, it must be pretty good  
>>> to work this well in this situation.  If you have more questions,  
>>> let me know.
>>> David
>>> On Wed, Aug 24, 2011 at 7:15 AM, Jeff <jeff at> wrote:
>>> Hi all,
>>> I don't have easy access to a server at the minute, and not sure  
>>> where the settings are anyway; but I've been wondering about this  
>>> for a while and am just hoping that someone can point me in the  
>>> right direction:
>>> A week or so ago when I was onsite at a school, I ran a binary  
>>> tcpdump to get an indication of network usage with approximately  
>>> 12 thin clients working.
>>> It wasn't a very precisely measured test or anything, but the  
>>> server sent/received a Gigabyte of traffic in about a couple of  
>>> minutes.
>>> So I'm just wondering whether SSH compression is enabled by  
>>> default or not? And if it is, whether there's any way to tweak it?
>>> Also, it occurs to me that SSH compression would have to be  
>>> lossless, by nature. So I'm wondering if there's any way to get  
>>> something like tight-vnc working; or whether we should try a  
>>> lightweight X desktop like XFCE?
>>> I'm not really happy about the performance, compared to terminal  
>>> server, for ex, or even the old Fedora/Gnome K12-LTSP we upgraded  
>>> from.
>>> Insights and pointers appreciated. Flames > /dev/null
>>> ;-)
>>> --
>>> Jeff Brown
>>> Tel:+27-74-101 5170
>>> Fax:+27-86-532 3508

Jeff Brown

Tel:+27-74-101 5170
Fax:+27-86-532 3508

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