[FreeNX-kNX] NX in higher latency environment

[Verner Kjærsgaard]

Mario Becroft skrev:
> ford prefect <fpmailinglists at googlemail.com> writes:
> 
>> Using a WAN emulator (WanEm) with DSL Settings (Speed: 1024/256 kb/s, Latency:
>> 300ms, Packet Loss: 0,1%) it was quite bad, using NX in comparison to Citrix.
>> When moving windows arond, there is a quite noteble delay which makes it hard
>> to drop windows where you want it. Also writing and clicking around seems to be
>> handled worse then in Citrix. Using connection delay's < 180ms there are not
>> really notable differences between Citrix and NX. >180ms, Citrix seems to be
>> more usable for me.
> 
> Nx essentially eliminates client-server round trips, which are normally
> a major problem with X11 on high-latency links, and heavily compresses
> and caches data. From what I have seen it is very effective as far as it
> goes.
> 
> I haven't used Citrix much but I am not sure what else it could do to
> improve performance in high latency conditions. I know it has a feature
> called speedscreen where it can paint characters locally in response to
> keypresses. This doesn't sound all that useful to me in practice, since
> if you are touch typing then you normally don't care about a 300ms delay
> in reading the characters on-screen. Still, it could give the impression
> of being faster. That said, I think this feature is available only on
> the Windows version of Citrix anyway.
> 
> You mentioned moving windows. Obviously this will require a round-trip
> to the server (assuming the window manager is running on the remote
> system). Unless Citrix is highly integrated with the remote window
> manager and able to do something ultra clever, like moving the window
> around locally, I don't see how it could be any better in this
> situation.
> 
> Or could it be that in the Citrix configuration, your window manager is
> running locally? This would account for a huge difference in the
> responsiveness of moving windows, but if you tried doing something that
> interacts with the application, like, say, popping up a menu or opening
> a new window, this would incur the full link latency. If so, then
> running nx in the same configuration should achieve similar results.
> 
> Perhaps you could do some more testing to pin down exactly what is
> faster in Citrix?
> 
> I would have thought that with latency in the region of 300 ms, any
> highly interactive application is going to get clumsy to use. I don't
> think there is much you can do about that, sadly, without an approach
> completely different to that of any current windowing system (or
> discovering an as-yet unknown law of physics).
> 
> Our users report that nx is quite good over a link with 250 ms rtt, but
> I reckon that is pushing it. Obviously, it depends on what you are
> doing. Reading a few web pages and doing some word processing will be
> less critical than, say, doing CAD work.
> 
Hi

I've used/am using NX in high latency situations. I do not  experience 
anything like what you say. I set the connection-type-slider all the 
right and go low (32K) on colour when using NX as a proxy/gateway to 
Win2003 applications.

Just for your info :-)



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Verner Kjærsgaard
Open Source Academy
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