[winswitch] high latency (was dpi switch..)

Thomas Esposito tmesposito00 at gmail.com
Fri Oct 7 05:05:45 BST 2016

As an experiment, I tried binding my xpra session to TCP port 5910, which
is within the range typically used by VNC (also no encryption, which is
fine because I'm on a private corporate intranet). The idea is to test out
a theory that the network admins have prioritized VNC traffic (because
there are a lot of people depending on remote VNC access) by classifying on
the TCP port.

It could be placebo, but it actually seems much better. I don't really see
the latency spikes that I was seeing before, although I'd have to use it
longer to be sure. It could also simply be that there is less network
traffic at this time of day. IF my theory is true, and VNC traffic
(identified by port) is being treated more favorably and consistently in
the network, perhaps this is reducing the probability that I will encounter
xpra bugs manifesting as catastrophic performance degradation triggered by
changing network conditions.

On Thu, Oct 6, 2016 at 12:06 AM, Antoine Martin <antoine at nagafix.co.uk>

> On 06/10/16 09:20, Thomas Esposito wrote:
> > Just to add a bit more info...
> >
> > I've tried x264, lz4, and png (32, 8, and gray scale) encodings and none
> > of these approach the responsiveness and perceived performance of
> > TigerVNC with Tight encoding.
> >
> > When I look at the stats and graphs under session info, I see lots of
> > latency spikes, particularly under Damage latency, which spikes into
> > several seconds.
> That would be a bug. Although xpra has been heavily optimized for fast
> networks, with relatively low latency and low packet loss, it should
> still adapt to more challenging network conditions.
> Others have reported this before but I've never seen it for myself
> directly, which makes it hard to fix. Could be the same as:
> http://xpra.org/trac/ticket/999
> Please add your information there.
> > I've also tried this on a Microsoft Azure Ubuntu VM that I've been
> > playing around with via a free trial account. The performance seems
> > better (same encodings), but occasionally gets pretty bad. Maybe it's
> > just intermittent network issues.
> Sounds like it.
> Cheers
> Antoine
> > I haven't been able to get VNC working
> > on this VM...

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