Mailinglist Archive: opensuse-factory (745 mails)

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[opensuse-factory] Re: ssh -X failing in 20180116
Hi Petr!


Petr Cerny wrote
(...)
Doesn't sound convincing. What is the most current definitive guide for
not using X11 forwarding? What should I tell a newby when he/she asks
*WHY* it should not be used?
(...)
2) speed - the X protocol is usually much more verbose when compared to
VNC, since it carries requests to draw things, while VNC only transports
bitmaps (compressed). Try running Firefox via ssh -X and through VNC.
I've also seen things that just didn't work via SSH-forwarded X11.
(...)

I've been following this discussion with a lot of interest, and I've been
learning a lot from it.

BTW, just out of curiosity: are you really saying that it is more "compact"
to send bitmaps through the network rather than sending plain text commands?
Because I have always thought to the contrary, and that that was one of the
great advantages of X forwarding.

Actually, I've always been experiencing bad results (talking about visual
quality here) with VNC unless on very fast and not-congested networks, while
X forwarding is just like running a local application.

I know that bitmaps can be compressed, but bitmaps are not very compressible
unless you want to lose on the quality of the image (i.e. lossy
compression). And as the network speed/congestion gets bad, so is the
quality of the image to the point where, sometimes, you cannot even clearly
read text.

On the other hand, even a very verbose *text* protocol can be very easily
compressed down to nearly nothing, and you always get perfect graphics
because they are rendered locally.
Also, there should be no overhead on the server, because the X11 protocol
works the same way when used locally or remotely. That's exactly why it can
be forwarded. At least that's what I learned back when I was in school, I
don't know what's the situation right now with compositors and all that
stuff.

That said, I use X forwarding only when I have to use the occasional GUI
application window; when I have to grab a whole remote desktop I usually use
current NoMachine's NX, which is a lot more reliable than VNC in my
experience (despite not being open source).
But that is usually because I have to grab the desktop of another user, not
because of efficiency considerations (with respect to X11 forwarding, I
mean).

I've been trying to use xrdp *server* too, but I find it too much unstable
in my experience. OTOH I use xfreerdp client all the time when I have to
connect to Windows server (due to my work) and I find it quite fast and
stable.

Just my 2c.

Cris




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