On 06/28/2014 09:16 AM, Chris Angelico wrote:
>> I remember approx. 10 years ago a neighboring dept. at my work effectively
>> killed our 10 MB/s Ethernet segment with such traffic (due to a
>> misconfigured switch/router?). Running an ethernet analyzer showed a single
>> X11 host-server session occupied ~80% bandwidth.  AFAICR, it was a Sun
>> workstation.
>> A real PITA.
> Either that was a horribly inefficient X11 connection (as mine was -
> the virtual machine sent basically a constantly-updated bitmapped
> image to rdesktop, which then couldn't do anything more efficient than
> feed that image to the X server), or something was horribly
> misconfigured. I've frequently done much more reasonable X11
> forwarding, with high success and low traffic;

Only the most primitive X11 apps are at all fast over network
forwarding.  If the app uses any modern toolkit, then it's basically
just sending a bunch of bitmaps over the wire (changes), which would be
fine, but X11 involves a lot of server round trips.  Forwarding works
fine over SSH on a LAN (compression with -X helps too), but anything
slower than that is very nearly unusable.  I used to run XEmacs over a
modem (I know; I just preferred it to Emacs and I didn't know ViM), and
it worked great with server-side drawing and fonts, as X11 was designed
to do 90s-style.  But now if I need to run X11 apps over a slower link
these days I use OpenNX which dramatically helps by eliminating round
trips, and applying bitmap compression.  But the fact remains X11 kind
of sucks these days, and "network transparency" now basically means a
slightly suckier version of VNC in effect.  RDP protocol is actually
much more efficient than X11 forwarding with modern apps.  So your
rdesktop example is actually not a horribly inefficient X11 connection,
other than the fact that X11 is inefficient.  Honestly once Wayland has
per-app RDP built into it, there'll be no reason at all to cheer for X11.


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