SSH Compression - Block Deduplication

[Morty Abzug]

On Mon, Sep 12, 2011 at 08:26:41AM -0700, Matt Olson wrote:

> Nomachine, being a commercial product, is not likely to achieve ubiquity.
[snip]
> I may look around and see if I can find a library that does another
> layer of tunneling or a Xorg addon to provide deduplication.

Have you looked at VNC?  Especially the x11vnc implementation, in
service mode, with "Tight" encoding.  IME, one gets amazingly good
performance via that specific combination.  Use it in service mode and
you can do one master port redirection instead of per-user port
redirection.  This makes X11 useful even over slow WAN links.

If you have a COTS WAN dedupe, I would be curious to see how raw x11 +
block dedupe does against VNC in Tight encoding mode with a poorly
behaved app, such as wireshark with gtk2+.  X11 has at least three
subtleties that create unnecessary traffic: (1) X11 applications can
redraw themselves even when there has been no change within the app;
(2) applications can communicate all kinds of data to the X server
that isn't actually user-visible; (3) pointer movements result in a
lot of data traffic across the network.  Block-level dedupe can, at
best, only reduce that traffic.  Tight VNC can completely eliminate
the first two, and enormously reduce most of the need for the latter.
So I would expect Tight VNC to perform better than block dedupe.  But
a test would be a lot better. . .

That said, setting up VNC currently requires additional effort.  Doing
something like this transparently in openssh would save a lot of
trouble.

- Morty