SSH Compression - Block Deduplication

[Matt Olson]

On Wed, 14 Sep 2011, Morty Abzug wrote:

> On Tue, Sep 13, 2011 at 09:28:24AM -0700, Matt Olson wrote:
>
>> The approach of possibly improving gzip/LZ77 performance still semms
>> like it might be worth while and have value beyond X11 tunneling.
>
> While a compression approach would certain help, please note that
> there are a lot of X11 performance problems that cannot be solved with
> compression.

My thing is not so much compression for the sake of bandwidth, rather, to 
eliminate latency which is at the core of X11 remote performance problems.

Example: transmission from host A (any number of bytes) which takes 100ms 
to fully transmit to host B; if host A can hash transmission data block, 
find that block in the cache, transmit a token all in 25ms total time from 
host A to host B, then you're effective reduced the amount of latency, as 
well as reduce the amount of data to transmit.

It's a tall order for the hosts on each end to process data fast enough to 
do this.  But modern hardware has also come a long way.

Personally I'm not in favor of adding compression or RFB specifically for 
X11.  I'd rather see a generalized solution, like block deduplication, 
that has potential benefits for other use cases.

X11 has problems.  A highly interactive protocol with serially dependent 
operations will suffer from any significant increase in network latency; 
I.e. under 1-2ms for local networks vs 25-250ms for wide area networks. 
There's no getting around that without fixing X11.

Matt