TLS compression (was: Re: GPLv3)

Simon Josefsson simon at
Mon Dec 17 12:49:12 CET 2007

Simon Josefsson <simon at> writes:

> Still, I'm not sure if it makes sense for GnuTLS to enable LZO
> compression by default any more.  It is not a standard TLS compression
> algorithm.  What do people think?  It would also be interesting to
> compare it with LZMA, which has gained some popularity lately:
> Btw, liblzo* has rather few reverse dependencies on Debian, so except
> for gnutls liblzo isn't that widely used.  Dropping it might save space
> on most installation.

I found this quote:

  Igor Pavlov is the developer behind the amazing 7-Zip compressor,
  which has always been available under the GPL. Igor has now created a
  separate LZMA SDK, which implements his compression algorithm in a way
  that makes it suitable for embedded applications.

  On the SDK web page, Igor says that the LZMA code can decompress up to
  1 MB/s on a 100 MHz ARM, MIPS, or other RISC CPU. The memory
  requirements for decompression are as low as 8-23 KB, and the code may
  take up as little as 2-8KB.

  This sounds like a great piece of work for embedded developers. Up
  until now, the best library out there for this community has been LZO,
  which has a few problems that hold it back. Perhaps Igor's product
  will now be the go-to library for this community.

Perhaps we should do some work in this area...

Does anyone know of any real-world benchmarks of TLS compression?  I'd
guess that network traffic compression have different properties than
file compression.  I would guess that network traffic actually is easier
to compress than files, on average; a lot of network traffic are verbose
text protocols.


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