Re: Choosing a header compression algorithm

[Roberto Peon <[e-mail]>]

For larger buffer sizes, it can make a fair difference, but it is an easy
thing to change, for sure.
-=R


On Wed, Mar 27, 2013 at 5:29 PM, James M Snell <[e-mail]> wrote:

> On Wed, Mar 27, 2013 at 5:14 PM, Roberto Peon <[e-mail]> wrote:
> > I've checked in some changes to delta2 which expands and documents
> various
> > options for delta2 in the README.md.
> >
> > After running a number of variations of delta2, The following defaults
> look
> > good for small buffer sizes:
> >
> > delta2=max_entries=256, small_index=1
>
> Oh excellent. I had hit on this as well. To be honest, I'm not sure
> max_entry > 256 would ever really make much practical sense.
>
> - James
>
> >
> > small_index basically says use a uint8 instead of a uint16 for
> representing
> > indices, and is the kind of thing that could be messaged somewhere
> (opcode,
> > flag, whatever).
> >
> > The best headerdiff option which I believe is safe against CRIME in the
> > future is:
> >   headerdiff=delta_type=false,huffman
> >
> > I removed prefix matching from delta some months ago (~6 I think?) after
> > cogitating on it for a while and then speaking with security folks.. I
> just
> > couldn't come up with a way I could prove was safe, unlike the
> > atom-matching, which one can prove is no worse than a brute-force attack.
> >
> > I've appended runs with these values@4k buffer size for delta2 and
> > headerdiff below.
> > -=R
> >
> >
> >
> > * TOTAL: 5949 req messages
> >
> > size  time | ratio min   max   std
> >
> > http1     3,460,925  0.13 | 1.00  1.00  1.00  0.00
> >   delta2 (max_byte_size=4096, max_entries=256, small_index=1,
> hg_adjust=0,
> > implicit_hg_add=0, refcnt_vals=0)       664,683  4.16 | 0.19  0.02  0.83
> > 0.15
> >                                                          headerdiff
> > (buffer=4096, delta_type=false, huffman)       759,783  2.03 | 0.22  0.01
> > 0.78  0.18
> >
> > * TOTAL: 5948 res messages
> >
> > size  time | ratio min   max   std
> >
> > http1     2,186,162  0.12 | 1.00  1.00  1.00  0.00
> >   delta2 (max_byte_size=4096, max_entries=256, small_index=1,
> hg_adjust=0,
> > implicit_hg_add=0, refcnt_vals=0)       585,475  5.32 | 0.27  0.02  1.28
> > 0.13
> >                                                          headerdiff
> > (buffer=4096, delta_type=false, huffman)       543,047  3.29 | 0.25  0.02
> > 0.73  0.14
> >
> >
> >
>