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Re: Choosing a header compression algorithm

From: James M Snell <jasnell@gmail.com>
Date: Wed, 27 Mar 2013 17:29:12 -0700
Message-ID: <CABP7RbfN0Gf_qJkkj1ugJaDyjLZhQp9xoL+8H2B+4mGH=AcZGA@mail.gmail.com>
To: Roberto Peon <grmocg@gmail.com>
Cc: RUELLAN Herve <Herve.Ruellan@crf.canon.fr>, "agl@google.com" <agl@google.com>, Mark Nottingham <mnot@mnot.net>, "ietf-http-wg@w3.org Group" <ietf-http-wg@w3.org>
On Wed, Mar 27, 2013 at 5:14 PM, Roberto Peon <grmocg@gmail.com> 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
>
>
>
Received on Thursday, 28 March 2013 00:29:59 UTC

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