Re: [bitcoin-dev] request BIP number for: "Support for Datastream Compression"

From: Bob McElrath <bob_bitcoin@mcelrath•org>
To: Peter Tschipper <peter.tschipper@gmail•com>
Cc: Bitcoin Dev <bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] request BIP number for: "Support for Datastream Compression"
Date: Mon, 9 Nov 2015 21:04:49 +0000	[thread overview]
Message-ID: <20151109210449.GE5886@mcelrath.org> (raw)
In-Reply-To: <5640F172.3010004@gmail.com>

I would expect that since a block contains mostly hashes and crypto signatures,
it would be almost totally incompressible.  I just calculated compression ratios:

zlib    -15%    (file is LARGER)
gzip     28%
bzip2    25%

So zlib compression is right out.  How much is ~25% bandwidth savings worth to
people?  This seems not worth it to me.  :-/

Peter Tschipper via bitcoin-dev [bitcoin-dev@lists•linuxfoundation.org] wrote:
> This is my first time through this process so please bear with me. 
> 
> I opened a PR #6973 this morning for Zlib Block Compression for block
> relay and at the request of @sipa  this should have a BIP associated
> with it.   The idea is simple, to compress the datastream before
> sending, initially for blocks only but it could theoretically be done
> for transactions as well.  Initial results show an average of 20% block
> compression and taking 90 milliseconds for a full block (on a very slow
> laptop) to compress.  The savings will be mostly in terms of less
> bandwidth used, but I would expect there to be a small performance gain
> during the transmission of the blocks particularly where network latency
> is higher. 
> 
> I think the BIP title, if accepted should be the more generic, "Support
> for Datastream Compression"  rather than the PR title of "Zlib
> Compression for block relay" since it could also be used for
> transactions as well at a later time.
> 
> Thanks for your time...
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> 
> 
> !DSPAM:5640ff47206804314022622!
--
Cheers, Bob McElrath

"For every complex problem, there is a solution that is simple, neat, and wrong."
    -- H. L. Mencken 