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From: Kaz Wesley <keziahw@gmail.com>
Date: Thu, 31 Jul 2014 14:41:33 -0700
Message-ID: <CA+iPb=Fa4YSTjPuCfyWy0wB2XBV=Mi99G3Hb84gjy+muNDin+g@mail.gmail.com>
To: Gregory Maxwell <gmaxwell@gmail.com>
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Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Squashing redundant tx data in blocks on
 the wire
Precedence: list

> the need to have transmitted the transaction list [..] first

32 bits per transaction is at least double the communication overhead
of the simple approach, and only offers a bound on the probability of
needing a round trip.

On Thu, Jul 31, 2014 at 2:29 PM, Gregory Maxwell <gmaxwell@gmail.com> wrote:
> On Thu, Jul 31, 2014 at 1:47 PM, Kaz Wesley <keziahw@gmail.com> wrote:
>> trip to request the missing tx; if we could somehow get the "What's
>> the Difference" approach to effectively operate on full transactions
>> instead
>
> I explain how to do this on the network block coding page.
>
> Given that you know the sizes and orders of the transactions (e.g.
> from a reconciliation step first), the sender sends non-syndromic
> forward error correcting code data somewhat larger than their estimate
> of how much data the user is missing.  Then you drop the data you know
> into place and then recover the missing blocks using the fec.
>
> There is no overhead in this approach except for FEC blocks that are
> incompletely missing (and so must be completely discarded), and the
> need to have the transmitted the transaction list and sizes first.
> (note, that just more bandwidth, not an additional round trip).