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From: Jeff Garzik <jgarzik@bitpay.com>
Date: Fri, 18 Jul 2014 09:53:35 -0400
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To: Gavin Andresen <gavinandresen@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

On Thu, Jul 17, 2014 at 6:46 PM, Gavin Andresen <gavinandresen@gmail.com> wrote:
> I'd encourage you to code up a prototype first (or at the same time), in
> whatever programming language / networking library you're most familiar
> with.

+1

> Maybe not even using the existing p2p protocol; there could be a mining-only
> very-fast-block-propagation network separate from the existing p2p network.
>
> Combining your optimizations with "broadcast as many near-miss blocks as
> bandwidth will allow" on a mining backbone network should allow insanely
> fast propagation of most newly solved blocks.


Yes, I would encourage thinking along these lines.  That was the
motivation of the UDP P2P protocol extension I wrote:
https://bitcointalk.org/index.php?topic=156769.0

The intention was to experiment with sending block header + tx list +
coinbase, via UDP best effort broadcast.

Incentives:

If your neighbors receiving this message already have the TXs in the
TX list, then the block is complete, and may be relayed further.

If your neighbors do not have all TXs in the block, they must fetch
them at additional time/latency cost.

Thus, you have an incentive to relay blocks containing TXs already
distributed out into network mempools and cached in the signature
cache.

We want to capture that incentive in whatever protocol is eventually
used.  Miners have a TX fee incentive to include many transactions.
In theory, they want to include as many TX as possible.  It will help
us scale quite a bit to solve this problem.