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Date: Fri, 11 Apr 2014 09:54:44 -0700
Message-ID: <CAAS2fgS3cU4-yJMSMA4TSY4_mrw53d--543OVmize2BYVjUAqQ@mail.gmail.com>
From: Gregory Maxwell <gmaxwell@gmail.com>
To: Tier Nolan <tier.nolan@gmail.com>
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Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Bitcoind-in-background mode for SPV
	wallets
Precedence: list

On Thu, Apr 10, 2014 at 10:30 AM, Tier Nolan <tier.nolan@gmail.com> wrote:
> Error correction is an interesting suggestion.

Though I mentioned it, it was in jest=E2=80=94 I think right now it would b=
e
an over-design at least for the basic protocol.  Also, storing
'random' blocks has some locality problems, when verifying blocks you
need to obtain them contiguously, and so we can take advantage of the
locality of reference.  For the non-error-coded case I believe nodes
with random spans of blocks works out asymptotically to the same
failure rates as random.

One thing that I like to point out is that there is absolutely no need
for the entire network to use the same p2p protocol. Diversity here
would be very good.  I think it would be really good for someone to
have an alternative p2p protocol using these techniques even though I
think they aren't yet compelling enough to be table stakes in the
basic protocol.

There are some very helpful things you can do with forward error
correction for faster and more efficient block relaying too:
https://en.bitcoin.it/wiki/User:Gmaxwell/block_network_coding

(The conversation Peter Todd was referring to was one where I was
pointing out that with suitable error coding you also get an
anti-censorship effect where its very difficult to provide part of the
data without potentially providing all of it)

> If there was 10000 nodes and each stored 0.1% of the blocks, at random, t=
hen
> the odds of a block not being stored is 45 in a million.

I think in the network we have today and for the foreseeable future we
can reasonably count on there being a reasonable number of nodes that
store all the blocks... quite likely not enough to satisfy the
historical block demand from the network alone, but easily enough to
supply blocks that have otherwise gone missing.