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Date: Tue, 12 May 2015 16:41:10 -0400
Message-ID: <CANJO25+yXnkQm8ATq694PurDKGBPTkCcJzD4fJaPS4Jy9HmbTg@mail.gmail.com>
From: gabe appleton <gappleto97@gmail.com>
To: Jeff Garzik <jgarzik@bitpay.com>
Content-Type: multipart/alternative; boundary=089e0111e0dabf1a560515e88382
Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Proposed additional options for pruned
	nodes
Precedence: list

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I suppose this begs two questions:

1) why not have a partial archive store the most recent X% of the
blockchain by default?

2) why not include some sort of torrent in QT, to mitigate this risk? I
don't think this is necessarily a good idea, but I'd like to hear the
reasoning.
On May 12, 2015 4:11 PM, "Jeff Garzik" <jgarzik@bitpay.com> wrote:

> True.  Part of the issue rests on the block sync horizon/cliff.  There is
> a value X which is the average number of blocks the 90th percentile of
> nodes need in order to sync.  It is sufficient for the [semi-]pruned nodes
> to keep X blocks, after which nodes must fall back to archive nodes for
> older data.
>
> There is simply far, far more demand for recent blocks, and the demand for
> old blocks very rapidly falls off.
>
> There was even a more radical suggestion years ago - refuse to sync if too
> old (>2 weeks?), and force the user to download ancient data via torrent.
>
>
>
> On Tue, May 12, 2015 at 1:02 PM, Gregory Maxwell <gmaxwell@gmail.com>
> wrote:
>
>> On Tue, May 12, 2015 at 7:38 PM, Jeff Garzik <jgarzik@bitpay.com> wrote:
>> > One general problem is that security is weakened when an attacker can
>> DoS a
>> > small part of the chain by DoS'ing a small number of nodes - yet the
>> impact
>> > is a network-wide DoS because nobody can complete a sync.
>>
>> It might be more interesting to think of that attack as a bandwidth
>> exhaustion DOS attack on the archive nodes... if you can't get a copy
>> without them, thats where you'll go.
>>
>> So the question arises: does the option make some nodes that would
>> have been archive not be? Probably some-- but would it do so much that
>> it would offset the gain of additional copies of the data when those
>> attacks are not going no. I suspect not.
>>
>> It's also useful to give people incremental ways to participate even
>> when they can't swollow the whole pill; or choose to provide the
>> resource thats cheap for them to provide.  In particular, if there is
>> only two kinds of full nodes-- archive and pruned; then the archive
>> nodes take both a huge disk and bandwidth cost; where as if there are
>> fractional then archives take low(er) bandwidth unless the fractionals
>> get DOS attacked.
>>
>
>
>
> --
> Jeff Garzik
> Bitcoin core developer and open source evangelist
> BitPay, Inc.      https://bitpay.com/
>

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<p dir=3D"ltr">I suppose this begs two questions:</p>
<p dir=3D"ltr">1) why not have a partial archive store the most recent X% o=
f the blockchain by default?</p>
<p dir=3D"ltr">2) why not include some sort of torrent in QT, to mitigate t=
his risk? I don&#39;t think this is necessarily a good idea, but I&#39;d li=
ke to hear the reasoning. </p>
<div class=3D"gmail_quote">On May 12, 2015 4:11 PM, &quot;Jeff Garzik&quot;=
 &lt;<a href=3D"mailto:jgarzik@bitpay.com">jgarzik@bitpay.com</a>&gt; wrote=
:<br type=3D"attribution"><blockquote class=3D"gmail_quote" style=3D"margin=
:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr">T=
rue.=C2=A0 Part of the issue rests on the block sync horizon/cliff.=C2=A0 T=
here is a value X which is the average number of blocks the 90th percentile=
 of nodes need in order to sync.=C2=A0 It is sufficient for the [semi-]prun=
ed nodes to keep X blocks, after which nodes must fall back to archive node=
s for older data.<div><br></div><div>There is simply far, far more demand f=
or recent blocks, and the demand for old blocks very rapidly falls off.<br>=
<div><br></div><div>There was even a more radical suggestion years ago - re=
fuse to sync if too old (&gt;2 weeks?), and force the user to download anci=
ent data via torrent.</div><div><br></div><div><br></div></div></div><div c=
lass=3D"gmail_extra"><br><div class=3D"gmail_quote">On Tue, May 12, 2015 at=
 1:02 PM, Gregory Maxwell <span dir=3D"ltr">&lt;<a href=3D"mailto:gmaxwell@=
gmail.com" target=3D"_blank">gmaxwell@gmail.com</a>&gt;</span> wrote:<br><b=
lockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px =
#ccc solid;padding-left:1ex"><span>On Tue, May 12, 2015 at 7:38 PM, Jeff Ga=
rzik &lt;<a href=3D"mailto:jgarzik@bitpay.com" target=3D"_blank">jgarzik@bi=
tpay.com</a>&gt; wrote:<br>
&gt; One general problem is that security is weakened when an attacker can =
DoS a<br>
&gt; small part of the chain by DoS&#39;ing a small number of nodes - yet t=
he impact<br>
&gt; is a network-wide DoS because nobody can complete a sync.<br>
<br>
</span>It might be more interesting to think of that attack as a bandwidth<=
br>
exhaustion DOS attack on the archive nodes... if you can&#39;t get a copy<b=
r>
without them, thats where you&#39;ll go.<br>
<br>
So the question arises: does the option make some nodes that would<br>
have been archive not be? Probably some-- but would it do so much that<br>
it would offset the gain of additional copies of the data when those<br>
attacks are not going no. I suspect not.<br>
<br>
It&#39;s also useful to give people incremental ways to participate even<br=
>
when they can&#39;t swollow the whole pill; or choose to provide the<br>
resource thats cheap for them to provide.=C2=A0 In particular, if there is<=
br>
only two kinds of full nodes-- archive and pruned; then the archive<br>
nodes take both a huge disk and bandwidth cost; where as if there are<br>
fractional then archives take low(er) bandwidth unless the fractionals<br>
get DOS attacked.<br>
</blockquote></div><br><br clear=3D"all"><div><br></div>-- <br><div>Jeff Ga=
rzik<br>Bitcoin core developer and open source evangelist<br>BitPay, Inc. =
=C2=A0 =C2=A0 =C2=A0<a href=3D"https://bitpay.com/" target=3D"_blank">https=
://bitpay.com/</a></div>
</div>
</blockquote></div>

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