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Date: Fri, 10 Jul 2015 13:51:00 -0400
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From: Alex Morcos <morcos@gmail.com>
To: Justus Ranvier <justus@openbitcoinprivacyproject.org>
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Cc: bitcoin-dev@lists.linuxfoundation.org
Subject: Re: [bitcoin-dev] Why not Child-Pays-For-Parent?
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I think the biggest problem with merging CPFP right now is that at least in
its current implementation it is not efficient enough in certain
situations,.

On Fri, Jul 10, 2015 at 1:02 PM, Justus Ranvier <
justus@openbitcoinprivacyproject.org> wrote:

> On 07/10/2015 11:31 AM, Jeff Garzik wrote:
> > This is a good explanation but it does not address reachability.  TX_a,
> the
> > first tx sent out on the network, presumably has insufficient fee to get
> > mined - which also means it did not necessarily even reach all miners.
> >
> > Simply sending out TX_b with added fee does not guarantee that nodes
> > suddenly have TX_a, which they may have ignored/dropped before.
>
> I'm not sure why that's actually a problem.
>
> CPFP is initiated by the recipient of the parent transaction, and so if
> the recipient is creating this transaction in the first place they must
> have a copy of the parent transaction which can/should broadcast at the
> same time.
>
> If the child reaches a CPFP miner, then presumably the parents made it
> as well (any path between the sender and the miner that doesn't relay
> the parent should reject the child as trying to spend non-existent
> coins), so both of the transactions can be mined at the same time.
>
> --
> Justus Ranvier
> Open Bitcoin Privacy Project
> http://www.openbitcoinprivacyproject.org/
> justus@openbitcoinprivacyproject.org
> E7AD 8215 8497 3673 6D9E 61C4 2A5F DA70 EAD9 E623
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>

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<div dir=3D"ltr">I think the biggest problem with merging CPFP right now is=
 that at least in its current implementation it is not efficient enough in =
certain situations,.</div><div class=3D"gmail_extra"><br><div class=3D"gmai=
l_quote">On Fri, Jul 10, 2015 at 1:02 PM, Justus Ranvier <span dir=3D"ltr">=
&lt;<a href=3D"mailto:justus@openbitcoinprivacyproject.org" target=3D"_blan=
k">justus@openbitcoinprivacyproject.org</a>&gt;</span> wrote:<br><blockquot=
e class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc sol=
id;padding-left:1ex"><span class=3D"">On 07/10/2015 11:31 AM, Jeff Garzik w=
rote:<br>
&gt; This is a good explanation but it does not address reachability.=C2=A0=
 TX_a, the<br>
&gt; first tx sent out on the network, presumably has insufficient fee to g=
et<br>
&gt; mined - which also means it did not necessarily even reach all miners.=
<br>
&gt;<br>
&gt; Simply sending out TX_b with added fee does not guarantee that nodes<b=
r>
&gt; suddenly have TX_a, which they may have ignored/dropped before.<br>
<br>
</span>I&#39;m not sure why that&#39;s actually a problem.<br>
<br>
CPFP is initiated by the recipient of the parent transaction, and so if<br>
the recipient is creating this transaction in the first place they must<br>
have a copy of the parent transaction which can/should broadcast at the<br>
same time.<br>
<br>
If the child reaches a CPFP miner, then presumably the parents made it<br>
as well (any path between the sender and the miner that doesn&#39;t relay<b=
r>
the parent should reject the child as trying to spend non-existent<br>
coins), so both of the transactions can be mined at the same time.<br>
<span class=3D"HOEnZb"><font color=3D"#888888"><br>
--<br>
Justus Ranvier<br>
Open Bitcoin Privacy Project<br>
<a href=3D"http://www.openbitcoinprivacyproject.org/" rel=3D"noreferrer" ta=
rget=3D"_blank">http://www.openbitcoinprivacyproject.org/</a><br>
<a href=3D"mailto:justus@openbitcoinprivacyproject.org">justus@openbitcoinp=
rivacyproject.org</a><br>
E7AD 8215 8497 3673 6D9E 61C4 2A5F DA70 EAD9 E623<br>
</font></span><br>_______________________________________________<br>
bitcoin-dev mailing list<br>
<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev@lists.=
linuxfoundation.org</a><br>
<a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" =
rel=3D"noreferrer" target=3D"_blank">https://lists.linuxfoundation.org/mail=
man/listinfo/bitcoin-dev</a><br>
<br></blockquote></div><br></div>

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