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From: Jonathan Toomim <j@toom.im>
In-Reply-To: <CAOG=w-t=+0Zdoy+d4Y2t9nbRkyO30N_Az9kbRarGo69yHCpSwA@mail.gmail.com>
Date: Mon, 14 Dec 2015 19:21:43 +0800
Message-Id: <3292B7BA-13A8-4BD9-AB08-4F5EBE534771@toom.im>
References: <CABsx9T0nxcqAkEt7+pVm9oZEZH_HCJ9D3J00v0bKJYeUcDv1hQ@mail.gmail.com>
	<1449897228198.c655b3ae@Nodemailer>
	<CAOG=w-t=+0Zdoy+d4Y2t9nbRkyO30N_Az9kbRarGo69yHCpSwA@mail.gmail.com>
To: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Capacity increases for the Bitcoin system.
Precedence: list


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This means that a server supporting SW might only hear of the tx data =
and not get the signature data for some transactions, depending on how =
the relay rules worked (e.g. if the SW peers had higher minrelaytxfee =
settings than the legacy peers). This would complicate fast block relay =
code like IBLTs, since we now have to check to see that the recipient =
has both the tx data and the witness/sig data.

The same issue might happen with block relay if we do SW as a soft fork. =
A SW node might see a block inv from a legacy node first, and might =
start downloading the block from that node. This block would then be =
marked as in-flight, and the witness data might not get downloaded. This =
shouldn't be too hard to fix by creating an inv for the witness data as =
a separate object, so that a node could download the block from e.g. =
Peer 1 and the segwit data from Peer 2.

Of course, the code would be simpler if we did this as a hard fork and =
we could rely on everyone on the segwit fork supporting the segwit data. =
Although maybe we want to write the interfaces in a way that supports =
some nodes not downloading the segwit data anyway, just because not =
every node will want that data.

I haven't had time to read sipa's code yet. I apologize for talking out =
of a position of ignorance. For anyone who has, do you feel like sharing =
how it deals with these network relay issues?

By the way, since this thread is really about SegWit and not about any =
other mechanism for increasing Bitcoin capacity, perhaps we should =
rename it accordingly?


On Dec 12, 2015, at 11:18 PM, Mark Friedenbach via bitcoin-dev =
<bitcoin-dev@lists.linuxfoundation.org> wrote:

> A segwit supporting server would be required to support relaying =
segwit transactions, although a non-segwit server could at least inform =
a wallet of segwit txns observed, even if it doesn't relay all =
information necessary to validate.
>=20
> Non segwit servers and wallets would continue operations as if nothing =
had occurred.
>=20
> If this means essentially that a soft fork deployment of SegWit will =
require SPV wallet servers to change their logic (or risk not being able =
to send payments) then it does seem to me that a hard fork to deploy =
this non controversial change is not only cleaner (on the data structure =
side) but safer in terms of the potential to affect the user experience.
>=20
>=20
> =97 Regards,


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<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html =
charset=3Dwindows-1252"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: =
after-white-space;"><div>This means that a server supporting SW might =
only hear of the tx data and not get the signature data for some =
transactions, depending on how the relay rules worked (e.g. if the SW =
peers had higher minrelaytxfee settings than the legacy peers). This =
would complicate fast block relay code like IBLTs, since we now have to =
check to see that the recipient has both the tx data and the witness/sig =
data.</div><div><br></div><div>The same issue might happen with block =
relay if we do SW as a soft fork. A SW node might see a block inv from a =
legacy node first, and might start downloading the block from that node. =
This block would then be marked as in-flight, and the witness data might =
not get downloaded. This shouldn't be too hard to fix by creating an inv =
for the witness data as a separate object, so that a node could download =
the block from e.g. Peer 1 and the segwit data from Peer =
2.&nbsp;</div><div><br></div><div>Of course, the code would be simpler =
if we did this as a hard fork and we could rely on everyone on the =
segwit fork supporting the segwit data. Although maybe we want to write =
the interfaces in a way that supports some nodes not downloading the =
segwit data anyway, just because not every node will want that =
data.</div><div><br></div><div>I haven't had time to read sipa's code =
yet. I apologize for talking out of a position of ignorance. For anyone =
who has, do you feel like sharing how it deals with these network relay =
issues?</div><div><br></div><div>By the way, since this thread is really =
about SegWit and not about any other mechanism for increasing Bitcoin =
capacity, perhaps we should rename it =
accordingly?</div><div><br></div><div><br></div><div><div>On Dec 12, =
2015, at 11:18 PM, Mark Friedenbach via bitcoin-dev &lt;<a =
href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev@lists.li=
nuxfoundation.org</a>&gt; wrote:</div><br =
class=3D"Apple-interchange-newline"><blockquote type=3D"cite"><p =
dir=3D"ltr">A segwit supporting server would be required to support =
relaying segwit transactions, although a non-segwit server could at =
least inform a wallet of segwit txns observed, even if it doesn't relay =
all information necessary to validate.</p><p dir=3D"ltr">Non segwit =
servers and wallets would continue operations as if nothing had =
occurred.</p>
<div class=3D"gmail_quot&lt;blockquote class=3D" style=3D"margin: 0px =
0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, =
204); border-left-style: solid; padding-left: 1ex; position: static; =
z-index: auto;">
<div>If this means essentially that a soft fork deployment of SegWit =
will require SPV wallet servers to change their logic (or risk not being =
able to send payments) then it does seem to me that a hard fork to =
deploy this non controversial change is not only cleaner (on the data =
structure side) but safer in terms of the potential to affect the user =
experience.&nbsp;</div>
<div><br></div>
<div>
<br>=97
Regards, </div>
</div></blockquote></div><br></body></html>=

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