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From: Jeremy <jlrubin@mit.edu>
Date: Fri, 21 Aug 2020 14:17:32 -0700
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To: Jeremy <jlrubin@mit.edu>
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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Generalizing feature negotiation when new p2p
connections are setup
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As for an example of where you'd want multi-round, you could imagine a
scenario where you have a feature A which gets bugfixed by the introduction
of feature B, and you don't want to expose that you support A unless you
first negotiate B. Or if you can negotiate B you should never expose A, but
for old nodes you'll still do it if B is unknown to them. An example of
this would be (were it not already out without a feature negotiation
existing) WTXID/TXID relay.
The SYNC primitve simply codifies what order messages should be in and when
you're done for a phase of negotiation offering something. It can be done
without, but then you have to be more careful to broadcast in the correct
order and it's not clear when/if you should wait for more time before
responding.
On Fri, Aug 21, 2020 at 2:08 PM Jeremy <jlrubin@mit.edu> wrote:
> Actually we already have service bits (which are sadly limited) which
> allow negotiation of non bilateral feature support, so this would supercede
> that.
> --
> @JeremyRubin <https://twitter.com/JeremyRubin>
> <https://twitter.com/JeremyRubin>
>
--0000000000008d4be305ad69c454
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
<div dir=3D"ltr"><div><span class=3D"gmail_default" style=3D"font-family:ar=
ial,helvetica,sans-serif;font-size:small;color:rgb(0,0,0)">As for an exampl=
e of where you'd want multi-round, you could imagine a scenario where y=
ou have a feature A which gets bugfixed by the introduction of feature B, a=
nd you don't want to expose that you support A unless you first negotia=
te B. Or if you can negotiate B you should never expose A, but for old node=
s you'll still do it if B is unknown to them. An example of this would =
be (were it not already out without a feature negotiation existing) WTXID/T=
XID relay.<br></span></div><div><span class=3D"gmail_default" style=3D"font=
-family:arial,helvetica,sans-serif;font-size:small;color:rgb(0,0,0)"><br></=
span></div><div><span class=3D"gmail_default" style=3D"font-family:arial,he=
lvetica,sans-serif;font-size:small;color:rgb(0,0,0)">The SYNC primitve simp=
ly codifies what order messages should be in and when you're done for a=
phase of negotiation offering something. It can be done without, but then =
you have to be more careful to broadcast in the correct order and it's =
not clear when/if you should wait for more time before responding.</span><b=
r></div><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote"><div dir=
=3D"ltr" class=3D"gmail_attr">On Fri, Aug 21, 2020 at 2:08 PM Jeremy <<a=
href=3D"mailto:jlrubin@mit.edu">jlrubin@mit.edu</a>> wrote:<br></div><b=
lockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-le=
ft:1px solid rgb(204,204,204);padding-left:1ex"><div dir=3D"ltr"><div style=
=3D"font-family:arial,helvetica,sans-serif;font-size:small;color:rgb(0,0,0)=
">Actually we already have service bits (which are sadly limited) which all=
ow negotiation of non bilateral feature support, so this would supercede th=
at.<br clear=3D"all"></div><div><div dir=3D"ltr"><div dir=3D"ltr">--<br><a =
href=3D"https://twitter.com/JeremyRubin" target=3D"_blank">@JeremyRubin</a>=
<a href=3D"https://twitter.com/JeremyRubin" target=3D"_blank"></a></div></d=
iv></div></div></blockquote></div></div>
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