From: Rusty Russell <rusty@rustcorp.com.au>
To: Gleb Naumenko <naumenko.gs@gmail.com>,
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
In-Reply-To: <8914e269-e922-43f4-8846-9fb21a8044f3@Spark>
References: <c06eeb3e-4611-4196-8d2f-f3c3470aeea3@Spark>
	<8914e269-e922-43f4-8846-9fb21a8044f3@Spark>
Date: Fri, 27 Sep 2019 11:38:27 +0930
Message-ID: <87wodu7ap0.fsf@rustcorp.com.au>
MIME-Version: 1.0
Content-Type: text/plain
Subject: Re: [bitcoin-dev] New BIP for p2p messages/state enabling
	reconciliation-based protocols (Erlay)
Precedence: list

Hi Gleb,

        Minor feedback on reading the draft:

> sendrecon:
> uint32 	version 	Must be exactly 1 currently.

At risk of quoting myself[1]: data doesn't have requirements.  Actors do.
In this case, I assume you mean "writers must set this to 1".  What do
readers do if it's not?

> reqreconcil
> uint8 	q 	Coefficient used to estimate set difference.

You describe how to calculate q (as a floating point value), but not how
to encode it?

> Every node stores sets of 128-bit truncated IDs per every peer

"*a* set..." or is it "two sets" (if you include the snapshot?).

And " *for* every peer" (maybe "which supports tx reconciliation?")

> To the best of our knowledge, PinSketch is more bandwidth efficient
> than IBLT, especially for the small differences in sets we expect to
> operate over.

Remove "To the best of our knowledge, ": that makes it sound like it's
up for debate.  I've implemented and experimented with IBLT, and it's
worse.

Cheers,
Rusty.

[1] https://github.com/lightningnetwork/lightning-rfc/blob/master/CONTRIBUTING.md#writing-the-requirements