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Cc: Matt Corallo <matt@chaincode.com>
Subject: Re: [bitcoin-dev] [PROPOSAL] Emergency RBF (BIP 125)
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+1
From an incentive-compatible point of view, miners should be accepting tran=
sactions that increase the amount of fees that can achieved with 4M weight =
of transactions, so it seems like a pretty sane plan.
One common problem I've run into with RBF is since you're using RBF you pro=
bably want to low ball fees. With good coin selection (*cough* coinsayer.co=
m *cough*), it'll use that opportunity to consolidate inputs. But now let's=
say fees suddenly spike (pretty common), you might want to fee bump your n=
ow stuck transaction. But now that fees are high, it doesn't make sense to =
be consolidating so ideally you'd just replace it with a much smaller trans=
action (that pays higher fee rate).
So if anything, I think your proposal doesn't go far enough. I think even i=
n "non-emergency" cases, we could get away with removing the requirement to=
increase the absolute fee (as long as the fee rate is increased); which al=
so makes it incentive compatible if you assume a reasonable fee-market.
I realize it does open potential DoS vectors, but they seem reasonably smal=
l.
-Ryan
=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90 Original Me=
ssage =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90
On Saturday, June 1, 2019 9:41 PM, Rusty Russell via bitcoin-dev <bitcoin-d=
ev@lists.linuxfoundation.org> wrote:
> Hi all,
>
> I want to propose a modification to rules 3, 4 and 5 of BIP 125:
>
> To remind you of BIP 125:
> 3. The replacement transaction pays an absolute fee of at least the sum
> paid by the original transactions.
>
> 4. The replacement transaction must also pay for its own bandwidth at
> or above the rate set by the node's minimum relay fee setting.
>
> 5. The number of original transactions to be replaced and their
> descendant transactions which will be evicted from the mempool must not
> exceed a total of 100 transactions.
>
> The new "emergency RBF" rule:
>
> 6. If the original transaction was not in the first 4,000,000 weight
> units of the fee-ordered mempool and the replacement transaction is,
> rules 3, 4 and 5 do not apply.
>
> This means:
>
> 1. RBF can be used in adversarial conditions, such as lightning
> unilateral closes where the adversary has another valid transaction
> and can use it to block yours. This is a problem when we allow
> differential fees between the two current lightning transactions
> (aka "Bring Your Own Fees").
>
> 2. RBF can be used without knowing about miner's mempools, or that the
> above problem is occurring. One simply gets close to the required
> maximum height for lightning timeout, and bids to get into the next
> block.
>
> 3. This proposal does not open any significant new ability to RBF spam,
> since it can (usually) only be used once. IIUC bitcoind won't
> accept more that 100 descendents of an unconfirmed tx anyway.
>
> 4. This proposal makes RBF miner-incentive compatible. Currently the
> protocol tells miners they shouldn't accept the highest bidding tx
> for the good of the network. This conflict is particularly sharp
> in the case where the replacement tx would be immediately minable,
> which this proposal addresses.
>
> Unfortunately I haven't found time to code this up in bitcoin, but if
> there's positive response I can try.
>
> Thanks for reading!
> Rusty.
>
>
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
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