14 votes

Replace-by-Fee vs Child-pays-for-Parent?

Replace-by-fee means transactions spending the same coin to the same addresses are not considered double-spends by the network and are still relayed, as long as they pay a higher fee than the ...
maservant's user avatar
  • 1,021
8 votes

Do unconfirmed transactions expire after some time?

In addition to Mark S.'s answer, since Bitcoin Core 0.12 there actually is an expiration in the mempool, which evicts unconfirmed transactions after N hours, where N is set by -mempoolexpiry, and ...
Pieter Wuille's user avatar
6 votes
Accepted

Spending output of a low-fee transaction by following with higher-fee transaction

There are 3 cases. Case 1a: if Fee(Tx1) < Dust Fee then Tx1 gets dropped by nodes that do not offer Free Relay Policy. Then all other transaction dependent on the outputs of Tx1 will never be ...
rny's user avatar
  • 2,418
5 votes

CPFP: Child Pays For Parent Clarification Needed

No, it's not a matter of sending to the same address multiple times, rather, CPFP works by spending the output of a previous transaction in a second transaction with a higher fee. Example: An ...
Murch's user avatar
  • 75.4k
5 votes
Accepted

A question about CPFP relaying policy

Correct. tx0 is removed, and tx0child is "invalid" because it spends a UTXO that does not exist in the current chain or mempool. This could change in the future with package RBF and package ...
glozow's user avatar
  • 313
5 votes
Accepted

What are all the rules related to CPFP fee bumping?

There are no specific relay policy rules that apply to CPFP, because unlike RBF, CPFP is not a relay policy. It's a completely normal new, additional, transaction that gets relayed. The fee-bumping ...
Pieter Wuille's user avatar
4 votes
Accepted

Does miner with CPFP look through all the possible combinations of descendants to find the one with the highest fee?

If we run the getrawmempool true RPC, we can look at the data Bitcoin Core has for each of its mempool transactions. Here's an example: "...
David A. Harding's user avatar
4 votes

Spending output of a low-fee transaction by following with higher-fee transaction

To my knowledge there is not a widespread practice of miners to do this, but it certainly can be programmed. As transaction fees continue to rise and these type of stuck transaction become more of a ...
254123179's user avatar
  • 355
4 votes
Accepted

Why do Anchor Outputs need to enforce an nSequence of 1?

Because there must always be exactly one directly spendable output per party, in order to avoid one party to be able to "exhaust" the carve-out. With two CPFP-ble outputs, one party could ...
Antoine Poinsot's user avatar
4 votes
Accepted

Transaction with a high fee keeps getting skipped... Reason why?

$ src/bitcoin-cli getmempoolentry ed45c837d26c25fb6a763708376a87f1875ff57efbb0f56d1b26d00a16c1899e { "fees": { "base": 0.00012042, "modified": 0.00012042, &...
sdaftuar's user avatar
  • 599
4 votes
Accepted

what is meant by DEFAULT_ANCESTOR_LIMIT in child pay for parent?

Bitcoin Core by default does not forward a transaction to its peers, when the full tree of its ancestor transactions contains more than 25 unconfirmed transactions or 101 kvB of unconfirmed ...
Murch's user avatar
  • 75.4k
4 votes
Accepted

Comparison between CPFP and BIP125 for fee bumping

First off, note that BIP125 does not prescribe any network ("consensus") rule. A Bitcoin node may not follow this replacement policy. In fact most nodes on the network are running Bitcoin ...
Antoine Poinsot's user avatar
4 votes

Best Practices with Multiple CPFPs & CPFP + RBF

Unfortunately, I'm not sure there are great answers to these questions right now, but I'll try to explain how things work today. If doing a 2nd CPFP should you boost the original tx, or boost the ...
sdaftuar's user avatar
  • 599
4 votes
Accepted

What types of RBF exist and which one does Bitcoin Core support and use by default?

The original software release included a mechanism that allowed transactions with a higher sequence on inputs to supersede transactions with a lower sequence. This mechanism was not incentive-...
Murch's user avatar
  • 75.4k
3 votes
Accepted

Do miners have an incentive to confirm various transactions from same address?

It sounds like you have rediscovered a mechanism called child pays for parent. Generally, no, two independent transactions could get included in any order even when they were sent from the same wallet ...
Murch's user avatar
  • 75.4k
3 votes
Accepted

Is it possible to get CPFP information from full node, without requesting full mempool dump?

The answer is getmempoolentry. https://chainquery.com/bitcoin-api/help/getmempoolentry
Karel Bílek's user avatar
  • 2,695
3 votes
Accepted

Why won't a transaction with 888/byte confirm after 11+ hours?

It won't confirm because the grandparent and parent of your child transaction aren't confirmed. The grandparent transaction was also paid with a really low fee(51.573 sat/B). I did the math for you....
Chak's user avatar
  • 1,301
3 votes
Accepted

How does one create another transaction when all funds are tied up in an unconfirmed previous transaction?

It depends on your wallet software. Some may simply refuse to create the transaction. Others will spend the change output of the unconfirmed transaction. CPFP and RBF typically only occur when you ...
Ava Chow's user avatar
  • 70.5k
3 votes
Accepted

Do unconfirmed transactions expire after some time?

The newest version of bitcoin core 0.12 introduced a feature called replace by fee. This can be used to issue a transaction with a higher fee spending coins that have not yet been picked up in a block....
Mark S.'s user avatar
  • 2,730
3 votes

Why are negative fees not allowed?

Very interesting brain teaser. I agree that this could be interesting in combination with CPFP. The sender could defer the transaction fees to the recipient which would probably be an interesting ...
Murch's user avatar
  • 75.4k
3 votes
Accepted

spending unconfirmed utxos which exist in the tail of mempool queue

The mempool of a node is limited in size (300MB by default). Once it's filled and the node keeps receiving transactions it will start evicting some transactions. The transactions less attractive to ...
Antoine Poinsot's user avatar
3 votes

spending unconfirmed utxos which exist in the tail of mempool queue

Since transactions bidding 1 ṩ/vB were dropped from almost all mempools in the past few months, most nodes would no longer know about the transaction that created the UTXO you are trying to spend (the ...
Murch's user avatar
  • 75.4k
3 votes
Accepted

How does Bitcoin core knows whether CPFP carve out rule is already used?

You can only use the carve-out rule once since it creates a 26th descendant. The CPFP carve out rule can only be used when a transaction has 25 descendants (including itself), not more. That's the ...
Antoine Poinsot's user avatar
2 votes

How to issue a CPFP?

From the glossary: Selecting transactions for mining not just based on their fees but also based on the fees of their ancestors (parents) and descendants (children). Thus, we understand that ...
skang404's user avatar
  • 616
2 votes
Accepted

Does parent also pay for child?

Does it also work the other way - that is, does transaction with high fee pays for child transaction that has low fees, given that they are both in the mempool? Or is the policy only "one way", from ...
G. Maxwell's user avatar
  • 7,727
2 votes
Accepted

Does bitcoin core node relay those child-pay-for-parent transactions?

(updated based on Pieter's comments below) There are (essentially) two sets of UTXOs at play. One is constructed from the blockchain itself, by reading the blocks on disk and updating with any new ...
Raghav Sood's user avatar
2 votes
Accepted

What happens if the commitment tx fee is too low?

Only if the state changes fees are negotiated (and for mutual closing the channel) so in case the onchain fees change and the channel is not used for a long time just send a fake payment hash to adapt ...
Rene Pickhardt's user avatar
2 votes

Bitcoin.conf setting for CPFP - how can I enable longer 'chains' of unconfirmed transactions?

The maximum unconfirmed descendant count is a mempool setting, not a wallet one. Assuming most of the network run with the default of 25, even if you changed your own mempool to accept a longer chain ...
Antoine Poinsot's user avatar
2 votes

How to do RBF using the Ledger Nano / Ledger Live

I have been unable to find anything for RBF in line with Ledger Live. So far as I can tell, the "Ledger Live" app does not support RBF. You can use Electrum with a Ledger Nano. Electrum ...
RedGrittyBrick's user avatar
2 votes

How does Bitcoin core knows whether CPFP carve out rule is already used?

Nodes generally will only permit a new transaction into their mempool if it does not increase an existing transaction’s descendant set count past 25 and doesn’t make a descendant set exceed 100'000 vB ...
Murch's user avatar
  • 75.4k

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