<ol>
<li><p>Nodes will only relay if <code>mempoolreplacement</code> hasn't set to false (most nodes probably do relay because the default is <code>true</code>).</p>
</li>
<li><p>There are several rules for accepting a replacement after <a href="https://bips.xyz/125" rel="nofollow noreferrer">BIP125</a> (check the BIP for more details). In general: <code>The replacement must pay greater fees than the transactions it replaces.</code>—Otherwise the bandwidth used by those conflicting transactions would not be paid for.</p>
</li>
<li><p>The mempool rules are relevant since nodes only relay transactions after accepting them to their mempool.</p>
</li>
</ol>

CC BY-SA 4.0
2017-03-30T18:39:34.117Z
2022-12-16T21:03:22.457Z
2022-12-16T21:03:22.457Z
Jonas Schnelli
<p>Let's say I broadcast a transation tx0 signaling <a href="https://github.com/bitcoin/bips/blob/master/bip-0125.mediawiki" rel="nofollow noreferrer">RBF</a> replaceability. Later on, I realize it has a small amount of fees, so I send another transaction tx1 that spends the same inputs than tx0, but this time with higher fees. </p>

<p>Which is the default bitcoind/bitcoin-qt behaviour regarding the relaying of tx1? Would all nodes broadcast the new version of the transaction or does the relay policy depend on the <code>mempoolreplacement</code> parameter? Do any special rules apply to the relaying of the replacement transaction?</p>

<p>I have seen that Peter Todd's RBF proposal included a <a href="https://github.com/bitcoin/bitcoin/commit/93411077df9dab72b79316387e59ba683b2f0cdd" rel="nofollow noreferrer">NODE_REPLACE_BY_FEE</a> service bit. Is anything like this included in the current version?</p>

<network><relay><replace-by-fee>
What is the default relaying policy for RBF double spend transactions?
cpsola
# What is the default relaying policy for RBF double spend transactions?

(Asked by: username_0 on 2017-03-30)

Let's say I broadcast a transation tx0 signaling [RBF](https://github.com/bitcoin/bips/blob/master/bip-0125.mediawiki) replaceability. Later on, I realize it has a small amount of fees, so I send another transaction tx1 that spends the same inputs than tx0, but this time with higher fees.

Which is the default bitcoind/bitcoin-qt behaviour regarding the relaying of tx1? Would all nodes broadcast the new version of the transaction or does the relay policy depend on the `mempoolreplacement` parameter? Do any special rules apply to the relaying of the replacement transaction?

I have seen that Peter Todd's RBF proposal included a [NODE\_REPLACE\_BY\_FEE](https://github.com/bitcoin/bitcoin/commit/93411077df9dab72b79316387e59ba683b2f0cdd) service bit. Is anything like this included in the current version?

**Tags:** network, relay, replace-by-fee


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## 1 answers

### Answer by username_1 on 2017-03-30. Score: 2 | Accepted answer

1. Nodes will only relay if `mempoolreplacement` hasn't set to false (most nodes probably do relay because the default is `true`).
2. There are several rules for accepting a replacement after [BIP125](https://bips.xyz/125) (check the BIP for more details). In general: `The replacement must pay greater fees than the transactions it replaces.`—Otherwise the bandwidth used by those conflicting transactions would not be paid for.
3. The mempool rules are relevant since nodes only relay transactions after accepting them to their mempool.


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