Pre-segwit nodes think about segwit transactions non-standard and won’t settle for them to their mempool and due to this fact additionally not ahead them. They might solely take part in relay of unconfirmed non-segwit transactions. Right now, about 94% of transactions use at the least one segwit enter.
Subsequently, pre-segwit nodes would see a small fraction of unconfirmed transactions. This may probably cut back the bandwidth-use of such a node, since segwit friends would additionally not ahead unconfirmed segwit transactions. Segwit is backward- and forward-compatible within the sense that pre-segwit nodes would nonetheless course of the most-work blockchain, since they’d assess segwit transactions as legitimate even whereas non-standard, and arrive on the similar chainstate. They might nevertheless be incapable of assessing validity of segwit transactions and be basically relegated to blindly trusting that the most-work chain is in actual fact legitimate attributable to not processing witness information. This may open pre-segwit nodes as much as accepting a sequence of invalid blocks designed to allow doublespend assaults on such nodes. A pre-segwit node can also have considerably skewed feerate estimation, attributable to seeing such a small portion of the queuing unconfirmed transactions.
Bitcoin Core 0.12.1 was launched in November 2016 and has been end-of-life since late 2017. Beside all of the efficiency enhancements within the final 7 years, additionally fixes to safety points found within the mission that will have an effect on that launch haven’t been backported. It’s unclear what advantages a consumer would possibly anticipate working a shopper this outdated. If the motivation is the bandwidth-use discount, they might obtain the identical and extra by working in -blocksonly mode with a maintained model. In the event that they explicitly need to solely relay legacy transactions, I believe {that a} small patch may change a node’s conduct that might make the node current itself as a non-segwit node with out really downgrading to unmaintained software program.
Nodes that don’t take part within the relay of unconfirmed transactions would usually be slower in propagating new blocks since they’d not be capable to make use of compact block relay. Bitcoin Core’s peer supervisor protects just a few of its friends from eviction by advantage of that peer having been the primary to supply a brand new block these days. I believe that even when a super-majority of nodes (e.g. 90%) switched to pretense non-segwit conduct, the remaining nodes would kind a well-connected compact-block-relay spine that might be hardly affected in any respect.
My suspicion could be that any customers working both the outdated node software program, or a pretense non-segwit node would largely downgrade their very own expertise with out affecting different nodes a lot.
If miners downgraded to solely mining non-segwit transactions, they’d choose from a smaller pool of unconfirmed transactions whereas passing on the upper feerate segwit transactions within the mempool. This may result in their very own block-rewards being decreased to the advantage of miners that don’t take part.
Total, I don’t see any advantages to this concept past it maybe giving the adopter a fuzzy feeling of doing one thing, and since all of the downsides apply to the adopters themselves, I wouldn’t fear in anyway if I noticed some folks implement it.
