The new Bitcoin Core client will “immediately disconnect peers” (nodes) that use the segwit2x BTC1 client with the merge request seemingly finding the support of most, if not all, current Bitcoin Core developers. Matt Corallo, a former Blockstream employee, stated:
“Staying connected to nodes on other networks only prevents both sides from reaching consensus quickly, wastes network resources on both sides, etc.”
Jeff Garzik, a former Bitcoin Core developer who is now lead maintainer of the segwit2x client, stated the move will cause a chain split. Garzik says:
“This creates chain splits even though Bitcoin Core and segwit2x nodes are validating 100% the same rules today; it creates chain splits because of a presumed future rule deviation.”
It’s not clear how many miners are actually using the segwit2x client. It currently has 156 btc1 nodes, which seems very low if miners are indeed using it in production.
That compares with nearly 800 BitcoinABC nodes, one of the main clients for Bitcoin Cash, and some 5,500 Bitcoin Core nodes, but some miners have stated they are using btc1, in which case it could lead to a split.
However, Bitcoin Core developers suggested that not all nodes would upgrade and one node without the rule change would be sufficient for blocks to be relayed, therefore a chain-split was unlikely. While Jorge Timón, another Blockstream employee, stated:
“Who cares about those nodes not diverging today? Those sevice bits are used because you plan to diverge. We can start preparing today.”
Segwit2x is a “compromise” solution to the scalability debate proposed after an agreement was reached by many bitcoin businesses and miners following a meeting led or organized by Barry Silber, an investor in Blockstream and many other bitcoin companies.
The “compromise” is meant to implement segregated witnesses (segwit) in live production. Which it now has successfully done with segwit locked in on the Bitcoin Core client, soon to go live around the end of the month.
Then, the segwit2x client is meant to hardfork around November so as to increase its base size from 1MB to 2MB, giving total capacity of around 3.4MB in combination with segwit, rather than the 1.7MB that segwit alone provides dependent on its use by the ecosystem.
The 2MB hardfork part is now clearly strongly opposed by Bitcoin Core developers and Blockstream employees specifically. Which is exactly what Bitcoin Cash supporters predicted, leading them to hardfork chain split on August 1st 2017.
The move therefore is seen by segwit2x developers as political rather than technical, with Jeff Garzik stating:
“Consider the signal it sends to the community, and other protocol/implementation developers, when changing Bitcoin Core to reject otherwise-working, otherwise-interoperable network clients.
This is akin to a Web server rejecting connections with a client string “Internet Explorer” while accepting client strings that include “Mozilla”, but are otherwise 100% interoperable.”
That was met with a lengthy reply by Gregory Maxwell, Blockstream’s CTO, who justified the, in effect, locking out of segwit2x node clients by stating:
“A Bitcoin node depends on information being easy to spread and hard to stifle, but this assumption doesn’t hold when you’re surrounded with peers with incompatible rules – the incompatible peers will stifle your communications with the Bitcoin network.
The only way to be sure to have robust connections to peers with compatible rules when some event happens is to have them well before the event, so they enjoy protected high priority slots.”
That translates to a clear statement that the Bitcoin Core client intends to fork off from the segwit2x client and instead of waiting until November they are doing so now.
With the Bitcoin Core maintainer and lead developer, Wladimir Van Der Laan, approving the above rule change, it now seems a split is guaranteed in November if miners and businesses do go ahead with the 2x part.
Which is why few think they indeed will. Not least because the current “compromise” is the exact “compromise” reached in February 2016 that led to no such compromise at all as far as the network is concerned.
Back then, miners backed out, with some, reaching as high as 40%, even mining for segwit, while another 40% mined for bigger blocks.
It is probable the 40% segwit miners will again back out, especially now that the Bitcoin Core client has so strongly come out against it. But what the 40% bigger block miners will do remains to be seen.