Bitcoin developers and miners are fighting over how to expand the network, and the summer of 2017 has crystallized two competing paths forward: BIP 148 and SegWit2x. Both proposals would activate Segr
Bitcoin developers and miners are fighting over how to expand the network, and the summer of 2017 has crystallized two competing paths forward: BIP 148 and SegWit2x. Both proposals would activate Segregated Witness, a technical upgrade that has stalled for months. But they disagree on how and when to do it.
BIP 148 came from a pseudonymous developer named Shaolinfry. The proposal uses an economic hammer. Starting August 1st, nodes running BIP 148 will reject blocks from miners that refuse to signal support for SegWit. If fewer than half the network's mining power backs SegWit by that date, the chain splits. The original Bitcoin chain would remain intact, but BIP 148 miners would follow a separate path. Since SegWit is a soft fork—a backwards-compatible change—the minority chain could fade away if enough miners defect to rejoin the SegWit side. Miners switch chains when they follow the money.
SegWit2x emerged from a meeting of Bitcoin companies at Consensus 2017 in New York. Its backers want miners to activate SegWit once 80 percent of them signal support, then move on to a second phase: a hard fork that raises the base block size limit to 2MB. Combined with SegWit's own block size expansion, this would let the network handle more than 4MB of data per block. Miners controlling more than 80 percent of the network's hashing power have agreed to run this code starting July 21st.
The two proposals have different timelines. BIP 148 targets August 1st. SegWit2x developers are working on a slower schedule. If BIP 148 activates first without miner majority support, it triggers a chain split before SegWit2x has time to deliver SegWit activation through its 80-percent signaling threshold.
James Hilliard posted a fix. His pull request to the SegWit2x repository would accelerate SegWit activation, ensuring it happens before August 1st as long as SegWit2x stays on schedule and the 80-percent coalition of miners deploys the code together. Other developers have reviewed the change on GitHub with approval. It should reach the final code.
That solves the short-term collision. The longer-term threat remains. SegWit2x plans a hard fork within six months to bump the block size cap to 2MB. Unlike soft forks, hard forks break backwards compatibility. Any hard fork will split the chain unless everyone follows it. If SegWit2x miners execute their 2MB hard fork and a significant portion of nodes and miners reject it, Bitcoin would fork the way Ethereum did when it hard forked to reverse the DAO hack. Two coins emerged from that: Ethereum and Ethereum Classic.
Conditions between now and the hard fork attempt could change everything. August 1st should pass without a chain split.
