Quote from: Kprawn on June 24, 2016, 05:03:35 PM

When is activation?

It depends on the miners. Any miners that choose to upgrade to 0.12.2 can produce blocks that are like a vote for segwit. After 95% of blocks have been produced by miners "voting" for segwit in a 2,016-block long retarget period segwit will be locked-in, about two weeks after that it will activate.

https://bitcoincore.org/en/2016/06/24/segwit-next-steps/

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Deployment plan

The following plan describes how segwit is expected to be deployed.

Merge to master (without mainnet activation code): after Bitcoin Core developers ACK (approve) the final segwit pull request, it will be merged into the Bitcoin Core master Git repository branch. The code that is being merged will include everything in segwit except for the activation code. This will make it easy for developers to test other features on top of segwit, such as compact blocks. Activation on testnet has already occurred so users and developers may experiment and test segwit on testnet.

Backport to 0.12 branch: the unactivated code will be backported to the 0.12 maintenance branch and the backport will receive its own testing.

Choosing the BIP9 parameters: BIP9 is a soft fork deployment mechanism that allows miners to signal their readiness to enforce new consensus rules. Each soft fork made with BIP9 chooses when miners can begin signaling for the soft fork, when the soft fork is considered unsuccessful if not enough miners have signaled for it, and which bit in the block header version field will be used by miners to signal their readiness. These parameters will be selected at this time and implemented along with the code to activate segwit on both the master and 0.12 branches.

Release candidate phase: after all developer testing is successfully concluded, a release candidate (probably named 0.12.2RC1) will be publicly provided to anyone willing to test the code. Miners, merchants, and wallet vendors are especially encouraged to test. If any problems are found, they will be fixed and a new release candidate will be issued. This will be repeated as necessary until a release candidate is found with no known problems.

Binary release: the final release candidate will have its version changed to the final release version (expected to be 0.12.2) and will be released for all users to download and begin running at their leisure (segwit is a soft fork, so upgrading is only required if they plan to use segwit features).

Miners upgrade: miners who choose to upgrade to 0.12.2 will be able to start producing blocks that signal readiness to enforce segwit once the date defined as segwits BIP9 started date is reached.

Lock-in: once 95% of blocks in a 2,016-block long retarget period have signaled that their miners are ready to enforce segwit, segwit will lock-in meaning that unless the blockchain is rolled back at that point, segwit will become active (see next point).

Activation: 2,016 blocks (about two weeks) after segwit is locked-in, it will activate. That means all full nodes running segwit-aware code will begin requiring miners to enforce the new segwit consensus rules.

Wallets upgrade: similar to the P2SH soft fork in 2012, after segwit activates it will not immediately be safe for wallets to upgrade to support segwit. Thats because spends from segwit transactions look like unsecured transactions to older nodes, so if the blockchain is forked soon after segwit activates, those spends could be placed in an earlier block that is not subject to segwits rules. For this reason, it is suggested that wallets avoid upgrading for a few weeks after segwit activates. Allowing that extra time to pass provides extra security to wallet users, although anyone who wants to test with a small amount of money they can afford to lose can begin spending as soon as segwit activates. Users can also begin testing immediately using testnet or regtest with the proposed segwit code or (when available) any release containing segwit.

However on May 23, 2016 bitcoinmagazine said antpool will not "vote" for segwit without a block size increase.

https://bitcoinmagazine.com/articles/antpool-will-not-run-segwit-without-block-size-increase-hard-fork-1464028753