What is (Segwit2x) BIP148?
BIP148 is a UASF that is designed to cause the existing SegWit MASF deployment to cause activation in all existing SegWit capable node software (which currently is 80% of the network nodes). How does BIP148 Work? From August 1st, 2017, miners are required to signal readiness for SegWit by creating blocks with the version bit 1. This will cause all SegWit ready nodes, which make up over 80% of the network.
Is (Segwit2x) BIP148 a hard fork?
No, BIP148 isn’t a hard fork. A hard fork is often confused with a chain split. A hard fork is a type of chain split where the rules are loosened to allow previously disallowed blocks or transactions. A soft fork is a tightening of the rules. A soft fork will result in a converged chain if the majority of hashpower enforces its rules.
Why was the date of August 1, 2017 chosen?
Because BIP9 is time based, BIP148 needs to account for the possibility for some of the hash power to exit (eg. to mine another fork) which would make block intervals longer. The August 1st date allows for the economic majority to successfully activate SegWit. Theoretically, if the hashpower drops by up to 85%, it might take up to 13 weeks to complete an activation period. In this scenario, SegWit will still activate for all BIP148 compliant nodes.