Polkadot主网中的重要参数

在kusama和mainnet中，epoch就是session

A session is a period of time that has a constant set of validators. Validators can only join or exit the validator set at a session change. It is measured in block numbers. The block where a session is ended is determined by the ShouldSessionEnd trait. When the session is ending, a new validator set can be chosen by OnSessionEnding implementations.

1 session == 2400 blocks (4 hours)  
1 era == 6 sessions == 14400 blocks (24 hours)

"validator set" 一个4小时选一次

来源：https://my.oschina.net/u/855913/blog/3110132