Mar 25, 2021

As for unconfirmed header state, and unconfirmed block download state. These are not currently broadcast but could be. There is logically a pool of peers with header list requests outstanding, a pool of unique blocks requested (by header) but not received (unpopulated blocks of unknown size in the strong chain), knowledge of the top confirmed and top candidate block (therefore times and heights), a config (time) setting that determines when the stronger candidate chain is current enough to start downloading.