PoH handoff between leaders

Question

I tried to understand how PoH works based on the whitepaper and various blogs: leaders generating hashes, adding to the ledger and transmitting entries and ticks as shreds before even finishing the block. (The end of the block is appearently marked with a last tick?)

What I still don’t understand is how the “handoff” happens between leaders? (I know a leader has 4 slots, so between those it’s clear, but not clear between different leaders.) Say, leader A finished his last block by sending the last shred with a PoH hash. When would the next leader B start processing transactions and start publishing shreds? How are the PoH sequences connected?

Say there is 100ms network delay between A and B. Will then B wait for 100ms to get the last shred before his slot begins and starts his own block? Or will it start processing transactions and adding to the ledger based off of the second to last block it received from A? Effectively creating a fork?

Answer 1

I'm still not sure about the exact implementation details, but found this post in the docs:

https://docs.solanalabs.com/implemented-proposals/leader-leader-transition

which explains the "handover" - the transition leader-to-leader.

So I think the short answer to my question is that: up to a given timeout configured on the validator, the next leader will wait for the previous slot entries to be delivered and reset its PoH when it's start producing its own block. Otherwise I guess it will fork.