The reason I ask is because I'm trying to figure out how to best set up a redundant DHCP server, in case the original fails for whatever reason.
First, I laud your interest in learning more about the protocol. That is a good plan.
Second, I thank you for explaining your goal; I think it will help you get a good answer.
Finally, my answer:
For whichever DHCP server you choose to go with, there is likely a failover / redundancy configuration that permits you to set up a redundant DHCP server that can take over automatically (I believe Windows has such, and I know the ISC's DHCP server can). That would be my first choice, as it typically addresses issues with leases given out by the primary DHCP server before its failure, and because it recovers automatically and quickly.
Second choice would be to fully duplicate the configuration on another machine so that you can bring the other machine up manually in case of failure of the first. This isn't as optimal because you'll lose existing lease information and because of the implicit down-time between the first DHCP server failing and when you bring up the replacemnt.