Hey Sumant and all,
as I think Lagapides also explains, the problem is mostly just a question about the OSI layers, which means that:
if a protocol is able to distinguish endpoints on layer 2 it does it that way and this is a very robust way, but in extend all other Layers can be involved. So is Layer 4 with Port 68 and a Transaction ID in the upper layers and so on. It really depends on the protocol.
As a network engineer just keep in mind wich layers are involved or altered (ip dhcp snooping Option 82…) and how the protocol is implemented in your environment.
It’s just that easy,