I need to have an intelligent conversation with several co-workers who have not yet been sold on embracing tried and trusted message queuing libraries such as MSMQ, ZeroMQ, RabbitMQ, etc and we need this type of messaging in our solution.
But to be able to sell to my colleagues the benefits of using established solutions, I need to understand the fundamental difference between PGM and UDP. What is PGM solving that UDP multicast could not solve?