Every diameter message uses two types of identifiers "Hop-by-Hop" Id and "End-to-End" Id to maintain the uniqueness of message. I mean to say, when a node sends a diameter message to another node and it travels through so many intermediate nodes, in that case every node adds Hop-by-Hop Id but these intermediate nodes don't modify End-to-End Id of the received message. End-to-End Is is used to find out duplicate messages at the end nodes.
