What's the Slop in Network Communication?

Each message includes transmitted over the network that that particular i d number. I see, asow, you ing these on the different machines, and that allows you to trace what work was done on behalf of that call  and the messages between the machines. O ky, that makes sense. How about this term slop you used in network communication? It sounds like a very informal term, but how do you measure it and how do you decrease it? Well, if you have two machines connected with something like an ether net, and machine a sends a message or request to machine b, and machine b gets that and works on it and sends an answer back to machine a,. And