The diagrams are informative and makes me appreciate the fact that I don't usually need to worry about UDP and TCP/IP low level things anymore (different in the 1980s, at least for the work I did back then).

BTW, a comment on UML sequence diagrams: I used to be a proponent of UML (Paul Harmon and I wrote a UML book together in ancient history) but sequence diagrams are the only type of UML diagram that I use anymore in my work: the most bang for the buck, communication wise.