> Well when I started in "Networking" about a thousand years ago when we
> used puffs of smoke for communication, a "Datagram" was a single packet
A lot has changed since then.
> signaling. Data would go in-band. UDP (Unix Datagram Protocol) are
User Datagram Protocal.
> (were) datagrams with an IP Header. If the IP "layer" now allows one
> to fragment, i.e., use datagrams that no longer consist of a single
> packet, then the whole reason for using datagrams has disappeared.
Fragmentation at lower layers has little to do with why one uses
UDP to tranport a protocal. What happens when your "single packet"
hits a network with a smaller MTU than yours?