> That said, most protocol implementations that I'm aware of over UDP have one or more of "retry/order checking/etc" on top of them. But it's a common false be

> That said, most protocol implementations that I'm aware of over UDP have one or more of "retry/order checking/etc" on top of them. But it's a common false belief that it would be "reimplementing TCP". Some guarantees of reliability are required for most practical applications but TCP's "in-order stream of bytes" isn't suitable for everything. For any kind of real time data, when packet loss occurs, TCP will re-send data that may already be outdated, and causing later packets to arrive even later. In real time uses, TCP makes any networking problems worse. It's also worth noting that under ideal conditions (ie. no packet loss), TCP and UDP behave almost identically (after startup, that is). The issues only appear when you're working in less than ideal conditions and are worse the longer the physical distances are.