This is true for simple UDP, but reliable transports are often built over UDP. As with anything in computing, there are trade-offs between the approaches. One

This is true for simple UDP, but reliable transports are often built over UDP. As with anything in computing, there are trade-offs between the approaches. One example is QUIC now widespread in browsers. MoldUDP64 is used by various exchanges (that's NASDAQ's name, others do something close). It's a simple UDP protocol with sequence numbers; works great on quality networks with well-tuned receivers (or FPGAs). This is an old-school blog article about the earlier MoldUDP: https://www.fragmentationneeded.net/2012/01/dispatches-from-trading-floor-moldudp.html https://www.fragmentationneeded.net/2012/01/dispatches-from-... Another is Aeron.io, which is a high-performance messaging system that includes a reliable unicast/multicast transport. There is so much cool stuff in this project and it is useful to study. I saw this deep-dive into the Aeron reliable multicast protocol live and it is quite good, albeit behind a sign-up. https://aeron.io/other/handling-data-loss-with-aeron/ https://aeron.io/other/handling-data-loss-with-aeron/