> No one would argue that implementing a reliable byte stream service, bundled with a fair congestion control algorithm, should be left to the application. Use

> No one would argue that implementing a reliable byte stream service, bundled with a fair congestion control algorithm, should be left to the application. User-land TCP stacks exist. Sure, that's not "leaving it to the application", but still. Re: HPC and RDMA, yes, if you want every ounce of performance (HPC) then you want RDMA. Lustre was doing that, what, 20+ years ago? But the price you pay is that you get no congestion control, and you have to plan everything. That works great in certain data centers -- it works great if you're CERN recording petabytes of data from one particle physics experiment. It also works great in data centers in general if you don't exceed limits. > Saving the best for last, my third observation is the consequence of an exchange between David Reed and John Ousterhout. David argued that “RPC was one big reason for creating UDP as a datagram ‘process addressing’ support layer” and that “...argument passing and waiting for a return was way too high level for a transport protocol.” Er, UDP goes back at least to 1980, and as such it predates the RPCs of the 80s (Apollo Domain, Sun's ONC RPC, etc).