At a high level, FC lost the write without responding to the write in a timely fashion while other I/Os went through. The write request never gets through from the host to the target, and the host ends up timing out the write then throws an I/O error => that seems like a lost write to me at a higher level. Lossless only applies at the lowest layer of the stack; any holistic view of the system would view this scenario as lossy.
I have implemented ARP and UDP on FPGAs for some toy projects, and it's really not that difficult. One of the use-cases I played around with was getting debug data out of an FPGA at multigigabit rates -- things like PCIe TLPs and raw SERDES data from an EPON implementation to debug a burst mode CDR. The fact that the protocol was IPv4/UDP was no impediment to having it push data through at line rate. Once you've implemented parallel CRC32 for ethernet packets from scratch on a 256-512 bit wide data bus where packets can start and end on arbitrary 32 bit boundaries, the complexity of IPv4 and UDP checksums is dead simple in comparison.
I understand and agree with throwing out TCP in TTPoE. I do not agree with throwing out IPv4 / IPv6. Heck, you don't even need ARP for v6, you could get away with link local addresses using the ethernet MAC address you already need to have anyways.
