Comment by Filligree
Delivery is what happens when the signals cross from the wire into the network interface card.
Depending on the layer you’re operating on, you might instead say it’s the call to recv, or the DMA transfer. The point is that it’s logically a memcpy with no further processing. Just a memcpy. The physical data transfer.
It’s easy to build a reliable message-passing system on top of that, but any such system will either involve further processing or else be vulnerable to data loss.
> Delivery is what happens when the signals cross from the wire into the network interface card.
If you look at this sibling comment [1] you will find someone who disagrees with your definition.
[1] https://news.ycombinator.com/item?id=41601562
On your definition, yes, exactly-once delivery is not possible. But I think your definition is neither reasonable nor authoritative.