Packet Travel


A packet is received by the NIC

the NIC hardware DMAs it into the RX ring in RAM, provided by the driver
this assumes NICs built in this century. there were really really stupid ones before that didn't do DMA.
there are still really really stupid and inefficient NICs, but they all do DMA now
RX ring is usually built from mbuf clusters
ignore jumbos for now
details differ a lot between drivers, let us look at the simple case, ok?

then it interrupts to notify the CPU
every half-decent NIC does not interrupt once per packet, but for a bunch at once. details differ.