Comment by drewg123

Probably because the ethernet driver or hardware has a bug, and the rx buffer is full, and it has been configured to enable pause.

I once took down an entire corp. net by doing serial kernel debugging on a machine with pause frames enabled. Once the debugger took control of the kernel, the driver's rx interrupt handler stopped running, and the rx buffers filled. Eventually, the rx buffers were totally consumed, and the NIC started to send pause frames rather than dropping the packets. To make matters worse, I was remote, so I had to call somebody to powercycle the box.