Chain payloads bigger than this when vectored I/O is enabled. The remote
will never advertise a max frame size less than this (well, the spec says
the max frame size can’t be less than 16kb, so not even close).
Chain payloads bigger than this when vectored I/O is not enabled.
A larger value in this scenario will reduce the number of small and
fragmented data being sent, and hereby improve the throughput.