SNTP/NTP Broadcast Mode.
none - no broadcast SNTP packets are received or sent.
Receive - host only receive SNTP packets that were sent
to broadcast address (were not directed to
the host). This is multicast mode in the RFC.
Send - host only send SNTP packets and wait for replies
directed to the host. This is anycast mode in
the RFC.
ReceiveSend - host receive broadcast messages (destination
is broadcast address in the received messages)
and send SNTP packets to wait for replies
directed to the host (destination address
of the reply is the host address). This mode
combines anycast and multicast modes in the
RFC.