Rules for ARP
ARP does not run on top of IP and therefore has no IP headers.
ARP requests are transmitted in broadcast so that all stations receive the packet.
New EtherType defined 0x0806 for both the ARP request and reply.
ARP replies are sent directly to the requesting station (unicast, not broadcast).
ARP tables should age out their entries.
An attachment should answer an ARP sent to itself.