ARP protoco O A knows bs IP address, wants to learn physical address of b O A broadcasts arP query pkt, containing B's IP address o all machines on LAN receive ARP query o B receives ARP packet, replies to A with its(Bs) physical layer address O A caches(saves)IP-to-physical address pairs until information becomes old (times out) o soft state: information that times out (goes away) unless refreshed 5: DataLink Layer 5a-85: DataLink Layer 5a-8 ARP protocol  A knows B's IP address, wants to learn physical address of B  A broadcasts ARP query pkt, containing B's IP address  all machines on LAN receive ARP query  B receives ARP packet, replies to A with its (B's) physical layer address  A caches (saves) IP-to-physical address pairs until information becomes old (times out)  soft state: information that times out (goes away) unless refreshed