Protocol

In IPv4, a host needed several different protocols just to start talking. ARP found MAC addresses, ICMP Router Discovery advertised the gateway, DHCP handed out addresses, and ICMP Redirect fixed routes, each running independently. IPv6 folds these four jobs into five message types over ICMPv6, and that consolidation mechanism is NDP (Neighbor Discovery Protocol). Following what each of those five messages looks like, and the order they fly in when a host joins a network, shows how NDP works. ...

What is ARP ARP (Address Resolution Protocol) is a network protocol defined in RFC 826 by the IETF in 1982. In TCP/IP networks, it dynamically discovers the MAC address (physical address) associated with a given IP address. It sits at the boundary between Layer 2 (Data Link Layer) and Layer 3 (Network Layer) of the OSI 7-layer model and maps logical addresses (IP) to physical addresses (MAC). In network communication, actual data transmission between devices relies on MAC addresses. The upper layer (Network Layer) works with IP addresses, but the lower layer (Data Link Layer) needs the destination’s MAC address to send packets. ARP performs this IP-to-MAC conversion. It broadcasts a query across the network, and only the device that owns the target IP responds. Because of this, ARP is an essential protocol in most local network environments, including Ethernet networks. ...