Internet Protocol (IP)

Internet Protocol, commonly abbreviated IP, is a network protocol (xeer) that defines how data is divided into packets and transmitted from one device to another across different networks. IP is the foundation of the internet: it assigns each device an address for identification, and it specifies the packet header and how routers determine the path a packet will take.

IP operates at the network layer of the TCP/IP model. Its service is connectionless and provides no guarantee that each packet will arrive, arrive in order, or arrive at all. Tasks of verification and retransmission are left to protocols at higher layers such as TCP, while UDP operates similarly to IP itself.

Types: IPv4 and IPv6

IPv4 uses a 32-bit address typically written as four numbers separated by periods, for example 192.0.2.1. The number of addresses it can provide is limited, which has led to methods such as NAT (network address translation) and CIDR allocation. IPv6 uses a 128-bit address written in hexadecimal notation separated by colons (:), providing an vastly larger number of addresses and also simplifying packet header processing and device configuration.

How packets travel

Each packet has a header and payload. The header contains the source address, destination address, and information about the packet's lifetime (TTL/hop limit) to prevent packets from circulating indefinitely. Routers examine the destination address, consult their routing table for the next path, and forward the packet accordingly. Packets with the same destination can take different routes.

Related protocols

IP works with supporting protocols: ICMP, which handles error messages and testing (for example ping); ARP, which connects IP addresses to device addresses (MAC) in IPv4; and DHCP, which automatically assigns addresses. DNS translates network names into IP addresses.

Management and development

IP specifications are published in RFC documents maintained by the IETF (Internet Engineering Task Force), while address allocation and related numbers are managed by IANA and regional address authorities. Migration to IPv6 is ongoing, with many networks currently using both types.