Networking
An Internet Protocol address (IP address) is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. It serves two principal functions: host or network interface identification and location addressing. The original IP address format, IPv4, is a 32-bit number, while the newer IPv6 uses 128 bits, vastly expanding the address space.
An IP address is a unique identifier for a network interface. It is used for addressing and routing packets across networks. IPv4 addresses are 32-bit numbers typically written in dotted-decimal notation (e.g., 192.168.1.1), divided into four octets. IPv6 addresses are 128-bit, written in hexadecimal groups separated by colons (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334).1
IP addresses are hierarchical: they consist of a network prefix and a host identifier. The subnet mask or prefix length (e.g., /24) defines the boundary. This structure enables efficient routing through the Internet's decentralized architecture.2
IPv4, defined in RFC 791 (1981), provides approximately 4.3 billion addresses, which proved insufficient for the growth of the Internet. IPv6, standardized in RFC 2460 (1998), offers 2^128 addresses, eliminating scarcity. IPv6 also simplifies packet processing and includes built-in security (IPsec) and auto-configuration.3
Transition mechanisms like dual-stack and tunneling allow coexistence. As of 2024, IPv6 adoption exceeds 40% globally, with countries like India and Belgium leading.4
IP addresses are allocated by the Internet Assigned Numbers Authority (IANA) to Regional Internet Registries (RIRs), which assign them to ISPs and organizations. The five RIRs cover Africa, Asia-Pacific, Europe, Latin America, and North America.5
Dynamic Host Configuration Protocol (DHCP) assigns addresses dynamically, while static addresses are manually configured. Private addresses (e.g., 10.0.0.0/8, 192.168.0.0/16) are used within local networks and are not routable on the public Internet, requiring Network Address Translation (NAT) for external connectivity.6
Certain IP addresses are reserved for specific functions. 127.0.0.1 is the loopback address, referring to the local host. 0.0.0.0 is used for default routes or to mean "any" address. Broadcast addresses (e.g., 255.255.255.255) send packets to all hosts on a subnet. Link-local addresses (169.254.0.0/16) are self-assigned when no DHCP server is available.7
Documentation ranges (e.g., 192.0.2.0/24) are reserved for examples in documentation. Multicast addresses (224.0.0.0/4) are used for one-to-many communication, such as streaming media.8
IP addresses have surprising historical and technical facets. The first ARPANET connection used a form of addressing that predates IP, and the term "Internet Protocol" was coined by Vint Cerf and Bob Kahn in the 1970s.1
Geolocation databases can approximate a device's location based on its IP address, but accuracy varies. IP addresses are also used in cybersecurity for blocking malicious traffic, and in digital rights management to enforce regional restrictions. The exhaustion of IPv4 addresses led to a market where blocks are traded, with some /8 blocks valued at millions of dollars.5
IP addresses are fundamental to Internet communication, with ongoing evolution to meet future demands.
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