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Globally Unique IP Addresses
Return to RFC 1918 Address Allocation for Private Internets
Globally unique IP addresses are essential for devices that need to communicate directly over the internet. These addresses are publicly routable and are assigned by Regional Internet Registries ([RIRs) to ensure that each address is distinct across the global internet infrastructure. Every device that connects to the internet and requires external communication must use a globally unique IP address to ensure that data sent to or from that device reaches the correct destination. The related RFC is RFC 1918, which defines the private IP address ranges that are not globally routable and are used internally within organizations to conserve globally unique addresses. https://en.wikipedia.org/wiki/IP_address https://tools.ietf.org/html/rfc1918
Unlike private IP addresses defined in RFC 1918, globally unique IP addresses are used for external communication across public networks. These addresses are allocated to Internet Service Providers (ISPs) or large organizations by RIRs, which manage the distribution of IP address blocks in different regions. RIRs such as ARIN for North America, RIPE NCC for Europe, and APNIC for Asia-Pacific allocate public address blocks that ensure each address remains unique across the global internet. The related RFC is RFC 2050, which describes the policies governing IP address allocation and the role of RIRs in managing these resources. https://en.wikipedia.org/wiki/Regional_Internet_registry https://tools.ietf.org/html/rfc2050
The structure of globally unique addresses is defined by the Internet Protocol (IP), which provides the addressing system for communication across networks. In the IPv4 system, addresses are 32-bit numeric values that allow for approximately 4.3 billion unique addresses. Due to the rapid growth of the internet and the proliferation of devices requiring unique IP addresses, IPv4 address space is now exhausted, and many organizations are transitioning to IPv6, which provides a significantly larger pool of addresses with a 128-bit addressing system. The related RFC is RFC 2460, which defines the IPv6 addressing scheme and its role in providing a vastly expanded address space. https://en.wikipedia.org/wiki/IPv6 https://tools.ietf.org/html/rfc2460
IPv4 address exhaustion led to the widespread use of Network Address Translation (NAT), a technique that allows multiple devices on a private network to share a single public IP address. While NAT conserves public address space, it introduces challenges related to end-to-end connectivity because private addresses are not globally unique and must be translated to public addresses for external communication. However, devices using globally unique IP addresses do not require NAT, as they can communicate directly with other devices on the internet without address translation. The related RFC is RFC 3022, which defines the operation of NAT in conjunction with private and public IP addresses. https://en.wikipedia.org/wiki/Network_address_translation https://tools.ietf.org/html/rfc3022
Globally unique IP addresses are critical for maintaining the integrity and reachability of services on the internet. Services such as web hosting, email servers, and cloud applications rely on these addresses to ensure that users and systems can access them from anywhere in the world. Without globally unique IP addresses, routing on the internet would become impossible, as there would be no way to uniquely identify each endpoint. The related RFC is RFC 1035, which describes the Domain Name System (DNS) that maps domain names to IP addresses, providing a human-readable way to access services using globally unique IP addresses. https://en.wikipedia.org/wiki/Domain_Name_System https://tools.ietf.org/html/rfc1035
The management of globally unique IP addresses is critical to the operation of the internet. RIRs allocate blocks of IP addresses to ISPs and large organizations, who then assign addresses to their customers and devices. This hierarchical structure ensures that address allocation is efficient and that no two devices on the internet are assigned the same IP address. To prevent address exhaustion and encourage efficient use of the available space, RIRs implement policies that govern how IP addresses are allocated and reclaimed when they are no longer needed. The related RFC is RFC 2050, which outlines the allocation framework for IP addresses and the responsibilities of RIRs in managing these resources. https://en.wikipedia.org/wiki/Regional_Internet_registry https://tools.ietf.org/html/rfc2050
The introduction of IPv6 addresses a major limitation of IPv4 by vastly expanding the available pool of IP addresses. With IPv6, the total number of addresses available is so large that it effectively eliminates the possibility of IP address exhaustion for the foreseeable future. This allows for direct communication between devices using globally unique IP addresses, without the need for NAT or other workarounds. However, the transition from IPv4 to IPv6 has been gradual, with many networks and devices still operating on the older IPv4 infrastructure. The related RFC is RFC 4291, which defines the addressing architecture for IPv6 and its role in global networking. https://en.wikipedia.org/wiki/IPv6 https://tools.ietf.org/html/rfc4291
Conclusion
The title of this RFC is “Address Allocation for Private Internets.” Globally unique IP addresses are fundamental to the functioning of the internet, enabling devices and services to communicate reliably across the globe. Managed by RIRs and allocated according to strict policies, these addresses ensure that every device on the internet has a unique identifier, allowing for seamless routing and connectivity. While IPv4 address exhaustion has led to the adoption of NAT and other address-conservation techniques, the advent of IPv6 provides a long-term solution to the limitations of the older addressing system. RFC 1918 and related documents provide guidance on the use of private IP addresses, while globally unique IP addresses continue to be the backbone of internet communication.