The Protocol That Holds the Internet Together and Keeps Breaking It

On the morning of October 4, 2021, millions of users attempted to access Facebook, Instagram, and WhatsApp, only to find the apps and websites unresponsive. No error messages or spinning wheels appeared; the services were simply inaccessible. This blackout lasted for nearly six hours, shattering one of the most sophisticated and complex systems in human history.

The culprit was not a cyberattack, power failure, software bug, or database corruption. It was a result of a routine configuration change implemented by a Facebook engineer, a change that silently instructed the rest of the internet to disregard Facebook's existence.

Most individuals who utilize the internet daily are unaware of this system. Even many developers who create software operating on the internet have never given BGP (Border Gateway Protocol) a thought. BGP operates at a foundational level, hidden beneath the surface and unattended by the average user. Often regarded as the most fragile critical system in existence, BGP's fragility is evident in its lack of authentication and reliance on trust. Despite its simple design, BGP breaks regularly, a fact that is both common and concerning.

The genesis of BGP dates back to January 1989, a period marked by the internet's struggle with routing technology. The Exterior Gateway Protocol (EGP) had been the standard, but it proved inadequate as the internet expanded beyond its original scope. By 1989, the internet had grown too intricate for the hierarchical structure of EGP to manage effectively.

Networks began forming connections that bypassed the traditional hierarchy, prompting operators to implement ad-hoc solutions to ensure traffic flowed correctly. These solutions were manually managed and required significant expertise to maintain.

At the 12th meeting of the Internet Engineering Task Force held in Austin, Texas, Yakov Rekhter, a software engineer from IBM, and Kirk Lougheed from Cisco, over a lunch break, conceived a groundbreaking solution. They sketched a new protocol that would eliminate the need for a hierarchical structure and rely on trust instead. Their innovation involved treating every network on the internet as an autonomous system, complete with its own internal routing policy and unique identifier (ASN).

Each autonomous system would then announce the IP address prefixes it could reach, including the complete path of autonomous systems the route traversed. By including this path information, networks could determine whether a route had looped back to itself, a common issue in earlier protocols. If an autonomous system received a route through its own ASN, it would reject the route, preventing loops.

This ingenious idea became the foundation for BGP, culminating in RFC 1105, the first specification of the protocol, published in June 1989. The napkin sketches that originated that fateful lunch have vanished, but their legacy endures. BGP has undergone four major revisions since its inception, with the current version, RFC 4271, still governing the internet's routing in 2026. Remarkably, the protocol's core architecture remains unchanged, a testament to its enduring functionality and adaptability.