BGP in review for 2025

In this episode of PING, APNIC Chief Scientist Geoff Huston returns with his annual review of BGP, reflecting on developments across 2025. Geoff has been publishing this year-in-review analysis of BGP dynamics for more than a decade, and this time he has uncovered some genuinely surprising shifts. His 2025 analysis has been published in two parts on the APNIC Blog. Border Gateway Protocol (BGP) is the mechanism by which network operators announce their Internet address space to the rest of the world and, in turn, learn about the addresses announced by others. Operators participating in the global default-free zone receive all publicly announced routes, each expressed as an IP prefix and associated with its originating Autonomous System Number (ASN). Every BGP speaker has a unique ASN, and all routing information is exchanged and interpreted through this fundamental identifier. In effect, the ASN is the basic unit of interdomain routing. BGP also carries path information that describes how routing announcements traverse the network. This data informs routing policy decisions — which paths to prefer, and through which commercial or technical relationships. While the protocol itself is well understood, the system as a whole is anything but simple. When more than 100,000 ASes are continuously exchanging routing information, complexity is unavoidable. Speaking BGP is about telling things and learning things, but it’s also about deciding what to do with what has been learned. This is the work behind a router, and involves holding all the information and performing routing decisions on it, so the ‘size’ of the information shared and learned has a direct impact on the ‘cost’ of operating as a BGP speaker (cost here ultimately means memory and CPU). For most of the Internet’s history, BGP growth has been relentless, forcing operators to continually ask whether their current routing infrastructure can accommodate future growth. All technology adoption has a life cycle, and is often referred to as the ‘technology adoption curve’. New technologies start out expensive and scarce, become cheaper and widely adopted, and eventually reach a point of saturation where growth slows and replacement becomes the dominant driver. For much of its existence, the Internet has remained firmly in the rapid growth phase of this curve, with sustained increases in users, networks, and routing information. Geoff has detected changes in the pace of growth for both IPv4 and IPv6, which suggest the underlying economics behind investment in Internet, and growth in customers has reached it’s saturation point: We are entering a time where BGP growth may not have the same dynamics we’ve been used to, and questions about capital investment in BGP routing and underlying Internet Addressing are not the same.