BGP (Border Gateway Protocol)

BGP is the inter-AS (autonomous system) routing protocol that determines how packets flow between major networks on the internet. Each AS — typically an ISP, large enterprise, or hosting operator — announces which IP prefixes it can reach, and other ASes use those announcements to build their routing tables. BGP is what makes anycast possible (announce the same prefix from multiple ASes), what enables traffic engineering, and what occasionally causes large-scale outages when an operator misconfigures an announcement.

For offshore hosting customers, BGP usually doesn't matter directly — the host runs its own BGP session with upstream carriers and you don't see it. BGP becomes visible when: (a) the host advertises 'multi-homed' connectivity (BGP sessions with multiple upstreams for redundancy), (b) the customer wants to bring their own IP block (BYOIP), or (c) a routing incident causes asymmetric performance.