Networking also: Border Gateway Protocol

BGP

How autonomous systems on the internet exchange routes.


In plain terms

Path-vector protocol with policy. Most internet outages that "took down half the internet" were BGP misconfigurations.

Origin

BGP-4 — the current version — is RFC 4271 (2006). The 2008 Pakistan/YouTube incident, the 2019 Cloudflare/Verizon leak, and the 2021 Facebook outage are all classroom examples of how a single misconfigured BGP announcement can break large parts of the internet.

Where it shows up in production
  • Every internet backbone AT&T, NTT, Lumen, GTT — they peer with each other over BGP. There is no other choice at this layer.
  • Facebook 2021 outage A BGP withdrawal during routine maintenance disconnected fb.com globally for six hours.
On Semicolony
Sources & further reading
Found this useful?