world wide convergence of BGP

Daniel Dib asked recently on Twitter about BGP convergence time for world wide operations. two hours he got in response from his friend seemed a bit too long. I did recently help to spin up new ASN with new IPv4 prefix (well, both came from second hand, but you get the point) and as far as I could tell, propagation took around 15 minutes maximum. so in the interest of self-education, I started digging.

I quickly found interesting whitepaper from year 2007, that mentioned typical times of 15-30 minut, and then another one, this time from 2019, that reported times of around four minutes. this makes perfect sense, as number of redundant paths between ASNs grows, router capacities and performance grows as well, and BGP protocol itself is tuned over time - in this context mainly by reducing MRAI (Minimum Route Advertisement Interval) to zero.

of course, it’s worth to note that due to distributed nature, world wide BGP never actually converges - there are constantly some changes and something always changes somewhere around the world. on the other side, it’s protocol that keeps the whole internet running.