* First level of loadbalancing is DNS[2]. here we try to map user to a closest PoP based on metrics from our clients.
* User to a PoP path after that mostly depends on our BGP peering with other ISPs (we have an open peering policy[3], please peer with us!)
* Within the PoP we use BGP ECMP and a set of L4 loadbalancers (previously IPVS, now Katran[4]) that encapsulate traffic and DSR it to L7 balancers (previously nginx, now mostly Envoy.)
Overall, we have ~25 PoPs and 4 datacenters.
[1] https://dropbox.tech/infrastructure/dropbox-traffic-infrastr... [2] https://dropbox.tech/infrastructure/intelligent-dns-based-lo...
[3] https://www.dropbox.com/peering [4] https://github.com/facebookincubator/katran