Cloudflare deploys software load balancers in all its datacenters, with every machine capable of acting as an LB for every other machine (and itself) within the datacenter. More here: https://blog.cloudflare.com/unimog-cloudflares-edge-load-bal...

Unimog is key to making the deployment described in the paper work.

Another way of thinking about this is that we have a single virtual load balancer (backed by all the physical machines in the DC) sitting in front of services that transform/terminate/filter/etc customer traffic.