Based on the outage people noticed the other day with www.cloudflare.com, we actually know that www is delegated to other nameservers.
Notice that there is an SOA and NS records for www.cloudflare.com if you dig for them.
Given this, they can't just CNAME from one zone to the other (if they want to include additionals from the subzone). So my guess is that the resolution of cloudflare.com is relying on rules setup for an HTTP 301, as opposed to the relying on DNS aliasing.
Notice that there is an SOA and NS records for www.cloudflare.com if you dig for them.
Given this, they can't just CNAME from one zone to the other (if they want to include additionals from the subzone). So my guess is that the resolution of cloudflare.com is relying on rules setup for an HTTP 301, as opposed to the relying on DNS aliasing.