There is an internet plan in my ISP that allows only Facebook, and because Facebook uses Akamai it is included also. So any server that belongs to Akamai can be accessed. How does the firewall know all the servers of Akamai because requesting the IP address of the server works fine, so it's not based on domain name.
I did a little searching Firewall defined Akamai IP Range
and I found out that it is not possible to know all the servers, so any theories and how can I confirm it?