For example, through Vodafone DNS servers
www.facebook.com resolves to 184.108.40.206
arstechnica.com resolves to 220.127.116.11
guardian.co.uk resolves to 18.104.22.168
If you access those IPs dirctly on a web browser on a Telecom connection, what would happen?
The caching server are only caching contents based on domain name, right? If you can't even access websites based on IP addresses, it must be a network congestion rather than a DNS problem?