Domain name resolution is a necessity, some providers are better than others that’s the reason why I keep a list of public DNS servers mostly for testing. The list includes the IP addresses for two public DNS providers (Level3 Communications and OpenDNS), use their services at your own discretion.
Level 3 Communications
126.96.36.199 188.8.131.52 184.108.40.206 220.127.116.11 18.104.22.168 22.214.171.124
There are more public DNS providers, but I rarely use them.