Domain Name System (DNS) PDF

06 Domain name system *[ Source: DNS security presentation ]()* A Domain Name System (DNS) translates a domain name such as www.example.com [ ]() to an IP address...

06 Domain name system *[ Source: DNS security presentation ]()* A Domain Name System (DNS) translates a domain name such as www.example.com [ ]() to an IP address. DNS is hierarchical, with a few authoritative servers at the top level. Your router or ISP provides information about which DNS server(s) to contact when doing a lookup. Lower level DNS servers cache mappings, which could become stale due to DNS propagation delays. DNS results can also be cached by your browser or OS for a certain period of time, determined by the time to live (TTL). [ ]()  ** NS record (name server) - Specifies the DNS servers for your domain/ ** subdomain. ** MX record (mail exchange) - Specifies the mail servers for accepting messages. ** ** A record (address) - Points a name to an IP address. ** ** CNAME (canonical) - Points a name to another name or CNAME (example.com to ** ` ` [ www.example.com) or to an A record. ]() ` ` ⠀ Services such as CloudFlare and Route 53 provide managed DNS services. Some DNS [ ]() [ ]() services can route traffic through various methods: [ Weighted round robin ]() Prevent traffic from going to servers under maintenance Balance between varying cluster sizes A/B testing [ Latency-based ]() [ Geolocation-based ]() ⠀ Disadvantage(s): DNS Accessing a DNS server introduces a slight delay, although mitigated by caching described above. DNS server management could be complex and is generally managed by [ governments, ISPs, and large companies. ]() DNS services have recently come under DDoS attack, preventing users from [ ]() accessing websites such as Twitter without knowing Twitter's IP address(es).