Navigating the Internet with DNS

As a network service, domain name system (DNS) has evolved from simple host name‐to‐IP address lookup utility to enabling very sophisticated “look‐up” applications supporting voice, data, multimedia, and security applications. The global domain name system is effectively a distributed hierarchical database. To illustrate how domain information is organized and how a DNS server leverages this hierarchical data structure, the chapter looks at an example name resolution. It introduces the common domain name‐to‐IP address resolution process, comprised of locating a DNS server authoritative for the domain name, then seeking an authoritative response to the query. Another popular form of query is for IP address‐to‐name resolution. This “reverse” form of resolution is commonly used as a security check when establishing VPN connections or for general IP address‐to‐hostname lookups. IPv6 reverse domain mapping follows a similar approach, albeit with much longer domain names.