A High-Availability Architecture for the Dynamic Domain Name System

The Domain Name System (DNS) provides a mapping between host names and Internet Protocol (IP) addresses. Hosts that are configured using the Dynamic Host Configuration Protocol (DHCP) can have their assigned IP addresses updated in a Dynamic DNS (DDNS). DNS and DDNS are critical components of the Internet. Most applications use host names rather than IP addresses, allowing the underlying operating system (OS) to translate these host names to IP addresses on behalf of the application. When the DDNS service is unavailable, applications that use DNS cannot contact the hosts served by that DDNS server. Unfortunately, the current DDNS implementation cannot continue to operate under failure of a master DNS server. Although a slave DNS server can continue to translate names to addresses, new IP addresses or changes to existing IP addresses cannot be added. Therefore, those new hosts cannot be reached by the DDNS. A new architecture is presented that eliminates this single point of failure. In this design, instead of storing resource records in a flat text file, all name servers connect to a Lightweight Directory Access Protocol (LDAP) directory to store and retrieve resource records. These directory servers replicate all resource records across each other using a multi-master replication mechanism. The DHCP servers can add records to any of the functioning DNS servers in event of an outage. In this scheme, all DNS servers use the anycast Border Gateway Protocol (BGP). This allows any of the DNS servers to answer queries sent to a single IP address. The DNS clients always use the same IP address to send queries. The routing system removes routes to non-functional name