Stateful IPv4-IPv6 DNS application level gateway for handling topologies with coexisting IPv4-only, Ipv6-only and dual-stack devices

摘要

Disclosed are methods and apparatus for efficiently and reliably handling DNS (domain name service) queries and responses. In general terms, mechanisms are provided for forwarding only one DNS response to a DNS client when two DNS responses having different protocols (IPv4 or IPv6) may be received, e.g., within a DNS handling device for a particular DNS query. The DNS handling device determines whether to forward or hold a first received DNS response based on a number of criteria. The DNS handling device also determines whether to forward a first or second received response to the DNS client when a first and second response for a particular query is received. In certain cases, a first received DNS response for a particular DNS query may be held until a second better response is received or a timer expires.