DNS is a hierarchical distributed naming system for computers, services, or any resources connected to the Internet or a private network, which is implemented by DNS servers and DNS protocol. The rules for the creation of domain names and domain themselves as well as mechanisms for mutual translation of domain names and IP addresses of network nodes are part of the DNS system. The fundamentals of DNS protocol are defined in RFC 1035. Domain names are used for convenience of users and allow using symbolic names of network nodes instead of IP addresses that are arranged in a hierarchical structure.
Amendments and differences in DNS, which the IPv6 implementation has requested are listed below. Therefore, it is necessary that the student should have basic knowledge of the DNS protocol.
Standardization of the DNS for IPv6 was complex and walked a long way before it has stabilized. Current DNS implementation for IPv6 solves two problems:
These problems are substantially independent. The host can communicate with DNS server via IPv4 and exchange information about IPv6 and vice versa.
There are several informational RFC documents dealing with the issues of IPv6 and DNS coexistence. RFC 3901 deals with recursive servers in local networks that solve DNS queries of local hosts. RFC 4074 describes the possible error states of DNS servers when they receive a DNS query for AAAA record type. RFC 4472 describes the issues of IPv6 and DNS coexistence complexly. It mainly deals with questions like: "What IPv6 addresses should or should not be written into DNS?" and "What communication protocol should be used if the computer uses both protocols?" The answers to both questions are briefly described below.