RFC 3364 (rfc3364) - Page 3 of 11
Tradeoffs in Domain Name System (DNS) Support for Internet Protocol version 6 (IPv6)
Alternative Format: Original Text Document
RFC 3364 Tradeoffs in DNS Support for IPv6 August 2002 Main Advantages of Going with AAAA The AAAA RR proposed in [RFC 1886], while providing only a subset of the functionality provided by the A6 RR proposed in [RFC 2874], has two main points to recommend it: - AAAA RRs are essentially identical (other than their length) to IPv4's A RRs, so we have more than 15 years of experience to help us predict the usage patterns, failure scenarios and so forth associated with AAAA RRs. - The AAAA RR is "optimized for read", in the sense that, by storing a complete address rather than making the resolver fetch the address in pieces, it minimizes the effort involved in fetching addresses from the DNS (at the expense of increasing the effort involved in injecting new data into the DNS). Less Compelling Arguments in Favor of A6 Since the A6 RR allows a zone administrator to write zone files whose description of addresses maps to the underlying network topology, A6 RRs can be construed as a "better" way of representing addresses than AAAA. This may well be a useful capability, but in and of itself it's more of an argument for better tools for zone administrators to use when constructing zone files than a justification for changing the resolution protocol used on the wire. Less Compelling Arguments in Favor of AAAA Some of the pressure to go with AAAA instead of A6 appears to be based on the wider deployment of AAAA. Since it is possible to construct transition tools (see discussion of AAAA synthesis, later in this note), this does not appear to be a compelling argument if A6 provides features that we really need. Another argument in favor of AAAA RRs over A6 RRs appears to be that the A6 RR's advanced capabilities increase the number of ways in which a zone administrator could build a non-working configuration. While operational issues are certainly important, this is more of argument that we need better tools for zone administrators than it is a justification for turning away from A6 if A6 provides features that we really need. Austein Informational
