RFC 3363 (rfc3363) - Page 2 of 6

Representing Internet Protocol version 6 (IPv6) Addresses in the Domain Name System (DNS)

RFC 3363        Representation of IPv6 Addresses in DNS      August 2002


   The main arguments and the issues are covered in a separate document
   [RFC 3364] that reflects the current understanding of the issues.
   This document summarizes the outcome of these discussions.

   The issue of the root of reverse IPv6 address map is outside the
   scope of this document and is covered in a different document
   [RFC 3152].

1.1 Standards Action Taken

   This document changes the status of RFCs 2673 and 2874 from Proposed
   Standard to Experimental.

2.  IPv6 Addresses: AAAA RR vs A6 RR

   Working group consensus as perceived by the chairs of the DNSEXT and
   NGTRANS working groups is that:

   a) AAAA records are preferable at the moment for production
      deployment of IPv6, and

   b) that A6 records have interesting properties that need to be better
      understood before deployment.

   c) It is not known if the benefits of A6 outweigh the costs and
      risks.

2.1 Rationale

   There are several potential issues with A6 RRs that stem directly
   from the feature that makes them different from AAAA RRs: the ability
   to build up addresses via chaining.

   Resolving a chain of A6 RRs involves resolving a series of what are
   nearly-independent queries.  Each of these sub-queries takes some
   non-zero amount of time, unless the answer happens to be in the
   resolver's local cache already.  Other things being equal, we expect
   that the time it takes to resolve an N-link chain of A6 RRs will be
   roughly proportional to N.  What data we have suggests that users are
   already impatient with the length of time it takes to resolve A RRs
   in the IPv4 Internet, which suggests that users are not likely to be
   patient with significantly longer delays in the IPv6 Internet, but
   terminating queries prematurely is both a waste of resources and
   another source of user frustration.  Thus, we are forced to conclude
   that indiscriminate use of long A6 chains is likely to lead to
   increased user frustration.





Bush, et. al.                Informational