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Network Working Group                                   T.  T.  Sajitha
Internet-Draft                                          Hewlett-Packard
Expires:  Aug 28, 2004                                  27 Feb 2003




             DNS QTYPE to retrieve IPv4 and IPv6 address
                draft-sajitha-dnsext-qtype-addr-00.txt

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on Aug 28, 2004.

Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

   This document proposes a new query type to be used in the
   DNS [RFC1035] implementation. This is used to retrieve all the
   IPv4 as well as IPv6 addresses of a host using a single query.

1. Introduction

   Currently there is no mechanism to get all the v4 and v6 addresses
   of a host with a single query. This proposal defines a new query type
   "ADDR" which can be used by a client while querying the DNS server.
   While processing this query type, the server should  return all the
   records of type T_A & T_AAAA for the QNAME in question, in the answer
   section of the response.


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2. Rationale

   In DNS IPv4 address is identified by the RR type T_A and IPv6
   address by T_AAAA. As the IPv6 deployment is increasing, the dual
   stack implementations are becoming more common. In this case each
   hosts will have IPv4 as well as IPv6 address. This calls for the
   need of retrieving all the v4 as well as v6 address for a
   particular host. Currently this is achieved by using more than
   one queries.

   Most of the internet services need to know the addresses of a host
   inorder to communicate with it.  When DNS is used for address
   resolution, the queries and responses has to travel over the network
   and so the time taken to resolve the address of a host becomes very
   critical.

3. The ADDR qtype

   The ADDR query type is defined with mnemonic ADDR and type code [TBD].
   This is defined for the IN class. Using this query type, client can
   request for all the addresses of a host using a single query.

   While processing this query type, the server should  return all the
   records of type T_A & T_AAAA for the host in question. All these
   records should be provided in the answer section of the response.

   The server may order all the T_AAAA types first and followed by
   T_A types. A6 record type is not considered as it is deprecated.

4. Advantage over "ALL" QTYPE

   The query type denoted by "*" with a value of 255 [see RFC1035
   Section 3.2.3] will cause the server to return all types of records
   corresponding to the QNAME in question. This include A, NS, MX, SOA,
   CNAME, HINFO etc. For a client looking for the addresses of a host,
   it is inefficient to process all these records and choose the T_A
   and T_AAAA.

   For a DNS server, it has to provide all the RR types of the
   QNAME if queried with "ALL" QTYPE. This is an overhead to the server.
   Moreover the DNS packet size will be a limitation to provide all the
   types of records in a response.


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5. Operational Consideration

   The existing clients can be easily modified to use this QTYPE and
   if does not get an answer, fall back to the two query sequence as
   they do now.

   The old servers which does not support this query type, will return
   a not implemented RCODE whereas the servers which supports this
   query type will return the T_A and T_AAAA RRs.

6. Security consideration

   The ADDR query type as such does not introduce any new security
   problems into the DNS.

7 - References

   [RFC1035]  P. Mockapetris, ``Domain Names - Implementation and
              Specification,'' RFC 1035, USC/Information Sciences
              Institute, November 1987.

8. IANA Considerations

   IANA is requested to allocate a QTYPE value for the ADDR query type.

Author's Address

   Sajitha T. T.
   Hewlett-Packard STSD-I
   29, Cunningham Road
   Bangalore - 560052
   India

   Phone: +91-80-2053091
   E-Mail: sajitha@india.hp.com


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   Copyright (C) The Internet Society (2003).  All Rights Reserved.

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   followed, or as required to translate it into languages other than
   English.


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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.


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