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
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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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