dnsop J. Yao
Internet-Draft P. Vixie
Intended status: Standards Track CNNIC-Farsight Joint Laboratory
Expires: April 27, 2017 N. Kong
X. Li
CNNIC
October 24, 2016
A DNS Query including A Main Question with Accompanying Questions
draft-yao-dnsop-accompanying-questions-01
Abstract
This document enables DNS initiators to send a main question
accompanying with several related questions in a single DNS query,
and enables DNS responders to put the answers into a single DNS
response. This mechanism can reduce the number of DNS round-trips
per application work-unit.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Mechanism for a main question with accompanying questions . . 3
4. Responder Processing . . . . . . . . . . . . . . . . . . . . 5
5. Initiator Processing . . . . . . . . . . . . . . . . . . . . 5
6. Query and Response Example . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
10. Change History . . . . . . . . . . . . . . . . . . . . . . . 7
10.1. draft-yao-dnsop-accompanying-questions: Version 00 . . . 7
10.2. draft-yao-dnsop-accompanying-questions: Version 01 . . . 7
11. Normative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
There are many scenarios in which an application must send several
related questions to a DNS responder. For examples, when asking
about a QTYPE=A RRset, a QTYPE=AAAA RRset may also be of use [RFC
5321]; When asking for some RRset of www.example.com about A and
AAAA, records of a sub-domain name such as _443._tcp.www.example.com
for TLSA may be of interest[RFC 6698].
Query example.com for A and AAAA
Query www.example.com for A and AAAA, and _443._tcp.www.example.com
for TLSA
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This document describes a method by which DNS initiators can send a
main question accompanying with several related questions in a single
DNS query, and enables DNS responders place all related answers into
a single DNS response. This mechanism can reduce the number of DNS
round-trips per application work-unit, by carrying several related
queries in a single query transaction.
2. Terminology
The basic key words such as "MUST", "MUST NOT", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "MAY", and "MAYNOT" are to be interpreted as
described in [RFC2119].
The basic DNS terms used in this specification are defined in the
documents [RFC1034] and [RFC1035].
3. Mechanism for a main question with accompanying questions
The initiator still puts a main question into the question section of
the DNS query packet, as described in [RFC1035]. Accompanying
questions will be put into the variable part of an OPT RR [RFC6891].
The variable part of an OPT RR is encoded in its RDATA and is
structured as the following:
+0 (MSB) +1 (LSB)
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
0: | OPTION-CODE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
2: | OPTION-LENGTH |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
4: | |
/ OPTION-DATA /
/ /
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
OPTION-CODE (Assigned by IANA.)
OPTION-LENGTH Size (in octets) of OPTION-DATA.
OPTION-DATA including at most 8 accompanying questions with AQ-RCODE.
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|AQ | Count | AQ-RCODE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| AQ-TYPE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| |
/ Prefix /
/ /
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|AQ | Seq | AQ-RCODE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| AQ-TYPE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| |
/ Prefix /
/ /
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|AQ | Seq | AQ-RCODE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| AQ-TYPE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| |
/ Prefix /
/ /
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| |
/ ...... /
/ /
o AQ field indicates whether this accompanying question is the first
question. If it is set as 1, this question is the first question.
o Count field represents the total numbers of all accompanying
questions. Seq field represents the sequence number of
accompanying questions from 1 to 7 There will have at most 8
accompanying questions.
o AQ-RCODE field will be set to 111111110100 bits when being
initialized. The AQ-RCODE with the value of 111111110100 bits
means that the mechanism for accompanying has not been
implemented, where "0100" in the RCODE value is "not been
implemented". The AQ aware responders will put the RCODE value
for the query of this question into AQ-RCODE fields.
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o Prefix field is a substring between the main domain name of the
main quesiton and the accompanying domain name of the accompanying
question. That is, if the main domain name is string S and the
accompanying domain name is string S1, the prefix is (S-S1). For
an example, if the main domain name is example.com and the
accompanying domain name is mail.example.com, the prefix is
"mail.".
4. Responder Processing
The AQ aware responder will check the main question first, and put
the results into the DNS response packet. If the AQ OPT is present,
the responder assembles the prefix with the main domain name and make
it to be an accompanying question, checks the accompanying questions
in order, and put the results into the DNS answer section of the
response following RFC 1034; but the response code is placed in the
respective AQ-RCODE field in AQ OPT of the response. The RCODE field
in the DNS response header refers to the main question only. An AQ
unaware responder is expected to ignore the AQ OPT of the query, and
may echo the received OPT back into additional section of the
response message.
5. Initiator Processing
An AQ aware initiator will put the main question into the question
section of the DNS query packet, and put related accompanying
questions into the Accompanying Question fields of OPTION-DATA of OPT
RR. AQ-RCODE value will be sent as 111111110100 bits. The AQ value
should be set to 1 and Count value should be set to total number of
accompanying questions, if the accompanying question is the first
one; For the remain accompanying questions, the AQ value should be
set to 0 and Seq value should be set to the sequence of the
corresponding accompanying questions. The AQ-TYPE value should be
set as the query type related accomanying questions. The Prefix
should be set as the substring between the main domain name of the
main quesiton and the accompanying domain name of the accompanying
question. If the main domain name and the accompanying domain name
are same, the Prefix should be set as all zero bits.
If the initial value of the AQ-RCODE is unchanged in the response, it
indicates that the responder is AQ unaware. In that case, the
responder will deal with the main question only. The initiator
should sent the accompanying questions one by one via the normal DNS
query. In such followup related queries, AQ processing should
probably not be attempted, to reduce waste of network resources.
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6. Query and Response Example
Example: one main question with 2 accompanying questions
The query would look like:
+---------------------------------------------------+
Header | OPCODE=SQUERY |
+---------------------------------------------------+
Question | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=A |
+---------------------------------------------------+
Answer | |
+---------------------------------------------------+
Authority | <empty> |
+---------------------------------------------------+
Additional | |
| AQ=1,Count=2,AQ-TYPE=AAAA,AQ-RCODE=111111110100, |
| Prefix=0, |
| AQ=0, SEQ=1,AQ-TYPE=TLSA,,AQ-RCODE=111111110100, |
| Prefix=_443._tcp., |
+---------------------------------------------------+
The response from AQ aware responders would be:
+---------------------------------------------------+
Header | OPCODE=SQUERY, RESPONSE, AA, RCODE=NOERROR |
+---------------------------------------------------+
Question | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=A |
+---------------------------------------------------+
Answer | example.com IN A 192.168.0.1 |
| example.com. IN AAAA 2001:cc8::1 |
| _443._tcp.example.com. IN TLSA |
| ( 3 0 0 30820307308201efa003020102020... ) |
+---------------------------------------------------+
Authority | <empty> |
+---------------------------------------------------+
Additional | |
| AQ=1, COUNT=2, AQ-TYPE=AAAA, AQ-RCODE=NOERROR, |
| Prefix=0, |
| AQ=0, SEQ=1, AQ-TYPE=TLSA, AQ-RCODE=NOERROR, |
| Prefix=443._tcp., |
+---------------------------------------------------+
The response from AQ unaware responders would be:
+---------------------------------------------------+
Header | OPCODE=SQUERY, RESPONSE, AA, RCODE=NOERROR |
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+---------------------------------------------------+
Question | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=A |
+---------------------------------------------------+
Answer | example.com IN A 192.168.0.1 |
+---------------------------------------------------+
Authority | <empty> |
+---------------------------------------------------+
Additional | |
| AQ=1, COUNT=2, AQ-TYPE=AAAA,AQ-RCODE=111111110100,|
| Prefix=0, |
| AQ=0, SEQ=1, AQ-TYPE=TLSA, AQ-RCODE=111111110100, |
| Prefix=443._tcp., |
+---------------------------------------------------+
7. IANA Considerations
IANA should allocate DNS EDNS0 Option Codes (OPT) following this
document. IANA should reserve RCODE with the value of 111111110100
bits for this document.
8. Security Considerations
TBD
9. Acknowledgements
The authors thank the members in DNSOP mailing list for helpful
discussions, and especially thank Kazunori Fujiwara for kind
comments, suggestions and improvments for the document.
10. Change History
RFC Editor: Please remove this section.
10.1. draft-yao-dnsop-accompanying-questions: Version 00
o A Mechanism for DNS query including one main question with several
accompanying questions
10.2. draft-yao-dnsop-accompanying-questions: Version 01
o Simpilfy the mechanism.
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11. Normative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<http://www.rfc-editor.org/info/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <http://www.rfc-editor.org/info/rfc1035>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
DOI 10.17487/RFC5321, October 2008,
<http://www.rfc-editor.org/info/rfc5321>.
[RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
of Named Entities (DANE) Transport Layer Security (TLS)
Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August
2012, <http://www.rfc-editor.org/info/rfc6698>.
[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", STD 75, RFC 6891,
DOI 10.17487/RFC6891, April 2013,
<http://www.rfc-editor.org/info/rfc6891>.
Authors' Addresses
Jiankang Yao
CNNIC-Farsight Joint Laboratory
4 South 4th Street,Zhongguancun,Haidian District
Beijing, Beijing 100190
China
Phone: +86 10 5881 3007
Email: yaojk@cnnic.cn
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Paul Vixie
CNNIC-Farsight Joint Laboratory
4 South 4th Street,Zhongguancun,Haidian District
Beijing, Beijing 100190
China
Phone: +1 650 489 7919
Email: vixie@fsi.io
Ning Kong
CNNIC
4 South 4th Street,Zhongguancun,Haidian District
Beijing, Beijing 100190
China
Phone: +86 10 5881 3147
Email: nkong@cnnic.cn
Xiaodong Li
CNNIC
4 South 4th Street,Zhongguancun,Haidian District
Beijing, Beijing 100190
China
Phone: +86 10 5881 3020
Email: xl@cnnic.cn
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