dnsop                                                             J. Yao
Internet-Draft                                                  P. Vixie
Intended status: Standards Track         CNNIC-Farsight Joint Laboratory
Expires: April 27, May 3, 2017                                             N. Kong
                                                                   X. Li
                                                                   CNNIC
                                                        October 24, 30, 2016

   A DNS Query including A Main Question with Accompanying Questions
               draft-yao-dnsop-accompanying-questions-01
               draft-yao-dnsop-accompanying-questions-02

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.

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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
   6.  Query and Response Example  . . . . . . . . . . . . . . . . .   6   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7   8
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   7   8
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7   8
   10. Change History  . . . . . . . . . . . . . . . . . . . . . . .   7   8
     10.1.  draft-yao-dnsop-accompanying-questions: Version 00 . . .   7   9
     10.2.  draft-yao-dnsop-accompanying-questions: Version 01 . . .   7   9
     10.3.  draft-yao-dnsop-accompanying-questions: Version 02 . . .   9
   11. Normative References  . . . . . . . . . . . . . . . . . . . .   8   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8   9

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
   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.

         0   1   2   3   4   5   6   7   8   9   0   1   2   3   4   5
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
     |AQ
       |   Count  Reserved     |                 AQ-RCODE                      |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                  AQ-TYPE                                      |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                 AQ-ANCOUNT                                    |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                 AQ-NSCOUNT                                    |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                 AQ-ARCOUNT                                    |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                                                               |
       /             Prefix                                            /
       /                                                               /
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
     |AQ
       |    Seq  Reserved     |                 AQ-RCODE                      |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                  AQ-TYPE                                      |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                 AQ-ANCOUNT                                    |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                 AQ-NSCOUNT                                    |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                 AQ-ARCOUNT                                    |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                                                               |
       /             Prefix                                            /
       /                                                               /
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
     |AQ
       |    Seq  Reserved     |                 AQ-RCODE                      |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                  AQ-TYPE                                      |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                 AQ-ANCOUNT                                    |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                 AQ-NSCOUNT                                    |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                 AQ-ARCOUNT                                    |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                                                               |
       /             Prefix                                            /
       /                                                               /
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
       |                                                               |
       /                          ......                               /
       /                                                               /

   o  AQ  Reserved 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 kept for the sequence number of
      accompanying questions from 1 to 7 There will have at most 8
      accompanying questions. future use.

   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 means "not been
      implemented".  The AQ aware responders will put the RCODE value
      for the query of this question into AQ-RCODE fields.

   o  Prefix  AQ-ANCOUNT field is a substring between will indicate the main domain name number of resource records in
      the
      main quesiton and the answer section for this accompanying domain question.  The AQ aware
      responders will put the ANCOUNT value for the query of this
      question into AQ-ANCOUNT field.

   o  AQ-NSCOUNT field will indicate the number of name server resource
      records in the authority records section for this accompanying
      question.  The AQ aware responders will put the NSCOUNT value for
      the query of this question into AQ-NSCOUNT field.

   o  AQ-ARCOUNT field will indicate the number of resource records in
      the additional records section for this accompanying question.  That is, if
      The AQ aware responders will put the main ARCOUNT value for the query
      of this question into AQ-ARCOUNT field.

   o  Prefix field indicates a domain name is string S and with the
      accompanying form of a pointer or
      a sequence of labels ending with a pointer using the message
      compression defined in section 4.1.4. of RFC 1035.  The domain
      name is string S1, for accompanying questions MUST be same with the prefix is (S-S1). domain name
      for a main question or be children name of it.  For an example, if
      the main domain name is example.com and the accompanying domain
      name is mail.example.com, mail.example.com., the prefix is
      "mail.". "mail." ending with a
      pointer pointing to "example.com.".

4.  Responder Processing

   The AQ aware responder will check the main question first, and put
   the results into the DNS response packet. packet following RFC 1034.  If the
   AQ OPT is present, the responder assembles the prefix with the main
   domain name and make makes it to be an accompanying question, checks the
   accompanying questions in order, and put the results into the DNS
   answer section, authority section or additional records 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
   The AQ
   unaware responder is expected to ignore aware responders will put the ANCOUNT, NSCOUNT and ARCOUNT
   value for the query of this accompanying question into the respective
   AQ-ANCOUNT, AQ-NSCOUNT and AQ-ARCOUNT fields.  The ANCOUNT, NSCOUNT
   and ARCOUNT fields in the DNS response header refer to the main
   question only.  When the answer is negative for the accompanying
   question, the SOA resource record will be put in the authority
   section.

   The mechanism proposed in this document is intended for both between
   stub resolvers and recursive resolvers, and between recursive
   resolvers and authoritative servers.  Most DNS resource records
   needed to process parallel query are normally located in the same
   zone.  In case of that some children domain names are delegated and
   not in the main domain name's zone, the delegation information will
   be returned to the recursive resolvers.  The recursive resolvers then
   check the children domain based on the delegation information, and
   get the answer for the respective children domain names.

   When a stub resolver sends an AQ query to the recursive resolver, the
   recursive resolver may have some answers for one or more questions in
   the cache, but not for all questions.  Under that case, the recursive
   resolver SHOULD forward this AQ query to some relative authoritative
   servers for full answers instead of using the existing insufficient
   cache information.

   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 related accompanying question fields of OPTION-DATA 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 to
   accompanying questions.  The Prefix value should be set as a pointer
   or a sequence of labels ending with a pointer pointing to the substring between the
   main domain name of the main quesiton and question for the respective accompanying
   domain name of the accompanying question.  If

   An AQ aware initiator SHOULD set the main domain name and limitation of what is the
   maximum number of accompanying domain name
   are same, questions a AQ query can bring.  This
   document suggests that the Prefix should be maximum number is six since most DNS
   resource records which need parallel query will not larger than six.
   The implementers may set six as all zero bits. the defaul value in the
   implementation.  The responder can refuse to answer the AQ query if
   the maximum number of the accompanying questions is larger than the
   default maximum value, and return "not been implemented, too many
   accompanying-questions." information to the initiator.

   If the initial value of the AQ-RCODE is unchanged in the response, response or
   the AQ OPT is not echo back, 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.

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, AQ-TYPE=AAAA,AQ-RCODE=111111110100,               |
                  | Prefix=0, Prefix=EXAMPLE.COM.,                              |
                  | AQ=0, SEQ=1,AQ-TYPE=TLSA,,AQ-RCODE=111111110100, AQ-TYPE=TLSA,,AQ-RCODE=111111110100,              |
                  | Prefix=_443._tcp., Prefix=_443._tcp.EXAMPLE.COM.,                    |
                  +---------------------------------------------------+

       The response from AQ aware responders would be:

                  +---------------------------------------------------+
       Header     | OPCODE=SQUERY,  RESPONSE, AA, RCODE=NOERROR       |
                  |      ANCOUNT=1, ARCOUNT=1, NSCOUNT=0              |
                  +---------------------------------------------------+
       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, AQ-ANCOUNT=1,     |
                  |                   AQ-ARCOUNT=0, AQ-NSCOUNT=0,     | Prefix=0,
                  | Prefix=EXAMPLE.COM.,                              |
                  | AQ=0, SEQ=1, AQ-TYPE=TLSA, AQ-RCODE=NOERROR, AQ-ANCOUNT=1,     |
                  |                   AQ-ARCOUNT=0, AQ-NSCOUNT=0,     |
                  | Prefix=443._tcp., Prefix=_443._tcp.EXAMPLE.COM.,                    |
                  +---------------------------------------------------+

           The response from AQ unaware responders  would be:

                  +---------------------------------------------------+
       Header     | OPCODE=SQUERY,  RESPONSE, AA, RCODE=NOERROR       |
                  +---------------------------------------------------+
       Question   | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=A            |
                  +---------------------------------------------------+
       Answer     |        example.com        example.com.  IN A 192.168.0.1             |
                  +---------------------------------------------------+
       Authority  | <empty>                                           |
                  +---------------------------------------------------+
       Additional |                                                   |
                  | AQ=1, COUNT=2, AQ-TYPE=AAAA,AQ-RCODE=111111110100,| AQ-TYPE=AAAA,AQ-RCODE=111111110100,               | Prefix=0,
                  | Prefix=EXAMPLE.COM.,                              |
                  | AQ=0, SEQ=1, AQ-TYPE=TLSA, AQ-RCODE=111111110100,              |
                  | Prefix=443._tcp., Prefix=_443._tcp.EXAMPLE.COM.,                    |
                  +---------------------------------------------------+

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 Fujiwara, JINMEI Tatuya
   and Bob Harold for kind comments, suggestions and improvments improvements for
   the document.  The authors also thanks Likun Zhang for helpful
   discussion about some topics related to implementation.

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.

10.3.  draft-yao-dnsop-accompanying-questions: Version 02

   o  Remove the AQ and Count bits, and add AQ-ANCOUNT AQ-ARCOUNT AQ-
      NSCOUNT

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

   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