dnsop J. Yao Internet-Draft P. Vixie Intended status: Standards Track CNNIC-Farsight Joint Laboratory Expires: October 30, 2016 N. Kong X. Li CNNIC April 28, 2016 A DNS Query including A Main Question with Accompanying Questions draft-yao-dnsop-accompanying-questions-00 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 This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on October 30, 2016. Copyright Notice Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must Yao, et al. Expires October 30, 2016 [Page 1] Internet-Draft accompanying-queries April 2016 include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. 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 . . . . . . . . . . . . . . . . . . . . 6 6. Query and Response Example . . . . . . . . . . . . . . . . . 6 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 8. Security Considerations . . . . . . . . . . . . . . . . . . . 7 9. Change History . . . . . . . . . . . . . . . . . . . . . . . 7 9.1. draft-yao-dnsop-accompanying-questions: Version 00 . . . 8 10. 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; When asking for an A RRset, an MX RRset might also be of interest; When asking for some RRset of example.com, records of a sub-domain name such as www.example.com may be of interest. Query example.com for A and AAAA Query example.com for A and MX Query example.com for A and www.example.com for A This document describes a method by which DNS initiators can send a main question accompanying with several related questions in a single Yao, et al. Expires October 30, 2016 [Page 2] Internet-Draft accompanying-queries April 2016 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]. A new UAQ (Understand Accompanying Questions) bit in the EDNS flags field [RFC6891] signals that the initiator may have included accompanying questions in OPT RR of EDNS0. If the query has accompanying questions, the accompanying questions enabled initiators MUST set the UAQ bit in the query. The AQ aware responder receiving the UAQ bit will indicate in the UAQ bit of the response whether it implements this specification. [EDIT: Should we just use the presence of an AQ OPT, without also adding a UAQ flag bit, to indicate the use of the AQ feature? We can discuss it in WG if this document is adopted.] Below are Updated EDNS extended RCODE and Flags fields [RFC6891]: +0 (MSB) +1 (LSB) +--+---+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 0: | EXTENDED-RCODE | VERSION | +--+---+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 2: |DO|UAQ| Z | +--+---+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ The variable part of an OPT RR is encoded in its RDATA and is structured as the following: Yao, et al. Expires October 30, 2016 [Page 3] Internet-Draft accompanying-queries April 2016 +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/Seq | AQ-RCODE | +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ | | / Accompanying Question / / / +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ |AQ | Count/Seq | AQ-RCODE | +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ | | / Accompanying Question / / / +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ |AQ | Count/Seq | AQ-RCODE | +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ | | / Accompanying Question / / / +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ | | / ...... / / / o AQ field indicates whether this accompanying question is the first question. If it is set as 1, this question is the first question. Yao, et al. Expires October 30, 2016 [Page 4] Internet-Draft accompanying-queries April 2016 o Count/Seq field represents the sequence number of accompanying questions from 1 to 7 or the total numbers of all accompanying questions. If AQ is set as 0, the Count/Seq will represent the sequence number of this accompanying question. If AQ is set as 1, the Count/Seq will represent the total numbers of all accompanying questions. 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. The AQ aware responders will put the RCODE value for the query of this question into AQ-RCODE fields. o Accompanying Question field is a question, in the format of a "question" as defined in section 4.1.2 of RFC1035, shown below. Within the QNAME, label compression pointers may be used. 1 1 1 1 1 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ | | / QNAME / / / +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ | QTYPE | +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ | QCLASS | +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ 4. Responder Processing The AQ aware responder will check the main question first, and put the results into the DNS response packet. If the UAQ bit is set [EDIT: or perhaps, if the AQ OPT is present], the responder 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 UAQ bit and the AQ OPT of the query, and may echo the received OPT back into additional section of the response message. Yao, et al. Expires October 30, 2016 [Page 5] Internet-Draft accompanying-queries April 2016 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/Seq value should be set to total number of accompanying questions if the accompanying question is the first one; For other accompanying questions, the AQ value should be set to 0 and Count/Seq value should be set to the sequence of the accompanying questions. The UAQ bit should also be set when sending accompanying questions. 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. 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 | | +---------------------------------------------------+ Additional | UAQ=1 | | AQ=1, COUNT/SEQ=2,AQ-RCODE=111111110100, | | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=AAAA | | AQ=0, COUNT/SEQ=1,AQ-RCODE=111111110100, | | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=MX | +---------------------------------------------------+ The response from AQ aware responders would be: +---------------------------------------------------+ Header | OPCODE=SQUERY, RESPONSE, AA, RCODE=NOERROR | +---------------------------------------------------+ Question | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=A | +---------------------------------------------------+ Yao, et al. Expires October 30, 2016 [Page 6] Internet-Draft accompanying-queries April 2016 Answer | example.com IN A 192.168.0.1 | | example.com. IN AAAA 2001:cc8::1 | | example.com. IN MX MAIL.EXAMPLE.COM. | +---------------------------------------------------+ Authority | | +---------------------------------------------------+ Additional | UAQ=1 | | AQ=1, COUNT/SEQ=2,AQ-RCODE=NOERROR, | | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=AAAA | | AQ=0, COUNT/SEQ=1,AQ-RCODE=NOERROR, | | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=MX | +---------------------------------------------------+ 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 IN A 192.168.0.1 | +---------------------------------------------------+ Authority | | +---------------------------------------------------+ Additional | UAQ=1 | | AQ=1, COUNT/SEQ=2,AQ-RCODE=111111110100, | | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=AAAA | | AQ=0, COUNT/SEQ=1,AQ-RCODE=111111110100, | | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=MX | +---------------------------------------------------+ 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. Change History RFC Editor: Please remove this section. Yao, et al. Expires October 30, 2016 [Page 7] Internet-Draft accompanying-queries April 2016 9.1. draft-yao-dnsop-accompanying-questions: Version 00 o A Mechanism for DNS query including one main question with several accompanying questions 10. Normative References [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, . [RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, November 1987, . [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, DOI 10.17487/RFC1321, April 1992, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms for DNS (EDNS(0))", STD 75, RFC 6891, DOI 10.17487/RFC6891, April 2013, . 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 Yao, et al. Expires October 30, 2016 [Page 8] Internet-Draft accompanying-queries April 2016 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 Yao, et al. Expires October 30, 2016 [Page 9]