draft-yao-dnsop-accompanying-questions-03.txt   draft-yao-dnsop-accompanying-questions-04.txt 
dnsop J. Yao dnsop J. Yao
Internet-Draft P. Vixie Internet-Draft P. Vixie
Intended status: Standards Track CNNIC-Farsight Joint Laboratory Intended status: Standards Track CNNIC-Farsight Joint Laboratory
Expires: December 25, 2017 N. Kong Expires: March 21, 2018 N. Kong
X. Li X. Li
CNNIC CNNIC
June 23, 2017 September 17, 2017
A DNS Query including A Main Question with Accompanying Questions A DNS Query including A Main Question with Accompanying Questions
draft-yao-dnsop-accompanying-questions-03 draft-yao-dnsop-accompanying-questions-04
Abstract Abstract
This document enables DNS initiators to send a main question This document enables DNS initiators to send a main question
accompanying with several related questions in a single DNS query, accompanying with several related questions in a single DNS query,
and enables DNS responders to put the answers into a single DNS and enables DNS responders to put the answers into a single DNS
response. This extension enables a range of initiators to look up response. This extension enables a range of initiators to look up
"X, or failing that, Y" in a better way than both current "X, or failing that, Y" in a better way than both current
alternatives. This mechanism can reduce the number of DNS round- alternatives. This mechanism can reduce the number of DNS round-
trips per application work-unit. trips per application work-unit.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 25, 2017. This Internet-Draft will expire on March 21, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
This document may contain material from IETF Documents or IETF This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this 10, 2008. The person(s) controlling the copyright in some of this
skipping to change at page 2, line 37 skipping to change at page 2, line 37
4. Responder Processing . . . . . . . . . . . . . . . . . . . . 6 4. Responder Processing . . . . . . . . . . . . . . . . . . . . 6
5. Initiator Processing . . . . . . . . . . . . . . . . . . . . 7 5. Initiator Processing . . . . . . . . . . . . . . . . . . . . 7
6. Query and Response Example . . . . . . . . . . . . . . . . . 7 6. Query and Response Example . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
10. Change History . . . . . . . . . . . . . . . . . . . . . . . 9 10. Change History . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. draft-yao-dnsop-accompanying-questions: Version 00 . . . 9 10.1. draft-yao-dnsop-accompanying-questions: Version 00 . . . 9
10.2. draft-yao-dnsop-accompanying-questions: Version 01 . . . 9 10.2. draft-yao-dnsop-accompanying-questions: Version 01 . . . 9
10.3. draft-yao-dnsop-accompanying-questions: Version 02 . . . 9 10.3. draft-yao-dnsop-accompanying-questions: Version 02 . . . 9
10.4. draft-yao-dnsop-accompanying-questions: Version 03 . . . 9 10.4. draft-yao-dnsop-accompanying-questions: Version 03 . . . 10
11. Normative References . . . . . . . . . . . . . . . . . . . . 9 10.5. draft-yao-dnsop-accompanying-questions: Version 04 . . . 10
11. Normative References . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
Sometimes, when DNS lookup of X, an application will lookup Y if X Sometimes, when DNS lookup of X, an application will lookup Y if X
fails. For examples, the initiator may fall back to A record if the fails. For examples, the initiator may fall back to A record if the
lookup of MX record fails. lookup of MX record fails.
Some initiators do it in sequence, X and after a few seconds, then Y. Some initiators do it in sequence, X and after a few seconds, then Y.
Although it is simple, this leads to unpleasant waiting whenever X Although it is simple, this leads to unpleasant waiting whenever X
skipping to change at page 4, line 23 skipping to change at page 4, line 23
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
4: | | 4: | |
/ OPTION-DATA / / OPTION-DATA /
/ / / /
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
OPTION-CODE (Assigned by IANA.) OPTION-CODE (Assigned by IANA.)
OPTION-LENGTH Size (in octets) of OPTION-DATA. OPTION-LENGTH Size (in octets) of OPTION-DATA.
OPTION-DATA including at most 8 accompanying questions with AQ-RCODE. OPTION-DATA including at most 6 accompanying questions with AQ-RCODE.
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| Reserved | AQ-RCODE | | Reserved | AQ-RCODE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| AQ-TYPE | | AQ-TYPE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| AQ-ANCOUNT | | AQ-ANCOUNT |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| AQ-NSCOUNT | | AQ-NSCOUNT |
skipping to change at page 6, line 5 skipping to change at page 6, line 5
o AQ-NSCOUNT field will indicate the number of name server resource o AQ-NSCOUNT field will indicate the number of name server resource
records in the authority records section for this accompanying records in the authority records section for this accompanying
question. The AQ aware responders will put the NSCOUNT value for question. The AQ aware responders will put the NSCOUNT value for
the query of this question into AQ-NSCOUNT field. the query of this question into AQ-NSCOUNT field.
o AQ-ARCOUNT field will indicate the number of resource records in o AQ-ARCOUNT field will indicate the number of resource records in
the additional records section for this accompanying question. the additional records section for this accompanying question.
The AQ aware responders will put the ARCOUNT value for the query The AQ aware responders will put the ARCOUNT value for the query
of this question into AQ-ARCOUNT field. of this question into AQ-ARCOUNT field.
o Prefix field indicates a domain name with the form of a pointer or o Prefix field indicates a domain name with the form of a dot or a
a sequence of labels ending with a pointer using the message sequence of labels ending with a pointer using the message
compression defined in section 4.1.4. of RFC 1035. The domain compression defined in section 4.1.4. of RFC 1035. The domain
name for accompanying questions MUST be same with the domain name name for accompanying questions MUST be same with the domain name
for a main question or be children name of it. For an example, if 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 the main domain name is example.com and the accompanying domain
name is mail.example.com., the prefix is "mail." ending with a name is mail.example.com., the prefix is "mail." ending with a
pointer pointing to "example.com.". pointer pointing to "example.com.".
4. Responder Processing 4. Responder Processing
The AQ aware responder will check the main question first, and put The AQ aware responder will check the main question first, and put
skipping to change at page 6, line 29 skipping to change at page 6, line 29
domain name and makes it to be an accompanying question, checks the domain name and makes it to be an accompanying question, checks the
accompanying questions in order, and put the results into the DNS accompanying questions in order, and put the results into the DNS
answer section, authority section or additional records section of answer section, authority section or additional records section of
the response following RFC 1034; but the response code is placed in 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 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. field in the DNS response header refers to the main question only.
The AQ aware responders will put the ANCOUNT, NSCOUNT and ARCOUNT The AQ aware responders will put the ANCOUNT, NSCOUNT and ARCOUNT
value for the query of this accompanying question into the respective value for the query of this accompanying question into the respective
AQ-ANCOUNT, AQ-NSCOUNT and AQ-ARCOUNT fields. The ANCOUNT, NSCOUNT AQ-ANCOUNT, AQ-NSCOUNT and AQ-ARCOUNT fields. The ANCOUNT, NSCOUNT
and ARCOUNT fields in the DNS response header refer to the main and ARCOUNT fields in the DNS response header refer to the main
question only. When the answer is negative for the accompanying question and its accompanying questions. Since the value for the
accompanying questions' ANCOUNT, NSCOUNT and ARCOUNT can be known
from the respective value of AQ-ANCOUNT, AQ-NSCOUNT and AQ-ARCOUNT,
the actual value of the main question's ANCOUNT, NSCOUNT and ARCOUNT
can be calculated from the ANCOUNT, NSCOUNT and ARCOUNT in the DNS
response header. When the answer is negative for the accompanying
question, the SOA resource record will be put in the authority question, the SOA resource record will be put in the authority
section. section.
The mechanism proposed in this document is intended for both between The mechanism proposed in this document is intended for both between
stub resolvers and recursive resolvers, and between recursive stub resolvers and recursive resolvers, and between recursive
resolvers and authoritative servers. Most DNS resource records resolvers and authoritative servers. If some DNS resource records
needed to process parallel query are normally located in the same are needed to be processed at the same time, the DNS administrator
zone. In case of that some children domain names are delegated and may configure it together. In case of that some children domain
not in the main domain name's zone, the delegation information will names are delegated and not in the main domain name's zone, the
be returned to the recursive resolvers. The recursive resolvers then delegation information will be returned to the recursive resolvers.
check the children domain based on the delegation information, and The recursive resolvers then check the children domain based on the
get the answer for the respective children domain names. 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 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 recursive resolver may have some answers for one or more questions in
the cache, but not for all questions. Under that case, the recursive the cache, but not for all questions. Under that case, the recursive
resolver SHOULD forward this AQ query to some relative authoritative resolver SHOULD forward this AQ query to some relative authoritative
servers for full answers instead of using the existing insufficient servers for full answers instead of using the existing insufficient
cache information. cache information.
An AQ unaware responder is expected to ignore the AQ OPT of the 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 query, and may echo the received OPT back into additional section of
the response message. the response message.
5. Initiator Processing 5. Initiator Processing
An AQ aware initiator will put the main question into the question An AQ aware initiator will put the main question into the question
section of the DNS query packet, and put related accompanying section of the DNS query packet, and put each accompanying question
questions into the related accompanying question fields of OPTION- into the related accompanying question fields of OPTION-DATA of OPT
DATA of OPT RR. AQ-RCODE value will be sent as 111111110100 bits. RR. AQ-RCODE value will be sent as 111111110100 bits. The AQ-TYPE
The AQ-TYPE value should be set as the query type related to value should be set as the query type related to accompanying
accompanying questions. The Prefix value should be set as a pointer questions. The Prefix value should be set as a dot or a sequence of
or a sequence of labels ending with a pointer pointing to the the labels ending with a pointer pointing to the the main domain name of
main domain name of the main question for the respective accompanying the main question for the respective accompanying domain name of the
domain name of the accompanying question. accompanying question.
An AQ aware initiator SHOULD set the limitation of what is the An AQ aware initiator SHOULD set the limitation of what is the
maximum number of accompanying questions a AQ query can bring. This maximum number of accompanying questions a AQ query can bring. This
document suggests that the maximum number is six since most DNS document suggests that the maximum number is six since most DNS
resource records which need parallel query will not larger than six. resource records which need parallel query will not larger than six.
The implementers may set six as the defaul value in the The implementers may set six as the defaul value in the
implementation. The responder can refuse to answer the AQ query if implementation. The responder can refuse to answer the AQ query if
the maximum number of the accompanying questions is larger than the the maximum number of the accompanying questions is larger than the
default maximum value, and return "not been implemented, too many default maximum value, and return "not been implemented, too many
accompanying-questions." information to the initiator. accompanying-questions." information to the initiator.
skipping to change at page 7, line 46 skipping to change at page 8, line 4
Example: one main question with 2 accompanying questions Example: one main question with 2 accompanying questions
The query would look like: The query would look like:
+---------------------------------------------------+ +---------------------------------------------------+
Header | OPCODE=SQUERY | Header | OPCODE=SQUERY |
+---------------------------------------------------+ +---------------------------------------------------+
Question | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=A | Question | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=A |
+---------------------------------------------------+ +---------------------------------------------------+
Answer | | Answer | |
+---------------------------------------------------+ +---------------------------------------------------+
Authority | <empty> | Authority | <empty> |
+---------------------------------------------------+ +---------------------------------------------------+
Additional | | Additional | |
| AQ-TYPE=AAAA,AQ-RCODE=111111110100, | | AQ-TYPE=AAAA,AQ-RCODE=111111110100, |
| Prefix=EXAMPLE.COM., | | Prefix=., |
| AQ-TYPE=TLSA,,AQ-RCODE=111111110100, | | AQ-TYPE=TLSA,,AQ-RCODE=111111110100, |
| Prefix=_443._tcp.EXAMPLE.COM., | | Prefix=_443._tcp., |
+---------------------------------------------------+ +---------------------------------------------------+
The response from AQ aware responders would be: The response from AQ aware responders would be:
+---------------------------------------------------+ +---------------------------------------------------+
Header | OPCODE=SQUERY, RESPONSE, AA, RCODE=NOERROR | Header | OPCODE=SQUERY, RESPONSE, AA, RCODE=NOERROR |
| ANCOUNT=1, ARCOUNT=1, NSCOUNT=0 | | ANCOUNT=3, ARCOUNT=1, NSCOUNT=0 |
+---------------------------------------------------+ +---------------------------------------------------+
Question | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=A | Question | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=A |
+---------------------------------------------------+ +---------------------------------------------------+
Answer | example.com IN A 192.168.0.1 | Answer | example.com IN A 192.168.0.1 |
| example.com. IN AAAA 2001:cc8::1 | | example.com. IN AAAA 2001:cc8::1 |
| _443._tcp.example.com. IN TLSA | | _443._tcp.example.com. IN TLSA |
| ( 3 0 0 30820307308201efa003020102020... ) | | ( 3 0 0 30820307308201efa003020102020... ) |
+---------------------------------------------------+ +---------------------------------------------------+
Authority | <empty> | Authority | <empty> |
+---------------------------------------------------+ +---------------------------------------------------+
Additional | | Additional | |
| AQ-TYPE=AAAA, AQ-RCODE=NOERROR, AQ-ANCOUNT=1, | | AQ-TYPE=AAAA, AQ-RCODE=NOERROR, AQ-ANCOUNT=1, |
| AQ-ARCOUNT=0, AQ-NSCOUNT=0, | | AQ-ARCOUNT=0, AQ-NSCOUNT=0, |
| Prefix=EXAMPLE.COM., | | Prefix=., |
| AQ-TYPE=TLSA, AQ-RCODE=NOERROR, AQ-ANCOUNT=1, | | AQ-TYPE=TLSA, AQ-RCODE=NOERROR, AQ-ANCOUNT=1, |
| AQ-ARCOUNT=0, AQ-NSCOUNT=0, | | AQ-ARCOUNT=0, AQ-NSCOUNT=0, |
| Prefix=_443._tcp.EXAMPLE.COM., | | Prefix=_443._tcp., |
+---------------------------------------------------+ +---------------------------------------------------+
The response from AQ unaware responders would be: The response from AQ unaware responders would be:
+---------------------------------------------------+ +---------------------------------------------------+
Header | OPCODE=SQUERY, RESPONSE, AA, RCODE=NOERROR | Header | OPCODE=SQUERY, RESPONSE, AA, RCODE=NOERROR |
+---------------------------------------------------+ +---------------------------------------------------+
Question | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=A | Question | QNAME=EXAMPLE.COM., QCLASS=IN, QTYPE=A |
+---------------------------------------------------+ +---------------------------------------------------+
Answer | example.com. IN A 192.168.0.1 | Answer | example.com. IN A 192.168.0.1 |
+---------------------------------------------------+ +---------------------------------------------------+
Authority | <empty> | Authority | <empty> |
+---------------------------------------------------+ +---------------------------------------------------+
Additional | | Additional | |
| AQ-TYPE=AAAA,AQ-RCODE=111111110100, | | AQ-TYPE=AAAA,AQ-RCODE=111111110100, |
| Prefix=EXAMPLE.COM., | | Prefix=., |
| AQ-TYPE=TLSA, AQ-RCODE=111111110100, | | AQ-TYPE=TLSA, AQ-RCODE=111111110100, |
| Prefix=_443._tcp.EXAMPLE.COM., | | Prefix=_443._tcp., |
+---------------------------------------------------+ +---------------------------------------------------+
7. IANA Considerations 7. IANA Considerations
IANA should allocate DNS EDNS0 Option Codes (OPT) following this IANA should allocate DNS EDNS0 Option Codes (OPT) following this
document. IANA should reserve RCODE with the value of 111111110100 document. IANA should reserve RCODE with the value of 111111110100
bits for this document. bits for this document.
8. Security Considerations 8. Security Considerations
TBD TBD
9. Acknowledgements 9. Acknowledgements
The authors thank the members in DNSOP mailing list for helpful The authors thank the members in DNSOP mailing list for helpful
discussions, and especially thank Kazunori Fujiwara, JINMEI Tatuya, discussions, and especially thank Kazunori Fujiwara, JINMEI Tatuya,
Bob Harold, Arnt Gulbrandsen and Olafur Gudmundsson for kind Bob Harold, Arnt Gulbrandsen, Olafur Gudmundsson and Stephane
comments, suggestions and improvements for the document. The authors Bortzmeyer for kind comments, suggestions and improvements for the
also thanks Likun Zhang for helpful discussion about some topics document. The authors also thanks Likun Zhang for helpful discussion
related to implementation. about some topics related to implementation.
10. Change History 10. Change History
RFC Editor: Please remove this section. RFC Editor: Please remove this section.
10.1. draft-yao-dnsop-accompanying-questions: Version 00 10.1. draft-yao-dnsop-accompanying-questions: Version 00
o A Mechanism for DNS query including one main question with several o A Mechanism for DNS query including one main question with several
accompanying questions accompanying questions
skipping to change at page 9, line 46 skipping to change at page 10, line 9
10.3. draft-yao-dnsop-accompanying-questions: Version 02 10.3. draft-yao-dnsop-accompanying-questions: Version 02
o Remove the AQ and Count bits, and add AQ-ANCOUNT AQ-ARCOUNT AQ- o Remove the AQ and Count bits, and add AQ-ANCOUNT AQ-ARCOUNT AQ-
NSCOUNT NSCOUNT
10.4. draft-yao-dnsop-accompanying-questions: Version 03 10.4. draft-yao-dnsop-accompanying-questions: Version 03
o Improve the introduction and explains the motivation of this draft o Improve the introduction and explains the motivation of this draft
10.5. draft-yao-dnsop-accompanying-questions: Version 04
o Improve the document
11. Normative References 11. Normative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<http://www.rfc-editor.org/info/rfc1034>. <https://www.rfc-editor.org/info/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and [RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <http://www.rfc-editor.org/info/rfc1035>. November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, [RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
DOI 10.17487/RFC5321, October 2008, DOI 10.17487/RFC5321, October 2008,
<http://www.rfc-editor.org/info/rfc5321>. <https://www.rfc-editor.org/info/rfc5321>.
[RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication [RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
of Named Entities (DANE) Transport Layer Security (TLS) of Named Entities (DANE) Transport Layer Security (TLS)
Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August
2012, <http://www.rfc-editor.org/info/rfc6698>. 2012, <https://www.rfc-editor.org/info/rfc6698>.
[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms [RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", STD 75, RFC 6891, for DNS (EDNS(0))", STD 75, RFC 6891,
DOI 10.17487/RFC6891, April 2013, DOI 10.17487/RFC6891, April 2013,
<http://www.rfc-editor.org/info/rfc6891>. <https://www.rfc-editor.org/info/rfc6891>.
Authors' Addresses Authors' Addresses
Jiankang Yao Jiankang Yao
CNNIC-Farsight Joint Laboratory CNNIC-Farsight Joint Laboratory
4 South 4th Street,Zhongguancun,Haidian District 4 South 4th Street,Zhongguancun,Haidian District
Beijing, Beijing 100190 Beijing, Beijing 100190
China China
Phone: +86 10 5881 3007 Phone: +86 10 5881 3007
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