< draft-ietf-dnsop-nsec-aggressiveuse-04.txt   draft-ietf-dnsop-nsec-aggressiveuse-05.txt >
Network Working Group K. Fujiwara Network Working Group K. Fujiwara
Internet-Draft JPRS Internet-Draft JPRS
Updates: 4035 (if approved) A. Kato Updates: 4035 (if approved) A. Kato
Intended status: Standards Track Keio/WIDE Intended status: Standards Track Keio/WIDE
Expires: April 10, 2017 W. Kumari Expires: April 23, 2017 W. Kumari
Google Google
October 7, 2016 October 20, 2016
Aggressive use of NSEC/NSEC3 Aggressive use of NSEC/NSEC3
draft-ietf-dnsop-nsec-aggressiveuse-04 draft-ietf-dnsop-nsec-aggressiveuse-05
Abstract Abstract
The DNS relies upon caching to scale; however, the cache lookup The DNS relies upon caching to scale; however, the cache lookup
generally requires an exact match. This document specifies the use generally requires an exact match. This document specifies the use
of NSEC/NSEC3 resource records to allow DNSSEC validating resolvers of NSEC/NSEC3 resource records to allow DNSSEC validating resolvers
to generate negative answers within a range, and positive answers to generate negative answers within a range, and positive answers
from wildcards. This increases performance / decreases latency, from wildcards. This increases performance / decreases latency,
decreases resource utilization on both authoritative and recursive decreases resource utilization on both authoritative and recursive
servers, and also increases privacy. It may also help increase servers, and also increases privacy. It may also help increase
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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 http://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 April 10, 2017. This Internet-Draft will expire on April 23, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 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
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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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.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
4. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Aggressive Caching . . . . . . . . . . . . . . . . . . . . . 5 5. Aggressive Negative Caching . . . . . . . . . . . . . . . . . 5
5.1. NSEC . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. NSEC . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.2. NSEC3 . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.2. NSEC3 . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.3. Wildcards . . . . . . . . . . . . . . . . . . . . . . . . 7 5.3. Wildcards . . . . . . . . . . . . . . . . . . . . . . . . 7
5.4. Consideration on TTL . . . . . . . . . . . . . . . . . . 7 5.4. Consideration on TTL . . . . . . . . . . . . . . . . . . 7
6. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Update to RFC 4035 . . . . . . . . . . . . . . . . . . . . . 8 7. Update to RFC 4035 . . . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. Security Considerations . . . . . . . . . . . . . . . . . . . 9 9. Security Considerations . . . . . . . . . . . . . . . . . . . 9
10. Implementation Status . . . . . . . . . . . . . . . . . . . . 9 10. Implementation Status . . . . . . . . . . . . . . . . . . . . 9
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
11.1. Change History . . . . . . . . . . . . . . . . . . . . . 10 11.1. Change History . . . . . . . . . . . . . . . . . . . . . 10
11.1.1. Version draft-fujiwara-dnsop-nsec-aggressiveuse-01 . 12 11.1.1. Version draft-fujiwara-dnsop-nsec-aggressiveuse-01 . 12
11.1.2. Version draft-fujiwara-dnsop-nsec-aggressiveuse-02 . 12 11.1.2. Version draft-fujiwara-dnsop-nsec-aggressiveuse-02 . 13
11.1.3. Version draft-fujiwara-dnsop-nsec-aggressiveuse-03 . 13 11.1.3. Version draft-fujiwara-dnsop-nsec-aggressiveuse-03 . 13
11.2. new section . . . . . . . . . . . . . . . . . . . . . . 13 11.2. new section . . . . . . . . . . . . . . . . . . . . . . 13
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
12.1. Normative References . . . . . . . . . . . . . . . . . . 13 12.1. Normative References . . . . . . . . . . . . . . . . . . 13
12.2. Informative References . . . . . . . . . . . . . . . . . 14 12.2. Informative References . . . . . . . . . . . . . . . . . 14
Appendix A. Detailed implementation notes . . . . . . . . . . . 14 Appendix A. Detailed implementation notes . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 Appendix B. Procedure for determining ENT vs NXDOMAN . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
A DNS negative cache exists, and is used to cache the fact that a A DNS negative cache exists, and is used to cache the fact that a
name does not exist. This method of negative caching requires exact name does not exist. This method of negative caching requires exact
matching; this leads to unnecessary additional lookups, increases matching; this leads to unnecessary additional lookups, increases
latency, leads to extra resource utilization on both authoritative latency, leads to extra resource utilization on both authoritative
and recursive servers, and decreases privacy by leaking queries. and recursive servers, and decreases privacy by leaking queries.
This document updates RFC 4035 to allow recursive resolvers to use This document updates RFC 4035 to allow recursive resolvers to use
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"Closest Encloser" is also defined in NSEC3 [RFC5155], as is "Next "Closest Encloser" is also defined in NSEC3 [RFC5155], as is "Next
closer name". closer name".
3. Problem Statement 3. Problem Statement
The DNS negative cache caches negative (non-existent) information, The DNS negative cache caches negative (non-existent) information,
and requires an exact match in most instances [RFC2308]. and requires an exact match in most instances [RFC2308].
Assume that the (DNSSEC signed) "example.com" zone contains: Assume that the (DNSSEC signed) "example.com" zone contains:
apple.example.com IN A 192.0.2.1 albatross.example.com IN A 192.0.2.1
elephant.example.com IN A 192.0.2.2 elephant.example.com IN A 192.0.2.2
*.example.com IN A 192.0.2.3 zebra.example.com IN A 192.0.2.3
zebra.example.com IN A 192.0.2.4
If a validating resolver receives a query for cat.example.com, it If a validating resolver receives a query for cat.example.com, it
contacts its resolver (which may be itself) to query the example.com contacts its resolver (which may be itself) to query the example.com
servers and will get back an NSEC record starting that there are no servers and will get back an NSEC record starting that there are no
records (alphabetically) between apple and elephant, or an NSEC3 records (alphabetically) between albatross and elephant, or an NSEC3
record stating there is nothing between two hashed names. The record stating there is nothing between two hashed names. The
resolver then knows that cat.example.com does not exist; however, it resolver then knows that cat.example.com does not exist; however, it
does not use the fact that the proof covers a range (apple to does not use the fact that the proof covers a range (albatross to
elephant) to suppress queries for other labels that fall within this elephant) to suppress queries for other labels that fall within this
range. This means that if the validating resolver gets a query for range. This means that if the validating resolver gets a query for
ball.example.com (or dog.example.com) it will once again go off and ball.example.com (or dog.example.com) it will once again go off and
query the example.com servers for these names. query the example.com servers for these names.
Further, if a query is received for lion.example.com, it contacts its Now, assume that the (DNSSEC signed) "example.org" zone contains:
resolver (which may be itself) to query the example.com servers and
will get back an NSEC record stating that there are no records avocado.example.org IN A 192.0.2.1
(alphabetically) between elephant and zebra (or an NSEC3 record *.example.org IN A 192.0.2.2
zucchini.example.org IN A 192.0.2.3
If a query is received for leek.example.org, it contacts its resolver
(which may be itself) to query the example.org servers and will get
back an NSEC record stating that there are no records
(alphabetically) between avocado and zucchini (or an NSEC3 record
stating there is nothing between two hashed names), as well as an stating there is nothing between two hashed names), as well as an
answer for lion.example.com, with the label count of the signature answer for leek.example.org, with the label count of the signature
set to two (see [RFC7129], section 5.3 for more details). set to two (see [RFC7129], section 5.3 for more details).
Apart from wasting bandwidth, this also wastes resources on the Apart from wasting bandwidth, this also wastes resources on the
recursive server (it needs to keep state for outstanding queries), recursive server (it needs to keep state for outstanding queries),
wastes resources on the authoritative server (it has to answer wastes resources on the authoritative server (it has to answer
additional questions), increases latency (the end user has to wait additional questions), increases latency (the end user has to wait
longer than necessary to get back an NXDOMAIN answer), can be used by longer than necessary to get back an NXDOMAIN answer), can be used by
attackers to cause a DoS (see additional resources), and also has attackers to cause a DoS (see additional resources), and also has
privacy implications (e.g: typos leak out further than necessary). privacy implications (e.g: typos leak out further than necessary).
4. Background 4. Background
DNSSEC [RFC4035] and [RFC5155] both provide "authenticated denial of DNSSEC [RFC4035] and [RFC5155] both provide "authenticated denial of
existence"; this is a cryptographic proof that the queried for name existence"; this is a cryptographic proof that the queried for name
does not exist, accomplished by providing a (DNSSEC secured) record does not exist, accomplished by providing a (DNSSEC secured) record
containing the names which appear alphabetically before and after the containing the names which appear alphabetically before and after the
queried for name. In the example above, if the (DNSSEC validating) queried for name. In the first example above, if the (DNSSEC
recursive server were to query for dog.example.com it would receive a validating) recursive server were to query for dog.example.com it
(signed) NSEC record stating that there are no labels between "apple" would receive a (signed) NSEC record stating that there are no labels
and "elephant" (or, for NSEC3, a similar pair of hashed names). This between "albatross" and "elephant" (or, for NSEC3, a similar pair of
is a signed, cryptographic proof that these names are the ones before hashed names). This is a signed, cryptographic proof that these
and after the queried for label. As dog.example.com falls within names are the ones before and after the queried for label. As
this range, the recursive server knows that dog.example.com really dog.example.com falls within this range, the recursive server knows
does not exist. that dog.example.com really does not exist.
This document specifies that this NSEC/NSEC3 record should be used to This document specifies that this NSEC/NSEC3 record should be used to
generate negative answers for any queries that the validating server generate negative answers for any queries that the validating server
receives that fall within the range covered by the record (for the receives that fall within the range covered by the record (for the
TTL for the record). This document also specifies that a positive TTL for the record). This document also specifies that a positive
answer should be generated for any queries that the validating server answer should be generated for any queries that the validating server
receives that are proven to be covered by a wildcard record. receives that are proven to be covered by a wildcard record.
Section 4.5 of [RFC4035] says: Section 4.5 of [RFC4035] says:
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We believe this recommendation can be relaxed because, in the absense We believe this recommendation can be relaxed because, in the absense
of this technique, a lookup for the exact name could have come in of this technique, a lookup for the exact name could have come in
during this interval, and so a negative answer could already be during this interval, and so a negative answer could already be
cached (see [RFC2308] for more background). This means that zone cached (see [RFC2308] for more background). This means that zone
operators should have no expectation that an added name would work operators should have no expectation that an added name would work
immediately. With DNSSEC and Aggressive NSEC, the TTL of the NSEC immediately. With DNSSEC and Aggressive NSEC, the TTL of the NSEC
record is the authoritative statement of how quickly a name can start record is the authoritative statement of how quickly a name can start
working within a zone. working within a zone.
5. Aggressive Caching 5. Aggressive Negative Caching
Section 4.5 of [RFC4035] says that "In theory, a resolver could use Section 4.5 of [RFC4035] says that "In theory, a resolver could use
wildcards or NSEC RRs to generate positive and negative responses wildcards or NSEC RRs to generate positive and negative responses
(respectively) until the TTL or signatures on the records in question (respectively) until the TTL or signatures on the records in question
expire. However, it seems prudent for resolvers to avoid blocking expire. However, it seems prudent for resolvers to avoid blocking
new authoritative data or synthesizing new data on their own. new authoritative data or synthesizing new data on their own.
Resolvers that follow this recommendation will have a more consistent Resolvers that follow this recommendation will have a more consistent
view of the namespace". view of the namespace".
This document relaxes this this restriction, as follows: This document relaxes this this restriction, as follows:
+--------------------------------------------------------------+ +--------------------------------------------------------------+
| Once the records are validated, DNSSEC enabled validating | | Once the records are validated, DNSSEC enabled validating |
| resolvers MAY use wildcards and NSEC/NSEC3 resource records | | resolvers MAY use wildcards and NSEC/NSEC3 resource records |
| to generate positive and negative responses until the | | to generate positive and negative responses until the |
| effective TTLs or signatures for those records expire. | | effective TTLs or signatures for those records expire. |
+--------------------------------------------------------------+ +--------------------------------------------------------------+
If the validating resolver's cache has sufficient information to If the negative cache of the validating resolver has sufficient
validate the query, the resolver SHOULD use NSEC/NSEC3/wildcard information to validate the query, the resolver SHOULD use NSEC,
records aggressively. Otherwise, it MUST fall back to send the query NSEC3 and wildcard records aggressively. Otherwise, it MUST fall
to the authoritative DNS servers. back to send the query to the authoritative DNS servers.
5.1. NSEC It is recommended that resolvers that implement Aggressive Negative
Caching provide a configuration switch to disable the feature.
Separate configuration switches may be implemented for the aggressive
use of NSEC, NSEC3 and wildcard records, and it is recommended to
enable aggressive negative caching by default.
Implementations which support aggressive use of NSEC SHOULD enable 5.1. NSEC
this by default. Implementations MAY provide a configuration switch
to disable aggressive use of NSEC and allow it to be enabled or
disabled per domain.
The validating resolver needs to check the existence of an NSEC RR The validating resolver needs to check the existence of an NSEC RR
matching/covering the source of synthesis and an NSEC RR covering the matching/covering the source of synthesis and an NSEC RR covering the
query name. query name.
If denial of existence can be determined according to the rules set If denial of existence can be determined according to the rules set
out in Section 5.4 of [RFC4035], using NSEC records in the cache, out in Section 5.4 of [RFC4035], using NSEC records in the cache,
then the resolver can immediately return an NXDOMAIN or NODATA (as then the resolver can immediately return an NXDOMAIN or NODATA (as
appropriate) response. appropriate) response.
5.2. NSEC3 5.2. NSEC3
NSEC3 aggressive negative caching is more difficult than NSEC NSEC3 aggressive negative caching is more difficult than NSEC
aggressive caching. If the zone is signed with NSEC3, the validating aggressive caching. If the zone is signed with NSEC3, the validating
resolver needs to check the existence of non-terminals and wildcards resolver needs to check the existence of non-terminals and wildcards
which derive from query names. which derive from query names.
A validating resolver implementation MAY support aggressive use of
NSEC3. If it does support aggressive use of NSEC3, it SHOULD enable
this by default. It MAY provide a configuration switch to disable
aggressive use of NSEC3 and allow it to be enabled or disabled for
specific zones.
If denial of existence can be determined according to the rules set If denial of existence can be determined according to the rules set
out in [RFC5155] sections 8.4, 8.5, 8.6, 8.7,using NSEC3 records in out in [RFC5155] Sections 8.4, 8.5, 8.6, 8.7, using NSEC3 records in
the cache, then the resolver can immediately return an NXDOMAIN or the cache, then the resolver can immediately return an NXDOMAIN or
NODATA response (as appropriate). NODATA response (as appropriate).
If a covering NSEC3 RR has Opt-Out flag, the covering NSEC3 RR does If a covering NSEC3 RR has Opt-Out flag, the covering NSEC3 RR does
not prove the non-existence of the domain name and the aggressive not prove the non-existence of the domain name and the aggressive
negative caching is not possible for the domain name. negative caching is not possible for the domain name.
5.3. Wildcards 5.3. Wildcards
The last paragraph of [RFC4035] Section 4.5 also discusses the use of The last paragraph of [RFC4035] Section 4.5 also discusses the use of
wildcards and NSEC RRs to generate positive responses and recommends wildcards and NSEC RRs to generate positive responses and recommends
that it not be relied upon. Just like the case for the aggressive that it not be relied upon. Just like the case for the aggressive
use of NSEC/NSEC3 for negative answers, we revise this use of NSEC/NSEC3 for negative answers, we revise this
recommendation. recommendation.
As long as the validating resolver can determine that a name would As long as the validating resolver can determine that a name would
not exist without the wildcard match, it MAY synthesize an answer for not exist without the wildcard match, determined according to the
that name using the cached deduced wildcard. If the corresponding rules set out in Section 5.3.4 of [RFC4035] (NSEC), or in Section 8.8
wildcard record is not in the cache, it MUST fall back to send the of [RFC5155], it SHOULD synthesize an answer for that name using the
query to the authoritative DNS servers. cached deduced wildcard. If the corresponding wildcard record is not
in the cache, it MUST fall back to send the query to the
An implementation MAY support aggressive use of wildcards. It SHOULD authoritative DNS servers.
provide a configuration switch to disable aggressive use of
wildcards.
5.4. Consideration on TTL 5.4. Consideration on TTL
The TTL value of negative information is especially important, The TTL value of negative information is especially important,
because newly added domain names cannot be used while the negative because newly added domain names cannot be used while the negative
information is effective. information is effective.
Section 5 of [RFC2308] states that the maximum number of negative Section 5 of [RFC2308] states that the maximum number of negative
cache TTL value is 3 hours (10800). It is RECOMMENDED that cache TTL value is 3 hours (10800). It is RECOMMENDED that
validating resolvers limit the maximum effective TTL value of validating resolvers limit the maximum effective TTL value of
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Decreased authorative server load: Because recursive servers can Decreased authorative server load: Because recursive servers can
answer (negative) queries without asking the authoritative server, answer (negative) queries without asking the authoritative server,
the authoritative servers receive fewer queries. This decreases the authoritative servers receive fewer queries. This decreases
the authoritative server bandwidth, queries per second and CPU the authoritative server bandwidth, queries per second and CPU
utilization. utilization.
The scale of the benefit depends upon multiple factors, including the The scale of the benefit depends upon multiple factors, including the
query distribution. For example, at the time of this writing, around query distribution. For example, at the time of this writing, around
65% of queries to Root Name servers result in NXDOMAIN responses (see 65% of queries to Root Name servers result in NXDOMAIN responses (see
statis [root-servers.org]); this technique will eliminate a sizable statistics from [root-servers.org]); this technique will eliminate a
quantity of these. sizable quantity of these.
The technique described in this document may also mitigate so-called The technique described in this document may also mitigate so-called
"random QNAME attacks", in which attackers send many queries for "random QNAME attacks", in which attackers send many queries for
random sub-domains to resolvers. As the resolver will not have the random sub-domains to resolvers. As the resolver will not have the
answers cached, it has to ask external servers for each random query, answers cached, it has to ask external servers for each random query,
leading to a DoS on the authoritative servers (and often resolvers). leading to a DoS on the authoritative servers (and often resolvers).
Aggressive NSEC may help mitigate these attacks by allowing the Aggressive NSEC may help mitigate these attacks by allowing the
resolver to answer directly from cache for any random queries which resolver to answer directly from cache for any random queries which
fall within already requested ranges. It will not always work as an fall within already requested ranges. It will not always work as an
effective defense, not least because not many zones are DNSSEC signed effective defense, not least because not many zones are DNSSEC signed
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(minutes or hours), their RRSIG expiration time can be much further (minutes or hours), their RRSIG expiration time can be much further
in the future (weeks). An attacker who is able to successfully spoof in the future (weeks). An attacker who is able to successfully spoof
responses might poison a cache with old NSEC/NSEC3 records. If the responses might poison a cache with old NSEC/NSEC3 records. If the
resolver is NOT making aggressive use of NSEC/NSEC3, the attacker has resolver is NOT making aggressive use of NSEC/NSEC3, the attacker has
to repeat the attack for every query. If the resolver IS making to repeat the attack for every query. If the resolver IS making
aggressive use of NSEC/NSEC3, one successful attack would be able to aggressive use of NSEC/NSEC3, one successful attack would be able to
suppress many queries for new names, up to the negative TTL. suppress many queries for new names, up to the negative TTL.
10. Implementation Status 10. Implementation Status
Unbound currenty implements aggressive negative caching, as does [ Editor note: RFC Editor, please remove this entire section.
RFC6982 says: "Since this information is necessarily time dependent,
it is inappropriate for inclusion in a published RFC." ]
Unbound currently implements aggressive negative caching, as does
Google Public DNS. Google Public DNS.
11. Acknowledgments 11. Acknowledgments
The authors gratefully acknowledge DLV [RFC5074] author Samuel Weiler The authors gratefully acknowledge DLV [RFC5074] author Samuel Weiler
and the Unbound developers. and the Unbound developers.
The authors would like to specifically thank Stephane Bortzmeyer, The authors would like to specifically thank Stephane Bortzmeyer,
Tony Finch, Tatuya JINMEI for extensive review and comments, and also Tony Finch, Tatuya JINMEI for extensive review and comments, and also
Mark Andrews, Casey Deccio, Alexander Dupuy, Olafur Gudmundsson, Bob Mark Andrews, Casey Deccio, Alexander Dupuy, Olafur Gudmundsson, Bob
Harold, Shumon Huque, John Levine, Pieter Lexis and Matthijs Mekking Harold, Shumon Huque, John Levine, Pieter Lexis and Matthijs Mekking
(who even sent pull requests!). (who even sent pull requests!). Mark Andrews also provided the text
(https://www.ietf.org/mail-archive/web/dnsop/current/msg18332.html)
which we made into Appendix B
11.1. Change History 11.1. Change History
RFC Editor: Please remove this section prior to publication. RFC Editor: Please remove this section prior to publication.
-04 to -05:
o Bob pointed out that I did a stupid - when I added the wildcard to
'example.com' I made the example wrong / confusing. I have
attempted to fix this by adding a second example zone
(example.org) with the wildcard instead.
o More helpful changes (in a pull request, thanks!) from Matthijs
o Included Mark Andrew's useful explanation of how to tell ENT from
NXD as an Appendix.
-03 to -04: -03 to -04:
o Working group does want the "positive" answers, not just negative o Working group does want the "positive" answers, not just negative
ones. This requires readding what used to be Section 7, and a ones. This requires reading what used to be Section 7, and a
bunch of cleanup, including: bunch of cleanup, including:
* Additional text in the Problem Statement * Additional text in the Problem Statement
* Added a wildcard record to the zone. * Added a wildcard record to the zone.
* Added "or positive answers from wildcards" type text (where * Added "or positive answers from wildcards" type text (where
appropriate) to explain that this isn't just for negative appropriate) to explain that this isn't just for negative
answers. answers.
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expanded.) expanded.)
o The aggressive negative caching may be inserted at the cache o The aggressive negative caching may be inserted at the cache
lookup part of the recursive resolvers. lookup part of the recursive resolvers.
o If errors happen in aggressive negative caching algorithm, o If errors happen in aggressive negative caching algorithm,
resolvers MUST fall back to resolve the query as usual. "Resolve resolvers MUST fall back to resolve the query as usual. "Resolve
the query as usual" means that the resolver must process the query the query as usual" means that the resolver must process the query
as though it does not implement aggressive negative caching. as though it does not implement aggressive negative caching.
Appendix B. Procedure for determining ENT vs NXDOMAN
Thanks to Mark Andrews for providing these helpful notes for
implementors. As they are more general than for Aggressive NSEC we
have placed them in an appendix.
If the NSEC record has not been verified as secure discard it.
If the given name sorts before or matches the NSEC owner name discard
it as it does not prove the NXDOMAIN or ENT.
If the given name is a subdomain of the NSEC owner name and the NS
bit is present and the SOA bit is absent then discard the NSEC as it
is from a parent zone.
If the next domain name sorts after the NSEC owner name and the given
name sorts after or matches next domain name then discard the NSEC
record as it does not prove the NXDOMAIN or ENT.
If the next domain name sorts before or matches the NSEC owner name
and the given name is not a subdomain of the next domain name then
discard the NSEC as it does not prove the NXDOMAIN or ENT.
You now have a NSEC record that proves the NXDOMAIN or ENT.
If the next domain name is a subdomain of the given name you have a
ENT otherwise you have a NXDOMAIN.
Authors' Addresses Authors' Addresses
Kazunori Fujiwara Kazunori Fujiwara
Japan Registry Services Co., Ltd. Japan Registry Services Co., Ltd.
Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda
Chiyoda-ku, Tokyo 101-0065 Chiyoda-ku, Tokyo 101-0065
Japan Japan
Phone: +81 3 5215 8451 Phone: +81 3 5215 8451
Email: fujiwara@jprs.co.jp Email: fujiwara@jprs.co.jp
 End of changes. 28 change blocks. 
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