--- 1/draft-ietf-dnsop-nsec-aggressiveuse-03.txt 2016-10-07 17:15:57.578577368 -0700 +++ 2/draft-ietf-dnsop-nsec-aggressiveuse-04.txt 2016-10-07 17:15:57.610578257 -0700 @@ -1,35 +1,36 @@ Network Working Group K. Fujiwara Internet-Draft JPRS Updates: 4035 (if approved) A. Kato Intended status: Standards Track Keio/WIDE -Expires: April 7, 2017 W. Kumari +Expires: April 10, 2017 W. Kumari Google - October 4, 2016 + October 7, 2016 Aggressive use of NSEC/NSEC3 - draft-ietf-dnsop-nsec-aggressiveuse-03 + draft-ietf-dnsop-nsec-aggressiveuse-04 Abstract The DNS relies upon caching to scale; however, the cache lookup generally requires an exact match. This document specifies the use of NSEC/NSEC3 resource records to allow DNSSEC validating resolvers - to generate negative answers within a range. This increases - performance / decreases latency, decreases resource utilization on - both authoritative and recursive servers, and also increases privacy. - It may also help increase resilience to certain DoS attacks in some - circumstances. + to generate negative answers within a range, and positive answers + from wildcards. This increases performance / decreases latency, + decreases resource utilization on both authoritative and recursive + servers, and also increases privacy. It may also help increase + resilience to certain DoS attacks in some circumstances. This document updates RFC4035 by allowing validating resolvers to - generate negative answers based upon NSEC/NSEC3 records. + generate negative based upon NSEC/NSEC3 records (and positive answers + in the presence of wildcards). [ Ed note: Text inside square brackets ([]) is additional background information, answers to frequently asked questions, general musings, etc. They will be removed before publication.This document is being collaborated on in Github at: https://github.com/wkumari/draft-ietf- dnsop-nsec-aggressiveuse. The most recent version of the document, open issues, etc should all be available here. The authors (gratefully) accept pull requests.] Status of This Memo @@ -39,77 +40,81 @@ 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 April 7, 2017. + + This Internet-Draft will expire on April 10, 2017. 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 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. Table of Contents - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 4. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 5. Aggressive Negative Caching . . . . . . . . . . . . . . . . . 5 - 5.1. NSEC . . . . . . . . . . . . . . . . . . . . . . . . . . 5 + 5. Aggressive Caching . . . . . . . . . . . . . . . . . . . . . 5 + 5.1. NSEC . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.2. NSEC3 . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 5.3. Consideration on TTL . . . . . . . . . . . . . . . . . . 6 - 6. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 7. Update to RFC 4035 . . . . . . . . . . . . . . . . . . . . . 7 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 - 9. Security Considerations . . . . . . . . . . . . . . . . . . . 8 - 10. Implementation Status . . . . . . . . . . . . . . . . . . . . 8 - 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 - 12. Change History . . . . . . . . . . . . . . . . . . . . . . . 8 - 12.1. Version draft-fujiwara-dnsop-nsec-aggressiveuse-01 . . . 10 - 12.2. Version draft-fujiwara-dnsop-nsec-aggressiveuse-02 . . . 10 - 12.3. Version draft-fujiwara-dnsop-nsec-aggressiveuse-03 . . . 10 - 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 13.1. Normative References . . . . . . . . . . . . . . . . . . 11 - 13.2. Informative References . . . . . . . . . . . . . . . . . 11 - Appendix A. Detailed implementation notes . . . . . . . . . . . 12 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 + 5.3. Wildcards . . . . . . . . . . . . . . . . . . . . . . . . 7 + 5.4. Consideration on TTL . . . . . . . . . . . . . . . . . . 7 + 6. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . 8 + 7. Update to RFC 4035 . . . . . . . . . . . . . . . . . . . . . 8 + 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 + 9. Security Considerations . . . . . . . . . . . . . . . . . . . 9 + 10. Implementation Status . . . . . . . . . . . . . . . . . . . . 9 + 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10 + 11.1. Change History . . . . . . . . . . . . . . . . . . . . . 10 + 11.1.1. Version draft-fujiwara-dnsop-nsec-aggressiveuse-01 . 12 + 11.1.2. Version draft-fujiwara-dnsop-nsec-aggressiveuse-02 . 12 + 11.1.3. Version draft-fujiwara-dnsop-nsec-aggressiveuse-03 . 13 + 11.2. new section . . . . . . . . . . . . . . . . . . . . . . 13 + 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 + 12.1. Normative References . . . . . . . . . . . . . . . . . . 13 + 12.2. Informative References . . . . . . . . . . . . . . . . . 14 + Appendix A. Detailed implementation notes . . . . . . . . . . . 14 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 1. Introduction 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 matching; this leads to unnecessary additional lookups, increases latency, leads to extra resource utilization on both authoritative and recursive servers, and decreases privacy by leaking queries. This document updates RFC 4035 to allow recursive resolvers to use - NSEC/NSEC3 resource records to synthetize negative answers from the + NSEC/NSEC3 resource records to synthesize negative answers from the information they have in the cache. This allows validating resolvers to respond with NXDOMAIN immediately if the name in question falls into a range expressed by a NSEC/NSEC3 resource record already in the - cache. + cache. It also allows the synthesis of positive answers in the + presence of wildcard records. Aggressive Negative Caching was first proposed in Section 6 of DNSSEC Lookaside Validation (DLV) [RFC5074] in order to find covering NSEC records efficiently. Section 3 of [I-D.vixie-dnsext-resimprove] "Stopping Downward Cache Search on NXDOMAIN" and [I-D.ietf-dnsop-nxdomain-cut] proposed another approach to use NXDOMAIN information effectively. 2. Terminology @@ -128,255 +133,344 @@ closer name". 3. Problem Statement The DNS negative cache caches negative (non-existent) information, and requires an exact match in most instances [RFC2308]. Assume that the (DNSSEC signed) "example.com" zone contains: apple.example.com IN A 192.0.2.1 - elephant.example.com IN A 192.0.2.2 + *.example.com IN A 192.0.2.3 + zebra.example.com IN A 192.0.2.4 - zebra.example.com IN A 192.0.2.3 - - If a validating resolver gets a query for cat.example.com, it will - query the example.com servers and will get back an NSEC (or NSEC3) - record starting that there are no records between apple and elephant. - The 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 + If a validating resolver receives a query for cat.example.com, it + 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 + records (alphabetically) between apple and elephant, or an NSEC3 + record stating there is nothing between two hashed names. The + 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 elephant) to suppress queries for other labels that fall within this 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 query the example.com servers for these names. + Further, if a query is received for lion.example.com, it contacts its + resolver (which may be itself) to query the example.com servers and + will get back an NSEC record stating that there are no records + (alphabetically) between elephant and zebra (or an NSEC3 record + stating there is nothing between two hashed names), as well as an + answer for lion.example.com, with the label count of the signature + set to two (see [RFC7129], section 5.3 for more details). + Apart from wasting bandwidth, this also wastes resources on the recursive server (it needs to keep state for outstanding queries), wastes resources on the authoritative server (it has to answer additional questions), increases latency (the end user has to wait longer than necessary to get back an NXDOMAIN answer), can be used by attackers to cause a DoS (see additional resources), and also has privacy implications (e.g: typos leak out further than necessary). 4. Background DNSSEC [RFC4035] and [RFC5155] both provide "authenticated denial of existence"; this is a cryptographic proof that the queried for name does not exist, accomplished by providing a (DNSSEC secured) record containing the names which appear alphabetically before and after the queried for name. In the example above, if the (DNSSEC validating) - recursive server were to query for lion.example.com it would receive - a (signed) NSEC/NSEC3 record stating that there are no labels between - "elephant" and "zebra". This is a signed, cryptographic proof that - these names are the ones before and after the queried for label. As - lion.example.com falls within this range, the recursive server knows - that lion.example.com really does not exist. This document specifies - that this NSEC/NSEC3 record should be used to generate negative - answers for any queries that the recursive server receives that fall - within the range covered by the record (for the TTL for the record). + recursive server were to query for dog.example.com it would receive a + (signed) NSEC record stating that there are no labels between "apple" + and "elephant" (or, for NSEC3, a similar pair of hashed names). This + is a signed, cryptographic proof that these names are the ones before + and after the queried for label. As dog.example.com falls within + this range, the recursive server knows that dog.example.com really + does not exist. + + This document specifies that this NSEC/NSEC3 record should be used to + generate negative answers for any queries that the validating server + receives that fall within the range covered by the record (for the + TTL for the record). This document also specifies that a positive + answer should be generated for any queries that the validating server + receives that are proven to be covered by a wildcard record. Section 4.5 of [RFC4035] says: "In theory, a resolver could use wildcards or NSEC RRs to generate positive and negative responses (respectively) until the TTL or signatures on the records in question expire. However, it seems prudent for resolvers to avoid blocking new authoritative data or synthesizing new data on their own. Resolvers that follow this recommendation will have a more consistent view of the namespace." and "The reason for these recommendations is that, between the initial query and the expiration of the data from the cache, the authoritative data might have been changed (for example, via dynamic update).". In other words, if a resolver generates negative answers from an NSEC record, it will not send any queries for names within that NSEC range (for the TTL). If a new name is added to the zone - during this interval the resolver will not know this. + during this interval the resolver will not know this. Similarly, if + the resolver is generating responses from a wildcard record, it will + continue to do so (for the We believe this recommendation can be relaxed because, in the absense of this technique, a lookup for the exact name could have come in - during this interval, and so this could already be cached (see - [RFC2308] for more background). This means that zone operators - should have no expectation that an added name would work immediately. - With DNSSEC and Aggressive NSEC, the TTL of the NSEC record is the - authoritative statement of how quickly a name can start working - within a zone. + during this interval, and so a negative answer could already be + cached (see [RFC2308] for more background). This means that zone + operators should have no expectation that an added name would work + immediately. With DNSSEC and Aggressive NSEC, the TTL of the NSEC + record is the authoritative statement of how quickly a name can start + working within a zone. -5. Aggressive Negative Caching +5. Aggressive Caching - Section 4.5 of [RFC4035] shows 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 (respectively) until the TTL or signatures on the records in question expire. However, it seems prudent for resolvers to avoid blocking new authoritative data or synthesizing new data on their own. Resolvers that follow this recommendation will have a more consistent view of the namespace". This document relaxes this this restriction, as follows: +--------------------------------------------------------------+ | Once the records are validated, DNSSEC enabled validating | - | resolvers SHOULD use NSEC/NSEC3 resource records to generate | - | negative responses until their effective TTLs or signatures | - | for those records expire. | + | resolvers MAY use wildcards and NSEC/NSEC3 resource records | + | to generate positive and negative responses until the | + | effective TTLs or signatures for those records expire. | +--------------------------------------------------------------+ If the validating resolver's cache has sufficient information to validate the query, the resolver SHOULD use NSEC/NSEC3/wildcard records aggressively. Otherwise, it MUST fall back to send the query to the authoritative DNS servers. - If the query name has the matching NSEC/NSEC3 RR proving the - information requested does not exist, the validating resolver may - respond with a NODATA (empty) answer. - 5.1. NSEC Implementations which support aggressive use of NSEC SHOULD enable 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 matching/covering the source of synthesis and an NSEC RR covering the query name. - If the validating resolver's cache contains an NSEC RR covering the - source of synthesis and the covering NSEC RR of the query name, the - validating resolver may respond with NXDOMAIN error immediately. + 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, + then the resolver can immediately return an NXDOMAIN or NODATA (as + appropriate) response. 5.2. NSEC3 - NSEC3 aggressive negative caching is more difficult. If the zone is - signed with NSEC3, the validating resolver needs to check the - existence of non-terminals and wildcards which derive from query - names. + NSEC3 aggressive negative caching is more difficult than NSEC + aggressive caching. If the zone is signed with NSEC3, the validating + resolver needs to check the existence of non-terminals and wildcards + which derive from query names. - If the validating resolver's cache contains an NSEC3 RR matching the - closest encloser, an NSEC3 RR covering the next closer name, and an - NSEC3 RR covering the source of synthesis, it is possible for the - validating resolver to respond with NXDOMAIN immediately. + 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 + 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 + NODATA response (as appropriate). 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 negative caching is not possible for the domain name. - A validating resolver implementation MAY support aggressive use of - NSEC3. If it does aggressive use of NSEC3, it MAY provide a - configuration switch to disable aggressive use of NSEC3 and allow it - to be enabled or disabled for specific zones. +5.3. Wildcards -5.3. Consideration on TTL + The last paragraph of [RFC4035] Section 4.5 also discusses the use of + wildcards and NSEC RRs to generate positive responses and recommends + that it not be relied upon. Just like the case for the aggressive + use of NSEC/NSEC3 for negative answers, we revise this + recommendation. + + As long as the validating resolver can determine that a name would + not exist without the wildcard match, it MAY synthesize an answer for + that name using the cached deduced wildcard. If the corresponding + wildcard record is not in the cache, it MUST fall back to send the + query to the authoritative DNS servers. + + An implementation MAY support aggressive use of wildcards. It SHOULD + provide a configuration switch to disable aggressive use of + wildcards. + +5.4. Consideration on TTL The TTL value of negative information is especially important, because newly added domain names cannot be used while the negative - information is effective. Section 5 of RFC 2308 states that the - maximum number of negative cache TTL value is 3 hours (10800). It is - RECOMMENDED that validating resolvers limit the maximum effective TTL - value of negative responses (NSEC/NSEC3 RRs) to this same value. + information is effective. + + Section 5 of [RFC2308] states that the maximum number of negative + cache TTL value is 3 hours (10800). It is RECOMMENDED that + validating resolvers limit the maximum effective TTL value of + negative responses (NSEC/NSEC3 RRs) to this same value. + + Section 5 of [RFC2308]also states that a negative cache entry TTL is + taken from the minimum of the SOA.MINIMUM field and SOA's TTL. This + can be less than the TTL of an NSEC or NSEC3 record, since their TTL + is equal to the SOA.MINIMUM field (see [RFC4035]section 2.3 and + [RFC5155] section 3.) + + A resolver that supports aggressive use of NSEC and NSEC3 should + reduce the TTL of NSEC and NSEC3 records to match the TTL of the SOA + record in the authority section of a negative response, if the SOA + TTL is smaller. 6. Benefits The techniques described in this document provide a number of benefits, including (in no specific order): - Reduced latency By answering directly from cache, validating + Reduced latency: By answering directly from cache, validating resolvers can immediately inform clients that the name they are looking for does not exist, improving the user experience. - Decreased recursive server load By answering negative queries from - the cache, validating servers avoid having send a query and wait - for a response. In addition to decreasing the bandwidth used, it - also means that the server does not need to allocate and maintain - state, thereby decreasing memory and CPU load. + Decreased recursive server load: By answering negative queries from + the cache, validating servers avoid having to send a query and + wait for a response. In addition to decreasing the bandwidth + used, it also means that the server does not need to allocate and + maintain state, thereby decreasing memory and CPU load. - Decreased authorative server load Because recursive servers can + Decreased authorative server load: Because recursive servers can answer (negative) queries without asking the authoritative server, - the authoritative servers receive less queries. This decreases + the authoritative servers receive fewer queries. This decreases the authoritative server bandwidth, queries per second and CPU utilization. The scale of the benefit depends upon multiple factors, including the - query distribution. For example, currently around 65% of queries to - Root Name servers result in NXDOMAIN responses; this technique will - eliminate a sizable quantity of these. + query distribution. For example, at the time of this writing, around + 65% of queries to Root Name servers result in NXDOMAIN responses (see + statis [root-servers.org]); this technique will eliminate a sizable + quantity of these. The technique described in this document may also mitigate so-called "random QNAME attacks", in which attackers send many queries for 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). Aggressive NSEC may help mitigate these attacks by allowing the resolver to answer directly from cache for any random queries which fall within already requested ranges. It will not always work as an effective defense, not least because not many zones are DNSSEC signed - at all, but it will still provide an additional layer of defense. + at all -- but it will still provide an additional layer of defense. 7. Update to RFC 4035 Section 4.5 of [RFC4035] shows that "In theory, a resolver could use wildcards or NSEC RRs to generate positive and negative responses (respectively) until the TTL or signatures on the records in question expire. However, it seems prudent for resolvers to avoid blocking new authoritative data or synthesizing new data on their own. Resolvers that follow this recommendation will have a more consistent view of the namespace". The paragraph is updated as follows: +--------------------------------------------------------------+ | Once the records are validated, DNSSEC enabled validating | | resolvers MAY use wildcards and NSEC/NSEC3 resource records | - | to generate negative responses until their effective TTLs | - | or signatures for those records expire. | + | to generate positive and negative responses until the | + | effective TTLs or signatures for those records expire. | +--------------------------------------------------------------+ 8. IANA Considerations This document has no IANA actions. 9. Security Considerations + Use of NSEC / NSEC3 resource records without DNSSEC validation may + create serious security issues, and so this technique requires DNSSEC + validation. + Newly registered resource records may not be used immediately. However, choosing suitable TTL value and negative cache TTL value (SOA MINIMUM field) will mitigate the delay concern, and it is not a security problem. It is also suggested to limit the maximum TTL value of NSEC / NSEC3 resource records in the negative cache to, for example, 10800 seconds (3hrs), to mitigate this issue. Implementations which comply with this proposal are recommended to have a configurable maximum value of NSEC RRs in the negative cache. - Aggressive use of NSEC / NSEC3 resource records without DNSSEC - validation may create serious security issues, and so this technique - requires DNSSEC validation. + Although the TTL of NSEC/NSEC3 records is typically fairly short + (minutes or hours), their RRSIG expiration time can be much further + in the future (weeks). An attacker who is able to successfully spoof + responses might poison a cache with old NSEC/NSEC3 records. If the + resolver is NOT making aggressive use of NSEC/NSEC3, the attacker has + to repeat the attack for every query. If the resolver IS making + aggressive use of NSEC/NSEC3, one successful attack would be able to + suppress many queries for new names, up to the negative TTL. 10. Implementation Status Unbound currenty implements aggressive negative caching, as does Google Public DNS. 11. Acknowledgments The authors gratefully acknowledge DLV [RFC5074] author Samuel Weiler and the Unbound developers. - The authors would like to specifically thank Tatuya JINMEI for - extensive review and comments, and also Mark Andrews, Stephane - Bortzmeyer, Casey Deccio, Alexander Dupuy, Olafur Gudmundsson, Bob + The authors would like to specifically thank Stephane Bortzmeyer, + Tony Finch, Tatuya JINMEI for extensive review and comments, and also + Mark Andrews, Casey Deccio, Alexander Dupuy, Olafur Gudmundsson, Bob Harold, Shumon Huque, John Levine, Pieter Lexis and Matthijs Mekking (who even sent pull requests!). -12. Change History +11.1. Change History RFC Editor: Please remove this section prior to publication. + -03 to -04: + + o Working group does want the "positive" answers, not just negative + ones. This requires readding what used to be Section 7, and a + bunch of cleanup, including: + + * Additional text in the Problem Statement + + * Added a wildcard record to the zone. + + * Added "or positive answers from wildcards" type text (where + appropriate) to explain that this isn't just for negative + answers. + + * Reworded much of the Wildcard text. + + o Incorporated pull request from Tony Finch (thanks!): + https://github.com/wkumari/draft-ietf-dnsop-nsec-aggressiveuse/ + pull/1 + + o More fixups from Tony (including text): https://www.ietf.org/mail- + archive/web/dnsop/current/msg18271.html. This included much + clearer text on TTL, refernces to the NSEC / NSEC3 RFCs (instead + of my clumsy summary), good text on replays, etc. + + o Converted the "zone file" to a figure to make it more readable. + + o Text from Tim W: "If a validating resolver receives a query for + cat.example.com, it contacts its resolver (which may be itself) to + query..." - which satisfies Jinmei's concern (which I was too + dense to grock). + + o Fixup of the "validation required" in security considerations. + -02 to -03: o Integrated a bunch of comments from Matthijs Mekking - details in: https://github.com/wkumari/draft-ietf-dnsop-nsec-aggressiveuse/ pull/1. I decided to keep "Aggressive Negative Caching" instead of "Aggressive USE OF Negative Caching" for readability. o Attempted to address Bob Harold's comment on the readability issues with "But, it will be more effective when both are enabled..." in Section 5.4 - https://www.ietf.org/mail- @@ -440,54 +533,56 @@ o Improved wordings (from good comments) o Simplified pseudo code for NSEC3 o Added Warren as co-author. o Reworded much of the problem statement o Reworked examples to better explain the problem / solution. -12.1. Version draft-fujiwara-dnsop-nsec-aggressiveuse-01 +11.1.1. Version draft-fujiwara-dnsop-nsec-aggressiveuse-01 o Added reference to DLV [RFC5074] and imported some sentences. o Added Aggressive Negative Caching Flag idea. o Added detailed algorithms. -12.2. Version draft-fujiwara-dnsop-nsec-aggressiveuse-02 +11.1.2. Version draft-fujiwara-dnsop-nsec-aggressiveuse-02 o Added reference to [I-D.vixie-dnsext-resimprove] o Added considerations for the CD bit o Updated detailed algorithms. o Moved Aggressive Negative Caching Flag idea into Additional Proposals -12.3. Version draft-fujiwara-dnsop-nsec-aggressiveuse-03 +11.1.3. Version draft-fujiwara-dnsop-nsec-aggressiveuse-03 o Added "Partial implementation" o Section 4,5,6 reorganized for better representation o Added NODATA answer in Section 4 o Trivial updates o Updated pseudo code -13. References +11.2. new section -13.1. Normative References +12. References + +12.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ RFC2119, March 1997, . [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998, . @@ -502,37 +597,45 @@ [RFC5074] Weiler, S., "DNSSEC Lookaside Validation (DLV)", RFC 5074, DOI 10.17487/RFC5074, November 2007, . [RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS Security (DNSSEC) Hashed Authenticated Denial of Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008, . + [RFC7129] Gieben, R. and W. Mekking, "Authenticated Denial of + Existence in the DNS", RFC 7129, DOI 10.17487/RFC7129, + February 2014, . + [RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS Terminology", RFC 7719, DOI 10.17487/RFC7719, December 2015, . -13.2. Informative References +12.2. Informative References [I-D.ietf-dnsop-nxdomain-cut] Bortzmeyer, S. and S. Huque, "NXDOMAIN really means there is nothing underneath", draft-ietf-dnsop-nxdomain-cut-03 (work in progress), May 2016. [I-D.vixie-dnsext-resimprove] Vixie, P., Joffe, R., and F. Neves, "Improvements to DNS Resolvers for Resiliency, Robustness, and Responsiveness", draft-vixie-dnsext-resimprove-00 (work in progress), June 2010. + [root-servers.org] + IANA, "Root Server Technical Operations Assn", + . + Appendix A. Detailed implementation notes o Previously, cached negative responses were indexed by QNAME, QCLASS, QTYPE, and the setting of the CD bit (see RFC 4035, Section 4.7), and only queries matching the index key would be answered from the cache. With aggressive negative caching, the validator, in addition to checking to see if the answer is in its cache before sending a query, checks to see whether any cached and validated NSEC record denies the existence of the sought record(s). Using aggressive negative caching, a validator will