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DNSOP Working Group                                         J. Woodworth
Internet-Draft                                                 D. Ballew
Updates: 2308, 4033, 4034, 4035 (if                    CenturyLink, Inc.
         approved)                            S. Bindinganaveli Raghavan
Intended status: Standards Track                  Hughes Network Systems
Expires: May 3, 2018                                         D. Lawrence
                                                     Akamai Technologies
                                                        October 30, 2017


                       BULK DNS Resource Records
                       draft-woodworth-bulk-rr-07

Abstract

   The BULK DNS resource record type defines a method of pattern-based
   creation of DNS resource records based on numeric substrings of query
   names.  The intent of BULK is to simplify generic assignments in a
   memory-efficient way that can be easily shared between the primary
   and secondary nameservers for a zone.

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/vttale/bulk-
   rr>.  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

   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 https://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 May 3, 2018.




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Copyright Notice

   Copyright (c) 2017 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
   (https://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  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Background and Terminology  . . . . . . . . . . . . . . .   4
   2.  The BULK Resource Record  . . . . . . . . . . . . . . . . . .   4
     2.1.  BULK RDATA Wire Format  . . . . . . . . . . . . . . . . .   4
     2.2.  The BULK RR Presentation Format . . . . . . . . . . . . .   6
   3.  BULK Replacement  . . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Matching the Domain Name Pattern  . . . . . . . . . . . .   7
     3.2.  Record Generation using Replacement Pattern . . . . . . .   7
       3.2.1.  Delimiters  . . . . . . . . . . . . . . . . . . . . .   8
       3.2.2.  Delimiter intervals . . . . . . . . . . . . . . . . .   8
       3.2.3.  Padding length  . . . . . . . . . . . . . . . . . . .   8
       3.2.4.  Final processing  . . . . . . . . . . . . . . . . . .   9
   4.  Known Limitations . . . . . . . . . . . . . . . . . . . . . .   9
     4.1.  Unsupported Nameservers . . . . . . . . . . . . . . . . .   9
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
     5.1.  DNSSEC Signature Strategies . . . . . . . . . . . . . . .  10
       5.1.1.  On-the-fly Signatures . . . . . . . . . . . . . . . .  10
       5.1.2.  Alternative Signature Scheme  . . . . . . . . . . . .  10
       5.1.3.  Non-DNSSEC Zone Support Only  . . . . . . . . . . . .  11
     5.2.  DDOS Attack Vectors and Mitigation  . . . . . . . . . . .  11
     5.3.  Implications of Large-Scale DNS Records . . . . . . . . .  11
   6.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  12
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  12
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  12
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  13
   Appendix A.  BULK Examples  . . . . . . . . . . . . . . . . . . .  13
     A.1.  Example 1 . . . . . . . . . . . . . . . . . . . . . . . .  13
     A.2.  Example 2 . . . . . . . . . . . . . . . . . . . . . . . .  14
     A.3.  Example 3 . . . . . . . . . . . . . . . . . . . . . . . .  15



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   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   The BULK DNS resource record defines a pattern-based method for on-
   the-fly resource record generation.  It is essentially an enhanced
   wildcard mechanism, constraining generated resource record owner
   names to those that match a pattern of variable numeric substrings.
   It is also akin to the $GENERATE master file directive [bind-arm]
   without being limited to numeric values and without creating all
   possible records in the zone data.

   For example, consider the following record:

   example.com. 86400 IN BULK A (
                         pool-A-[0-255]-[0-255].example.com.
                         10.55.${1}.${2}
                      )

   It will answer requests for pool-A-0-0.example.com through pool-
   A-255-255.example.com with the IPv4 addresses 10.55.0.0 through
   10.55.255.255.

   Much larger record sets can be defined while minimizing the
   associated requirements for server memory and zone transfer network
   bandwidth.

   This record addresses a number of real-world operational problems
   that authoritative DNS service providers experience.  For example,
   operators who host many large reverse lookup zones, even for only
   IPv4 space in in-addr.arpa, would benefit from the disk space, memory
   size, and zone transfer efficiencies that are gained by encapsulating
   a simple record-generating algorithm versus enumerating all of the
   individual records to cover the same space.

   Production zones of tens of thousands of pattern-generated records
   currently exist, that could be reduced to just one BULK RR.  These
   zones can look deceptively small on the primary nameserver and
   balloon to 100MB or more when expanded,

   BULK also allows administrators to more easily deal with singletons,
   records in the pattern space that are an exception to the normal data
   generation rules.  Whereas a mechanism like $GENERATE may need to be
   adjusted to account for these individual records, the processing
   rules for BULK have explicit records more naturally override the
   dynamically generated ones.  This collision problem is not just a
   theoretical concern, but a real source of support calls for
   providers.



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   Pattern-generated records are also not only for the reverse DNS
   space.  Forward zones also occasionally have entries that follow
   patterns that would be well-addressed by the BULK RR.

1.1.  Background and Terminology

   The reader is assumed to be familiar with the basic DNS and DNSSEC
   concepts described in [RFC1034], [RFC1035], [RFC4033], [RFC4034], and
   [RFC4035]; subsequent RFCs that update them in [RFC2181] and
   [RFC2308]; and DNS terms in [RFC7719].

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119] when, and only when, they appear in all capitals, as shown
   here.

2.  The BULK Resource Record

   The BULK resource record enables an authoritative nameserver to
   generate RRs for other types based upon the query received.

   The Type value for the BULK RR type is TBD.

   The BULK RR is class-independent.

2.1.  BULK RDATA Wire Format

   The RDATA for a BULK RR is as follows:

                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Match Type          |                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+       Domain Name Pattern     /
   /                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                                                               /
   /                      Replacement Pattern                      /
   /                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Match Type identifies the type of the RRset to be generated by this
   BULK record.  It is two octets corresponding to an RR TYPE code as
   specified in [RFC1035], Section 3.2.1.

   Domain Name Pattern consists of a pattern encoded as a wire-format
   fully qualified domain name.  The full name is used so that numeric



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   substrings above the zone cut can be captured in addition to those in
   the zone.  It needs no length indicator for the entire field because
   the root label marks its end.

   Special characters are interpreted as per the following Augmented
   Backus-Naur Form (ABNF) notation from [RFC5234].

   match         =  1*(range / string)

   range         =  "[" [decnum "-" decnum] "]" /
                     "<" [hexnum "-" hexnum] ">"
                         ; create references for substitution
                         ; limit of 32 references
                         ; [] is syntactic sugar for 0-255
                         ; <> is syntactic sugar for 00-ff

   string        =  1*(ctext / quoted-char)

   decnum        =  1*decdigit
                         ; constrained to 65535 maximum.

   hexnum        =  1*hexdigit
                         ; constrained to ffff maximum.

   octet         =  %x00-FF

   decdigit      =  %x30-39
                         ; 0-9
   hexdigit      =  decdigit / 0x41-0x46 / 0x61-66
                         ; 0-9, A-F, a-f

   ctext         =  <any octet excepting "\">

   quoted-char   = "\" octet
                          ; to allow special characters as literals

   Interpretation of the Domain Name Pattern is described in detail in
   the "BULK Replacement" section.  Note that quoted-char must be stored
   in the wire format to preserve its semantics when the BULK RR is
   interpreted by nameservers.

   The limit of 32 references is meant to simplify implementation
   details.  It is largely but not entirely arbitrary, as it could
   capture every individual character of the text representation of a
   full IPv6 address.

   Replacement Pattern describes how the answer RRset MUST be generated
   for the matching query.  It needs no length indicator because its end



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   can be derived from the RDATA length minus Match Type and Domain Name
   Pattern lengths.  It uses the following additional ABNF elements:

   replace       =   1*(reference / string)

   reference     =   "$" "{" (positions / "*") [options] "}"

   positions     =   (position / posrange) 0*("," (position / posrange))

   posrange      =   position "-" position

   position      =   1*decnum

   options       =   delimiter [interval [padding]]

   delimiter     =   "|" 0*(ctext | quoted-char)
                           ; "\|" to use "|" as delimiter
                           ; "\\" to use "\" as delimiter

   interval      =   "|" *2decdigit

   padding       =   "|" *2decdigit


   [ Is the formatting complexity beyond simple ${1}, ${2}, etc, really
   worth it?  I definitely see how it could make for shorter replacement
   patterns, but does it enhance their clarity and usability, adding a
   feature someone really wants? ]

   The Replacement Pattern MUST end in the root label if it is intended
   to represent a fully qualified domain name.

2.2.  The BULK RR Presentation Format

   Match Type is represented as an RR type mnemonic or with [RFC3597]'s
   generic TYPE mechanism.

   Domain Name Pattern is represented as a fully qualified domain name
   as per [RFC1035] Section 5.1 rules for encoding whitespace and other
   special characters.

   Replacement Pattern is represented by the standard <character-string>
   text rules for master files as per [RFC1035] section 5.1.

   It is suggested that lines longer than 80 characters be wrapped with
   parenthetical line continuation, per [RFC1035] Section 5.1, starting
   after Match Type and ending after Replacement Pattern.




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3.  BULK Replacement

   When a BULK-aware authoritative nameserver receives a query for which
   it does not have a matching name or a covering wildcard, it MUST then
   look for BULK RRs at the zone apex, selecting all BULK RRs with a
   Match Type that matches the query type and a Domain Name Pattern that
   matches the query name.  Note that query type ANY will select all
   Match Types, and all query types match a CNAME or DNAME Match Type.
   One or more answer RRs will be generated per the replacement rules
   below.  Examples are provided in an appendix.

   By only triggering the BULK algorithm when the query name does not
   exist, administrators are given the flexibility to explicitly
   override the behaviour of specific names that would otherwise match
   the BULK record's Domain Name Pattern.  This is unlike BIND's
   $GENERATE directive, which adds the generated RRs to any existing
   names.

3.1.  Matching the Domain Name Pattern

   A query name matches the Domain Name Pattern if the characters that
   appear outside the numeric ranges match exactly and those within
   numeric ranges have values that fall within the range.  Numeric
   matches MUST be of the appropriate decimal or hexadecimal type as
   specified by the delimiters in the pattern.  For example, if a range
   is given as [0-255], then FF does not match even though its value as
   a hexadecimal number is within the range.  Leading zeros in the
   numeric part(s) of the qname MUST be ignored; for example,
   001.example.com, 01.example.com and 1.example.com would all match
   [].example.com.

   When a query name matches a Domain Name Pattern, the value in each
   numeric range is stored for use by the Replacement Pattern, with
   reference numbers starting at 1 and counting from the left.  For
   example, matching the query name host-24-156 against
   host-[0-255]-[0-255] assigns 24 to ${1} and 156 to ${2}.

3.2.  Record Generation using Replacement Pattern

   The Replacement Pattern generates the record data by replacing the
   ${...} references with data captured from the query name, and copying
   all other characters literally.

   The simplest form of reference uses only the reference number between
   the braces, "{" and "}".  The value of the reference is simply copied
   directly from the matching position of the query name.





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   The next form of reference notation uses the asterisk, "*".  With
   ${*}, all captured values in order of ascending position, delimited
   by its default delimiter (described below), are placed in the answer.

   Numeric range references, such as ${1-4}, replaces all values
   captured by those references, in order, delimited by the default
   delimiter described below.  To reverse the order in which they are
   copied, reverse the upper and lower values, such as ${4-1}.  This is
   useful for generating PTR records from query names in which the
   address is encoded in network order.

   Similar to range references, separating positions by commas creates
   sets for replacement.  For example, ${1,4} would be replaced by the
   first and fourth captured values, delimited its default delimiter.
   This notation may be combined with the numeric range form, such as
   ${3,2,1,8-4}.

3.2.1.  Delimiters

   A reference can specify a delimiter to use by following a vertical
   bar, "|", with zero or more characters.  Zero characters, such as in
   ${1-3|}, means no delimiter is used, while other characters up to an
   unescaped vertical bar or closing brace are copied between position
   values in the replacement.  The default delimiter is the hyphen, "-".

3.2.2.  Delimiter intervals

   A second vertical bar in the reference options introduces a delimiter
   interval.  The default behavior of a multi-position reference is to
   combine each captured value specified with a delimiter between each.
   With a delimiter interval the delimiters are only added between every
   Nth value.  For example, ${*|-|4} adds a hyphen between every group
   of four captured positions.  This can be a handy feature in the IPv6
   reverse namespace where every nibble is captured as a separate value
   and generated hostnames include sets of 4 nibbles.  An empty or 0
   value for the delimiter interval MUST be interpreted as the default
   value of 1.

3.2.3.  Padding length

   The fourth and final reference option determines the field width of
   the copied value.  Shorter values MUST be padded with leading zeroes
   ("0") and longer values MUST be truncated to the width.

   The default behavior, and that of an explicit empty padding length,
   is that the captured query name substring is copied exactly.  A width
   of zero "0" is a signal to "unpad", and any leading zeros MUST be
   removed. [ Unnecessary complexity? ]



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   If a delimiter interval greater than 1 is used, captured values
   between the intervals will be concatenated and the padding or
   unpadding applied as a unit and not individually.  An example of this
   would be ${*||4|4} which would combine each range of 4 captured
   values and pad or truncate them to a width of 4 characters.

   [ If this is kept, the element/feature should probably be renamed
   from "padding" since it is just as likely to truncate. ]

3.2.4.  Final processing

   The string that results from all replacements is converted to the
   appropriate RDATA format for the record type.  If the conversion
   fails, the SERVFAIL rcode MUST be set on the response, representing a
   misconfiguration that the server was unable to perform. [ The EDNS
   extended-error code would be useful here. ]

   The TTL of each RR generated by a BULK RR is the TTL of the
   corresponding BULK record itself.  [ BULK should probably have its
   own TTL field because using that of the record itself feels like bad
   design.  On the other hand, if BULK is never meant to be queried for
   directly and only appears in authoritative data, its own TTL is
   pretty useless normally. ]

   The class for the RRSet is the class of the BULK RR.

   If the generated record type is one that uses domain names in its
   resource record data, such as CNAME, a relative domain names MUST be
   fully qualified with the origin domain of the BULK RR.

4.  Known Limitations

   This section defines known limitations of the BULK resource type.

4.1.  Unsupported Nameservers

   Authoritative nameservers that do not understand the semantics of the
   new record type will not be able to deliver the intended answers even
   when the type appears in their zone data This significantly affects
   the interoperability of primary versus secondary authorities that are
   not all running the same software.  Adding new RRs which affect
   handling by authoritative servers, or being unable to add them, is an
   issue that needs to be explored more thoroughly within dnsop.








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5.  Security Considerations

   Two known security considerations exist for the BULK resource record,
   DNSSEC and DDOS attack vectors.

5.1.  DNSSEC Signature Strategies

   DNSSEC was designed to provide validation for DNS resource records,
   requiring each tuple of owner, class, and type to have its own
   signature.  This essentially defeats the purpose of providing large
   generated blocks of RRs in a single RR as each generated RR would
   require its own legitimate RRSIG record.

   In the following sections several options are discussed to address
   this issue.  Of the options, on-the-fly provides the most secure
   solution and NPN provides the most flexible.

5.1.1.  On-the-fly Signatures

   A significant design goal of DNSSEC was to be able to do offline
   cryptographic signing of zone contents, keeping the key material more
   secure.

   On-the-fly processing requires authoritative nameservers to sign
   generated records as they are created.  Not all authoritative
   nameserver implementations offer on-the-fly signatures, and even with
   those that do not all operators will want to keep signing keys
   online.  This solution would either require all implementations to
   support on-the-fly signing or be ignored by implementations which can
   not or will not comply.

   One possibly mitigation for addressing the risk of keeping the zone
   signing key online would be to continue to keep the key for signing
   positive answers offline and introduce a second key for online
   signing of negative answers.

   No changes to validating resolvers is required to support this
   solution.

5.1.2.  Alternative Signature Scheme

   Previous versions of this draft proposed a new signature scheme using
   a Numeric Pattern Normalization (NPN) RR.  It was a method to support
   offline signatures for BULK records, with the drawback that is
   required updates to DNSSEC-aware resolvers.






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   That mechanism is not specific to BULK and has been removed from the
   current draft.  If there is further interest in pursuing it, it can
   be reopened as a separate draft.

5.1.3.  Non-DNSSEC Zone Support Only

   As a final option zones which wish to remain entirely without DNSSEC
   support may serve such zones without either of the above solutions
   and records generated based on BULK RRs will require zero support
   from recursive resolvers.

5.2.  DDOS Attack Vectors and Mitigation

   As an additional defense against Distributed Denial Of Service (DDOS)
   attacks against recursive (resolving) nameservers it is highly
   recommended shorter TTLs be used for BULK RRs than others.  While
   disabling caching with a zero TTL is not recommended, as this would
   only result in a shift of the attack target, a balance will need to
   be found.  While this document uses 24 hours (86400 seconds) in its
   examples, values between 300 to 900 seconds are likely more
   appropriate and is RECOMMENDED.  What is ultimately deemed
   appropriate may differ from zone to zone and administrator to
   administrator.

   [ I am unclear how this helps DDOS mitigation against anyone at all,
   and suspect this section should be removed.. ]

5.3.  Implications of Large-Scale DNS Records

   The production of such large-scale records in the wild may have some
   unintended side-effects.  These side-effects could be of concern or
   add unexpected complications to DNS based security offerings or
   forensic and anti-spam measures.  While outside the scope of this
   document, implementers of technology relying on DNS resource records
   for critical decision making must take into consideration how the
   existence of such a volume of records might impact their technology.

   Solutions to the magnitude problem for BULK generated RRs are
   expected be similar if not identical to that of existing wildcard
   records, the core difference being the resultant RDATA will be unique
   for each requested Domain Name within its scope.

   The authors of this document are confident that by careful
   consideration, negative_side-effects produced by implementing the
   features described in this document can be eliminated from any such
   service or product.





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6.  Privacy Considerations

   The BULK record does not introduce any new privacy concerns to DNS
   data.

7.  IANA Considerations

   IANA is requested to assign numbers for the BULK RR.

8.  Acknowledgments

   This document was created as an extension to the DNS infrastructure.
   As such, many people over the years have contributed to its creation
   and the authors are appreciative to each of them even if not thanked
   or identified individually.

   A special thanks is extended for the kindness, wisdom and technical
   advice of Robert Whelton (CenturyLink, Inc.) and Gary O'Brien
   (Secure64 Software Corp).

9.  References

9.1.  Normative References

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <https://www.rfc-editor.org/info/rfc1034>.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
              November 1987, <https://www.rfc-editor.org/info/rfc1035>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2181]  Elz, R. and R. Bush, "Clarifications to the DNS
              Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997,
              <https://www.rfc-editor.org/info/rfc2181>.

   [RFC2308]  Andrews, M., "Negative Caching of DNS Queries (DNS
              NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998,
              <https://www.rfc-editor.org/info/rfc2308>.







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   [RFC2317]  Eidnes, H., de Groot, G., and P. Vixie, "Classless IN-
              ADDR.ARPA delegation", BCP 20, RFC 2317,
              DOI 10.17487/RFC2317, March 1998,
              <https://www.rfc-editor.org/info/rfc2317>.

   [RFC3597]  Gustafsson, A., "Handling of Unknown DNS Resource Record
              (RR) Types", RFC 3597, DOI 10.17487/RFC3597, September
              2003, <https://www.rfc-editor.org/info/rfc3597>.

   [RFC4033]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "DNS Security Introduction and Requirements",
              RFC 4033, DOI 10.17487/RFC4033, March 2005,
              <https://www.rfc-editor.org/info/rfc4033>.

   [RFC4034]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Resource Records for the DNS Security Extensions",
              RFC 4034, DOI 10.17487/RFC4034, March 2005,
              <https://www.rfc-editor.org/info/rfc4034>.

   [RFC4035]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Protocol Modifications for the DNS Security
              Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,
              <https://www.rfc-editor.org/info/rfc4035>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>.

9.2.  Informative References

   [bind-arm]
              Internet Systems Consortium, "BIND 9 Configuration
              Reference", 2016,
              <https://ftp.isc.org/isc/bind9/cur/9.9/doc/arm/
              Bv9ARM.html>.

   [RFC7719]  Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
              Terminology", RFC 7719, DOI 10.17487/RFC7719, December
              2015, <https://www.rfc-editor.org/info/rfc7719>.

Appendix A.  BULK Examples

A.1.  Example 1







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   $ORIGIN 2.10.in-addr.arpa.
   @ 86400 IN BULK PTR (
             [0-255].[0-255].[0-255].[0-255].in-addr.arpa.
             pool-${4-1}.example.com.
           )

   A query received for the PTR of 4.3.2.10.in-addr.arpa will create the
   references ${1} through ${4} with the first four labels of the query
   name.  The ${4-1} reference in the replacement pattern will then
   substitute them in reverse with the default delimiter of hyphen
   between every character and no special field width modifications.
   The TTL of the BULK RR is used for the generated record, making the
   response:

   4.3.2.10.in-addr.arpa 86400 IN PTR pool-10-2-3-4.example.com.

A.2.  Example 2

   $ORIGIN 2.10.in-addr.arpa.
   @ 86400 IN BULK PTR (
             [0-255].[0-255].[0-255].[0-255].in-addr.arpa.
             pool-${2,1|||3}.example.com.
           )

   Example 2 is similar to Example 1, except that it modifies the
   replacement pattern.  The empty option after the first vertical bar
   causes no delimiters to be inserted, while the second empty option
   that would keep the delimiter interval as 1.  The latter is relevant
   because the final value, padding of 3, is applied over each delimiter
   interval even when no delimiter is used.  Not all captures from the
   substring are required to be used in the response.

   The result is that a query for the PTR of 4.3.2.10.in-addr.arpa
   generates this response:

   4.3.2.10.in-addr.arpa 86400 IN PTR pool-003004.example.com.

   [ Admittedly you can't do this very effectively without the field
   width complexity.  Is this sort of name common?  Does it need
   support?  Admittedly $GENERATE had the feature, but is that reason
   enough? ]

   [ Change this to a hex matching example? ]








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A.3.  Example 3

   This example contains a classless IPv4 delegation on the /22 CIDR
   boundary as defined by [RFC2317].  The network for this example is
   "10.2.0/22" delegated to a nameserver "ns1.sub.example.com.".  RRs
   for this example are defined as:

   $ORIGIN 2.10.in-addr.arpa.
   @    7200 IN BULK CNAME [0-255].[0-3] ${*|.}.0-3
   0-3 86400 IN NS ns1.sub.example.com.

   A query for the PTR of 25.2.2.10.in-addr.arpa is received and the
   BULK record with the CNAME Match Type matches all query types.  25
   and 2 are captured as references, and joined in the answer by the
   period (".") character as a delimiter, with ".0-3" then appended
   literally and fully qualified by the origin domain.  The final
   synthesized record is:

   25.2.2.10.in-addr.arpa 7200 IN CNAME 25.2.0-3.2.10.in-addr.arpa.

   [ Without $* and options complexity, the pattern to get the same
   result is just ${1}.{$2}.0-3 which is not really significantly
   onerous to enter, and slightly less arcane looking to comprehend. ]

Authors' Addresses

   John Woodworth
   CenturyLink, Inc.
   4250 N Fairfax Dr
   Arlington  VA 22203
   USA

   Email: John.Woodworth@CenturyLink.com


   Dean Ballew
   CenturyLink, Inc.
   2355 Dulles Corner Blvd, Ste 200 300
   Herndon  VA 20171
   USA

   Email: Dean.Ballew@CenturyLink.com









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   Shashwath Bindinganaveli Raghavan
   Hughes Network Systems
   11717 Exploration Lane
   Germantown  MD 20876
   USA

   Email: shashwath.bindinganaveliraghavan@hughes.com


   David C Lawrence
   Akamai Technologies
   150 Broadway
   Cambridge  MA 02142-1054
   USA

   Email: tale@akamai.com



































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