path: root/doc/rfc/rfc8914.txt

Internet Engineering Task Force (IETF)                         W. Kumari
Request for Comments: 8914                                        Google
Category: Standards Track                                        E. Hunt
ISSN: 2070-1721                                                      ISC
                                                               R. Arends
                                                                   ICANN
                                                             W. Hardaker
                                                                 USC/ISI
                                                             D. Lawrence
                                                              Salesforce
                                                            October 2020


                          Extended DNS Errors

Abstract

   This document defines an extensible method to return additional
   information about the cause of DNS errors.  Though created primarily
   to extend SERVFAIL to provide additional information about the cause
   of DNS and DNSSEC failures, the Extended DNS Errors option defined in
   this document allows all response types to contain extended error
   information.  Extended DNS Error information does not change the
   processing of RCODEs.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8914.

Copyright Notice

   Copyright (c) 2020 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 and Background
     1.1.  Requirements Notation
   2.  Extended DNS Error EDNS0 Option Format
   3.  Extended DNS Error Processing
   4.  Defined Extended DNS Errors
     4.1.  Extended DNS Error Code 0 - Other
     4.2.  Extended DNS Error Code 1 - Unsupported DNSKEY Algorithm
     4.3.  Extended DNS Error Code 2 - Unsupported DS Digest Type
     4.4.  Extended DNS Error Code 3 - Stale Answer
     4.5.  Extended DNS Error Code 4 - Forged Answer
     4.6.  Extended DNS Error Code 5 - DNSSEC Indeterminate
     4.7.  Extended DNS Error Code 6 - DNSSEC Bogus
     4.8.  Extended DNS Error Code 7 - Signature Expired
     4.9.  Extended DNS Error Code 8 - Signature Not Yet Valid
     4.10. Extended DNS Error Code 9 - DNSKEY Missing
     4.11. Extended DNS Error Code 10 - RRSIGs Missing
     4.12. Extended DNS Error Code 11 - No Zone Key Bit Set
     4.13. Extended DNS Error Code 12 - NSEC Missing
     4.14. Extended DNS Error Code 13 - Cached Error
     4.15. Extended DNS Error Code 14 - Not Ready
     4.16. Extended DNS Error Code 15 - Blocked
     4.17. Extended DNS Error Code 16 - Censored
     4.18. Extended DNS Error Code 17 - Filtered
     4.19. Extended DNS Error Code 18 - Prohibited
     4.20. Extended DNS Error Code 19 - Stale NXDOMAIN Answer
     4.21. Extended DNS Error Code 20 - Not Authoritative
     4.22. Extended DNS Error Code 21 - Not Supported
     4.23. Extended DNS Error Code 22 - No Reachable Authority
     4.24. Extended DNS Error Code 23 - Network Error
     4.25. Extended DNS Error Code 24 - Invalid Data
   5.  IANA Considerations
     5.1.  A New Extended DNS Error Code EDNS Option
     5.2.  New Registry for Extended DNS Error Codes
   6.  Security Considerations
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Acknowledgements
   Authors' Addresses

1.  Introduction and Background

   There are many reasons that a DNS query may fail -- some of them
   transient, some permanent; some can be resolved by querying another
   server, some are likely best handled by stopping resolution.
   Unfortunately, the error signals that a DNS server can return are
   very limited and are not very expressive.  This means that
   applications and resolvers often have to "guess" at what the issue
   is, e.g., was the answer marked REFUSED because of a lame delegation
   or because the nameserver is still starting up and loading zones?  Is
   a SERVFAIL a DNSSEC validation issue, or is the nameserver
   experiencing some other failure?  What error messages should be
   presented to the user or logged under these conditions?

   A good example of issues that would benefit from additional error
   information are errors caused by DNSSEC validation issues.  When a
   stub resolver queries a name that is DNSSEC bogus [RFC8499] (using a
   validating resolver), the stub resolver receives only a SERVFAIL in
   response.  Unfortunately, the SERVFAIL Response Code (RCODE) is used
   to signal many sorts of DNS errors, and so the stub resolver's only
   option is to ask the next configured DNS resolver.  The result of
   trying the next resolver is one of two outcomes: either the next
   resolver also validates and a SERVFAIL is returned again or the next
   resolver is not a validating resolver and the user is returned a
   potentially harmful result.  With an Extended DNS Error (EDE) option
   enclosed in the response message, the resolver is able to return a
   more descriptive reason as to why any failures happened or add
   additional context to a message containing a NOERROR RCODE.

   This document specifies a mechanism to extend DNS errors to provide
   additional information about the cause of an error.  The Extended DNS
   Error codes described in this document can be used by any system that
   sends DNS queries and receives a response containing an EDE option.
   Different codes are useful in different circumstances, and thus
   different systems (stub resolvers, recursive resolvers, and
   authoritative resolvers) might receive and use them.

1.1.  Requirements Notation

   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
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Extended DNS Error EDNS0 Option Format

   This document uses an Extended Mechanism for DNS (EDNS0) [RFC6891]
   option to include Extended DNS Error (EDE) information in DNS
   messages.  The option is structured as follows:

                                                1   1   1   1   1   1
        0   1   2   3   4   5   6   7   8   9   0   1   2   3   4   5
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0: |                            OPTION-CODE                        |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   2: |                           OPTION-LENGTH                       |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   4: | INFO-CODE                                                     |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   6: / EXTRA-TEXT ...                                                /
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+


   Field definition details:

   OPTION-CODE:
      2 octets / 16 bits (defined in [RFC6891]) contains the value 15
      for EDE.

   OPTION-LENGTH:
      2 octets / 16 bits (defined in [RFC6891]) contains the length of
      the payload (everything after OPTION-LENGTH) in octets and should
      be 2 plus the length of the EXTRA-TEXT field (which may be a zero-
      length string).

   INFO-CODE:
      16 bits, which is the principal contribution of this document.
      This 16-bit value, encoded in network most significant bit (MSB)
      byte order, provides the additional context for the RESPONSE-CODE
      of the DNS message.  The INFO-CODE serves as an index into the
      "Extended DNS Errors" registry, defined and created in
      Section 5.2.

   EXTRA-TEXT:
      a variable-length, UTF-8-encoded [RFC5198] text field that may
      hold additional textual information.  This information is intended
      for human consumption (not automated parsing).  EDE text may be
      null terminated but MUST NOT be assumed to be; the length MUST be
      derived from the OPTION-LENGTH field.  The EXTRA-TEXT field may be
      zero octets in length, indicating that there is no EXTRA-TEXT
      included.  Care should be taken not to include private information
      in the EXTRA-TEXT field that an observer would not otherwise have
      access to, such as account numbers.

   The Extended DNS Error (EDE) option can be included in any response
   (SERVFAIL, NXDOMAIN, REFUSED, even NOERROR, etc.) to a query that
   includes an OPT pseudo-RR [RFC6891].  This document includes a set of
   initial codepoints but is extensible via the IANA registry defined
   and created in Section 5.2.

3.  Extended DNS Error Processing

   When the response grows beyond the requestor's UDP payload size
   [RFC6891], servers SHOULD truncate messages by dropping EDE options
   before dropping other data from packets.  Implementations SHOULD set
   the truncation bit when dropping EDE options.  Because long EXTRA-
   TEXT fields may trigger truncation (which is undesirable given the
   supplemental nature of EDE), implementers and operators creating EDE
   options SHOULD avoid lengthy EXTRA-TEXT contents.

   When a resolver or forwarder receives an EDE option, whether or not
   (and how) to pass along EDE information on to their original client
   is implementation dependent.  Implementations MAY choose to not
   forward information, or they MAY choose to create a new EDE option(s)
   that conveys the information encoded in the received EDE.  When doing
   so, the source of the error SHOULD be attributed in the EXTRA-TEXT
   field, since an EDNS0 option received by the original client will
   appear to have come from the resolver or forwarder sending it.

   This document does not allow or prohibit any particular extended
   error codes and information to be matched with any particular RCODEs.
   Some combinations of extended error codes and RCODEs may seem
   nonsensical (such as resolver-specific extended error codes received
   in responses from authoritative servers), so systems interpreting the
   extended error codes MUST NOT assume that a combination will make
   sense.  Receivers MUST be able to accept EDE codes and EXTRA-TEXT in
   all messages, including those with a NOERROR RCODE but need not act
   on them.  Applications MUST continue to follow requirements from
   applicable specifications on how to process RCODEs no matter what EDE
   values are also received.  Senders MAY include more than one EDE
   option and receivers MUST be able to accept (but not necessarily
   process or act on) multiple EDE options in a DNS message.

4.  Defined Extended DNS Errors

   This document defines some initial EDE codes.  The mechanism is
   intended to be extensible, and additional codepoints can be
   registered in the "Extended DNS Errors" registry (Section 5.2).  The
   INFO-CODE from the EDE EDNS option is used to serve as an index into
   the "Extended DNS Error" IANA registry, the initial values for which
   are defined in the following subsections.

4.1.  Extended DNS Error Code 0 - Other

   The error in question falls into a category that does not match known
   extended error codes.  Implementations SHOULD include an EXTRA-TEXT
   value to augment this error code with additional information.

4.2.  Extended DNS Error Code 1 - Unsupported DNSKEY Algorithm

   The resolver attempted to perform DNSSEC validation, but a DNSKEY
   RRset contained only unsupported DNSSEC algorithms.

4.3.  Extended DNS Error Code 2 - Unsupported DS Digest Type

   The resolver attempted to perform DNSSEC validation, but a DS RRset
   contained only unsupported Digest Types.

4.4.  Extended DNS Error Code 3 - Stale Answer

   The resolver was unable to resolve the answer within its time limits
   and decided to answer with previously cached data instead of
   answering with an error.  This is typically caused by problems
   communicating with an authoritative server, possibly as result of a
   denial of service (DoS) attack against another network.  (See also
   Code 19.)

4.5.  Extended DNS Error Code 4 - Forged Answer

   For policy reasons (legal obligation or malware filtering, for
   instance), an answer was forged.  Note that this should be used when
   an answer is still provided, not when failure codes are returned
   instead.  See Blocked (15), Censored (16), and Filtered (17) for use
   when returning other response codes.

4.6.  Extended DNS Error Code 5 - DNSSEC Indeterminate

   The resolver attempted to perform DNSSEC validation, but validation
   ended in the Indeterminate state [RFC4035].

4.7.  Extended DNS Error Code 6 - DNSSEC Bogus

   The resolver attempted to perform DNSSEC validation, but validation
   ended in the Bogus state.

4.8.  Extended DNS Error Code 7 - Signature Expired

   The resolver attempted to perform DNSSEC validation, but no
   signatures are presently valid and some (often all) are expired.

4.9.  Extended DNS Error Code 8 - Signature Not Yet Valid

   The resolver attempted to perform DNSSEC validation, but no
   signatures are presently valid and at least some are not yet valid.

4.10.  Extended DNS Error Code 9 - DNSKEY Missing

   A DS record existed at a parent, but no supported matching DNSKEY
   record could be found for the child.

4.11.  Extended DNS Error Code 10 - RRSIGs Missing

   The resolver attempted to perform DNSSEC validation, but no RRSIGs
   could be found for at least one RRset where RRSIGs were expected.

4.12.  Extended DNS Error Code 11 - No Zone Key Bit Set

   The resolver attempted to perform DNSSEC validation, but no Zone Key
   Bit was set in a DNSKEY.

4.13.  Extended DNS Error Code 12 - NSEC Missing

   The resolver attempted to perform DNSSEC validation, but the
   requested data was missing and a covering NSEC or NSEC3 was not
   provided.

4.14.  Extended DNS Error Code 13 - Cached Error

   The resolver is returning the SERVFAIL RCODE from its cache.

4.15.  Extended DNS Error Code 14 - Not Ready

   The server is unable to answer the query, as it was not fully
   functional when the query was received.

4.16.  Extended DNS Error Code 15 - Blocked

   The server is unable to respond to the request because the domain is
   on a blocklist due to an internal security policy imposed by the
   operator of the server resolving or forwarding the query.

4.17.  Extended DNS Error Code 16 - Censored

   The server is unable to respond to the request because the domain is
   on a blocklist due to an external requirement imposed by an entity
   other than the operator of the server resolving or forwarding the
   query.  Note that how the imposed policy is applied is irrelevant
   (in-band DNS filtering, court order, etc.).

4.18.  Extended DNS Error Code 17 - Filtered

   The server is unable to respond to the request because the domain is
   on a blocklist as requested by the client.  Functionally, this
   amounts to "you requested that we filter domains like this one."

4.19.  Extended DNS Error Code 18 - Prohibited

   An authoritative server or recursive resolver that receives a query
   from an "unauthorized" client can annotate its REFUSED message with
   this code.  Examples of "unauthorized" clients are recursive queries
   from IP addresses outside the network, blocklisted IP addresses,
   local policy, etc.

4.20.  Extended DNS Error Code 19 - Stale NXDOMAIN Answer

   The resolver was unable to resolve an answer within its configured
   time limits and decided to answer with a previously cached NXDOMAIN
   answer instead of answering with an error.  This may be caused, for
   example, by problems communicating with an authoritative server,
   possibly as result of a denial of service (DoS) attack against
   another network.  (See also Code 3.)

4.21.  Extended DNS Error Code 20 - Not Authoritative

   An authoritative server that receives a query with the Recursion
   Desired (RD) bit clear, or when it is not configured for recursion
   for a domain for which it is not authoritative, SHOULD include this
   EDE code in the REFUSED response.  A resolver that receives a query
   with the RD bit clear SHOULD include this EDE code in the REFUSED
   response.

4.22.  Extended DNS Error Code 21 - Not Supported

   The requested operation or query is not supported.

4.23.  Extended DNS Error Code 22 - No Reachable Authority

   The resolver could not reach any of the authoritative name servers
   (or they potentially refused to reply).

4.24.  Extended DNS Error Code 23 - Network Error

   An unrecoverable error occurred while communicating with another
   server.

4.25.  Extended DNS Error Code 24 - Invalid Data

   The authoritative server cannot answer with data for a zone it is
   otherwise configured to support.  Examples of this include its most
   recent zone being too old or having expired.

5.  IANA Considerations

5.1.  A New Extended DNS Error Code EDNS Option

   This document defines a new EDNS(0) option, entitled "Extended DNS
   Error", with the assigned value of 15 from the "DNS EDNS0 Option
   Codes (OPT)" registry:

           +=======+====================+==========+===========+
           | Value | Name               | Status   | Reference |
           +=======+====================+==========+===========+
           | 15    | Extended DNS Error | Standard | RFC 8914  |
           +-------+--------------------+----------+-----------+

                                  Table 1

5.2.  New Registry for Extended DNS Error Codes

   IANA has created and will maintain a new registry called "Extended
   DNS Error Codes" on the "Domain Name System (DNS) Parameters" web
   page as follows:

                +===============+=========================+
                | Range         | Registration Procedures |
                +===============+=========================+
                | 0 - 49151     | First Come First Served |
                +---------------+-------------------------+
                | 49152 - 65535 | Private Use             |
                +---------------+-------------------------+

                                  Table 2

   The "Extended DNS Error Codes" registry is a table with three
   columns: INFO-CODE, Purpose, and Reference.  The initial content is
   as below.

      +=============+==============================+===============+
      | INFO-CODE   | Purpose                      | Reference     |
      +=============+==============================+===============+
      | 0           | Other Error                  | Section 4.1   |
      +-------------+------------------------------+---------------+
      | 1           | Unsupported DNSKEY Algorithm | Section 4.2   |
      +-------------+------------------------------+---------------+
      | 2           | Unsupported DS Digest Type   | Section 4.3   |
      +-------------+------------------------------+---------------+
      | 3           | Stale Answer                 | Section 4.4   |
      |             |                              | and [RFC8767] |
      +-------------+------------------------------+---------------+
      | 4           | Forged Answer                | Section 4.5   |
      +-------------+------------------------------+---------------+
      | 5           | DNSSEC Indeterminate         | Section 4.6   |
      +-------------+------------------------------+---------------+
      | 6           | DNSSEC Bogus                 | Section 4.7   |
      +-------------+------------------------------+---------------+
      | 7           | Signature Expired            | Section 4.8   |
      +-------------+------------------------------+---------------+
      | 8           | Signature Not Yet Valid      | Section 4.9   |
      +-------------+------------------------------+---------------+
      | 9           | DNSKEY Missing               | Section 4.10  |
      +-------------+------------------------------+---------------+
      | 10          | RRSIGs Missing               | Section 4.11  |
      +-------------+------------------------------+---------------+
      | 11          | No Zone Key Bit Set          | Section 4.12  |
      +-------------+------------------------------+---------------+
      | 12          | NSEC Missing                 | Section 4.13  |
      +-------------+------------------------------+---------------+
      | 13          | Cached Error                 | Section 4.14  |
      +-------------+------------------------------+---------------+
      | 14          | Not Ready                    | Section 4.15  |
      +-------------+------------------------------+---------------+
      | 15          | Blocked                      | Section 4.16  |
      +-------------+------------------------------+---------------+
      | 16          | Censored                     | Section 4.17  |
      +-------------+------------------------------+---------------+
      | 17          | Filtered                     | Section 4.18  |
      +-------------+------------------------------+---------------+
      | 18          | Prohibited                   | Section 4.19  |
      +-------------+------------------------------+---------------+
      | 19          | Stale NXDomain Answer        | Section 4.20  |
      +-------------+------------------------------+---------------+
      | 20          | Not Authoritative            | Section 4.21  |
      +-------------+------------------------------+---------------+
      | 21          | Not Supported                | Section 4.22  |
      +-------------+------------------------------+---------------+
      | 22          | No Reachable Authority       | Section 4.23  |
      +-------------+------------------------------+---------------+
      | 23          | Network Error                | Section 4.24  |
      +-------------+------------------------------+---------------+
      | 24          | Invalid Data                 | Section 4.25  |
      +-------------+------------------------------+---------------+
      | 25-49151    | Unassigned                   |               |
      +-------------+------------------------------+---------------+
      | 49152-65535 | Reserved for Private Use     | Section 5.2   |
      +-------------+------------------------------+---------------+

                                 Table 3

6.  Security Considerations

   Though DNSSEC continues to be deployed, unfortunately a significant
   number of clients (~11% according to [GeoffValidation]) that receive
   a SERVFAIL from a validating resolver because of a DNSSEC validation
   issue will simply ask the next (potentially non-validating) resolver
   in their list and thus don't get the protections that DNSSEC should
   provide.

   EDE information is unauthenticated information, unless secured by a
   form of secured DNS transaction, such as [RFC2845], [RFC2931],
   [RFC8094], or [RFC8484].  An attacker (e.g., a man in the middle
   (MITM) or malicious recursive server) could insert an extended error
   response into untrusted data -- although, ideally, clients and
   resolvers would not trust any unauthenticated information.  As such,
   EDE content should be treated only as diagnostic information and MUST
   NOT alter DNS protocol processing.  Until all DNS answers are
   authenticated via DNSSEC or the other mechanisms mentioned above,
   there are some trade-offs.  As an example, an attacker who is able to
   insert the DNSSEC Bogus Extended Error into a DNS message could
   instead simply reply with a fictitious address (A or AAAA) record.
   Note that DNS RCODEs also contain no authentication and can be just
   as easily manipulated.

   By design, EDE potentially exposes additional information via DNS
   resolution processes that may leak information.  An example of this
   is the Prohibited EDE code (18), which may leak the fact that the
   name is on a blocklist.

7.  References

7.1.  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,
              <https://www.rfc-editor.org/info/rfc2119>.

   [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>.

   [RFC5198]  Klensin, J. and M. Padlipsky, "Unicode Format for Network
              Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008,
              <https://www.rfc-editor.org/info/rfc5198>.

   [RFC6891]  Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
              for DNS (EDNS(0))", STD 75, RFC 6891,
              DOI 10.17487/RFC6891, April 2013,
              <https://www.rfc-editor.org/info/rfc6891>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8499]  Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
              Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
              January 2019, <https://www.rfc-editor.org/info/rfc8499>.

   [RFC8767]  Lawrence, D., Kumari, W., and P. Sood, "Serving Stale Data
              to Improve DNS Resiliency", RFC 8767,
              DOI 10.17487/RFC8767, March 2020,
              <https://www.rfc-editor.org/info/rfc8767>.

7.2.  Informative References

   [GeoffValidation]
              Huston, G., "A quick review of DNSSEC Validation in
              today's Internet", June 2016, <http://www.potaroo.net/
              presentations/2016-06-27-dnssec.pdf>.

   [RFC2845]  Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B.
              Wellington, "Secret Key Transaction Authentication for DNS
              (TSIG)", RFC 2845, DOI 10.17487/RFC2845, May 2000,
              <https://www.rfc-editor.org/info/rfc2845>.

   [RFC2931]  Eastlake 3rd, D., "DNS Request and Transaction Signatures
              ( SIG(0)s )", RFC 2931, DOI 10.17487/RFC2931, September
              2000, <https://www.rfc-editor.org/info/rfc2931>.

   [RFC8094]  Reddy, T., Wing, D., and P. Patil, "DNS over Datagram
              Transport Layer Security (DTLS)", RFC 8094,
              DOI 10.17487/RFC8094, February 2017,
              <https://www.rfc-editor.org/info/rfc8094>.

   [RFC8484]  Hoffman, P. and P. McManus, "DNS Queries over HTTPS
              (DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
              <https://www.rfc-editor.org/info/rfc8484>.

Acknowledgements

   The authors wish to thank Joe Abley, Mark Andrews, Tim April,
   Vittorio Bertola, Stephane Bortzmeyer, Vladimir Cunat, Ralph Dolmans,
   Peter DeVries, Peter van Dijk, Mats Dufberg, Donald Eastlake, Bob
   Harold, Paul Hoffman, Geoff Huston, Shane Kerr, Edward Lewis, Carlos
   M. Martinez, George Michelson, Eric Orth, Michael Sheldon, Puneet
   Sood, Petr Spacek, Ondrej Sury, John Todd, Loganaden Velvindron, and
   Paul Vixie.  They also vaguely remember discussing this with a number
   of people over the years but have forgotten who all of them were.
   Apologies if we forgot to acknowledge your contributions.

   One author also wants to thank the band Infected Mushroom for
   providing a good background soundtrack.  Another author would like to
   thank the band Mushroom Infectors.  This was funny at the time we
   wrote it, but we cannot remember why...

Authors' Addresses

   Warren Kumari
   Google
   1600 Amphitheatre Parkway
   Mountain View, CA 94043
   United States of America

   Email: warren@kumari.net


   Evan Hunt
   ISC
   950 Charter St
   Redwood City, CA 94063
   United States of America

   Email: each@isc.org


   Roy Arends
   ICANN

   Email: roy.arends@icann.org


   Wes Hardaker
   USC/ISI
   P.O. Box 382
   Davis, CA 95617
   United States of America

   Email: ietf@hardakers.net


   David C Lawrence
   Salesforce
   415 Mission St
   San Francisco, CA 94105
   United States of America

   Email: tale@dd.org