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Versions: 00 01 02

Internet Engineering Task Force                              T. Pusateri
Internet-Draft                                             T. Wattenberg
Intended status: Standards Track                            Unaffiliated
Expires: September 5, 2019                                 March 4, 2019


                      DNS TIMEOUT Resource Record
                 draft-pusateri-dnsop-update-timeout-02

Abstract

   This specification defines a new DNS TIMEOUT resource record (RR)
   that associates a lifetime with one or more zone resource records
   with the same owner name, type, and class.  It is intended to be used
   to transfer resource record lifetime state between a zone's primary
   and secondary servers and to store lifetime state during server
   software restarts.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on September 5, 2019.

Copyright Notice

   Copyright (c) 2019 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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Sources of TIMEOUT Expiry Time  . . . . . . . . . . . . . . .   3
   4.  Resource Record Composition . . . . . . . . . . . . . . . . .   3
     4.1.  Represented Record Type . . . . . . . . . . . . . . . . .   4
     4.2.  Represented Record Count  . . . . . . . . . . . . . . . .   4
     4.3.  Method Identifiers  . . . . . . . . . . . . . . . . . . .   4
       4.3.1.  Method Identifier 0: NO METHOD  . . . . . . . . . . .   5
       4.3.2.  Method Identifier 1: RDATA  . . . . . . . . . . . . .   5
     4.4.  Expiry Time . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  TIMEOUT RDATA Wire Format . . . . . . . . . . . . . . . . . .   5
   6.  Primary Server Behavior . . . . . . . . . . . . . . . . . . .   7
   7.  Secondary Server Behavior . . . . . . . . . . . . . . . . . .   7
   8.  TIMEOUT RDATA Presentation Format . . . . . . . . . . . . . .   7
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   10. Security Considerations . . . . . . . . . . . . . . . . . . .   9
   11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   9
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     12.2.  Informative References . . . . . . . . . . . . . . . . .  10
   Appendix A.  Example TIMEOUT resource records . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   DNS Update [RFC2136] provides a mechanism to dynamically add/remove
   DNS resource records to/from a zone.  When a resource record is
   dynamically added, it remains in the zone until it is removed
   manually or via a subsequent DNS Update.  A zone administrator may
   want to enforce a default lifetime for dynamic updates (such as the
   DHCP lease lifetime) or the DNS Update may contain a lifetime using
   an EDNS(0) Update Lease option [I-D.sekar-dns-ul].  However, this
   lease lifetime is not communicated to secondary servers and will not
   endure through server software restarts.  Therefore, this
   specification defines a new DNS TIMEOUT resource record that
   associates a lifetime with one or more resource records with the same
   owner name, type, and class that can be transferred to secondary
   servers through normal AXFR [RFC5936], IXFR [RFC1995] transfer
   mechanisms.

   An UPDATE lifetime could be stored in a proprietary database on an
   authoritative primary server but there is an advantage to saving it
   as a resource record: redundant master servers and secondary servers



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   capable of taking over as the primary server for a zone automatically
   can benefit from the existing database synchronization of resource
   records.  In addition, primary and secondary servers from multiple
   vendors can synchronize the lifetimes through the open format
   provided by a resource record.

2.  Requirements Language

   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.  These words may also appear in this
   document in lower case as plain English words, absent their normative
   meanings.

3.  Sources of TIMEOUT Expiry Time

   The expire time may come from many different sources.  A few are
   listed here however, this list is not considered complete.

   1.  Via DHCP Dynamic Lease Lifetime communicated out of band.

   2.  Via EDNS(0) Update Lease option [I-D.sekar-dns-ul] communicated
       in DNS Update.

   3.  Via an administrative default server value such as one day (86400
       seconds).

4.  Resource Record Composition

   TIMEOUT resource records provide expiry times for a mixed variety of
   resource record types with the same owner name, type, and class.
   Since there could exist multiple records of the same record type with
   the same owner name and class, the TIMEOUT resource record must be
   able to identify each of these records individually with only
   different RDATA.  As an example, PTR records for service discovery
   [RFC6763] provide a level of indirection to SRV and TXT records by
   instance name.  The instance name is stored in the PTR RDATA and
   multiple PTR records with the same owner name but only differing
   RDATA often exist.

   In order to distinguish each individual record with potentially
   different expiry times, the TIMEOUT resource record contains an
   exipry time, the record type, a method to identify the actual records
   for which the expiry time applies, and a count of the number of
   records represented.  Multiple TIMEOUT records with the same owner
   name and class are created for each expiry time, record type, and



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   resource record representation.  If the expiry time is the same,
   multiple records can be combined into a single TIMEOUT record with
   the same owner name, class, and record type but this is NOT REQUIRED.

   The fields and their values in a TIMEOUT record are defined as:

4.1.  Represented Record Type

   A 16-bit field containing the resource record type to which the
   TIMEOUT record applies.  Multiple TIMEOUT records for the same owner
   name, class, and represented type can exist.

4.2.  Represented Record Count

   The Represented Record Count is a 8-bit value that specifies the
   number of records of the specified record type with this expiry time.

   An RR Count of zero indicates that it is not necessary to represent
   any records in the list.  This is a shortcut notation meaning all
   resource records with the same owner name, class, and record type use
   the same Expiry Time.  There MUST be only one TIMEOUT record for the
   same owner name, class, and record type if the Represented Record
   Count is zero.  If an additional TIMEOUT record exists with the same
   owner name, class, and record type, it MUST be ignored and SHOULD be
   removed.  When the Represented Record Count is 0, the Method
   Identifer is set to NO METHOD (0) on transmission and ignored on
   reception.

   In the unlikely event that the Represented Record Count exceeds 255
   which is the largest number representable in 8 bits, multiple
   instances of the same Expiry Time can exist.

4.3.  Method Identifiers

   The Method Identifier is a 8-bit value that specifies an identifier
   for the algorithm used to distinguish between resource records.  The
   identifiers are declared in a registry maintained by IANA for the
   purpose of listing acceptable methods for this purpose.  In addition
   to the method and the index, the registry MAY contain a fixed output
   length in bits of the method to be used or the term "variable" to
   denote a variable length output per record.  It is conceivable,
   though not likely, that the same method could be used with different
   fixed output lengths.  In this case, each fixed output length would
   require a different identifier in the registry.  Additions to this
   registry will be approved with additional documentation under expert
   review.  At the time that the registry is created by IANA, a group of
   expert reviewers will be established.




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   Additional methods of representing records such as hashes or other
   algorithms may be defined in the future.  If such methods are
   defined, a primary server could create TIMEOUT record using a new
   method that is not understood by a secondary server that could take
   over as the primary in the event of an outage or administrative
   change.  In this case, the new primary would not be able to identify
   the records it is supposed to TIMEOUT.  This is a misconfiguration
   and it is the responsibility of the administrator to ensure that
   secondary servers in a position to become primary understand the
   TIMEOUT record methods of the primary server.

4.3.1.  Method Identifier 0: NO METHOD

   The method identifier of 0 is defined as "NO METHOD" and MUST NOT be
   used if the represented record count is greater than 0.  The value of
   0 is to be included in the IANA registry of method identifier values.

4.3.2.  Method Identifier 1: RDATA

   The method identifier of 1 is defined as "RDATA".  It begins with the
   RDATA length as a 16-bit value containing the length of the RDATA in
   bytes followed by the number of bytes of RDATA as appears in the
   record being represented.  The record MUST be in canonical DNSSEC
   form as described in Section 6 of [RFC4034].

4.4.  Expiry Time

   The expiry time is a 64-bit number expressed as the number of seconds
   since the UNIX epoch (00:00:00 UTC on January 1, 1970).  This value
   is an absolute time at which the record will expire.  Lease times
   must be converted to an absolute expiry time when received.

5.  TIMEOUT RDATA Wire Format

   The TIMEOUT resource record follows the same pattern as other DNS
   resource records as defined in Section 3.2.1 of [RFC1035] including
   owner name, type, class, TTL, RDATA length, and RDATA.

   The RDATA section of the resource record with method identifier RDATA
   (1) is illustrated in Figure 1:











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      0                   1                   2                   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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      Represented RR Type      |   Count (n)   |   Method (1)  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       Expiry Time (64-bit)                    |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .    Represented RDATA LEN 1    |                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               .
     .                                                               .
     .                     Represented RDATA 1                       .
     .                                                               .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .    Represented RDATA LEN n    |                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               .
     .                                                               .
     .                     Represented RDATA n                       .
     .                                                               .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                  Figure 1: Method (1) RDATA Wire Format

   Figure 1 represents an arbitrary number of represented records with
   the same owner name, class, and represented type.  For each expiry
   time, a list of RDATA length and RDATA pairs are attached.  The
   overall RDATA length of the TIMEOUT record indicates when the last
   represented record is contained in the record.

   The RDATA section of the resource record with method identifier NO
   METHOD (0) is illustrated in Figure 2:


      0                   1                   2                   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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      Represented RR Type      |   Count (0)   |   Method (0)  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       Expiry Time (64-bit)                    |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                  Figure 2: Method (0) RDATA Wire Format




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   Figure 2 represents the TIMEOUT RDATA field of all matching records
   of the represented type for the same owner name and class.

6.  Primary Server Behavior

   A TIMEOUT resource record MUST be removed when the last resource
   record it covers has been removed.  This may be due to the record
   expiring (reaching the expiry time) or due to a subsequent DNS Update
   or administrative action.

   Upon receiving any DNS UPDATE deleting resource records that might
   have been covered by a TIMEOUT RR, a primary server MUST remove all
   represented records in all of the TIMEOUT records with the same owner
   name, class, and represented type.

   As a reminder from Section 3.3.13 of [RFC1035], the MINIMUM field of
   the SOA for the zone is used as a lower bound of the TTL for all
   records in the zone.  Therefore, even if the TIMEOUT record will
   expire in less time than the MINIMUM, the TTL is still set to the
   MINIMUM for records covered by the TIMEOUT record and the TIMEOUT
   record itself when a response is returned by an authoritative server.
   The TIMEOUT RR is mostly for the benefit of the authoritative server
   to know when to remove the records.  The fact that some records might
   live longer in the cache of a resolver is no different than other
   records that might get removed while still in a remote resolver
   cache.

7.  Secondary Server Behavior

   A secondary server may or may not understand TIMEOUT resource
   records.  If a secondary server does not understand them, they are
   treated like any other resource record that the server may not
   understand [RFC3597].

   A secondary server MUST NOT expire the records in a zone it maintains
   covered by the TIMEOUT resource record and it MUST NOT expire the
   TIMEOUT resource record itself when the last record it covers has
   expired.  The secondary server MUST always wait for the records to be
   removed or updated by the primary server.

8.  TIMEOUT RDATA Presentation Format

   Record Type:
         resource record type mnemonics.  When the mnemonic is unknown,
         the TYPE representation described in Section 5 of [RFC3597]

   Represented Record Count:
         unsigned decimal integer (0-255)



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   Method Identifier:
         unsigned decimal integer (0-255)

   Expiry Time:
         The Expiry Time is displayed as a compact numeric-only
         representation of ISO 8601.  All punctuation is removed.  This
         form is slightly different than the recommendation in [RFC3339]
         but is common for DNS protocols.  It is defined in Section 3.2
         of [RFC4034] as YYYYMMDDHHmmSS in UTC.  This form will always
         be exactly 14 digits since no component is optional.

         YYYY is the year;
         MM is the month number (01-12);
         DD is the day of the month (01-31);
         HH is the hour, in 24 hour notation (00-23);
         mm is the minute (00-59); and
         SS is the second (00-59).

   RDATA Length:
         unsigned decimal integer

   RDATA:
         record type specific




























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9.  IANA Considerations

   This document defines a new DNS Resource Record Type named TIMEOUT to
   be exchanged between authoritative primary and secondary DNS servers.
   It is assigned out of the DNS Parameters Resource Record (RR) Type
   registry.  The value for the TIMEOUT resource record type is TBA.

   This document establishes a new registry of DNS TIMEOUT Resource
   Record Method Identifier values.  The registry shall include a
   numeric identifier, a method name, a description of the method, and
   the length of the output function in bits or the keyword "variable".
   The identifier is to be used in the RDATA section of the TIMEOUT
   resource record.

   +-------+------------+----------------+-------------+---------------+
   |   ID  | Method     | Description    |    Length   | Definition    |
   |       | Name       |                |    (bits)   |               |
   +-------+------------+----------------+-------------+---------------+
   |   0   | NO METHOD  | All records    |      0      | Section 4.3.1 |
   |       |            | match          |             |               |
   |   1   | RDATA      | Actual RDATA   |   variable  | Section 4.3.2 |
   |       |            | of represented |             |               |
   |       |            | records        |             |               |
   +-------+------------+----------------+-------------+---------------+

               Table 1: TIMEOUT RR Method Identifier values

10.  Security Considerations

   There is no secure relationship between a TIMEOUT resource record and
   the represented resource records it applies to.  TIMEOUT records
   should typically only apply to resource records created through the
   UPDATE mechanism.  Protection for permanent resource records in a
   zone is advisable.

   Authenticated UPDATE operations MUST be REQUIRED at authoritative
   name servers supporting TIMEOUT resource records.

11.  Acknowledgments

   This idea was motivated through conversations with Mark Andrews.
   Thanks to Mark as well as Paul Vixie, Joe Abley, Ted Lemon, Tony
   Finch, Robert Story, Paul Wouters, and Dick Franks for their
   suggestions, review, and comments.







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12.  References

12.1.  Normative References

   [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>.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
              <https://www.rfc-editor.org/info/rfc3339>.

   [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>.

   [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>.

   [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>.

12.2.  Informative References

   [I-D.sekar-dns-ul]
              Cheshire, S. and T. Lemon, "Dynamic DNS Update Leases",
              draft-sekar-dns-ul-02 (work in progress), August 2018.

   [RFC1995]  Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995,
              DOI 10.17487/RFC1995, August 1996,
              <https://www.rfc-editor.org/info/rfc1995>.

   [RFC2136]  Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound,
              "Dynamic Updates in the Domain Name System (DNS UPDATE)",
              RFC 2136, DOI 10.17487/RFC2136, April 1997,
              <https://www.rfc-editor.org/info/rfc2136>.

   [RFC5936]  Lewis, E. and A. Hoenes, Ed., "DNS Zone Transfer Protocol
              (AXFR)", RFC 5936, DOI 10.17487/RFC5936, June 2010,
              <https://www.rfc-editor.org/info/rfc5936>.



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   [RFC6763]  Cheshire, S. and M. Krochmal, "DNS-Based Service
              Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
              <https://www.rfc-editor.org/info/rfc6763>.

Appendix A.  Example TIMEOUT resource records

   The following example shows sample TIMEOUT resource records based on
   DNS UPDATEs containing A and AAAA address records plus the
   corresponding PTR records.

   A host sending a name registration at time Tn for "A" and "AAAA"
   records with lease lifetime Ln would have a series of UPDATEs (one
   for each zone) that contain:

   +-------------------------------------------+------+----------------+
   | Name                                      | RR   | Value          |
   |                                           | Type |                |
   +-------------------------------------------+------+----------------+
   | s.example.com.                            | A    | 192.0.2.5      |
   | s.example.com.                            | AAAA | 12001:db8::5   |
   | 5.2.0.192.in-addr.arpa.                   | PTR  | s.example.com. |
   | 5.0.0.0.0.0.0.0.0.0.0.0.b8.0d.01.20.ip6.a | PTR  | s.example.com. |
   | rpa. (bytes)                              |      |                |
   +-------------------------------------------+------+----------------+

                  Table 2: Example Address Records Update

   Next, consider the TIMEOUT resource records that would be generated
   for the records in Table 2.  Notice that none of the 4 TIMEOUT
   records on the server would require a hash:

   +------------------------------+------+-------+--------+------------+
   | Owner Name                   | For  | Count | Method | Expiration |
   |                              | Type |       |        |            |
   +------------------------------+------+-------+--------+------------+
   | s.example.com.               | A    | 0     | 0      | Tn + Ln    |
   | s.example.com.               | AAAA | 0     | 0      | Tn + Ln    |
   | 5.2.0.192.in-addr.arpa.      | PTR  | 0     | 0      | Tn + Ln    |
   | 5.0.0.0.0.0.0.0.0.0.0.0.b8.0 | PTR  | 0     | 0      | Tn + Ln    |
   | d.01.20.ip6.arpa. (bytes)    |      |       |        |            |
   +------------------------------+------+-------+--------+------------+

                     Table 3: Address TIMEOUT records

   Next, assume there are two hosts advertising the same service type
   (different service types will have different owner names).  We will
   use _ipp._tcp.example.com as an example.




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   Host A sends an UPDATE at time Ta with lease life La for PTR, SRV, A,
   AAAA, and TXT records.  Host B sends an UPDATE at time Tb with lease
   life Lb for PTR, SRV, A, and TXT records.

   +--------------------------------+------+---------------------------+
   | Owner name                     | RR   | Value                     |
   |                                | Type |                           |
   +--------------------------------+------+---------------------------+
   | _ipp._tcp.example.com.         | PTR  | p1._ipp._tcp.example.com. |
   | p1._ipp._tcp.example.com.      | SRV  | 0 0 631 p1.example.com.   |
   | p1._ipp._tcp.example.com.      | TXT  | paper=A4                  |
   | p1.example.com.                | A    | 192.0.2.1                 |
   | p1.example.com.                | AAAA | 2001:db8::1               |
   +--------------------------------+------+---------------------------+

                      Table 4: DNS UPDATE from Host A

   +--------------------------------+------+---------------------------+
   | Owner name                     | RR   | Value                     |
   |                                | Type |                           |
   +--------------------------------+------+---------------------------+
   | _ipp._tcp.example.com.         | PTR  | p2._ipp._tcp.example.com. |
   | p2._ipp._tcp.example.com.      | SRV  | 0 0 631 p2.example.com.   |
   | p2._ipp._tcp.example.com.      | TXT  | paper=B4                  |
   | p2.example.com.                | A    | 192.0.2.2                 |
   +--------------------------------+------+---------------------------+

                      Table 5: DNS UPDATE from Host B

   For these printer registrations, the TIMEOUT records on the server
   would look like the following:




















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   +---------------------------+------+---+-----+----------------------+
   | Owner Name                | For  | C | Met | Expire /             |
   |                           | Type | o | hod | RDLEN RDATA          |
   |                           |      | u |     |                      |
   |                           |      | n |     |                      |
   |                           |      | t |     |                      |
   +---------------------------+------+---+-----+----------------------+
   | _ipp.tcp.example.com.     | PTR  | 1 | 1   | Ta + La 25 p1._ipp._ |
   |                           |      |   |     | tcp.example.com.     |
   | _ipp.tcp.example.com.     | PTR  | 1 | 1   | Tb + Lb 25 p2._ipp._ |
   |                           |      |   |     | tcp.example.com.     |
   | p1._ipp._tcp.example.com. | SRV  | 0 | 0   | Ta + La              |
   | p1._ipp._tcp.example.com. | TXT  | 0 | 0   | Ta + La              |
   | p2._ipp._tcp.example.com. | SRV  | 0 | 0   | Tb + Lb              |
   | p2._ipp._tcp.example.com. | TXT  | 0 | 0   | Tb + Lb              |
   | p1.example.com.           | A    | 0 | 0   | Ta + La              |
   | p1.example.com.           | AAAA | 0 | 0   | Ta + La              |
   | p2.example.com.           | A    | 0 | 0   | Tb + Lb              |
   +---------------------------+------+---+-----+----------------------+

                     Table 6: Service TIMEOUT records

Authors' Addresses

   Tom Pusateri
   Unaffiliated
   Raleigh, NC
   USA

   Email: pusateri@bangj.com


   Tim Wattenberg
   Unaffiliated
   Cologne
   Germany

   Email: mail@timwattenberg.de













Pusateri & Wattenberg   Expires September 5, 2019              [Page 13]


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