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The IPv6 Segment Routing (SRv6) Domain Name System (DNS) Resource Record
draft-eastlake-dnsop-rrtype-srv6-06

Document Type Active Internet-Draft (individual)
Authors Donald E. Eastlake 3rd , Haoyu Song
Last updated 2024-08-23
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draft-eastlake-dnsop-rrtype-srv6-06
DNSOP                                                        D. Eastlake
Internet-Draft                                               Independent
Intended status: Standards Track                                 H. Song
Expires: 24 February 2025                         Futurewei Technologies
                                                          23 August 2024

The IPv6 Segment Routing (SRv6) Domain Name System (DNS) Resource Record
                  draft-eastlake-dnsop-rrtype-srv6-06

Abstract

   A Domain Name System (DNS) Resource Record (RR) Type is specified for
   storing IPv6 Segment Routing (SRv6) Information in the DNS.

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
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   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 24 February 2025.

Copyright Notice

   Copyright (c) 2024 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
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   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  IPv6 Segment Routing  . . . . . . . . . . . . . . . . . .   2
     1.2.  The SRV6 RR Type  . . . . . . . . . . . . . . . . . . . .   3
     1.3.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  SRV6 RR Type RDATA  . . . . . . . . . . . . . . . . . . . . .   4
   3.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   7.  Informative References  . . . . . . . . . . . . . . . . . . .   7
   Appendix A.  SRV6 RR Type Template  . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The Domain Name System (DNS) is a hierarchical, distributed, highly
   available database with a variety of security features [RFC4034]
   [RFC4035] used for bi-directional mapping between domain names and
   addresses, for email routing, and for other information [RFC1034]
   [RFC1035].  This data is formatted into resource records (RRs) whose
   content type and structure are indicated by the RR Type field.
   General familiarity with the DNS and its terminology [RFC9499] is
   assumed in this document.

1.1.  IPv6 Segment Routing

   Internet Protocol versions 4 (IPv4, [RFC0791]) and 6 (IPv6,
   [RFC8200]) have long provided header options that support including
   an ordered sequence of addresses in a packet header so the packet
   travels in order through the nodes specified by that sequence of
   addresses.  This is sometimes referred to as "source routing" because
   the route or path the packet follows is set, at least in part, when
   the sequence of addresses is added to the packet, usually at the
   packet's source, rather than being dynamically determined as the
   packet proceeds through the network.

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   IPv6 Segment Routing (SRv6, [RFC8402]) extends "source routing" by
   generalizing the IPv6 sized "address" quantities in a source
   "routing" sequence to be "instructions".  [RFC8754] specifies a
   particular Segment Routing Header (SRH) that may be use used as part
   of the headers of an IPv6 packet to indicate an IPv6 Segment Routing
   sequence of addresses / instructions.  And [RFC8986] further
   specifies the structuring of an IPv6 address size quantity such that
   it may be composed of addressing information followed by a function
   designation which is optionally further followed by arguments to that
   function.  Thus, segment routing might encode a series of operations
   to be performed on a packet.

   Furthermore, because a sequence of SRv6 instructions may all start
   with the same constant addressing prefix, methods of compression have
   been specified [Compress] to represent this addressing prefix less
   often and pack an increased number of quantities into a Segment
   Routing Header where each quantity may consist optionally of
   additional address information and/or function designation and/or
   function arguments.

1.2.  The SRV6 RR Type

   This document specifies a SRV6 RR Type to return a sequence of IPv6
   Segment Routing addresses / instructions and optionally other data.

   In many ways, the data returned for an SRV6 DNS RR is like an
   address.  This RR supports a DNS client querying for SRV6 RRs at a
   name, inserting returned SRv6 information into the header of an IPv6
   packet, and transmitting that packet so addressed.  It would also be
   reasonable for an application using SRv6 to do a type SRV DNS query
   [RFC2782] followed by an SRV6 query at the resulting domain name if
   it was in a domain where SRv6 was in use.  Furthermore, as a fall
   back, if no SRV6 RR is present in the DNS at a domain name, a client
   application whose SRV6 query has failed could query for the AAAA IPv6
   address RR type.

   Segment Routing is intended to be used in a limited domain compared
   with the global Internet.  Furthermore, the DNS is commonly thought
   of as the source for global Internet addressing.  However, most DNS
   servers can be easily configured in a network so that some names are
   only visible locally and some RRs are only delivered locally.

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1.3.  Terminology

   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.

   The following acronyms are used in this document:

      DNS - Domain Name System

      IANA - Internet Assigned Number Authority

      IPv6 - Internet Protocol Version 6 [RFC8200]

      RR - DNS Resource Record

      SID - Segment Identifier [RFC8402]

      SRH - Segment Routing (IPv6) Header [RFC8754]

      SRv6 - IPv6 Segment Routing [RFC8402]

      SRV6 - Mnemonic for the SRv6 RR Type

      TLV - Type, Length, Value

2.  SRV6 RR Type RDATA

   The SRV6 RR type enables the storage and retrieval of an ordered
   sequence of SRv6 quantities each of which is the size of an IPv6
   [RFC8200] address.  The RDATA for this type of RR is a set of fields
   followed by a sequence of such quantities followed by optional data
   (see Figure 1) and will be ( 4 + N*16 + Opt) bytes long, where N is
   the number of such quantities present and Opt is the length of the
   optional data.

   The RR Type Code for the SRV6 RR is TBD1.

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      0 0 0 0 0 0 0 0 0 0 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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    SID Count  |   SRH Flags   |          SRH Tag              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     |             16-byte SRv6 Address/Instruction (SID)            |
     |                                                               |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                                                               .
     .     Additional 16-byte SRv6 Addresses/Instructions (SIDs)     .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .    Optional TLVs                                              .
     .................................................................

                         Figure 1: SRV6 RRTYPE Data

   The RDATA consists of a segment count followed by a flags byte, a 2
   byte tag, and then one or more 128-bit SRv6 SIDs followed by optional
   TLV data, all as further detailed as follows:

      SID Count - As unsigned one byte integer giving the number of
      16-byte SRv6 SIDs in the RDATA.

      SRH Flags - This byte gives a initial value for the Flags field of
      the Segment Routing Header (SRH, [RFC8754]).

      SRH Tag - This field is a suggested value for the Tag field of the
      SRH [RFC8754].

      SIDs - 16-byte SRv6 segment identifiers (SIDs, [RFC8402].

      Optional TLVs - Suggested TLVs for inclusion in a Segment Routing
      Header (SRH, [RFC8754]) created using this RDATA.

   If the RDATA length is less than (4 + (SID Count)*16) or if the
   Optional TLVs do not parse as SRH TLVs, then the RR is malformed and
   MUST be ignored.

   Circumstances and/or future definition of flags and TLV types may
   require, when an IPv6 packet header is contructed based on an SRV6
   RR, that some SRH FLags be set or clear regardless of the SRH Flags
   RR field and/or that some SRH TLVs be included or excluded regardless
   of the Optional TLV in the SRH RR.

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3.  Acknowledgements

   The suggestions and comments of the following persons are gratefully
   acknowledged:

      tbd

4.  IANA Considerations

   IANA is requested to assign an SRV6 RR Type (TBD1) as in the template
   in Appendix A.

5.  Security Considerations

   For information on DNS features that improve the authentication of
   retrieved RRs, see [RFC4034] and [RFC4035].

   For SRv6 Security Considerations, see [RFC8402] and Section 5 of
   [RFC8754].  For Security Considerations of SRv6 Network Programming,
   see [RFC8986]

6.  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>.

   [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>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

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   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [RFC8986]  Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
              D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
              (SRv6) Network Programming", RFC 8986,
              DOI 10.17487/RFC8986, February 2021,
              <https://www.rfc-editor.org/info/rfc8986>.

7.  Informative References

   [Compress] Cheng, W., Ed., Filsfils, C., Ed., Previdi, S., Li, Z.,
              Decraene, B., and F. Clad, "Compressed SRv6 Segment List
              Encoding in SRH", 13 September 2023,
              <https://datatracker.ietf.org/doc/draft-ietf-spring-srv6-
              srh-compression/>.

   [RFC0791]  Postel, J., "Internet Protocol", STD 5, RFC 791,
              DOI 10.17487/RFC0791, September 1981,
              <https://www.rfc-editor.org/info/rfc791>.

   [RFC2782]  Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
              specifying the location of services (DNS SRV)", RFC 2782,
              DOI 10.17487/RFC2782, February 2000,
              <https://www.rfc-editor.org/info/rfc2782>.

   [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>.

   [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>.

   [RFC8754]  Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
              Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
              (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
              <https://www.rfc-editor.org/info/rfc8754>.

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   [RFC9499]  Hoffman, P. and K. Fujiwara, "DNS Terminology", BCP 219,
              RFC 9499, DOI 10.17487/RFC9499, March 2024,
              <https://www.rfc-editor.org/info/rfc9499>.

Appendix A.  SRV6 RR Type Template

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   A. Submission Date: tbd

   B.1 Submission Type:  [X] New RRTYPE  [ ] Modification to RRTYPE
   B.2 Kind of RR:  [X] Data RR  [ ] Meta-RR

   C. Contact Information for submitter (will be publicly posted):
      Name: Donald Eastlake
      Email Address: d3e3e3@gmail.com
      International telephone number: +1-508-333-2270
      Other contact handles:

   D. Motivation for the new RRTYPE application.

      Enable storeage of IPv6 Segment Routing sequences in the DNS.

   E. Description of the proposed RR type.
      See draft-eastlake-dnsop-rrtype-srv6

   F. What existing RRTYPE or RRTYPEs come closest to filling that need
      and why are they unsatisfactory?

      Perhaps AAAA but that only returns a single IPv6 address, not an
      ordered sequence of IPv6 sized SRv6 instructions.

   G. What mnemonic is requested for the new RRTYPE (optional)?

      SRV6

   H. Does the requested RRTYPE make use of any existing IANA registry
      or require the creation of a new IANA subregistry in DNS
      Parameters?  If so, please indicate which registry is to be used
      or created.  If a new subregistry is needed, specify the
      allocation policy for it and its initial contents.

      Does not use any existing registry and does not create a new
      registry.

   I. Does the proposal require/expect any changes in DNS
      servers/resolvers that prevent the new type from being processed
      as an unknown RRTYPE (see [RFC3597])?

      No.

   J. Comments:  None.

Authors' Addresses

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   Donald Eastlake
   Independent
   2386 Panoramic Circle
   Apopka, FL 32703
   United States of America
   Phone: +1 508 333 2270
   Email: d3e3e3@gmail.com

   Haoyu Song
   Futurewei Technologies
   2220 Central Expressway
   Santa Clara, CA 95050
   United States of America
   Email: haoyu.song@futurewei.com

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