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A Domain Name System (DNS) Service Parameter and Resource Record for Tunneling Information
draft-eastlake-dnsop-svcb-rr-tunnel-05

Document Type Active Internet-Draft (individual)
Authors Donald E. Eastlake 3rd , Haoyu Song
Last updated 2024-05-07
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draft-eastlake-dnsop-svcb-rr-tunnel-05
DNSOP                                                        D. Eastlake
Internet-Draft                                               Independent
Intended status: Standards Track                                 H. Song
Expires: 8 November 2024                          Futurewei Technologies
                                                              7 May 2024

  A Domain Name System (DNS) Service Parameter and Resource Record for
                         Tunneling Information
                 draft-eastlake-dnsop-svcb-rr-tunnel-05

Abstract

   A Domain Name System (DNS) Service Binding (SVCB) Service Parameter
   Type and a DNS Resource Record (RR) Type are specified for storing
   connection tunneling / encapsulation 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
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   This Internet-Draft will expire on 8 November 2024.

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   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
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   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Tunneling . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  SVCB RR Service Parameter "tunnel"  . . . . . . . . . . . . .   4
   3.  TUNNEL RR Type RDATA  . . . . . . . . . . . . . . . . . . . .   4
   4.  Use of the Specified RRs  . . . . . . . . . . . . . . . . . .   6
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Appendix A.  Tunnel 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 used for bi-
   directional mapping between domain names and addresses, for email
   routing, and for other information [RFC1034] [RFC1035] [RFC4033].
   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.  Tunneling

   It is common for there to be a requirement to use or some benefit
   from using a "tunnel" or encapsulation scheme when connecting to a
   service/host.  For a reachability use case, see Section 1.3 of
   [RFC9012].  Typically, this involves taking a packet with a transport
   header addressed to the ultimate destination, adding a tunnel header
   to the packet, and then adding an outer transport header before
   transmitting the packet out of a network interface (port).  The
   resulting packet is illustrated in Figure 1.  In some cases, such as
   IP-in-IP, the Tunneling Header may be null.

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     +--------------------------------------------------------------+
     |                   Outer Transport Header                     |
     +--------------------------------------------------------------+
     |                   Tunneling Header                           |
     +--------------------------------------------------------------+
     |                   Inner Transport Header                     |
     +--------------------------------------------------------------+
     |                   Tunneled/Encapsulated Packet               |
     |                                                              |

                          Figure 1: Encapsulation

   The addition of the Outer Transport and Tunneling Headers will
   lengthen packets which may result in the need for fragmentation.
   Some tunneling protocol support fragmentation but for those that do
   not, fragmentation of the Tunneled Packet before encapsulation may be
   required.

   This document specifies a Domain Name System (DNS) Service Binding
   (SVCB) Service Parameter Type and a DNS Resource Record (RR) Type for
   storing connection tunneling / encapsulation information in the DNS.
   This enables the storage and retrieval of tunneling information that
   may be needed to connect to a remote service or host.

1.2.  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 [RFC1034][RFC1035].

      IANA - Internet Assigned Numbers Authority <www.iana.org>.

      RDATA - The data portion of an RR.

      RR - DNS Resource Record.

      RRType - The type field in an RR.

      SVCB - Service Binding.

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2.  SVCB RR Service Parameter "tunnel"

   The SVCB (Service Binding) RR is specified in [RFC9460].  It
   provides, when used in the "Service Mode", for the encoding of a
   variety of "Service Parameters" to assist in connecting to a service.

   The "tunnel" SVCB Service Parameter, whose numeric key value is TBD1,
   has a value consisting of the Tunnel Type, Tunnel Parameters Length,
   and Tunnel Parameters TLVs.  It uses the same Tunnel Type codes and
   parameter TLVs as are specified for the BGP Tunnel Encapsulation
   Attribute in [RFC9012] as shown in Figure 2.  The presentation format
   for this value is hexadecimal.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           Tunnel Type         |   Tunnel Parameters Length    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     /                                                               /
     /           Tunnel Parameters TLVs (variable length)            /
     /                                                               /
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 2: SVCB tunnel Service Parameter Value

   For further details on the fields in Figure 2 see Section 3 which re-
   uses these fields with the same names and specifies those details.

3.  TUNNEL RR Type RDATA

   The RDATA for this RR type includes the following as further
   explained below and illustrated in Figure 3:

   *  tunneling information in the format used in the BGP Tunnel
      Encapsulation Attribute [RFC9012], and

   *  a domain name that maps to the Inner Transport Header destination.

   The RRType Code for the TUNNEL RR is TBD2.

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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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           Priority            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           Tunnel Type         |   Tunnel Parameters Length    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     /                                                               /
     /           Tunnel Parameters TLVs (variable length)            /
     /                                                               /
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     /           Target Name (variable length)                       /
     /                                                               /
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Figure 3: TUNNEL RRTYPE Data

   The fields in Figure 3 are as explained below.  The contiguous Tunnel
   Type, Tunnel Parameters Length, and Tunnel Parameters TLV (Value) as
   a block of data are identical to the "Tunnel Encapsulation TLV"
   specified in [RFC9012] ("The BGP Tunnel Encapsulation Attribute").

   Prority  - This field is a two-byte unsigned integer using network
      byte order that is the priority of using this tunnel to the
      target.  A client MUST use the tunnel with the lowest priority RR
      that meets the following conditions:

      *  The client implements the Tunnel Type.
      *  The client can resolve the Target Name.
      *  The type of packet being tunneled in not prohibited by an
         optional Protocol Type Tunnel Parameters TLV (see Section 3.4.1
         of [RFC9012]).  For example, the tunneling could be restricted
         to TCP packets.

   Tunnel Type  - This is the Tunnel Type from the IANA "BFP Tunnel
      Encapsulation Attribute Tunnel Types" registry as specified in
      [RFC9012].

   Tunnel Parameters Length  - A two-byte unsigned integer using network
      byte order giving the number of octets in the Tunnel Parameters
      TLVs field.  Necessary because that field is not self-terminating.

   Tunnel Parameters TLVs  - This field consists of "Tunnel
      Encapsulation Attribute Sub-TLVs" as specified in [RFC9012].
      These TLVs can specify a variety of parameters, including the
      following, which may be useful in constructing the Outer Transport
      Header (Figure 1):

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      *  Tunnel Egress Endpoint
      *  Differentiated Services Field [RFC2474]
      *  UDP Destination Port

   Target Name  - The uncompressed domain name of the ultimate
      destination in DNS wire encoding format.  Used to obtain the
      destination address for the construction of the Inner Transport
      Header as shown in Figure 1.

4.  Use of the Specified RRs

   A client/application seeking to send packets to a host or service can
   query the DNS using the name of the host or service for the TUNNEL
   RR.  If that name is found and one or more TUNNEL RRs are returned,
   it can use the highest priority TUNNEL RR for which it has
   implemented the Tunnel Type indicated in that RR to create and
   populate a tunneling header as shown in Figure 1.  The Target Name in
   that TUNNEL RR can then be used to obtain an address for use in the
   Outer Transport Header as also shown in Figure 1.  With these
   headers, a packet is then transmitted.

   Where a client/application is already using the SVCB RR [RFC9012],
   similar logic applies using the tunnel SVCB Service Parameter.

5.  Acknowledgements

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

   tbd

6.  IANA Considerations

   IANA is requested to assign a value from the Service Parameter Keys
   Registry on the "DNS Service Bindings (SVCB)" IANA web page as
   follows:

       +========+========+=======================+=================+
       | Number | Name   | Meaning               | Reference       |
       +========+========+=======================+=================+
       | TBD1   | tunnel | Tunneling information | [this document] |
       +--------+--------+-----------------------+-----------------+

                                  Table 1

   IANA is requested to assign a TUNNEL RR Type (TBD2) as in the
   template in Appendix A.

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7.  Security Considerations

   tbd

8.  References

8.1.  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>.

   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474,
              DOI 10.17487/RFC2474, December 1998,
              <https://www.rfc-editor.org/info/rfc2474>.

   [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>.

   [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>.

   [RFC9012]  Patel, K., Van de Velde, G., Sangli, S., and J. Scudder,
              "The BGP Tunnel Encapsulation Attribute", RFC 9012,
              DOI 10.17487/RFC9012, April 2021,
              <https://www.rfc-editor.org/info/rfc9012>.

   [RFC9460]  Schwartz, B., Bishop, M., and E. Nygren, "Service Binding
              and Parameter Specification via the DNS (SVCB and HTTPS
              Resource Records)", RFC 9460, DOI 10.17487/RFC9460,
              November 2023, <https://www.rfc-editor.org/info/rfc9460>.

8.2.  Informative References

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   [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>.

   [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.  Tunnel 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.

      Need to store tunneling information in the DNS.

   E. Description of the proposed RR type.
      See draft-eastlake-dnsop-svcb-rr-tunnel

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

      The SRV RR provides connection information for a service/host but
      not tunneling information.

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

      TUNNEL

   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.

      Makes use of the Border Gateway Protocol (BGP) Tunnel
      Encapsulation Registry and subsidiary Registries under tha
      encapsulation registry. 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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