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Protocol Numbers for SCHC
draft-ietf-intarea-schc-protocol-numbers-01

Document Type Active Internet-Draft (intarea WG)
Authors Robert Moskowitz , Stuart W. Card , Adam Wiethuechter , Pascal Thubert
Last updated 2023-10-12
Replaces draft-ietf-intarea-schc-ip-protocol-number
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draft-ietf-intarea-schc-protocol-numbers-01
INTAREA                                                     R. Moskowitz
Internet-Draft                                            HTT Consulting
Intended status: Standards Track                                 S. Card
Expires: 14 April 2024                                   A. Wiethuechter
                                                      AX Enterprize, LLC
                                                              P. Thubert
                                                           Cisco Systems
                                                         12 October 2023

                       Protocol Numbers for SCHC
              draft-ietf-intarea-schc-protocol-numbers-01

Abstract

   This document requests an Internet Protocol Number, an Ethertype, and
   UDP port assignment for SCHC.  The Internet Protocol Number request
   is so that SCHC can be used for IP independent SCHC of other
   transports such as UDP and ESP.  The Ethertype is to support generic
   use of native SCHC over any IEEE 802 technology for IP and non-IP
   protocols.  The UDP port request is to support End-to-End SCHC
   through potentially blocking firewalls.

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 14 April 2024.

Copyright Notice

   Copyright (c) 2023 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.

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   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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Basic use case for SCHC as an Internet Protocol Number  .   3
     1.2.  Basic use case for SCHC as an Ethertype . . . . . . . . .   4
     1.3.  Basic use case for SCHC as a UDP port number  . . . . . .   5
   2.  Terms and Definitions . . . . . . . . . . . . . . . . . . . .   5
     2.1.  Requirements Terminology  . . . . . . . . . . . . . . . .   5
   3.  Internet Protocol Number for SCHC . . . . . . . . . . . . . .   5
   4.  Ethertype for SCHC  . . . . . . . . . . . . . . . . . . . . .   6
   5.  UDP Port Number for SCHC  . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  IANA Internet Protocol Number Registry Update . . . . . .   6
     6.2.  IANA Ethertype Request  . . . . . . . . . . . . . . . . .   6
     6.3.  IANA SCHC Ethertype Registry  . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The Static Context Header Compression (SCHC) Architecture
   [schc-architecture] originally envisioned SCHC used at the Network
   layer to enable IPv6 over selected Low-Power Wide Area Networking
   (LPWAN) radio technologies, encompassing IP and Transport, by the
   network provider.  Then SCHC would be used by the application; this
   would include any security envelope.

   This approach brakes down when dealing with Diet ESP [diet-esp].
   When Next Header is ESP, it is challenging for the ESP process to
   determine if an incoming ESP payload is regular ESP [RFC4303] or a
   diet ESP payload.  Careful allocation of the incoming SPI
   [ikev2-diet-esp] can mitigate this and have an implicit SCHC header,
   but it is not sound protocol design.  If the Next Header in the IP
   header were SCHC, not ESP, a clear segregation of incoming traffic is
   directly supportable.

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   Additionally, SCHC can then be the Next Header within the ESP header
   with 'regular' SCHC rules for processing this content.  This approach
   will greatly simplify [diet-esp].

   DTLS 1.3 [RFC9147] adds further complications.  DTLS 1.3 headers
   themselves are typically already very compressed and SCHC would not
   provide much value.  But the UDP header in front of DTLS would
   benefit of a separate compression from the IP Header compression.
   Where it is possible with ESP's SPI to mitigate inbound packet
   processing challenges implicit SCHC would generate, DTLS header does
   not safely even provide this and a SCHC IP number is necessary to
   separate traffic.

   New IETF work has started with the SCHC WH that is chartered to:

   |  provide specifications for the application of SCHC over underlying
   |  layers, where underlying layers include but are not limited to UDP
   |  tunnels, IP, PPP, and Ethernet, as well as the use of SCHC by
   |  upper-layer protocols.

   To achieve its charter, the SCHC working group needs the allocations
   that are requested in this document.

   These issues carry over to IP Header compression if SCHC were
   available as an Ethertype (for 802 networking) and if SCHC were
   available as a TCP/UDP port number (for firewall traversal
   challenges).  At each layer, SCHC solves a problem that protocol
   designers, using constrained networks, currently have to design
   around.

1.1.  Basic use case for SCHC as an Internet Protocol Number

   A mobile node, or network, may use different links over a period of
   time.  In some cases the node has the multiple interfaces and, in
   theory, could tune the compression to each interface.  In other
   cases, it is the whole network that is mobile and individual nodes
   have no "knowledge" of which link with what characteristics is
   actively handling the traffic.  In either case, the node
   administrator is aware that some links are constrained and use of
   SCHC compression is highly recommended.

   One example is an UA that uses different links over the duration of
   an operation (i.e. flight).

   *  Operation starts using Veriport's WiFi service.

   *  On gaining altitude, UA transitions to a Cellular service.

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   *  On gaining more altitude, UA transitions to a constrained 700MHz
      UHF service.

   *  On approach to destination vertiport, link transition is reversed.

   The UA could use SCHC compression only on the UHF link, but this may
   complicate the implementation.

   A more complex example is an Unmanned Cargo Aircraft that has
   multiple avionics systems, all Ethernet connected to an onboard
   router that has the multiple interfaces.  Here the nodes each manage
   their own secure path to their ground-based server, but have no
   knowledge of which link is in use to intelligently use compression.

1.2.  Basic use case for SCHC as an Ethertype

   In the case of a classical LPWAN link such as LoRa [RFC9011], the use
   of SCHC to compress the transported protocol, as well as the SCHC
   session (called instance) to use, are implicit.  The MAC-Layer
   endpoints are preconfigured so there can be only one session, and
   there can be only SCHC.  When extended to Ethernet and more powerful
   endpoint, this model is way too restrictive, and it is necessary to
   signal both the use of SCHC and the SCHC session to be used.  While
   the SCHC WG is charterd to produce the latter, the Ethertype defined
   in this document will be used to signal SCHC as the upper* layer
   protocol.

   As an example that will leverage this, Aircraft-to-anything (A2X)
   [drip-a2x-adhoc-session] and Aircraft-to-Ground
   [drip-efficient-a2g-comm] protocols are specific cases that can
   benefit from SCHC as an Ethertype.  These can use IEEE 802 wireless
   technology and lessen spectrum contention in high traffic or long-
   range situations by minimizing the datagram size via SCHC.

   In the above uses, SCHC compresses the IPv6 header completely (all 40
   bytes), leaving only destination address (32 bytes, source address
   calcuated from content), or only 8 bytes (needs both addresses) at
   the cost of the 1-byte SCHC RuleID.  The 2-byte payload length may be
   needed in some cases (as in Section 4).

   Since the whole point of SCHC is to reduce payload size, SCHC
   directly over an 802 technology cannot be addressed via the Ethernet
   Protocol Assignment under the IANA OUI.  A distinct Ethertype is
   needed by SCHC to actually reduce payload overhead.

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1.3.  Basic use case for SCHC as a UDP port number

   TBD

2.  Terms and Definitions

2.1.  Requirements 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.

3.  Internet Protocol Number for SCHC

   SCHC as the IP payload SHOULD be indicated in the IPv4 "Protocol"
   field or the IPv6 "Next Header" field with a value of TBD1
   (recommended: 145) as shown below:

    +=========+=========+================+================+===========+
    | Decimal | Keyword | Protocol       | IPv6 Extension | Reference |
    |         |         |                | Header         |           |
    +=========+=========+================+================+===========+
    |    TBD1 | SCHC    | Static Context |                | This RFC  |
    |   (145) |         | Header         |                |           |
    |         |         | Compression    |                |           |
    +---------+---------+----------------+----------------+-----------+

                     Table 1: Internet Protocol Numbers

   The SCHC compressed header with payload is shown below.  The size of
   the SCHC RuleID is variable as described in [RFC8724].  An
   implementation should have a table of source IP address and RuleID
   size.  The addresses should be represented in prefix format to allow
   for groups of addresses having the same RuleID size.

       |------- Compressed Header -------|
       +---------------------------------+--------------------+
       |  RuleID  |  Compression Residue |      Payload       |
       +---------------------------------+--------------------+

                           Figure 1: SCHC Packet

   The RuleID may be statically configured per [RFC8724], or may be
   negotiated within a protocol as in IKE [ikev2-diet-esp].

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4.  Ethertype for SCHC

   The use of SCHC as an Ethertype is similar to that as in Section 3,
   above.  Immediately after the SCHC Ethertype is the RuleID as in
   Figure 1.  If the rules for the RuleID does not provide the datagram
   length, the datagram length MUST be explicit in the Compression
   Residue, as the 802 header may not provide the needed length
   information to properly process the datagram.

5.  UDP Port Number for SCHC

   TBD

6.  IANA Considerations

6.1.  IANA Internet Protocol Number Registry Update

   This document requests IANA to make the following change to the
   "Assigned Internet Protocol Numbers" [IANA-IPN] registry:

   Internet Protocol Number:
      This document defines the new Internet Protocol Number value TBD1
      (suggested: 145) (Section 3) in the "Assigned Internet Protocol
      Numbers" registry.

    +=========+=========+================+================+===========+
    | Decimal | Keyword | Protocol       | IPv6 Extension | Reference |
    |         |         |                | Header         |           |
    +=========+=========+================+================+===========+
    |    TBD1 | SCHC    | Static Context |                | This RFC  |
    |   (145) |         | Header         |                |           |
    |         |         | Compression    |                |           |
    +---------+---------+----------------+----------------+-----------+

                                  Table 2

6.2.  IANA Ethertype Request

   IANA is requested using the process in Section 5.5 of
   [intarea-rfc7042bis], to request the Ethertype for SCHC.

6.3.  IANA SCHC Ethertype Registry

   A registry of SCHC RuleIDs for SCHC as an Ethertype may be needed.
   More discussion is needed to resolve this.  For example, split a
   1-byte RuleID in half.  The top half of 1-14 assigned to different
   domains of use, like for aviation.  A value of 15 designates that a
   2-byte RuleID is used.

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7.  Security Considerations

   TBD

8.  References

8.1.  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>.

   [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>.

8.2.  Informative References

   [diet-esp] Migault, D., Guggemos, T., Bormann, C., and D. Schinazi,
              "ESP Header Compression Profile", Work in Progress,
              Internet-Draft, draft-mglt-ipsecme-diet-esp-10, 29 June
              2023, <https://datatracker.ietf.org/doc/html/draft-mglt-
              ipsecme-diet-esp-10>.

   [drip-a2x-adhoc-session]
              Moskowitz, R., Card, S. W., and A. Gurtov, "Aircraft to
              Anything AdHoc Broadcasts and Session", Work in Progress,
              Internet-Draft, draft-moskowitz-drip-a2x-adhoc-session-02,
              23 July 2023, <https://datatracker.ietf.org/doc/html/
              draft-moskowitz-drip-a2x-adhoc-session-02>.

   [drip-efficient-a2g-comm]
              Moskowitz, R., Card, S. W., and A. Gurtov, "Efficient Air-
              Ground Communications", Work in Progress, Internet-Draft,
              draft-moskowitz-drip-efficient-a2g-comm-01, 28 September
              2023, <https://datatracker.ietf.org/doc/html/draft-
              moskowitz-drip-efficient-a2g-comm-01>.

   [IANA-IPN] IANA, "Assigned Internet Protocol Numbers",
              <https://www.iana.org/assignments/protocol-numbers/
              protocol-numbers.xhtml>.

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   [ikev2-diet-esp]
              Migault, D., Guggemos, T., and D. Schinazi, "Internet Key
              Exchange version 2 (IKEv2) extension for the ESP Header
              Compression (EHC)", Work in Progress, Internet-Draft,
              draft-mglt-ipsecme-ikev2-diet-esp-extension-03, 28 June
              2023, <https://datatracker.ietf.org/doc/html/draft-mglt-
              ipsecme-ikev2-diet-esp-extension-03>.

   [intarea-rfc7042bis]
              Eastlake, D. E., Abley, J., and Y. Li, "IANA
              Considerations and IETF Protocol and Documentation Usage
              for IEEE 802 Parameters", Work in Progress, Internet-
              Draft, draft-ietf-intarea-rfc7042bis-10, 9 October 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-intarea-
              rfc7042bis-10>.

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, DOI 10.17487/RFC4303, December 2005,
              <https://www.rfc-editor.org/info/rfc4303>.

   [RFC8724]  Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and JC.
              Zuniga, "SCHC: Generic Framework for Static Context Header
              Compression and Fragmentation", RFC 8724,
              DOI 10.17487/RFC8724, April 2020,
              <https://www.rfc-editor.org/info/rfc8724>.

   [RFC9011]  Gimenez, O., Ed. and I. Petrov, Ed., "Static Context
              Header Compression and Fragmentation (SCHC) over LoRaWAN",
              RFC 9011, DOI 10.17487/RFC9011, April 2021,
              <https://www.rfc-editor.org/info/rfc9011>.

   [RFC9147]  Rescorla, E., Tschofenig, H., and N. Modadugu, "The
              Datagram Transport Layer Security (DTLS) Protocol Version
              1.3", RFC 9147, DOI 10.17487/RFC9147, April 2022,
              <https://www.rfc-editor.org/info/rfc9147>.

   [schc-architecture]
              Pelov, A., Thubert, P., and A. Minaburo, "Static Context
              Header Compression (SCHC) Architecture", Work in Progress,
              Internet-Draft, draft-ietf-schc-architecture-01, 6 October
              2023, <https://datatracker.ietf.org/doc/html/draft-ietf-
              schc-architecture-01>.

Acknowledgments

   Discussions with Pascal Thubert, lpwan co-chair, helped develop this
   approach of using SCHC E2E below the current Transport Layers.

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Authors' Addresses

   Robert Moskowitz
   HTT Consulting
   Oak Park, MI 48237
   United States of America
   Email: rgm@labs.htt-consult.com

   Stuart W. Card
   AX Enterprize, LLC
   4947 Commercial Drive
   Yorkville, NY 13495
   United States of America
   Email: stu.card@axenterprize.com

   Adam Wiethuechter
   AX Enterprize, LLC
   4947 Commercial Drive
   Yorkville, NY 13495
   United States of America
   Email: adam.wiethuechter@axenterprize.com

   Pascal Thubert
   Cisco Systems, Inc
   Emerald Square, Batiment C
   rue Evariste Galois
   06410 BIOT - Sophia Antipolis
   France
   Phone: +33 497 23 26 34
   Email: pthubert@cisco.com

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