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Internet Draft                                 Dave Allan, Ericsson ed.
Intended status: Informational               Donald Eastlake, Futurewei
Expires: September 2020                          David Woolley, Telstra
                                                              July 2020

    5G Wireless Wireline Convergence User Plane Encapsulation (5WE)


   As part of providing wireline access to the 5G Core (5GC), deployed
   wireline networks carry user data between 5G residential gateways
   and the 5G Access Gateway Function (AGF). The encapsulation method
   specified in this document supports the multiplexing of traffic for
   multiple PDU sessions within a VLAN delineated access circuit,
   permits legacy equipment in the data path to snoop certain packet
   fields, carries 5G QoS information associated with the packet data,
   and provides efficient encoding.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet
   Engineering Task Force (IETF), its areas, and its working
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   This Internet-Draft will expire on January 2021.

Copyright and License Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://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...................................................2
   1.1. Requirements Language........................................3
   1.2. Acronyms.....................................................4
   2. Data Encapsulation Format......................................4
   3. Acknowledgements...............................................5
   4. Security Considerations........................................5
   5. IANA Considerations............................................6
   6. References.....................................................6
   6.1. Normative References.........................................6
   6.2. Informative References.......................................6
   7. Authors' Addresses.............................................7

1. Introduction

   Converged 5G ("fifth generation") wireline networks carry user data
   between 5G residential gateways (5G-RG) and the 5G Access Gateway
   Function (identified as an Fixed-AGF (FAGF) by 3GPP in [TS23716])
   across deployed access networks based on Broadband Forum [TR101] and

   The transport encapsulation used needs to meet a variety of
   requirements including the following:

   -  The ability to multiplex multiple logical connections (Protocol
     Data Unit (PDU) Sessions as defined by 3GPP) within a VLAN
     identified point to point logical circuit between a 5G-RG and an

   - To allow unmodified legacy equipment in the data path to identify
      the encapsulation and snoop specific fields in the payload. Some
      access nodes in the data path between the 5G-RG and the FAGF
      (Such as digital subscriber loop access multiplexers (DSLAMs) and
      optical line terminations (OLTs)) currently snoop into packets
      identified by specific Ethertypes to identify protocols such as
      the point to point protocol over ethernet (PPPoE), IP, ARP, and

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      IGMP. This may be for the purpose of enhanced QoS, policing of
      identifiers and other applications. Some deployments are
      dependent upon this snooping. Such devices are able to do this
      for PPPoE or IP over ethernet (IPoE) packet encodings but would
      be unable to do so if a new encapsulation, or an existing
      encapsulation using a new Ethertype, were used.

   -  To carry per packet 5G QoS information.

   -  Fixed access is very sensitive to the complexity of residential
     gateways, therefore encapsulation overhead and efficiency is an
     important consideration.

   A modified [RFC2516] PPPoE data encapsulation (referred to as the 5G
   WWC user plane Encapsulation or 5WE) can address these requirements.
   Currently deployed access nodes do not police the VER, TYPE and CODE
   fields of an RFC 2516 header, and only perform limited policing of
   stateful functions with respect to the procedures documented in RFC
   2516. Therefore, these fields may be repurposed to:

   -  Identify that the mode of operation for packets encapsulated in
     such a fashion uses non-access stratum (NAS, a logical control
     interface between user equipment (UE) and 5GC as specified by
     3GPP) based 5G WWC session establishment and life cycle
     maintenance procedures as documented in [TS23502][TS23716] instead
     of legacy PPP/PPPoE session establishment procedures (i.e. PADI
     discipline, LCP, NCP etc.).

   -  Permit the session ID field to be used to identify the 5G PDU
     session the encapsulated packet is part of.

   -  Communicate per-packet 5G QoS Flow Identifier (QFI) and
     Reflective QoS Indication (RQI) information from the 5GC to the

   This 5G specific repurposing of fields results in an encapsulation
   uniquely applicable to the requirements for the communication of PDU
   session traffic between the subscriber premises and the 5G system
   over wireline networks.  The 8 byte RFC 2516 data packet header is
   also the most frugal of the encapsulations that are currently
   supported by legacy access equipment that could be adapted to meet
   these requirements. This encapsulation is not suitable for other
   network environments, e.g., general use over the public Internet.

1.1. Requirements Language

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   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
   "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.

1.2. Acronyms

   This document uses the following acronyms:

   3GPP  3rd Generation Partnership Project
   5WE   5G WWC Encapsulation
   5GC   5th Generation Core (network)
   DSLAM Digital Subscriber Loop Access Multiplexer
   FAGF  Fixed Network Access Gateway Function
   IPoE  IP over Ethernet
   NAS   Non-Access Stratum
   OLT   Optical Line Termination
   PDU   Protocol Data Unit
   PPPoE PPP over Ethernet
   QFI   QoS Flow Identifier
   QoS   Quality of Service
   RG    Residential Gateway
   RQI   Reflective QoS Indicator
   WWC   Wireless Wireline Convergence

2. Data Encapsulation Format

   The Ethernet payload [IEEE802] for PPPoE [RFC2516] is indicated by
   an Ethertype of 0x8864. The information following that Ethertype
   uses a value of 2 in the VER field for the repurposing of the PPPoE
   data encapsulation as the 5G WWC user plane encapsulation (5WE). The
   5G WWC User Plane encapsulation is structured as follows:

       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
     |  VER  |  TYPE |     QFI   |R|0|           SESSION_ID          |
     |            LENGTH             |          PROTOCOL ID          |
     |                         DATA PAYLOAD         ~

   The description of each field is as follows:

      VER is the version. It MUST be set to 2.

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      TYPE is the message type. It MUST be set to 1.

      QFI encodes the 3GPP 5G QoS Flow Identifier[TS38415] to be used
          for mapping 5G QoS to IP DSCP/802.1 P-bits[IEEE802].

      R (short for RQI) encodes the one bit Reflective QoS Indicator.

      0 indicates the bit(s) MUST be sent as zero and ignored on

      SESSION_ID is a 16-bit unsigned integer in network byte order. It
          is used to distinguish different PDU sessions that are in the
          VLAN delineated multiplex.

      LENGTH is the length in bytes of the data payload including
          the initial Protocol ID. It is 16 bits in network byte order.

      PROTOCOL ID is the 16 bit identifier of the data payload type
          encoded using values from the IANA PPP DLL protocol numbers
          registry. (https://www.iana.org/assignments/ppp-numbers/ppp-

          The following values are valid in this field for 5G
          WWC use:

               0x0021: IPv4

               0x0031: Ethernet (referred to in PPP as "bridging")

               0x0057: IPv6

      DATA PAYLOAD is encoded as per the protocol ID.

3. Acknowledgements

   This memo is a result of comprehensive discussions by the Broadband
   Forum's Wireline Wireless Convergence Work Area.
   The authors would also like to thank Joel Halpern and Dirk Von Hugo
   for their detailed review of this draft.

4. Security Considerations

   5G NAS procedures used for session life cycle maintenance employ
   ciphering and integrity protection. They can be considered to be a
   more secure session establishment discipline than existing RFC 2516
   procedures, at least against man in the middle attacks.

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   The document's re-purposing of the RFC 2516 data encapsulation will
   not circumvent existing anti-spoofing and other security procedures
   in deployed equipment. The existing access equipment will be able to
   identify fields that they normally process and police as per
   existing RFC 2516 traffic.

   Therefore, the security of a fixed access network using 5WE will be
   equivalent or superior to current practice.

5. IANA Considerations

   IANA is requested to create a registry on the Point-to-Point (PPP)
   Protocol Field Assignments IANA Web page as follows:

      Registry Name: PPP Over Ethernet Versions
      Registration Procedure: Expert Review
      References: [RFC2516] [this document]

          VER     Description                        Reference
         -----   -----------------------------      -----------
            0     reserved                          [this document]
            1     Classic PPPoE                     [RFC2516]
            2     5G WWC User Plane Encapsulation   [this document]
         3-15     unassigned                        [this document]

   IANA is requested to add [this document] as an additional reference
   for Ethertype 0x8864 in the Ethertypes table on the IANA "IEEE 802
   Numbers" web page.(https://www.iana.org/assignments/ieee-802-

6. References

6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
          Requirement Levels", BCP 14, RFC 2119, March 1997.
[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>.
[RFC2516] "A Method for Transmitting PPP Over Ethernet (PPPoE)",
          IETF RFC 2516, February 1999
[TS38415] 3rd Generation Partnership Project; Technical
          Specification Group Radio Access Network; NG-RAN; PDU
          Session User Plane Protocol (Release 15), 3GPP TS38.415

6.2. Informative References
[TS23502] 3rd Generation Partnership Project; Technical

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          Specification Group Services and System Aspects;
          Procedures for the 5G System (Release 16), 3GPP TS23.502
[TS23716] 3rd Generation Partnership Project; Technical
          Specification Group Services and System Aspects; Study
          on the Wireless and Wireline Convergence for the 5G
          system architecture (Release 16), 3GPP TR23.716,
          November 2018
[TR101]   "Migrating to Ethernet Based Broadband Aggregation",
          Broadband Forum Technical Report: TR-101 issue 2, July
[TR178]   "Multi-service Broadband Network Architecture and Nodal
          Requirements", Broadband Forum Technical Report: TR-178,
          September 2014
[IEEE802] 802, IEEE, "IEEE Standard for Local and Metropolitan
          Networks: Overview and Architecture", IEEE Std 802-2014.
[RFC4937] "IANA Considerations for PPPoE", IETF RFC 4937, June

7. Authors' Addresses
   Dave Allan (editor)
   2455 Augustine Drive
   San Jose, CA  95054 USA
   Email: david.i.allan@ericsson.com

   Donald E. Eastlake 3rd
   Futurewei Technologies
   2386 Panoramic Circle
   Apopka, FL 32703 USA
   Phone: +1-508-333-2270
   Email: d3e3e3@gmail.com

   David Woolley
   Telstra Corporation
   242 Exhibition St
   Melbourne, 3000
   Email: david.woolley@team.telstra.com

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