Internet Draft Dave Allan, Ericsson ed. Intended status: Informational Donald Eastlake, Futurewei Expires: August 2021 David Woolley, Telstra February 2021 5G Wireless Wireline Convergence User Plane Encapsulation (5WE) draft-allan-5g-fmc-encapsulation-08 Abstract 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 inspect certain packet fields, carries 5G QoS information associated with the packet data, and provides efficient encoding. It achieves this by specific points of similarity with the RFC 2516 PPPoE data packet encapsulation. 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 groups. Note that other groups may also distribute working documents as Internet-Drafts. 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". The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 2021. Copyright and License Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. Allan et al., Expires August 2021 [Page 1]
Internet-Draft draft-allan-5g-fmc-encapsulation February 2021 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........................................4 1.2. Acronyms.....................................................4 2. Data Encapsulation Format......................................5 3. Acknowledgements...............................................6 4. Security Considerations........................................6 5. IANA Considerations............................................7 6. References.....................................................7 6.1. Normative References.........................................7 6.2. Informative References.......................................8 7. Authors' Addresses.............................................8 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 a Wireline-AGF (W-AGF) by 3GPP in [TS23316]) across deployed access networks based on Broadband Forum [TR101] and [TR178]. This form of wireline access is considered to be trusted non-3GPP access by the 5G system. 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 a W- AGF. - To allow unmodified legacy equipment in the data path to identify the encapsulation and inspect specific fields in the payload. Some access nodes in the data path between the 5G-RG and the W- AGF (Such as digital subscriber loop access multiplexers (DSLAMs) and optical line terminations (OLTs)) currently inspect packets identified by specific Ethertypes to identify protocols such as Allan et al., Expires April 2021 [Page 2]
Internet-Draft draft-allan-5g-fmc-encapsulation February 2021 the point to point protocol over ethernet (PPPoE), IP, ARP, and IGMP. This may be for the purpose of enhanced QoS, policing of identifiers and other applications. Some deployments are dependent upon this inspection. 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 completely new encapsulation, or an existing encapsulation using a new Ethertype, were used. - To carry per packet 5G QoS information. - Fixed access residential gateways are sensitive to the complexity of packet processing, therefore an encapsulation that minimizes processing is an important consideration. A data encapsulation that uses a common Ethertype and has certain fields appearing at the same offset as the PPPoE [RFC2516] data encapsulation can address these requirements. This data encapsulation is referred to as the 5G WWC user plane Encapsulation or 5WE. 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 have a different definition for 5WE and are used 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][TS23316] instead of legacy PPP/PPPoE session establishment procedures (i.e. PADI discipline, LCP, NCP etc.). In this scenario "discovery" is performed by means outside the scope of this document. - 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 5G-RG. This 5G specific redesign of fields not inspected by deployed equipment 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 6 byte RFC 2516 data packet header followed by a 2 byte PPP protocol ID is also the most frugal of the encapsulations that are Allan et al., Expires April 2021 [Page 3]
Internet-Draft draft-allan-5g-fmc-encapsulation February 2021 currently supported by legacy access equipment that could be adapted to meet these requirements. This encapsulation is expected to be used in environments where RFC 2516 is deployed. Therefore, implementations MUST examine the version number: - if the version number is 1, and PPPoE [RFC2516] is supported, process the frame further, else silently discard it. - if the version number is 2 and 5WE is supported, process the frame further, else silently discard it. In both cases frames for the supported version number should have session IDs corresponding to established sessions for the respective protocol models. A 5WE frame with an unrecognized session ID MUST be silently discarded. This encapsulation may have MTU issues when used for Ethernet multiplexing in networks where the underlying Ethernet payload is limited to 1500 bytes. This encapsulation is not suitable for other network environments, e.g., general use over the public Internet. 1.1. 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. 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 W-AGF Wireline Access Gateway Function IPoE IP over Ethernet NAS Non-Access Stratum OLT Optical Line Termination PDU Protocol Data Unit Allan et al., Expires April 2021 [Page 4]
Internet-Draft draft-allan-5g-fmc-encapsulation February 2021 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 0x02. TYPE is the message type. It MUST be set to 0x01. 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 Reflective QoS Indication [TS38415]) encodes the one bit RQI. It is set by the network side 5WE termination for downstream traffic and ignored by the network for upstream traffic. 0 indicates the bit(s) MUST be sent as zero and ignored on receipt. 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. A value of 0xffff is reserved for future use and MUST NOT be used. LENGTH is the length in bytes of the data payload including Allan et al., Expires April 2021 [Page 5]
Internet-Draft draft-allan-5g-fmc-encapsulation February 2021 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- numbers.xhtml#ppp-numbers-2) The following values are valid in this field for 5G WWC use: 0x0021: IPv4 0x0031: Ethernet (referred to in PPP as "bridging") 0x0057: IPv6 Packets received that do not contain one of the above protocol IDs are silently discarded. 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 [TS23502]. They can be considered to be a more secure session establishment discipline than existing RFC 2516 procedures, at least against on path attackers. The design of the 5WE 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 policed as per existing RFC 2516 traffic. Therefore, the security of a fixed access network using 5WE will be equivalent or superior to current practice. 5WE encapsulated traffic is used on what the 5GC considers to be trusted non-3GPP interfaces, therefore is not ciphered. 5WE is not suitable for use over an untrusted non-3GPP interface. Allan et al., Expires April 2021 [Page 6]
Internet-Draft draft-allan-5g-fmc-encapsulation February 2021 The security requirements of the 5G system are documented in [TS33501] 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: Specification Required References: [RFC2516] [this document] VER Description Reference ----- ----------------------------- ----------- 0 reserved [this document] 1 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- numbers/ieee-802-numbers.xhtml#ieee-802-numbers-1) 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 [TS23502] 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Procedures for the 5G System (Release 16), 3GPP TS23.502 [TS23316] 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Wireless and wireline convergence access support for the 5G System (5GS) (Release 16), 3GPP TS23.316, November 2018 Allan et al., Expires April 2021 [Page 7]
Internet-Draft draft-allan-5g-fmc-encapsulation February 2021 6.2. Informative References [TR101] "Migration to Ethernet Based Broadband Aggregation", Broadband Forum Technical Report: TR-101 issue 2, July 2011 [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. [TS33501] 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Security Architecture and Procedures for 5G System (Release 16), 3GPP TS33.501, December 2019 7. Authors' Addresses Dave Allan (editor) Ericsson 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 Australia Email: david.woolley@team.telstra.com Allan et al., Expires April 2021 [Page 8]