



SCONE                                                          S. Mishra
Internet-Draft                                                   Verizon
Intended status: Informational                                 Z. Sarker
Expires: 4 April 2026                                              Nokia
                                                                A. Tomar
                                                                    Meta
                                                                K. Abbas
                                                                 Verizon
                                                          1 October 2025


         Applicability & Manageability consideration for SCONE
            draft-mishra-scone-applicability-manageablity-02

Abstract

   This document addresses the applicability and manageability
   considerations involved in providing throughput advice to application
   endpoints in telecommunications service provider networks supporting
   the Standard Communication with Network Elements (SCONE) protocol.

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
   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 4 April 2026.

Copyright Notice

   Copyright (c) 2025 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/
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   Please review these documents carefully, as they describe your rights
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   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   4
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Generic Applicability and Manageability considerations  . . .   6
     4.1.  Flow session awareness  . . . . . . . . . . . . . . . . .   6
     4.2.  Per-Flow Signaling  . . . . . . . . . . . . . . . . . . .   7
     4.3.  QoS awareness . . . . . . . . . . . . . . . . . . . . . .   7
     4.4.  SCONE Hint to the Network . . . . . . . . . . . . . . . .   7
     4.5.  Retransmission of Advised Bit-Rate  . . . . . . . . . . .   7
     4.6.  Frequency of Updates  . . . . . . . . . . . . . . . . . .   7
     4.7.  Dynamic Updates . . . . . . . . . . . . . . . . . . . . .   8
     4.8.  Monitoring and Logging  . . . . . . . . . . . . . . . . .   8
     4.9.  Conformance Monitoring  . . . . . . . . . . . . . . . . .   8
     4.10. Standards Compliance  . . . . . . . . . . . . . . . . . .   8
     4.11. Interworking with Other Congestion Management
            Mechanisms . . . . . . . . . . . . . . . . . . . . . . .   9
   5.  SCONE Usage in a 5G Network . . . . . . . . . . . . . . . . .   9
     5.1.  Applicability of SCONE in a 5G Network  . . . . . . . . .   9
     5.2.  5G specific considerations  . . . . . . . . . . . . . . .  10
       5.2.1.  3GPP Defined PDU Session Establishment Procedures . .  10
       5.2.2.  PDU Session Awareness . . . . . . . . . . . . . . . .  11
       5.2.3.  Per-Flow Signaling  . . . . . . . . . . . . . . . . .  11
       5.2.4.  QoS and Bearer Considerations . . . . . . . . . . . .  11
       5.2.5.  Mobility Handling . . . . . . . . . . . . . . . . . .  12
       5.2.6.  SCONE Hint to the Network . . . . . . . . . . . . . .  12
       5.2.7.  Retransmission of Advised Bit-Rate  . . . . . . . . .  12
       5.2.8.  Dynamic Updates . . . . . . . . . . . . . . . . . . .  12
       5.2.9.  Operations Monitoring and Logging . . . . . . . . . .  12
   6.  SCONE Usage in a 4G/LTE Network . . . . . . . . . . . . . . .  12
     6.1.  Applicability of SCONE in a 4G/LTE Network  . . . . . . .  13
     6.2.  4G specific considerations  . . . . . . . . . . . . . . .  13
   7.  SCONE usage in a Wireline Network . . . . . . . . . . . . . .  14
     7.1.  Wireline specific considerations  . . . . . . . . . . . .  14
   8.  SCONE usage in a Wifi Networks  . . . . . . . . . . . . . . .  14
     8.1.  Other Miscellaneous topics  . . . . . . . . . . . . . . .  14
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     11.1.  Normative  . . . . . . . . . . . . . . . . . . . . . . .  15
     11.2.  Informative References . . . . . . . . . . . . . . . . .  15
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  15



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     12.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Appendix A.  Appendix A.  Additional Background details on role of
           UPF in 5G Mobile Packet Core  . . . . . . . . . . . . . .  16
     A.1.  Detailed view of the User Plane Network Element in Mobile
           Packet Core . . . . . . . . . . . . . . . . . . . . . . .  16
     A.2.  5G Mobile Network Architecture  . . . . . . . . . . . . .  17
     A.3.  N3 Interface  . . . . . . . . . . . . . . . . . . . . . .  18
     A.4.  N4 Interface  . . . . . . . . . . . . . . . . . . . . . .  18
     A.5.  N6 Interface  . . . . . . . . . . . . . . . . . . . . . .  18
     A.6.  N9 Interface  . . . . . . . . . . . . . . . . . . . . . .  18
     A.7.  User Plane Interface Between UPF and UE . . . . . . . . .  19
   Appendix B.  Appendix B.  Non-ASCII Characters  . . . . . . . . .  20
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21

1.  Introduction

   The SCONE protocol is a signaling mechanism that enables on-path
   network elements to communicate the maximum allowable bit rate to
   application endpoints, with particular relevance to adaptive bit-rate
   applications.  This document addresses the applicability and
   manageability considerations of deploying the SCONE protocol within
   telecommunications provider networks.

   The SCONE protocol operates on the basis of a UDP 4-tuple.  Network
   elements capable of rate limiting at this granularity can send
   notifications of the maximum allowable bit rate in each direction of
   the observed traffic.  Such network elements may also drop or delay
   packets within the corresponding UDP 4-tuple flows.  This implies an
   assumption that on-path network elements have certain capabilities:
   specifically, the ability to detect and maintain UDP 4-tuple flows,
   apply rate-limiting policies, and identify flows that include SCONE
   packets in order to insert throughput advice.

   In this document, on-path network elements are generally considered
   within the _access_ part of the telecommunications provider’s
   network.  However, their behavior may differ across _access_
   technologies.  For example, a wireless access network element may
   operate differently from one in a fixed broadband network.  Wi-Fi
   access networks represent another case, where enforcement is often
   per user or per Service Set Identifier (SSID), but visibility into
   UDP 4-tuples may be limited.  Among the different access networks
   considered, mobile networks offer the most fine-grained visibility
   into traffic flows and can act at the individual flow level.  In
   mobile networks, the User Plane Function (UPF) in 5G and the Packet
   Data Network Gateway (P-GW) in 4G can generate throughput advice to
   guide adaptive applications on a per-flow basis.  In wireline
   broadband networks, by contrast, rate limiting is typically applied



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   at a centralized Broadband Network Gateway (BNG) or at aggregation
   points where multiple Customer Premises Equipment (CPE) devices
   connect.

   Accordingly, applicability and manageability considerations must span
   a wide range of access-network scenarios, each of which handles per-
   flow rate limiting differently.  This document first describes
   generic considerations for the SCONE protocol and then provides
   network-specific considerations where throughput advisory signaling
   can enhance both resource utilization and user experience.

2.  Conventions and Definitions

   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.  Terminology

   *  4G - Fourth Generation mobile network technology, also known as
      Long-Term Evolution (LTE), defined by the 3rd Generation
      Partnership Project (3GPP).

   *  5G - Fifth Generation Mobile Networks The fifth generation of
      cellular mobile network technology defined by 3GPP.

   *  Adaptive Bit-Rate (ABR) Video Video streaming technology that
      adjusts video quality dynamically based on network conditions.

   *  BNG (Broadband Network Gateway) A network element that serves as
      the access point for subscribers in wireline broadband networks.
      It establishes and manages subscriber sessions, aggregates traffic
      from multiple subscriber access nodes, and routes this traffic to
      the service provider's core network.  BNG functions include
      subscriber authentication, IP address assignment, policy
      enforcement, and quality of service management.  It typically
      supports subscriber session protocols such as DHCP, PPPoE, or
      IPoE, and interacts with AAA and DHCP servers to enable secure and
      managed access to broadband services.

   *  Client App The user-facing application running on an operating
      system, which receives network throughput advice.

   *  Content Provider Entity or service that delivers media and data
      content accessed by end-users.




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   *  CPE - Customer Premise Equipment CPE refers to networking hardware
      located at the customer's site and used to connect to a service
      provider’s network.  Typical CPE includes routers, modems, or
      gateways that provide access and management for residential or
      enterprise services.

   *  DHCP - Dynamic Host Configuration Protocol A network management
      protocol used to dynamically assign IP addresses and other
      configuration parameters to devices on a network, enabling
      automatic and centralized network configuration.

   *  EPC - The Evolved Packet Core Is the all-IP core architecture for
      4G/LTE, responsible for managing user sessions, mobility, and the
      integration of data and voice traffic over packet-switched
      networks.

   *  EPS Bearer - Evolved Packet System Bearer In 4G LTE networks, an
      EPS bearer is a virtual transmission path with specific Quality of
      Service (QoS) parameters that carries user data between the User
      Equipment (UE) and the Packet Data Network Gateway (P-GW).  The
      EPS bearer ensures end-to-end delivery of IP packets with
      particular handling characteristics, such as priority, latency,
      and guaranteed bit rate.  There are two main types: the Default
      EPS Bearer which provides always-on best-effort connectivity, and
      Dedicated EPS Bearers configured for services with specialized QoS
      requirements, such as voice or video.

   *  EPS Gateway In 4G LTE networks, the EPS Gateway primarily refers
      to the combination of the Serving Gateway (S-GW) and the Packet
      Data Network Gateway (P-GW).  The Serving Gateway routes and
      forwards user data packets between the E-UTRAN access network and
      the Packet Data Network, acting as a mobility anchor during
      handovers.  The Packet Data Network Gateway provides connectivity
      from the user equipment (UE) to external packet data networks,
      performing functions such as policy enforcement, charging, and
      lawful interception.  Together, these gateways form the core user-
      plane interface of the Evolved Packet System (EPS).

   *  gNB - Next Generation Node B 5G radio access network node
      connecting user equipment to the 5G core network.

   *  IPoE IP over Ethernet A protocol that delivers IP packets directly
      over Ethernet without requiring a login or session establishment,
      commonly used in broadband networks in conjunction with DHCP for
      IP address assignment.

   *  LTE - Long-Term Evolution 4G wireless broadband technology and
      related network architecture.



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   *  P-GW - Public Data Network Gateway Is the network function within
      the Evolved Packet Core (EPC) that provides connectivity between
      the user equipment and external packet data networks, such as the
      Internet.

   *  PDU - Protocol Data Unit In 3GPP terminology, a PDU is a unit of
      information at a given protocol layer, such as an IP packet at the
      network layer.  Specifically in 5G, a PDU Session represents a
      logical connection that carries one or more PDUs between the User
      Equipment (UE) and a Data Network (DN) through the User Plane
      Function (UPF).  PDU Sessions support multiple types of PDUs,
      including IPv4, IPv6, Ethernet frames, and unstructured data, and
      are associated with one or more QoS Flows that define handling and
      quality requirements.  The PDU framework is essential for managing
      application data transport and quality of service within the 3GPP
      system architecture.

   *  PPP - Point-to-Point Protocol A data link layer communication
      protocol used to establish a direct connection between two nodes,
      commonly used for dial-up and broadband internet connections to
      provide authentication, encryption, and compression.

   *  SCONE - Standard Communication with Network Elements Protocol
      allowing throughput or rate advice signaling from the network to
      application endpoints.

   *  SMF - Session Management Function 5G network function that manages
      sessions and enforces policies.

   *  UE - User Equipment The mobile device or endpoint used by the
      subscriber to access the network.

   *  UPF - User Plane Function 5G core network element responsible for
      user-plane traffic routing and applying policy decisions.

   *  Wireline Network Broadband network based on fixed infrastructure
      (e.g., DSL, cable, fiber).

4.  Generic Applicability and Manageability considerations

4.1.  Flow session awareness

   SCONE signaling operates only over established sessions.  Network
   elements MUST be able to unambiguously associate throughput advice
   with application flows.  Each session is bound to an IP address and
   port, ensuring SCONE packets are routed precisely without affecting
   unrelated traffic.




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4.2.  Per-Flow Signaling

   Throughput advice is applied on a per–4-tuple basis.  Network
   elements MUST maintain flow-specific context to ensure signaling
   correctness.  This enables applications to receive targeted
   throughput advice while preventing unintended impact on unrelated
   flows.

4.3.  QoS awareness

   Networks can enforce Quality of Service (QoS) using various
   techniques.  In some cases, operators may wish to apply separate QoS
   policies to SCONE-enabled flows.  The network element that inserts
   SCONE advice does not need to interpret or enforce QoS policies
   directly—it only needs to provide the advice.  However, the operator
   SHOULD be able to identify SCONE-enabled flows and apply
   differentiated QoS treatment when desired.

4.4.  SCONE Hint to the Network

   SCONE-aware applications MUST provide hints to the network element,
   enabling it to generate appropriate throughput advice for a given
   4-tuple.  Such hints prevent unnecessary default rate-limiting, allow
   the network to signal the maximum allowable bit rate, and reduce CPU
   overhead by eliminating additional classification steps.

4.5.  Retransmission of Advised Bit-Rate

   Packet loss or non-delivery of SCONE advice reduces effectiveness.
   Both network elements and applications *SHOULD* support
   retransmission or periodic re-sending of SCONE packets to ensure
   reliable delivery.  Conformance depends on both network and endpoint
   behavior.

4.6.  Frequency of Updates

   The rate at which SCONE updates are issued depends on flow
   characteristics and available computational resources.  Excessively
   frequent updates may increase CPU load, while infrequent updates may
   reduce advisory effectiveness.  Network providers MAY define
   adjustable update intervals based on application requirements,
   network capacity, and operational constraints.  The SCONE protocol
   specifies a minimum interval of 67 seconds between updates [Editor’s
   Note: insert reference]







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4.7.  Dynamic Updates

   Networks may enforce dynamic rate limits during active sessions due
   to:

   *  Changes in access network type (requiring updated throughput
      advice)

   *  Subscriber policy updates (e.g., exceeding usage thresholds)

   *  Adjustments to maximum allowable throughput

   *  Periodic refreshes of throughput advice (e.g., timers for maximum
      update periodicity)

   In such cases, the network element SHOULD be able to initiate SCONE
   packets to provide updated advice, or applications should generate
   SCONE packets frequently enough to trigger network responses.

4.8.  Monitoring and Logging

   SCONE signaling can be integrated into existing operational and
   management frameworks to enable monitoring, troubleshooting, and
   fault isolation.  Metrics of interest include:

   *  Rate of SCONE advisory messages issued per session

   *  Correlation between SCONE advisories and user-plane throughput
      changes

   *  Error conditions where SCONE signaling fails to reach the intended
      endpoints

4.9.  Conformance Monitoring

   Network elements providing SCONE throughput advice MAY implement
   mechanisms to measure compliance, either per application flow or in
   aggregate.  This allows operators to validate advisory effectiveness
   and adjust policies.

4.10.  Standards Compliance

   SCONE signaling is expected to traverse the existing data path.  For
   example, in 3GPP-compliant networks, SCONE packets are carried within
   Protocol Data Unit (PDU) sessions established between the User
   Equipment (UE) and Internet endpoints.





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4.11.  Interworking with Other Congestion Management Mechanisms

   SCONE operates independently of transport-layer mechanisms such as
   Explicit Congestion Notification (ECN) or Low Latency, Low Loss, and
   Scalable throughput (L4S).  Operators MAY harmonize multiple
   congestion signaling methods by policy or scope deployments to avoid
   conflicting feedback.

5.  SCONE Usage in a 5G Network

   5G systems are built on a cloud-native Service-Based Architecture
   (SBA), which provides flexibility for introducing new functions such
   as SCONE.  The User Plane Function (UPF) serves as the natural anchor
   point for SCONE signaling because it handles packet forwarding, QoS
   enforcement, and interaction with the Session Management Function
   (SMF) and Policy Control Function (PCF).

5.1.  Applicability of SCONE in a 5G Network

   In 5G, the UPF is the on-path network element with access to
   subscriber policy and user-plane connectivity between the User
   Equipment (UE or client application endpoint) and the Internet.  The
   UPF is capable of generating SCONE throughput advice per application
   flow, enabling endpoints to adjust sending rates proactively.  SCONE
   signaling occurs over the existing data path.  The following diagram
   illustrates how throughput advice is conveyed within 5G, highlighting
   the role of user-plane network elements.
























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   +---------+
   |   PCF   |
   +---------+
        |
        v Policy Rules
   +---------+
   |   SMF   |
   +----+----+
        | Policy Rules
        v
   +--------+                 +------------------------+
   | Client |<===============>|                        |
   |   App  |     SCONE       |                        |
   +--------+     Advice      |            UPF         |
   |   OS   |                 |                        |
   +--------+                 |                        |
   |  Modem |                 |                        |
   +----+---+                 +------------------------+
        |                             |      |
        |   +-----+                   |      |
        +---+ gNB +-------------------+      |
            +-----+                          |
                 |                           v
                 v                   +--------------+
        +-----------------+          |  Internet    |
        | Content Provider|          +--------------+
        +-----------------+

            Figure 1: SCONE Integration within the 5G SA Network

5.2.  5G specific considerations

   This section describes how the SCONE protocol can be deployed and
   managed within 3GPP [_5G-Arch] networks, including support for SCONE
   packets over established PDU sessions.

5.2.1.  3GPP Defined PDU Session Establishment Procedures

   The following high-level functions, defined in 3GPP specifications,
   are relevant to SCONE manageability as SCONE packets traverse
   established PDU sessions:

   1.  PDN Connection / PDU Session (5G)
       A logical connection between the UE and the P-GW (4G) or UPF
       (5G), allowing the UE to exchange IP packets with external
       networks.  Each PDN Connection/PDU Session is associated with an
       APN (4G) or DNN (5G).




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   2.  IP Address Allocation
       During PDN Connection/PDU Session establishment, the UE is
       allocated an IP address (IPv4, IPv6, or both) used for
       communication with external networks.

   3.  Bearer Establishment
       Data traffic flows over bearers, each with defined QoS
       characteristics.  In 4G, a default bearer is created for Internet
       access, while dedicated bearers may be set up for specialized
       services.  In 5G, the equivalent construct is the QoS Flow.

   4.  Mobility Management The network ensures seamless UE mobility
       across cells and base stations while maintaining the ongoing
       session.

5.2.2.  PDU Session Awareness

   SCONE signaling operates only over established PDU sessions.  This
   enables network elements to unambiguously associate throughput advice
   with specific UEs and application flows.  Each session is bound to a
   DNN (5G) or APN (4G) and an allocated IP address, ensuring SCONE
   packets are routed precisely without affecting unrelated traffic.

5.2.3.  Per-Flow Signaling

   Throughput advice is applied on a per–4-tuple basis.  Network
   elements MUST maintain flow-specific context to ensure signaling
   correctness.  This enables applications to receive targeted
   throughput advice while preventing unintended impact on unrelated
   flows.

5.2.4.  QoS and Bearer Considerations

   In 5G, QoS is enforced at the granularity of QoS Flows, identified by
   a QoS Flow Identifier (QFI).  A single PDU session can contain
   multiple QoS Flows.  Operators MAY configure a distinct QFI for SCONE
   packets to ensure predictable handling, or allow SCONE packets to
   traverse the same bearer as user-plane traffic when no differentiated
   treatment is required.

   The PCF and SMF MUST be capable of assigning appropriate QoS
   attributes to SCONE flows so that congestion-control signaling is not
   degraded under high-load conditions.








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5.2.5.  Mobility Handling

   During mobility events (e.g., handover or UPF relocation), SCONE
   state MUST persist across control-plane and user-plane transitions.
   The SMF and UPF MUST ensure consistent delivery of SCONE packets
   during mobility procedures.

   Where advisory logic is stateful at the UPF, operators SHOULD provide
   synchronization mechanisms to avoid discontinuities.

5.2.6.  SCONE Hint to the Network

   SCONE-aware applications MUST provide hints to the UPF for a given
   4-tuple.  Such hints prevent unnecessary default rate-limiting and
   allow the network to generate the maximum allowable bit rate.

5.2.7.  Retransmission of Advised Bit-Rate

   Both UPF and applications SHOULD support retransmission or periodic
   re-sending of SCONE packets to ensure reliable delivery.

5.2.8.  Dynamic Updates

   Mobile networks can enforce dynamic rate limits during active
   sessions, for example on a per-bearer basis.

5.2.9.  Operations Monitoring and Logging

   Mobile operators may integrate SCONE signaling into existing
   operational and management frameworks to enable monitoring,
   troubleshooting, and fault isolation.  Metrics of interest include:

   *  Rate of SCONE advisory messages issued per session

   *  Correlation between SCONE advisories and user-plane throughput
      changes

   *  Error conditions where SCONE signaling fails to reach the UE

   Integration with analytics frameworks (e.g., NWDAF in 5G) *MAY* be
   used to assess effectiveness.

6.  SCONE Usage in a 4G/LTE Network

   In LTE/Evolved Packet Core (EPC) systems as defined by 3GPP
   [_4G-Arch], SCONE can be integrated at the PDN Gateway (P-GW) or the
   Serving Gateway (S-GW).  Unlike 5G, traffic granularity is bearer-
   based rather than per flow.



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   Below is an example diagram illustrating SCONE integration within the
   P-GW:

   +---------+
   |  PCRF   |
   +----+----+
        | Flow
        v Policy Rules
   +--------+          +--------------+
   | Client |<========>|  P-GW        |
   |  App   |   SCONE  |              |
   +--------+   advice +-------+------+
   |   OS   |                  |
   +--------+                  |
   |  Modem |                  |
   +----+---+                  |
        |                      |
        v                      v
     +--+---+              +---+---+
     |  eNB |--------------|  S-GW |
     +--+---+              +---+---+
                               |
                               v
                       +-------------+
                       |  Internet   |
                       +-------------+
                              |
                              v
                       +-----------------+
                       | Content Provider|
                       +-----------------+

             Figure 2: SCONE Integration within the 4G Network

6.1.  Applicability of SCONE in a 4G/LTE Network

   *  SCONE signaling maps to EPS bearers, enabling secure and targeted
      throughput advice between endpoints and EPC gateways.

6.2.  4G specific considerations

   TBD









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7.  SCONE usage in a Wireline Network

   SCONE can be deployed in wireline broadband networks at key access
   aggregation points such as Broadband Network Gateways (BNGs) or
   equivalent subscriber access nodes.  These network elements originate
   throughput advice, signaling maximum sustainable data rates to
   application endpoints for each subscriber session, typically
   identified by DHCP, PPP, or IPoE session contexts.

   Session granularity is typically based on subscriber sessions using
   PPP, DHCP, or IPoE protocols.  Below is a high-level view of SCONE
   within the wireline network:

+----------------+        +-----------------+        +------------------+
|  Subscriber    |<------>|       BNG       |<------>|  Content /       |
|  Session / UE  |  SCONE |                 |  SCONE |  Endpoint        |
+----------------+  Advice|                 |  Advice|                  |
                          |                 |        |                  |
                          +-----------------+        +------------------+

       Figure 3: SCONE Integration within the Wireline Network

7.1.  Wireline specific considerations

   TBD

8.  SCONE usage in a Wifi Networks

   TBD

   Editor's note : Home, enterprise and campus network have wifi access
   network.  The SCONE client can be in the wifi network for the whole
   time of the session or there can be handover/offloading case where
   SCONE client can be moved from cellular network to wifi network or
   vice versa.  The rate limit in such cases usually applied per user/
   device or SSIDs.  This need to be covered in the considerations.

8.1.  Other Miscellaneous topics

   *  SCONE signaling MUST NOT require changes to how a CSP determines
      video policy for a flow.

   *  The SCONE signal MUST be extensible beyond 4G/5G.

   *  Receiver adaptation behavior requires further specification.






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   *  In multi-UPF deployments, only the UPF associated with a given PDU
      session will send throughput advice.  Other UPFs may serve
      specialized roles but MUST NOT duplicate advisory functions.

   By addressing these above operational considerations, SCONE can be
   managed effectively in mobile networks to enable adaptive bit-rate
   applications optimize their performance while allowing network
   operators to utilize network resources efficiently.

9.  Security Considerations

   Security considerations are included separately in the SCONE protocol
   documents.

10.  IANA Considerations

   This document has no IANA actions.

11.  References

11.1.  Normative

   [RFC2119] [RFC8174]

11.2.  Informative References

   [_4G-Arch] [_5G-Arch]

12.  References

12.1.  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/rfc/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/rfc/rfc8174>.

12.2.  Informative References

   [SCONE-Charter]
              IETF, "SCONE Working Group Charter", 31 October 2024,
              <https://datatracker.ietf.org/wg/scone/about/>.





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   [_4G-Arch] 3GPP, "System architecture for the Evolved Packet Core
              (EPC)", 1 June 2020,
              <https://portal.3gpp.org/desktopmodules/Specifications/
              SpecificationDetails.aspx?specificationId=24300>.

   [_5G-Arch] 3GPP, "System architecture for the 5G System (5GS)", 7
              January 2025,
              <https://portal.3gpp.org/desktopmodules/Specifications/
              SpecificationDetails.aspx?specificationId=3144>.

Appendix A.  Appendix A.  Additional Background details on role of UPF
             in 5G Mobile Packet Core

A.1.  Detailed view of the User Plane Network Element in Mobile Packet
      Core

   This section describes 5G mobile packet core to explain the role of
   user-plane network element in mobile packet core and reasons why the
   5G User Plane Function (UPF) and 4G P-GW as network elements can be
   considered candidates for signaling the "throughput advice" to
   client-application-endpoint.  However, the applicability extends to
   network architectures beyond 4G/5G networks.

   The user plane network element in the 5G packet core, termed as the
   UPF, as shown in Figure 1.

               +-----+  Nudm/Nudr  +---------+
               | PCF +-------------+ UDM/UDR |
               +--+--+             +----+----+
                   |                    |
              Npcf |      +-----+       |Nudm
                   +------+ SMF +-------+
                          +--+--+      ___  __
                             | N4     (   )(  )
   +----+   +--------+    +--+--+    (         )    +------------------+
   | UE |---| gNodeB |----| UPF |----( Internet )---| Content Provider |
   +----+   +--------+ N3 +- -+-+ N6  (        )    +------------------+
                              | N9     (__(___)
                            +-+---+
                            | UPF |
                            +-----+

               Figure 4: 5G Mobile Network Architecture

   In the 4G packet core, the P-GW (as shown in Figure 2) performs the
   same role as the UPF does in the 5G mobile packet core.





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                    +-----+
                    | HSS |
                    +-----+
                       |
                    +-----+          +------+
                    | MME |          | PCRF |
                   /+-----+\         +------+
                  /         \            |
                 /           \           |         ___  __
                /             \          |        /   )(  \
   +----+   +-----+        +------+  +------+    (         )    +----------+
   | UE |---| eNB |--------| S-GW |--| P-GW |----( Internet )---| Content  |
   +----+   +-----+   S1u  +------+  +------+ SGi (        _)   | Provider |
                                                   (__(___)     +----------+

               Figure 5: 4G Mobile Network Architecture

A.2.  5G Mobile Network Architecture

   The UPF is a fundamental component of the 3GPP's 5G packet core
   network architecture.  UPF is on the data path between the end-user
   and the Internet, has access to subscriber policy via standard 3GPP
   N4 interface and is responsible for routing and forwarding user data
   packets.  UPF is the anchor point between the mobile infrastructure
   and the Packet Data Network.  The UPF is responsible for functions
   such as:

   *  Packet routing, forwarding, and interconnection to the Data
      Network (Internet)

   *  Allocation of User Equipment (UE) IP Address/prefix, in
      conjunction with Session Management Function (SMF)

   *  Quality of Service policy enforcement

   *  Handling of traffic filtering, steering and application detection

   *  Traffic usage reporting

   Note: This is not an exhaustive list of UPF functions.  For details
   refer to [_5G-Arch].

   To accomplish above mentioned functions, the UPF has four distinct
   reference points (interfaces) as defined by the 3GPP and as shown in
   the figure 1 above:

   1.  The N3 interface is between the UPF and the 5G Base station.




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   2.  The N4 interface is a connection between the UPF and the Session
       Management Function (SMF).

   3.  The N6 interface is between the UPF and the public data network
       or the Internet.

   4.  The N9 interface is between instances of UPFs.

A.3.  N3 Interface

   The N3 interfaces transfers user plane traffic, that is, user data
   packets between the gNodeB and the UPF.  It uses GPRS Tunneling
   Protocol - User Plane or GTP-U.  It replaces the S1-U interfaces from
   the 4G mobile packet core.

A.4.  N4 Interface

   The N4 interface connects the UPF and the 5G Session Management
   Function (SMF).  Through N4, the SMF informs the UPF about the
   subscriber policy and data plans.  Additionally, this interface is
   used to manage session setup, modification, deletion, and for
   configuring QoS and forwarding rules for user data.  The QoS rules
   contain parameters such as MBR.  The N4 interface among others uses
   Packet Forwarding Control Protocol (PFCP).

   Note: SMF also interacts with Policy Control Function (PCF) for
   functions such as QoS and Charging policy rules, Unified Data
   Management (UDM) and Unified Data Repository (UDR) for functions such
   as subscription data and policy plans.

A.5.  N6 Interface

   The N6 interface connects the UPF to external Data Networks, similar
   to the SGi interface between the P-GW and the external Data Network
   for access to services and applications.  The interface supports
   various transport protocols over IP.

A.6.  N9 Interface

   This interface interconnects two or more UPFs when used in a data
   path.  The interface uses GTP-U protocol for user traffic tunneling
   including roaming.

   Note: In the scenario of 2 or more UPFs in the data path, only one
   UPF that has access to subscriber policy would send "throughput
   advice" to the client-application-endpoint.





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A.7.  User Plane Interface Between UPF and UE

   This section describes the N3 interface (between the UPF and gNodeB
   or gNB) and the air interface between the gNB and UE.  For purposes
   of nomenclature, a Protocol Data Unit (PDU) session is a logical path
   between a UE and UPF to carry packets belonging to one or more IP
   flows between UE and DN.  A PDU session within a 5G mobile network
   consists of an air-interface between UE and gNB and GTP-U tunnel
   between gNB and UPF (N3 interface).  Application traffic flows with
   different QoS requirements get mapped to different QoS treatments
   based on packet filters and QoS rules configured on the UPF and UE.
   Below is an example of data flow to/from a UE to the UPF.

   1.  Uplink Data Flow

       *  Apps that are hosted on UE that generate application packets
          for communication (e.g. web browsing, video streaming).

       *  These packets are transmitted to the gNB over the air
          interface and get mapped to different QoS treatments based on
          packet filters and QoS rules provided to the UE

       *  N3 Encapsulation and Forwarding

          1.  The gNB then encapsulates this user-plane data using GTP-
              U.

          2.  It then forwards the encapsulated packets over the N3
              interface to the UPF in the 5G mobile packet core.

       *  UPF Routes Data to External Networks.

          1.  Within the UPF, UPF then removes the GTP-U header,
              processes the packet, and routes it over the N6 interface
              toward the destination (Internet, enterprise network,
              cloud services, etc.).

   2.  Downlink Data Flow

       *  UPF receives incoming data in downlink direction at N6
          interface (e.g. from the Internet).

       *  The UPF encapsulates incoming data using GTP-U and forwards it
          over the N3 interface to the gNB.  It maps traffic flows with
          different QoS requirements to different QoS treatments based
          on packet filters and QoS rules configured by SMF.





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       *  The gNB forwards the packets to the UE over the air-interface.
          UE-side modem stack then transparently passes the application
          packets to the app hosted on the UE.

   In summary, the UPF is responsible for packet routing and forwarding,
   packet inspection and filtering, participating in subscriber and flow
   policy enforcement, inline services (NAT, firewall, DNS etc) and QoS
   handling.

Appendix B.  Appendix B.  Non-ASCII Characters

   This document uses the following kramdown-rfc character escapes for
   common non-ASCII symbols:

   *  U+00A0 NO-BREAK SPACE → {nbsp}

   *  U+00AD SOFT HYPHEN → {shy}

   *  U+2011 NON-BREAKING HYPHEN → {nbhy}

   *  U+200B ZERO WIDTH SPACE → {zwsp}

   *  U+2060 WORD JOINER → {wj}

   *  U+2013 EN DASH → {ndash}

   *  U+2014 EM DASH → {mdash}

   *  U+201C LEFT DOUBLE QUOTATION MARK → {ldquo}

   *  U+201D RIGHT DOUBLE QUOTATION MARK → {rdquo}

   *  U+2018 LEFT SINGLE QUOTATION MARK → {lsquo}

   *  U+2019 RIGHT SINGLE QUOTATION MARK → {rsquo}

   *  U+20AC EURO SIGN → {euro}

Acknowledgments

   This document represents collaboration, comments, and inputs from
   others, including:

   *  Wesley Eddy

   *  Renjie Tang

   *  Kevin Smith



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   *  Tina Tsou

   *  Tianji Jiang

   *  Lucas Pardue

   *  Martin Thomson

Authors' Addresses

   Sanjay Mishra
   Verizon
   Email: sanjay.mishra@verizon.com


   Zaheduzzaman Sarker
   Nokia
   Email: zaheduzzaman.sarker@nokia.com


   Anoop Tomar
   Meta
   Email: anooptomar@meta.com


   Khurram Abbas
   Verizon
   Email: khurram.abbas@verizonwireless.com























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