



SCONE                                                          S. Mishra
Internet-Draft                                                   Verizon
Intended status: Informational                                  A. Tomar
Expires: 21 January 2026                                            Meta
                                                                K. Abbas
                                                                 Verizon
                                                               Z. Sarker
                                                                   Nokia
                                                            20 July 2025


   Applicability & Manageability of SCONE signal for a mobile network
            draft-mishra-scone-applicability-manageablity-00

Abstract

   This document identifies applicability of SCONE signal in a mobile
   network and outlines operational considerations, or manageability of
   SCONE signal in the operator network.  Importantly, this document
   also describes 3GPP network elements that are capable of rate-
   limiting a UDP 4-tuple to communicate an upper bound on achievable
   bitrate termed "throughput advice" to implement 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
   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 21 January 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/
   license-info) in effect on the date of publication of this document.



Mishra, et al.           Expires 21 January 2026                [Page 1]

Internet-Draft     SCONE Applicability & Manageability         July 2025


   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
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  User Plane Network Element in Mobile Packet Core  . . . . . .   3
     3.1.  N3 Interface  . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  N4 Interface  . . . . . . . . . . . . . . . . . . . . . .   4
     3.3.  N6 Interface  . . . . . . . . . . . . . . . . . . . . . .   5
     3.4.  N9 Interface  . . . . . . . . . . . . . . . . . . . . . .   5
     3.5.  User Plane Interface Between UPF and UE . . . . . . . . .   5
   4.  Applicability of SCONE Signal in Mobile Networks  . . . . . .   6
     4.1.  4G Mobile Network Architecture  . . . . . . . . . . . . .   6
     4.2.  Implementing SCONE In the Mobile Network  . . . . . . . .   7
   5.  SCONE Manageability & Operational considerations  . . . . . .   8
     5.1.  SCONE signal Hint from Client to the Network  . . . . . .   8
       5.1.1.  Packet Data Network (PDN) Connection / PDU Session
               (5G)  . . . . . . . . . . . . . . . . . . . . . . . .   8
       5.1.2.  IP address allocation . . . . . . . . . . . . . . . .   9
       5.1.3.  Bearer establishment  . . . . . . . . . . . . . . . .   9
       5.1.4.  Mobility Management . . . . . . . . . . . . . . . . .   9
     5.2.  Measuring conformance of advised bit-rate . . . . . . . .   9
     5.3.  Dynamic updates . . . . . . . . . . . . . . . . . . . . .   9
     5.4.  Other open issues . . . . . . . . . . . . . . . . . . . .  10
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   This document describes applicablity and manageablity of SCONE
   protocol in the networks and applicaiton endpoints.  It focuses on
   mobile networks, however, this document is also applicable to other
   access networks.








Mishra, et al.           Expires 21 January 2026                [Page 2]

Internet-Draft     SCONE Applicability & Manageability         July 2025


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.  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.  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.

   The UPF is a fundamental component of the 3GPP's 5G packet core
   network architecture.  UPF is the data path between the end-user and
   the Internet, has access to subscriber policy via standard 3GPP
   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 below:



Mishra, et al.           Expires 21 January 2026                [Page 3]

Internet-Draft     SCONE Applicability & Manageability         July 2025


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

               Figure 1: 5G Mobile Network Architecture

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

   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.

3.1.  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.

3.2.  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 forwarding rules for user data.  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.



Mishra, et al.           Expires 21 January 2026                [Page 4]

Internet-Draft     SCONE Applicability & Manageability         July 2025


3.3.  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 trasnport protocols over IP.

3.4.  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.

3.5.  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).  IP flows (aka service data flows
   or SDFs) may belong to one or more services.  All the service data
   flows with the same QoS maps onto one PDU session.  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 brownsing, video streaming).

       *  These packets are transmitted to the gNB over the air
          interface.

       *  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.




Mishra, et al.           Expires 21 January 2026                [Page 5]

Internet-Draft     SCONE Applicability & Manageability         July 2025


          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 sends it
          back over the N3 interface to the gNB.

       *  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, subscriber policy enforcement,
   inline services (NAT, firewall, DNS etc) and QoS handling.

4.  Applicability of SCONE Signal in Mobile Networks

   The UPF is a data path mobile packet core network element that routes
   and forwards application packets between the gNodeB and the DN and it
   has access to subscriber policy via standard 3GPP N3 interface.

   As a result, UPF is in the best position to send the throughput
   advice to client application over the data-path.

4.1.  4G Mobile Network Architecture

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

               Figure 2: 4G Mobile Network Architecture



Mishra, et al.           Expires 21 January 2026                [Page 6]

Internet-Draft     SCONE Applicability & Manageability         July 2025


4.2.  Implementing SCONE In the Mobile Network

   As described in sections above, UPF is the 3GPP on-path "network
   element" that has access to subscriber policy and provides the data
   pipe connectivity between UE and the Internet.  UPF is a network
   element that is capable of SCONE signaling over the data path.

   Below is a high-level view of SCONE signal path in a 5G network.
   Please see [Mishra-2025] for a more complete version of this diagram.

                             +---------+
                             |   PCF   |
                             +---------+
                                  | Subscriber
                                  V Policy Rules
                             +---------+
                             |   SMF   |
                             +----+----+
                                  | Subscriber
                                  v Policy Rules
   +--------+               + +---------+-+
   | Client |/--------------\ |  SCONE  | |       __
   |   App  |\--------------/ | Advisor | |    __(  )__
   +--------+     SCONE     | +---------+ |   (        )   +----------+
   |   OS   |  (advised bit |             +--( Internet )--+ Content  |
   +--------+   rate and    |     UPF     |   (         )  | Provider |
   |  Modem |   other IEs)  |             |    (__)(___)   +----------+
   +----+---+               +------+------+
        |                          |
        |         +-----+          |
        +---------+ gNB +----------+
                  +-----+

         Figure 3: SCONE Integration with Video Policy in 5G SA N/W

   Similarly, the SCONE signal for 4G network is shown below.  Please
   see [Mishra-2025] for a more complete version of this diagram.














Mishra, et al.           Expires 21 January 2026                [Page 7]

Internet-Draft     SCONE Applicability & Manageability         July 2025


                             +---------+
                             |  PCRF   |
                             +----+----+
                                  | Subscriber
                                  v Policy Rules
   +--------+               + +---------+-+
   | Client |/--------------\ |  SCONE  | |       __
   |   App  |\--------------/ | Advisor | |    __(  )__
   +--------+     SCONE     | +---------+ |   (        )   +----------+
   |   OS   |  (advised bit |             +--( Internet )--+ Content  |
   +--------+   rate and    |     P-GW    |   (         )  | Provider |
   |  Modem |   other IEs)  |             |    (__)(___)   +----------+
   +----+---+               +------+------+
        |                          |
        |         +-----+       +--+---+
        +---------+ eNB +-------+ S-GW |
                  +-----+       +------+

           Figure 4: SCONE Integration with Vido Policy in 4G N/W

5.  SCONE Manageability & Operational considerations

   The sections below describe SCONE signal manageability.

5.1.  SCONE signal Hint from Client to the Network

   In 3GPP networks (4G/5G), a User Equipment (UE) connects to the
   internet by establishing data sessions that traverse various network
   elements.  The key process involves allocating an IP address to the
   UE and routing its data traffic through the mobile network's core to
   the external data networks including the internet.  As this
   connection to the Internet is established and once the client App on
   the UE starts communicating with the application content provider, a
   hint for SCONE usage will allow UPF to then look for a SCONE packet
   for this specific user connection and avoid PGW/UPF any unnecessary
   CPU cycles for non-ABR video connections.  The section below provides
   a more detailed information on the UE and the mobile network for
   connecting to the external network.

5.1.1.  Packet Data Network (PDN) Connection / PDU Session (5G)

   This is the logical connection established between the UE and the
   Packet Data Network Gateway (P-GW in 4G) or User Plane Function (UPF
   in 5G).  It allows the UE to exchange IP packets with external
   networks.  Each PDN Connection/PDU Session is associated with a
   specific Access Point Name (APN), which identifies the type of
   service or external network the UE wants to connect to (e.g.,
   "internet" for general internet access).



Mishra, et al.           Expires 21 January 2026                [Page 8]

Internet-Draft     SCONE Applicability & Manageability         July 2025


5.1.2.  IP address allocation

   During the establishment of a PDN Connection/PDU Session, the UE is
   allocated an IP address (IPv4, IPv6, or both).  This IP address is
   used for communication with the internet.

5.1.3.  Bearer establishment

   Data traffic flows over bearers.  A bearer defines the QoS (Quality
   of Service) characteristics for a specific data flow.  For internet
   access, a default bearer is established first, and dedicated bearers
   can be set up for specific services requiring different QoS.

5.1.4.  Mobility Management

   The network handles the UE's mobility (e.g., moving between cells or
   base stations) while maintaining the ongoing data connection.

5.2.  Measuring conformance of advised bit-rate

   As the network element capable of advising bit-rate limit, the
   network element also would need capabilities to measure conformance
   on the advised bit-rate.

   Issue 35 [https://github.com/ietf-wg-scone/scone/issues/35] - Need to
   determine if the conformance is to be measured as an aggregate or on
   a per flow basis.

   Presentation given at interim session 6 provides results based on
   experimentation that recommends a suitable size for time window to be
   120 seconds.  This value is compatible with existing VOD applications
   when ~2 mbps is the advised bitrate. -
   [https://datatracker.ietf.org/meeting/interim-2025-scone-
   06/materials/slides-interim-2025-scone-06-sessa-time-window-duration-
   for-bitrate-measurement-00.pdf]

5.3.  Dynamic updates

   In networks, for example - radio networks, the avaible capacity of
   the network can dynamically change for a persistance of time that, or
   there could be sudden increase of network users, these could result
   in change of throughput advice for a particular scone capable flow.
   These changes need to be dynamically and immidiately updated in the
   rate signal to avoid unnecesarry rate shaping or degradated QoE.
   This means the network elements need to be able to initiate the
   sending of the rate signal if there is not sufficient frequency of
   scone packets send for that particular flow.




Mishra, et al.           Expires 21 January 2026                [Page 9]

Internet-Draft     SCONE Applicability & Manageability         July 2025


5.4.  Other open issues

   *  SCONE signaling MUST NOT require changes to how a CSP determines
      its video policy for a given flow.  That is there is MUST not be
      any dependency between a CSP's video policy and the SCONE
      protocol.

   *  SCONE signal MUST be extensible to networks beyond 4G/5G network.

   *  discussion on how the applications/receivers can adapt to the rate
      signals.

6.  Security Considerations

   Security considerations are included separately in the SCONE protocol
   documents.  Specific to the use case description in this document,
   there are no additional security considerations.

7.  IANA Considerations

   This document has no IANA actions.

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/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>.

8.2.  Informative References

   [I-D.joras-scone-video-optimization-requirements]
              Joras, M., Tomar, A., Tiwari, A., and A. Frindell, "SCONE
              Video Optimization Requirements", Work in Progress,
              Internet-Draft, draft-joras-scone-video-optimization-
              requirements-01, 12 May 2025,
              <https://datatracker.ietf.org/doc/html/draft-joras-scone-
              video-optimization-requirements-01>.

   [Mishra-2025]
              Mishra, S., "Leveraging the user plane function for
              network-side advisory signal", 6 February 2025,



Mishra, et al.           Expires 21 January 2026               [Page 10]

Internet-Draft     SCONE Applicability & Manageability         July 2025


              <https://datatracker.ietf.org/meeting/interim-2025-scone-
              01/materials/slides-interim-2025-scone-01-sessa-
              leveraging-the-user-plane-function-for-network-side-
              advisory-signal-00>.

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

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

Acknowledgments

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

   *  Wesley Eddy

   *  Renjie Tang

Authors' Addresses

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


   Anoop Tomar
   Meta
   Email: anooptomar@meta.com


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


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








Mishra, et al.           Expires 21 January 2026               [Page 11]
