Applicability & Manageability consideration for SCONE

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Table of Contents

1. Introduction

The SCONE protocol [I-D.ietf-scone-protocol] provides a signaling mechanism that enables on-path SCONE-capable network elements to communicate the maximum allowable bit rate to application endpoints, which is particularly relevant for adaptive bit-rate applications. This document addresses the applicability and manageability considerations for deploying the SCONE protocol within telecommunications service provider networks.¶

SCONE operates based on 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 that on-path SCONE-capable network elements (referred to as SCONE Network Elements in the rest of this document) are assumed to have the following capabilities: detect and maintain UDP 4-tuple flows, be aware of or configurable with rate-limiting policies, and identify flows that carry SCONE packets in order to insert throughput advice into those packets.¶

In this document, on-path SCONE Network Elements are generally considered within the access portion of the telecommunications provider’s network. However, multiple SCONE Network Elements may exist along a path between the communicating peers. Depending on their configuration and roles they are likely to generate different throughput advices for the SCONE enabled application traffic flows, specially when differnet access technologies are in use. SCONE protocol For example, a wireless access network element may operate differently from one in a fixed broadband network. Wi-Fi networks provide another example, where enforcement is often per user or per Service Set Identifier (SSID), but visibility into individual UDP 4-tuples may be limited. Among access networks, mobile networks offer the most fine-grained visibility into traffic flows and can act on individual flows. 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 contrast, wireline broadband networks typically apply rate limiting at a centralized Broadband Network Gateway (BNG) or at aggregation points serving multiple Customer Premises Equipment (CPE) devices.¶

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

2. Terms and Definitions

This document uses terms and definitions described in [I-D.ietf-scone-protocol], some more terms and definitions are described below in this section.¶

• 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.¶

• APN - Access Point Name The Access Point Name (APN) determines the specific Packet Data Network Gateway (PDN-GW in 4G/LTE) that the mobile device should use to access a service. The gateway acts as the access point to external networks such as the public internet or a private network. Different APNs can be used to provide different services, access privileges, or Quality of Service to a user's device.¶

• 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.¶

• 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.¶

• DNN - Data Network Name A Data Network Name (DNN) identifies the external data network that a User Equipment (UE) connects to within a 5G system. The DNN specifies the target data network (for example, the Internet or an enterprise network) and is used by the 5G Core to establish and manage the corresponding PDU session. It is functionally equivalent to the Access Point Name (APN) used in 4G/LTE systems.¶

• 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.¶

• 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).¶

3. Generic Applicability and Manageability considerations

4. SCONE Usage in a 5G Network

5G systems consist of a 5G Radio Access Network (RAN) and a 5G Packet Core. The 5G Packet Core is built on a cloud-native Service-Based Architecture (SBA) and introduces the concept of Network Functions (NFs), which provides flexibility for deploying SCONE in the network.¶

Appendix A describes the various network components of a 5G network.¶

In 5G, the User Plane Function (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 on a per-application-flow basis, enabling endpoints to adjust sending rates proactively. SCONE signaling occurs over the existing data path.¶

For a 5G network, the UPF serves as the natural anchor point for SCONE signaling. However, due to the flexibility of 5G’s SBA, any network component capable of meeting the applicability and manageability considerations may act as a SCONE Network Element.¶

The following diagram illustrates how throughput advice can be conveyed within a 5G network, highlighting the role of user-plane SCONE Network Elements.¶

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

5. 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.¶

The following diagram illustrates 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|
                  +-----------------+

6. SCONE usage in a Wireline Network

TBD¶

Editor's Note: 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 SCONE 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. We need to consider if aggregation points have flow level visibility or not, or whether there is a point to provide throughput advice at the aggregate level.¶

7. SCONE usage in a Wifi Networks

TBD¶

Editor's Note: Home, enterprise, and campus networks commonly use Wi-Fi access. The SCONE client may remain within the Wi-Fi network for the duration of a session, or it may be subject to handover or offloading, moving between a cellular network and a Wi-Fi network, and vice versa. In such scenarios, rate limiting is typically applied per user, device, or Service Set Identifier (SSID). These cases should be considered when defining applicability and manageability guidelines for SCONE deployments.¶

8. Security Considerations

Security considerations are included separately in the SCONE protocol documents.¶

9. IANA Considerations

This document has no IANA actions.¶

10. References

11. References

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

This section describes 5G mobile packet core in mobile packet core and reasons why the 5G User Plane Function (UPF) as SCONE network elements can be considered candidates for signaling the "throughput advice" to client-application-endpoint.¶

The user plane SCONE 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 |
                            +-----+

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

The authors would like to acknowledge and thank the SCONE working grouup and also the following individuals for their valuable feedback, discussions, and contributions that helped improve this document:¶

• Wesley Eddy¶

• Renjie Tang¶

• Kevin Smith¶

• Tina Tsou¶

• Tianji Jiang¶

• Lucas Pardue¶

• Martin Thomson¶

Authors' Addresses