Description
The Transport Service Provider (TSP) is a functional concept within the 3GPP service-based architecture, particularly defined for the 5G Core (5GC) network. It acts as a logical intermediary that offers transport connectivity services between various Network Functions (NFs), such as the Access and Mobility Management Function (AMF) and the Session Management Function (SMF), or between User Plane Functions (UPFs). The TSP is not a single physical node but a capability that can be implemented within network functions or as a dedicated service. Its primary role is to manage the transport layer aspects of communication, including the selection of appropriate transport protocols, quality of service (QoS) handling for the transport network, and potentially security aspects like encryption for the N2 (control plane) and N3 (user plane) interfaces.
Architecturally, the TSP interacts with other network functions via service-based interfaces (e.g., Nnssf, Nnef) or reference points. It utilizes transport profiles, which are sets of parameters defining the required transport characteristics (e.g., latency, bandwidth, reliability) for a given service data flow or network slice instance. The TSP consults the Network Slice Selection Function (NSSF) and Policy Control Function (PCF) to determine the appropriate transport resources aligned with the slice's Service Level Agreement (SLA). It then interfaces with the underlying transport network (e.g., managed by a Transport Network Controller) to establish the necessary connectivity, often leveraging technologies like Segment Routing or MPLS.
In operation, when a network function requires transport services, it invokes the TSP's capabilities through standardized APIs. The TSP evaluates the request against available network slice and subscriber policies, selects a transport path, and configures the transport network elements accordingly. This abstraction allows the core network functions to be agnostic of the specific transport technologies (e.g., IP, Ethernet, optical), facilitating multi-vendor interoperability and seamless evolution of the transport layer. The TSP is a key enabler for end-to-end network slicing, as it ensures the transport segment meets the specific performance and isolation requirements of each slice.
Purpose & Motivation
The TSP was introduced to address the growing complexity of managing transport resources in a decoupled, cloud-native 5G core network. In pre-5G architectures, transport connectivity was often tightly integrated with core network nodes, making it difficult to dynamically allocate resources for diverse services like enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC). This rigidity hindered efficient network slicing, where each slice requires distinct transport characteristics.
The TSP concept solves this by providing a standardized abstraction layer for transport services. It separates the service logic of the core network from the underlying transport infrastructure, allowing operators to manage and optimize the transport network independently. This enables flexible service deployment, automated provisioning of transport resources per slice, and improved utilization of network assets. Historically, without a TSP, achieving end-to-end QoS and slice isolation across the transport network required proprietary integrations, limiting scalability and innovation.
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (14 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-12, normative work from Rel-15.
In Release 15, the TSP (Transport Service Provider) function was introduced to enable transport-level packet marking for QoS Flows, where the SMF determines and provides the marking value (e.g., DSCP) to the UPF for downlink packet handling. This allows the UPF to perform packet marking on a per-QoS Flow basis, optionally considering PDU Set Importance to influence drop precedence within the transport network. The capability is managed via PCC rules, where the PCF derives TSP IDs for traffic steering enforcement and provides them to the SMF.
In Release 16, enhancements for the Transport Service Provider (TSP) function included the capability for the SMF to configure specific transport level packet marking values, such as DSCP, on a per-QoS Flow basis and provide them to the UPF for enforcement. This allowed for more granular QoS differentiation in the transport network, including optional marking based on PDU Set Importance to influence drop precedence without causing packet reordering. Additionally, the PCF could derive distinct TSP IDs for uplink and downlink directions as part of the N6-LAN Traffic Steering Enforcement Control information provided to the SMF.
In Release 17, the TSP function was enhanced with additional authorization functionality to support the Multimedia Priority Service (MPS) for Data Transport Service. It also introduced clarifications on the TSCTSF functionality and configuration for transport protocols, and enabled the transport of PMF information via the N4 interface.
- Multimedia Priority Service (MPS) Phase 2 support for Data Transport Service TS 23.501CR2536
- Additional authorization functionality in support of MPS for Data Transport Service TS 23.501CR2971
- KI#3, clarification on the TSCTSF functionality and configuration for transport protocols TS 23.501CR3160
- PMF information transported via N4 TS 23.501CR3110
In Release 18, the key new feature for the TSP function was the introduction of enablers for interworking with a Time Sensitive Networking (TSN) network deployed in the transport network. This specifically supports the fully centralized configuration model as defined in IEEE Std 802.1Qcc, allowing the 5G system to integrate with TSN-enabled transport infrastructure. The work included corrections and enhancements to ensure proper support for this TSN-enabled transport network capability.
In Release 19, enhancements were made to the Transport Service Provider function by enabling transport level packet marking to be based on PDU Set Importance, allowing differentiated drop precedence within a QoS Flow. This was specified for the UPF and the I-SMF, leveraging PDU Set QoS information for DSCP marking over N3 and N9 interfaces. The updates ensure that packet marking can vary per PDU set to influence transport network behavior while aiming to prevent packet reordering within a single QoS Flow.
- Leveraging PDU Set QoS information for DSCP marking over N3/N9 in the transport network TS 23.501CR5407
- XRM_Ph2_KI3 Leveraging PDU Set QoS information for DSCP marking over N3/N9 in the transport network TS 23.501CR6050
- Triggering of Transport Level Marking based on PDU Set Importance in I-SMF TS 23.501CR6193
- Transport level packet marking considering PSI TS 23.501CR6478
Explore further
Broader topics and technologies where TSP plays a role.
Defining Specifications
3GPP specifications that define or reference TSP, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 24.523 vj00 | NGCN-NGN Interconnection Scenarios | Rel-19 |