Description
The Control Plane (CP) in 3GPP systems constitutes the set of functions and protocols responsible for the signaling required to establish, manage, and terminate communication sessions and connections for User Equipment (UE). It operates separately from the User Plane (UP), which handles the actual user data payload. This separation of concerns, known as Control and User Plane Separation (CUPS), is a core architectural principle that enhances network flexibility, scalability, and independent evolution of network functions. The CP is responsible for critical procedures including authentication, registration, session establishment, mobility management (handovers, tracking area updates), policy and charging control, and connection management.
Architecturally, the CP comprises various Network Functions (NFs) that interact through standardized service-based interfaces (SBIs) in 5G, or reference points in earlier generations. Key CP functions include the Access and Mobility Management Function (AMF), Session Management Function (SMF), Policy Control Function (PCF), and Unified Data Management (UDM) in 5G Core (5GC). In the Evolved Packet Core (EPC), equivalent functions include the Mobility Management Entity (MME), Home Subscriber Server (HSS), and Policy and Charging Rules Function (PCRF). These functions exchange signaling messages using protocols such as NGAP, NAS, and HTTP/2 to orchestrate network resources and services for the UE.
The CP works by processing signaling messages initiated by the UE or other network functions. For instance, during initial registration, the UE sends a registration request via the Radio Access Network (RAN) to the AMF. The AMF then interacts with the UDM for authentication and subscriber profile retrieval, and with the SMF for potential PDU session establishment. The CP makes decisions based on subscriber policies, network conditions, and service requirements, and then instructs the User Plane functions (e.g., UPF, SGW-U/PGW-U) to set up the appropriate data paths. This orchestration ensures that user data can flow efficiently while maintaining security, QoS, and mobility support.
Its role is pivotal for network automation, slicing, and service delivery. By centralizing control logic, the CP enables dynamic network reconfiguration, efficient resource allocation across network slices, and the implementation of advanced services like network-assisted IoT device management or edge computing. The CP's design allows for cloud-native implementation, supporting stateless NFs, scalability, and resilience through redundancy and load balancing, which are essential for modern software-defined mobile networks.
Purpose & Motivation
The Control Plane exists to manage the complexity of mobile network operations by separating the signaling logic from data forwarding. This separation addresses the limitations of monolithic network architectures where control and data processing were tightly coupled, leading to scalability bottlenecks, inefficient resource utilization, and inflexibility in introducing new services. The CP/UP split allows each plane to scale independently based on demand; for example, the UP can be scaled to handle data traffic bursts, while the CP scales based on the number of connected devices and signaling load.
Historically, as networks evolved from circuit-switched to packet-switched IP-based architectures (GPRS, UMTS, LTE), the need for a robust, flexible control mechanism became paramount to support always-on connectivity, advanced QoS, and diverse services. The creation of a dedicated Control Plane standardized the signaling procedures for mobility, session management, and security across different access technologies (e.g., 3G, 4G, 5G-NR, non-3GPP WLAN), enabling seamless mobility and service continuity. It solved the problem of inefficient, proprietary control mechanisms that hindered interoperability and rapid service deployment.
Furthermore, the CP is the enabler for key technological advancements like Network Slicing and edge computing in 5G. It provides the orchestration layer that can instantiate, manage, and terminate isolated network slices with specific characteristics on a shared physical infrastructure. By centralizing policy and session control, the CP allows operators to offer differentiated services, implement sophisticated charging models, and dynamically adapt network behavior to application requirements, which was not feasible with earlier, more rigid architectural approaches.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (483 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-6, normative work from Rel-15.
In Release 15, key CP enhancements included the introduction of Service Gap Control for managing UE service access periods and the formalization of security mechanisms for UE Parameters Update via UDM control plane procedures. The release also introduced specific capabilities for Diameter Overload Control with new AVPs and focused on Control Plane latency reduction. Furthermore, it provided updates for NAS congestion control and clarified S-NSSAI based congestion control mechanisms.
- Enable T8 for CP procedures TS 23.682CR0302
- Introduction of Service Gap Control TS 23.682CR0374
- Introduction of Service Gap Control; basics and feature negotiation TS 24.301CR2982
- Service Gap Control feature; non supporting UEs TS 24.301CR2983
- Service Gap Control; UE behaviour service gap timer is running TS 24.301CR2984
- Service Gap Control feature cleanup and corrections TS 24.301CR3010
+ 111 more changes
In Release 16, the Control Plane (CP) function was enhanced with new mechanisms for managing Internet of Things (IoT) and small data traffic, including the introduction of Rate Control and Overload Control specifically for 5G CIoT. It also enabled more efficient data transfer by establishing User Plane connections during Control Plane data transfer and allowing network-requested reactivation of user-plane resources. Furthermore, control was extended to traffic forwarding in 5G-LAN and to influencing UPF selection based on analytics and AN user plane capability indications.
- Introducing Rate Control for 5G CIoT TS 23.501CR0752
- Introduction of data transfer in Control Plane CIoT 5GS Optimisation TS 23.501CR0889
- CIoT Introduction of Overload Control TS 23.501CR0894
- Introduction of Service Gap Control TS 23.501CR1014
- General description of solution 1 in 23.725 for user plane redundancy TS 23.501CR0753
- UL CL/BP controlled by I-SMF TS 23.501CR0848
+ 128 more changes
In Release 17, key CP function enhancements included the introduction of the Network Slice Admission Control Function (NSACF) for managing slice-based access, support for User Plane Remote Provisioning of UEs, and enabling Session Management Congestion Control Experience analytics. The release also extended control plane capabilities for EPS, such as introducing EPS User Plane Integrity Protection and mechanisms for paging timing collision control for MUSIM UEs. Furthermore, it added support for northbound API Load and Overload Control and explicit subscription to user plane events for service-based interfaces.
- TS23.501 KI#1 Network Slice Admission Control Function (NSACF) definition TS 23.501CR2679
- TS23.501 KI#2 Network Slice Admission Control Function (NSACF) definition TS 23.501CR2680
- Adding the usage of Session Management Congestion Control Experience analytics TS 23.501CR2708
- Enabling restricted PDU Session for remote provisioning of UE via User Plane TS 23.501CR2709
- Network access control by Credential Holder TS 23.501CR2717
- User Plane Remote Provisioning of UEs if PLMN as ON TS 23.501CR2802
+ 74 more changes
In Release 18, the Control Plane was enhanced with new features for policy, slicing, and access control, including UL and DL policy control based on Round-Trip latency requirements and improved network control of slice usage and admission. It also introduced support for Network-Controlled Repeaters, extending network control over these devices, and updated procedures for user plane inactivity detection and location reporting control. Furthermore, security and charging aspects were strengthened for location services and 5G Media Streaming (5GMS) in the Control Plane.
- Policy control enhancements to support multi-modal flows TS 23.501CR3864
- Improved network control of the UE beahviour for a network slice TS 23.501CR3939
- Network access control when the UE accesse an SNPN that provides access for Localized Services TS 23.501CR4270
- Network control of the slice usage TS 23.501CR4443
- Update to Support Network Controlled Repeater TS 23.501CR5273
- UE unavailability period reporting for enhanced discontinuous coverage overrides mobility management congestion control - EPS TS 24.301CR3939
+ 71 more changes
In Release 19, the Control Plane saw enhancements for RAT utilization control, extending it to EPS and satellite access networks while adding storage in non-volatile memory. It also introduced new control parameters for on-demand positioning system information and refined policies for UE access, energy efficiency, and QoS notification control for PDU Sets. Furthermore, the release added exposure capabilities for static IP assignment and user-plane security policies for 5G VN groups.
- Exposure enhancements for static UE IP address assignment and 5G VN group's User Plane Security Policy TS 23.501CR5492
- Control Plane and User Plane Protocol stacks involving the MWAB node TS 23.501CR5561
- KI#2: UE subscription and policy control for energy efficiency and energy saving TS 23.501CR5739
- Functional Description of Energy Efficiency Control Functionality TS 23.501CR5740
- Control of UE access to MWAB TS 23.501CR5468
- Support Alternative QoS profile with PDU Set QoS and Notification Control TS 23.501CR5524
+ 66 more changes
In Release 20, the Control Plane was enhanced to support new policy control for network energy saving, including an updated architecture and Exposure Interface Function (EIF). Furthermore, it introduced mechanisms for mitigation actions based on analytics of abnormal user plane traffic and enabled the exposure of energy consumption information for policy control.
Explore further
Broader topics and technologies where CP plays a role.
Defining Specifications
3GPP specifications that define or reference CP, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TR 21.905 vj00 | 3GPP Technical Terms and Definitions | Rel-19 |
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 23.682 vj30 | 3GPP TS 23682: MTC Architecture Enhancements | Rel-19 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TS 23.714 ve00 | Study on CP-UP separation in EPC | Rel-14 |
| TR 23.730 ve00 | Study on extended CIoT architecture | Rel-14 |
| TR 23.799 ve00 | Study on Next Generation System Architecture | Rel-14 |
| TS 23.868 v900 | Study on IMS Emergency Calls | Rel-9 |
| TS 24.167 vj00 | 3GPP IMS Management Object Specification | Rel-19 |
| TS 24.301 vj60 | NAS protocol for Evolved Packet System | Rel-19 |
| TS 24.502 vj20 | 5G Core Access via Non-3GPP Networks; Stage 3 | Rel-19 |
| TR 25.912 vj00 | Evolved UTRA and UTRAN Technical Report | Rel-19 |
| TR 26.917 vj00 | TV Service Enhancements over 3GPP | Rel-19 |
| TR 26.919 vj00 | Study on 5G Conversational Media Handling | Rel-19 |
| TR 26.930 vj00 | WebRTC Enhancements for Immersive RTC over 5G | Rel-19 |
| TR 26.981 vj00 | MBMS Provisioning & Content Ingestion Interface Study | Rel-19 |
| TS 28.531 vk00 | Management and Orchestration | Rel-20 |
| TS 28.620 vj20 | FMC Federated Network Information Model (FNIM) UIM | Rel-19 |
| TR 28.816 vh00 | Charging for 5G Cellular IoT | Rel-17 |
| TS 29.116 vj00 | REST-based protocol for xMB reference point | Rel-19 |
| TS 29.122 vj40 | T8 Reference Point for Northbound APIs | Rel-19 |
| TS 29.244 vj40 | PFCP Specification for Control/User Plane Separation | Rel-19 |
| TS 29.522 vj40 | 5G NEF Northbound APIs Stage 3 | Rel-19 |
| TS 29.598 vj40 | UDSF Service Based Interface Stage 3 Protocol | Rel-19 |
| TR 29.820 vh00 | Study on PFCP Best Practice | Rel-17 |
| TS 29.844 ve00 | Control and User Plane Separation for EPC Nodes | Rel-14 |
| TS 31.113 v1800 | USAT Interpreter Byte Code Specification | Rel-8 |
| TS 32.240 vj40 | Charging Management Architecture & Principles | Rel-19 |
| TS 32.251 vj00 | PS Domain Charging Management | Rel-19 |
| TS 32.253 vj00 | Charging for Control Plane Data Transfer | Rel-19 |
| TS 32.255 vk10 | Telecom Management; Charging for 5G Data Connectivity | Rel-20 |
| TS 32.297 vj00 | Charging Data Record File Transfer | Rel-19 |
| TS 32.298 vj30 | Charging Data Record (CDR) Parameter Specification | Rel-19 |
| TS 32.299 vj00 | Diameter Charging Applications for 3GPP | Rel-19 |
| TR 32.972 vj00 | Energy Efficiency Study for 5G Networks | Rel-19 |
| TS 33.127 vj50 | Lawful Interception Architecture and Functions | Rel-19 |
| TS 33.501 vk00 | 5G Security Architecture and Procedures | Rel-20 |
| TS 33.503 vj20 | Security for Proximity Services (ProSe) in 5G | Rel-19 |
| TR 33.740 vi10 | Security and Privacy Aspects of Proximity Based Services in 5G System Phase 2 | Rel-18 |
| TR 33.851 vh10 | Security for Industrial IoT in 5G | Rel-17 |
| TR 33.853 vh00 | Study on User Plane Integrity Protection | Rel-17 |
| TS 33.861 vg10 | CIoT Security Evolution for 5G System | Rel-16 |
| TS 36.104 vj10 | Base Station (BS) radio transmission and reception | Rel-19 |
| TS 36.116 vj00 | E-UTRA Relay RF Requirements | Rel-19 |
| TS 36.117 vj00 | E-UTRA Relay RF Test Methods & Requirements | Rel-19 |
| TS 36.141 vj00 | E-UTRA BS Conformance Testing | Rel-19 |
| TS 36.201 vj00 | LTE Physical Layer General Description | Rel-19 |
| TS 36.212 vj10 | LTE Multiplexing and Channel Coding | Rel-19 |
| TS 36.300 vj00 | E-UTRAN Radio Interface Protocol Architecture Overview | Rel-19 |
| TS 36.302 vj00 | E-UTRA Physical Layer Services | Rel-19 |
| TS 36.331 vj00 | LTE RRC Protocol Specification | Rel-19 |
| TS 36.825 vd00 | Study on Additional LTE TDD Configurations | Rel-13 |
| TS 36.855 vd00 | E-UTRA Positioning Enhancements Study | Rel-13 |
| TR 36.902 v931 | SON Use Cases and Solutions for LTE | Rel-9 |
| TS 36.938 v900 | E-UTRAN to 3GPP2/Mobile WiMAX Mobility | Rel-9 |
| TS 37.104 vj10 | MSR Base Station RF Characteristics | Rel-19 |
| TS 37.141 vj10 | RF Test Methods for Multi-Standard Radio Base Stations | Rel-19 |
| TS 37.145 vj10 | AAS Base Station Conducted Conformance Testing | Rel-19 |
| TS 37.483 vj10 | E1 Application Protocol (E1AP) | Rel-19 |
| TS 37.802 va10 | MSR BS RF Requirements for Non-Contiguous Spectrum | Rel-10 |
| TS 37.812 vb30 | Multi-band Multi-standard Radio BS Requirements | Rel-11 |
| TR 37.900 vj00 | Multi-Standard Radio (MSR) Base Station Requirements | Rel-19 |
| TR 37.901 vf10 | UE Application Layer Data Throughput Performance | Rel-15 |
| TS 38.133 vj20 | 5G UE Radio Requirements for RRC_IDLE Mobility | Rel-19 |
| TS 38.174 vj10 | NR Integrated Access and Backhaul Radio Spec | Rel-19 |
| TS 38.176 vj20 | IAB Conformance Testing Specification | Rel-19 |
| TS 38.191 vj00 | NR Ambient IoT RF Characteristics | Rel-19 |
| TS 38.201 vj00 | NR Physical Layer General Description | Rel-19 |
| TS 38.212 vj10 | NR Multiplexing and Channel Coding | Rel-19 |
| TS 38.213 vj10 | NR Physical Layer Control Procedures | Rel-19 |
| TS 38.214 vj10 | NR Physical Layer Procedures for Data | Rel-19 |
| TS 38.300 vj00 | NG-RAN Overall Description | Rel-19 |
| TS 38.331 vj00 | NR Radio Resource Control (RRC) Protocol Specification | Rel-19 |
| TS 38.413 vj10 | NG Application Protocol (NGAP) | Rel-19 |
| TS 38.423 vj10 | Xn Application Protocol (XnAP) specification | Rel-19 |
| TS 38.463 vj00 | E1 Application Protocol (E1AP) | Rel-19 |
| TS 38.473 vj10 | 5G F1 Application Protocol (F1AP) | Rel-19 |
| TS 38.769 vk00 | Ambient IoT Solutions in NR | Rel-20 |
| TR 38.808 vh00 | Study on NR above 52.6 GHz to 71 GHz | Rel-17 |
| TS 38.811 vf40 | Study on NR Support for Non-Terrestrial Networks | Rel-15 |
| TR 38.812 vg00 | Study on NOMA for NR | Rel-16 |
| TR 38.859 vi10 | Technical Report | Rel-18 |
| TR 38.889 vg00 | NR-based access to unlicensed spectrum study | Rel-16 |
| TR 38.912 vj00 | Study on New Radio Access Technology | Rel-19 |
| TS 45.820 vd10 | CIoT for Internet of Things | Rel-13 |
| TS 45.860 vb50 | Precoded EGPRS2 Downlink Study | Rel-11 |