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
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (37 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, key Control Plane enhancements were introduced to improve efficiency and reliability for CIoT and general operation. These included a new security mechanism for UE parameter updates via the UDM, specific procedures for control plane latency reduction, and corrections to the SERVICE ACCEPT handling and RRC Connection Re-establishment procedures for the control plane. The release also provided necessary corrections to the Control Plane protocol stacks and their descriptions.
- Security mechanism for UE Parameters Update via UDM Control Plane Procedure TS 33.501CR0484
- Control Plane latency reduction TS 36.331CR3453
- Correction on Control Plane protocol stacks TS 23.501CR0240
- Correction to SERVICE ACCEPT handling at control plane CIoT case TS 24.301CR2947
- Missing description of RRC Connection Re-establishment for the Control plane TS 36.300CR1094
- Correction to RRC Connection Re-establishment for the control plane TS 36.331CR3497
In Release 16, key enhancements to the Control Plane (CP) function focused on expanding and refining the Control Plane CIoT 5GS Optimisation. New capabilities included the introduction of data transfer and User Plane Forwarding within this optimisation, alongside support for Stateless IPv6 Address Autoconfiguration and its extension to NB-IoT and eMTC. The release also introduced clarifications and procedural handling for the Control Plane Only indicator, PDU session release, and interworking with EPS.
- Introduction of data transfer in Control Plane CIoT 5GS Optimisation TS 23.501CR0889
- User Plane Forwarding with Control Plane CIoT 5GS Optimisation TS 23.501CR0916
- Stateless IPv6 Address Autoconfiguration for Control Plane CIoT 5GS Optimisation TS 23.501CR1417
- Introduction of Control Plane CIoT 5GS Optimisation for NB-IOT and eMTC TS 38.413CR0173
- Corrections to Control Plane CIoT 5GS Optimisation description TS 23.501CR1580
- Control Plane CIoT 5GS Optimisations restriction on NR TS 23.501CR1690
+ 7 more changes
In Release 17, the Control Plane (CP) function saw enhancements for specific UE types and scenarios, including the introduction of procedures for RedCap UEs and Small Data Transmission (SDT). It also refined the Service Request procedure for MUSIM UEs using control plane CIoT EPS optimization and clarified security procedures for ProSe UE-to-Network Relay over the Control Plane. These updates provided corrections and clarifications to existing control plane mechanisms without altering the fundamental RRC sublayer definition or the defined RNTI types.
- Using Service Request procedure for removing paging restrictions in EPS for MUSIM UE that uses the control plane CIoT EPS optimization TS 24.301CR3564
- Clarification for ProSe UE-to-Network Relay security procedure over Control Plane TS 33.503CR0013
- Correction figure in ProSe UE-to-Network Relay security procedure over Control Plane in TS33.503 --> not implemented due to clash with 0012r1 (MCC) in the figure. TS 33.503CR0015
- Remote UE Report when security procedure over Control Plane is performed TS 33.503CR0026
- Corrections to control plane procedures for RedCap UEs TS 38.331CR3780
- Control plane corrections for SDT TS 38.331CR4114
In Release 18, the control plane was enhanced to support Lawful Interception (LI) for 5G Media Streaming (5GMS) services. It also provided clarifications for EAP message handling and control plane packets when a UE behind a 5G-RG accesses the 5G Core via a trusted non-3GPP network. Furthermore, updates were introduced for Proximity Services (ProSe), specifically regarding security for User-to-Network relay over the control plane.
In Release 19, key CP enhancements focused on corrections and refinements for CIoT EPS optimizations, specifically improving procedures for UE-initiated data transport, network negotiation, and the handling of the S&F wait time and T3440/T3448 timers. The release also introduced control plane protocol stacks for the MWAB node and defined peer remote UE control plane procedures for U2U Relays. Additionally, editorial corrections were made to the descriptions of NG Control Plane and Security handling in Control Plane CIoT 5GS Optimization.
- Control Plane and User Plane Protocol stacks involving the MWAB node TS 23.501CR5561
- Correction to T3440 timer handling with control plane data back-off timer T3448 TS 24.301CR4424
- Correction of UE initiated transport of user data via the control plane with overhead reduction TS 24.301CR4533
- Correction of S&F wait time duration in control plane CIoT EPS optimization with overhead reduction TS 24.301CR4538
- Correction of network procedures for negotiation of control plane CIoT EPS optimization with overhead reduction TS 24.301CR4623
- Correction for usage of EPS services with control plane CIoT EPS optimization and EPS services with control plane CIoT EPS optimization with overhead reduction TS 24.301CR4662
+ 3 more changes
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 |
