What is Control and User Plane Separation (CUPS)

Introduction

As mobile networks evolve to meet the demands of ultra-fast data, low latency, and massive device connectivity, the underlying architecture must also transform. One of the most significant innovations enabling this transformation is Control and User Plane Separation (CUPS). This architectural principle, which decouples the control plane from the user plane, is foundational to modern mobile networks—especially in the transition from 4G to 5G.

So, what is CUPS, and why does it matter? Traditionally, network nodes handled both control and user plane functions in a tightly integrated manner. The control plane manages signaling, session control, and mobility, while the user plane is responsible for forwarding user data packets. With CUPS, these functions are separated, allowing them to be deployed independently. This separation introduces a new level of flexibility and scalability, enabling operators to optimize network performance and resource allocation more effectively.

Why Was CUPS Introduced?

The introduction of Control and User Plane Separation (CUPS) was driven by the explosive growth in mobile data traffic, the rise of edge computing, and the need for more agile and cost-effective network deployments. In traditional 4G networks, control and user plane functions were tightly coupled within the same network nodes, such as the Serving Gateway (SGW) and Packet Data Network Gateway (PGW). While this design worked well in the early days of LTE, it began to show strain as mobile data consumption exploded. Key limitations included:

• Rigid Scaling: Operators had to scale both control and user plane resources together, even if only one needed expansion. This led to inefficient resource utilization and higher operational costs
• Centralized Processing: User data had to travel to centralized gateways, increasing latency—especially problematic for real-time applications like gaming, video conferencing, and IoT
• Limited Flexibility: The monolithic nature of 4G core components made it difficult to adapt to new services or deploy functions closer to the user
  
  

• Ultra-Low Latency: Applications like autonomous vehicles and industrial automation require end-to-end latency of less than 1 millisecond
• Massive Scalability: With billions of connected devices, networks must scale dynamically and efficiently
• Edge Computing: To meet latency and bandwidth demands, data processing must move closer to the user—at the network edge
• Network Slicing: 5G introduces the concept of creating multiple virtual networks on a shared infrastructure, each tailored to specific service requirements

• Independent Scaling: Operators can scale user plane functions in high-traffic areas without overprovisioning control plane resources
• Edge Deployment: User plane functions (UPFs) can be deployed at the edge to reduce latency and improve performance
• Cloud-Native Integration: CUPS aligns with cloud-native principles, supporting containerized deployments, microservices, and automation
• Service Agility: New services can be introduced faster, and network slices can be tailored with specific control and user plane configurations

To understand how CUPS meets these evolving demands, let’s look at how it functions within the network architecture. The introduction of CUPS was driven by the explosive growth in mobile data traffic, the rise of edge computing, and the need for more agile and cost-effective network deployments. By decoupling the control and user plane, operators can scale each independently, deploy user plane functions closer to the user for reduced latency, and support advanced capabilities like network slicing and cloud-native deployments.

How CUPS Works in Network Architecture

In a CUPS architecture, control plane functions such as the Session Management Function (SMF) handle session establishment, policy enforcement, and mobility management. Meanwhile, user plane functions (UPFs) are tasked with packet forwarding, traffic routing, and quality of service enforcement. These functions communicate over standardized interfaces, enabling seamless coordination while allowing for distributed deployment.

Benefits of Control and User Plane Separation

The benefits of this separation are substantial. Operators gain the ability to scale user plane resources in high-traffic areas without overprovisioning control plane capacity. Latency is reduced by deploying UPFs at the network edge, which is critical for applications like augmented reality, autonomous vehicles, and industrial automation. Additionally, CUPS supports cost efficiency by enabling targeted upgrades and deployments, and enhances network reliability by isolating failures within one plane from affecting the other.

Challenges and Considerations

However, implementing CUPS also introduces new challenges. Synchronization between control and user plane functions must be precise, and the increased number of interfaces can expand the network’s attack surface. Effective orchestration and management tools are essential to handle the added complexity, and ensuring interoperability between multi-vendor components remains a key consideration.

Axyom.Core’s Approach

That’s where Axyom.Core’s implementation of CUPS becomes especially relevant. Their architecture doesn’t just follow the standard—it’s built with the separation of control and user plane functions at its core. This design choice allows for a lot of flexibility in how and where different parts of the network are deployed. For example, user plane functions can be placed closer to the edge to reduce latency, while control functions can remain centralized for easier management. It’s a practical, forward-thinking approach that aligns well with the demands of modern 5G networks.

CUPS and the Path to 5G

CUPS is not just a 4G enhancement—it’s a foundational element of 5G architecture. In 5G, the Service-Based Architecture (SBA) further modularizes network functions, and CUPS enables network slicing, edge computing, and cloud-native deployments. The user plane in 5G is more dynamic and distributed than ever, and CUPS makes this possible by decoupling it from centralized control functions.

CUPS Use Cases

Here are some real-world scenarios where CUPS architecture shines:

• Smart Cities: Deploying user plane functions at the edge supports real-time traffic management, surveillance, and IoT applications
• Industrial IoT: Factories can host local UPFs to ensure ultra-low latency and high reliability for automation and robotics
• Content Delivery: Video streaming services benefit from edge-deployed UPFs that reduce buffering and improve user experience
• Private 5G Networks: Enterprises can deploy their own UPFs on-premises while relying on a centralized control plane managed by a service provider
  
  

Conclusion

Control and User Plane Separation (CUPS) is a transformative concept in mobile network architecture. By decoupling the control and user plane, CUPS enables more flexible, scalable, and efficient networks—paving the way for advanced 5G services and beyond. As data demands continue to grow and new use cases emerge, CUPS will remain a critical enabler of innovation in the telecom space. Whether you're a network architect, operator, or enterprise IT leader, understanding and leveraging CUPS architecture is essential for building the networks of the future.