CUPS (Control and User Plane Separation (EPC nodes))

CUPS, which stands for Control and User Plane Separation, is an architecture used in 4G and 5G networks that separates the control and user planes in the Evolved Packet Core (EPC) nodes. This separation allows network operators to dynamically allocate resources, improve network scalability, and provide better Quality of Service (QoS) to end-users.

In this article, we'll dive into the details of CUPS, including its benefits, components, and implementation challenges.

Benefits of CUPS

CUPS brings several benefits to mobile network operators (MNOs) and end-users. Here are some of the most important ones:

Scalability and Resource Optimization

CUPS enables network operators to dynamically allocate resources between the control and user planes, based on network traffic and resource utilization. This allows MNOs to optimize their network resources and improve scalability, especially during periods of high traffic.

Improved QoS

By separating the control and user planes, CUPS allows MNOs to provide better QoS to their customers. For example, network operators can prioritize the control plane traffic over the user plane traffic to ensure that signaling messages are delivered in a timely manner.

Network Slicing

CUPS enables network slicing, which allows MNOs to create multiple virtual networks on top of a single physical network. Each virtual network can have its own control and user plane, allowing MNOs to offer customized services to different customer segments.

Network Evolution

CUPS is an important step towards the evolution of the EPC architecture. By separating the control and user planes, CUPS enables MNOs to introduce new services and applications more easily, without disrupting the existing network.

CUPS Architecture

The CUPS architecture consists of two main components: the Control Plane (CP) and the User Plane (UP).

Control Plane (CP)

The Control Plane is responsible for managing network resources and signaling between the network elements. It includes the Mobility Management Entity (MME), the Serving Gateway (SGW), and the Packet Data Network (PDN) Gateway.

The MME is responsible for authenticating and tracking the location of the user equipment (UE) and is the control point for mobility between base stations. The SGW acts as the anchor point for the user plane traffic and is responsible for routing traffic between the UE and the PDN Gateway. The PDN Gateway provides access to external networks, such as the Internet or corporate networks.

In the CUPS architecture, the Control Plane can be further divided into two parts: the Centralized Control Plane (CCP) and the Distributed Control Plane (DCP).

The CCP includes the MME, which performs the centralized control functions, such as policy and charging control, authentication, and mobility management. The DCP includes the SGW and the PDN Gateway, which perform the distributed control functions, such as user plane data forwarding and IP address allocation.

User Plane (UP)

The User Plane is responsible for forwarding data packets between the UE and the external networks. It includes the Data Plane Function (DPF) and the User Plane Function (UPF).

The DPF is responsible for handling the packet processing, such as packet filtering and forwarding. The UPF is responsible for managing the user plane traffic and forwarding the packets to the appropriate external network.

In the CUPS architecture, the User Plane can be further divided into two parts: the Centralized User Plane (CUP) and the Distributed User Plane (DUP).

The CUP includes the DPF and the UPF, which are both located in the centralized part of the network. The DUP includes the UPF, which is located at the edge of the network, close to the UE.

CUPS Implementation Challenges

Implementing CUPS in a mobile network is not without its challenges. Here are some of the most common implementation challenges:

Complexity

CUPS introduces a higher level of complexity to the network architecture, which can make it more difficult to manage and troubleshoot. Network operators need to have a deep understanding of the different components and their interactions to ensure that the network operates correctly.

Interoperability

CUPS requires interoperability between different network elements, which can be challenging to achieve, especially when using equipment from multiple vendors. Network operators need to ensure that all the components work together seamlessly to provide the expected functionality.

Performance

CUPS can have a significant impact on network performance, especially if the network is not properly dimensioned or if the resources are not allocated correctly. Network operators need to carefully plan and test the network to ensure that it can handle the expected traffic volumes.

Security

CUPS introduces new security challenges, such as the need to secure the interfaces between the different components and to protect the network against attacks on the control plane. Network operators need to implement appropriate security measures to ensure the integrity, confidentiality, and availability of the network.

CUPS and 5G

CUPS is an essential component of the 5G network architecture, as it enables the network to scale and evolve to meet the demands of new use cases and applications. 5G networks are designed to support a wide range of use cases, from enhanced mobile broadband to mission-critical services and massive IoT.

In the 5G network architecture, the CUPS concept is extended to include the Distributed Unit (DU) and the Centralized Unit (CU). The DU is responsible for the lower layers of the protocol stack, while the CU is responsible for the upper layers.

The DU and the CU can be deployed in different configurations, depending on the network topology and the service requirements. For example, in a standalone (SA) 5G network, the DU and the CU can be deployed together in the same location, while in a non-standalone (NSA) network, the DU can be deployed in the radio access network (RAN) and the CU in the core network.

Conclusion

CUPS is a critical component of the EPC and 5G network architectures, as it enables network operators to dynamically allocate resources, improve network scalability, and provide better QoS to end-users. However, implementing CUPS can be challenging, due to the complexity, interoperability, performance, and security requirements.

Network operators need to carefully plan and test the network to ensure that it can handle the expected traffic volumes and provide the expected functionality. As 5G networks continue to evolve, CUPS will play an increasingly important role in enabling new use cases and applications.