Control and User Plane Separation of EPC nodes (CUPS).
CUPS being the 3GPP Relase 14 standards, but most fundamental aspect in evolution of Next Generation Networks Architecture, As we since last 3-4 years have been in continuous support of complete separation of control and user plan for bringing capability in network for required flexibility in terms of service creation and required scalability.
Though all IP paradigm shif since the inception of 4G has taken the first step towards it but recent advancement on virtualisation like of cloud and NFV has taken the troll ahead.
in terms of 3GPP word..
CUPS stands for ontrol and ser lane eparation of EPC nodes and provides the architecture enhancements for the separation of functionality in the Evolved Packet Core’s SGW, PGW and TDF. This enables flexible network deployment and operation, by distributed or centralized deployment and the independent scaling between control plane and user plane functions - while not affecting the functionality of the existing nodes subject to this split.
CUPS allows for:
- Reducing Latency on application service, e.g. by selecting User plane nodes which are closer to the RAN or more appropriate for the intended UE usage type without increasing the number of control plane nodes.
- Supporting Increase of Data Traffic, by enabling to add user plane nodes without changing the number of SGW-C, PGW-C and TDF-C in the network.
- Locating and Scaling the CP and UP resources of the EPC nodes independently.
- Independent evolution of the CP and UP functions.
- Enabling Software Defined Networking to deliver user plane data more efficiently.
Architecture principles (Working Group SA2)
The following high-level principles were adopted:
- The CP function terminates the Control Plane protocols: GTP-C, Diameter (Gx, Gy, Gz).
- A CP function can interface multiple UP functions, and a UP function can be shared by multiple CP functions.
- An UE is served by a single SGW-CP but multiple SGW-UPs can be selected for different PDN connections. A user plane data packet may traverse multiple UP functions.
- The CP function controls the processing of the packets in the UP function by provisioning a set of rules in Sx sessions, i.e. Packet Detection Rules for packets inspection, Forwarding Action Rules for packets handling (e.g. forward, duplicate, buffer, drop), Qos Enforcement Rules to enforce QoS policing on the packets, Usage Reporting Rules for measuring the traffic usage.
- All the 3GPP features impacting the UP function (PCC, Charging, Lawful Interception, etc) are supported, while the UP function is designed as much as possible 3GPP agnostic. For example, the UPF is not aware of bearer concept.
- Charging and Usage Monitoring are supported by instructing the UP function to measure and report traffic usage, using Usage Reporting Rule(s). No impact is expected to OFCS, OCS and the PCRF.
- The CP or UP function is responsible for GTP-u F-TEID allocation.
- A legacy SGW, PGW and TDF can be replaced by a split node without effecting connected legacy nodes.
Protocol Design (Working Group CT4)
- ease of implementation on simple forwarding devices,
- no transport Head-Of-Line blocking,
- low latency,
- capabilities to support all the existing 3GPP features
- ease to extend and maintain the protocols to support 3GPP features,
- backward compatibility across releases