Evolution of CUPS in 3GPP Networks

SGSNs of 2G days brought their fair share of interesting problems to deal with. One of those complains you would regularly hear from your customers was “Your SGSN is not able to achieve the capacity you promised”

SGSN capacity planning was an extremely complex exercise, and involved extensive capacity benchmarking against hundreds of parameters by quality assurance teams. SGSNs of those days were designed to be the centre of both signalling and data-paths in 3gpp networks, and did ciphering too, thus reducing the overall SGSN capacity drastically. It was always difficult to estimate the right mix of different types of signalling events, packet-sizes and the ciphering algorithms used by UEs in real networks; and at some time or other, estimations failed and SGSNs in field ran out of capacity.

On top of this, operators mostly ended up having a higher per-user network cost due to presence to two nodes (SGSN and GGSN) handling data. That’s because, even as same data that passed through SGSN and then GGSN, operator had to buy capacity on both the nodes separately. This was especially true if an operator decided to buy SGSNs and GGSNs from different vendors.

And that’s how, for me, the need of CUPS was born. CUPS stands for “Control and User Plan Separation”, and has been touted as one of the fundamental design aspect of 5G networks. In this blog, I intend to summarise evolution of CUPS and the resulting packet core architectures across various 3GPP releases, and how I view the road ahead.


LinkedIn (to continue reading): https://www.linkedin.com/pulse/evolution-cups-3gpp-networks-varini-gupta/

CUPS means Control and User Plane Separation 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.

Why CUPS Architecture Required?

  • Large Volume Data Support: Mobile operator’s user data traffic has been doubling on an annual basis in recent years. The reasons for this growth in traffic are the rapidly increasing use of smart devices, the proliferation of video and other applications that they support and the use of USB modem dongles & personal hot-spots using cellular networks.
  • Rich Communication Services (RCS): The penetration of mobile terminals is increasing worldwide and the interest in content-rich multi-media services (e.g. OTT video streaming services, Person to person video, content sharing) rising, this trend of rapidly increasing data traffic is expected to continue and accelerate.
  • Customer Experience and Low Latency : There is a strong consumer demand for user experience improvements, with lower latency being one of the critical KPIs to be met on the way.

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