Key Principles for Designing a 5G Packet Core

Cloud-native will be the winning approach for 5G packet cores.

May 25, 2021

4 Min Read
Key Principles for Designing a 5G Packet Core

5G is the first truly multiservice network. Thus, as well as needing to be very reliable, it needs to be extremely flexible and scalable. In order to accomplish this the core must be architected to support many different configurations. Multi-access edge computing (MEC) will be important for distributing specific core processes close to the end device to achieve low-latency, industrial automation use cases.

Disaggregation and micro-services within the packet core

Cloud-native architectures are ideally suited to distributed web applications that need to scale very fast, usually being built on Kubernetes (K8s) using containers and micro-services. The packet core fits this profile, but there are some key differences from the architecture of webscale applications that relate to the architecture of mobile networks and the unique needs of the packet core.

The key benefit of cloud-native packet core applications is their ability to efficiently use the underlying compute and storage resources. This is best accomplished by breaking down functions into the smallest parts so that when scaling needs to happen quickly, only those functions that are needed are scaled up.

For instance, key parts of the cloud-native packet core that can be distributed involve the separation of the control and user planes (CUPS). There are certain services that demand very little from the user plane but a lot from the control plane. A micro-services architecture can re-allocate resources to the control plane or to the user plane dependent on the service.

Containers are the most efficient way to package micro-services. Unlike virtual machines (VMs), containers leverage host OS functions. This means they take up less memory than VMs and spin-up faster for scaling and healing.

Containers are also very portable. A cloud-native network function (CNF) can run seamlessly in a multiple environments, and their associated workloads are easy to redistribute onto private, public or hybrid clouds.

Maximising throughput and minimizing latency

Typical packet core network gateway implementations require external elements for frequently used IP services. Some examples of these IP services are deep packet inspection (DPI), firewall (FW) and network address translation (NAT).

The majority of data traffic requires these IP services. If external to the packet core gateway, packets need to be pulled from and put back into separate network elements resulting in increased processing and additional latency.

Packet core architectures with an ultra-low latency gateway with integrated IP services minimize latency, eliminate function-to-function traffic and reduce server footprint as packets only need to be processed once.

Deployment flexibility

Packet cores must be able to scale to support huge capacities, with large deployments having the ability to scale to over 1Tbps. Highly distributed deployments at the edge of the network (for example, MEC) are at the opposite end of the scale, mandating a small server footprint.

Minimal server footprint deployments must still provide impressive throughput capabilities. For example, a fully functional 5G user plane function (UPF) should deliver over 5 Gb/s of throughput with all the integrated IP services previously described.

Maintaining state in a cloud-native packet core

For maximum flexibility, it is ideal in micro-services architectures that entities be state-efficient. However, the state of some entities must be preserved. For instance, in the packet core control plane, individual subscriber sessions must be processed according to 3GPP standards, which requires the caching of session states during processing and then the storing of that state information.

The data store must be optimized to work with temporary caching, which allows efficient transaction processing at high rates, while optimizing redundancy and scaling operations by preserving state information to process future subscriber transactions.

Managing multi-generational networks and protocols

Unlike webscale services, CSPs are not building their cloud-native cores in a greenfield scenario. Most CSPs are still running 2G, 3G and 4G services today. It makes more sense to use a common core platform to run these multi-generational services.

When a multi-generational packet core is deployed within a K8s environment, functions for tunneling and packet forwarding will be needed, as well as authentication, authorization and accounting. The packet core also needs to support multiple network interfaces, preserve source and destination IP addresses and have the ability for canary-style upgrades.

Harnesses innovation

You should evaluate vendors based on the degree to which they have combined cloud-native principles into their core network design. The shift to 5G is both incremental and a step-change at the same time. On the one hand, there is a great deal of continuity between 4G and 5G. But on the other hand, it is a massive cultural transformation to leverage the efficiencies of the webscale way of working. Find competitive differentiation in the speed and rapidity with which you innovate, leveraging the larger community to build solutions faster to meet differing customer needs. Cloud-native will be the winning approach for 5G packet cores.

Want to know more? Visit our Cloud Packet Core solutions page to see how our cloud-native features and capabilities help you deploy a webscale-class packet core.

— Robert McManus, Senior Product Marketing Manager, Nokia

This content is sponsored by Nokia.

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