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Thursday, 11 November 2021

Network Slicing using User Equipment Route Selection Policy (URSP)

Google announced that its latest smartphone OS will include support for 5G network slicing. Last week Telecom TV brought this news to my attention. The article explains:

It's a move designed to leverage its expertise in devices in order to give it the edge over its rival hyperscalers.

It comes in two flavours. The first is for enterprise-owned handsets, and routes all data sent and received by a device over the network slices provided by that company's mobile operator. Android 12 gives operators the ability to manage slices using a new dynamic policy control mechanism called User Equipment Route Selection Policy (URSP). URSP enables devices to automatically switch between different network slices according to which application they are using. For example, someone working for a financial institution might require a highly-secure network slice for sending and receiving sensitive corporate data, but will then require a reliable, high-throughput, low-latency slice so they can participate in a video meeting.

The second flavour is implemented in the work profile. For years, enterprises have had the option of creating work profiles on Android devices – irrespective of whether they are owned by the organisation or the individual – to use as a separate repository for enterprise apps and data. When Android 12 comes out next year, enterprises will be able to route data to and from that repository over a network slice.

Google said it has already carried out network slicing tests with both Ericsson and Nokia using test versions of its recently released Pixel 6 smartphone running on the as-yet-unreleased Android 12 OS.

Last week Taiwanese operator Far EasTone (FET) and Ericsson announced they have completed the world’s first proof of concept (PoC) for simultaneously connecting multiple network slices per device running on Android 12 commercial release. The press release said:

The trial, carried out on FET’s 5G standalone (SA) infrastructure built on Ericsson’s radio access network and cloud-native Core network, successfully demonstrated the 5G user equipment slicing policy feature (User Equipment Route Selection Policy, or URSP) on multiple Android devices. This marks a breakthrough in network slicing capabilities on a 5G standalone network and paves the way for further ecosystem development in this important area.

With more 5G networks evolving to standalone architecture around the globe, end-to-end network slicing, which includes Ericsson RAN Slicing to secure Quality of Service (QoS) differentiation, plays a key role in enabling new services for end users, with which multiple virtual 5G networks are created on top of one physical network. The 5G trial, in collaboration with FET, Ericsson and Android, went even further in network slicing capabilities by introducing and demonstrating 5G user equipment (UE) slicing policy (URSP) features that allow devices to simultaneously operate on dynamic policy control and selection between multiple 5G network slices. This enables the steering of applications and services with specific requirements to defined slices without switching devices.

Multiple slices allow devices to have multiple profiles to secure different levels of experience, security, and privacy requirements, based on the needs of the different applications and in correspondence with the user profile.  For instance, a device can have a personal profile with private data from apps or off-work entertainment, and a work profile with enterprises productivity apps. With URSP features, employers can customize the work profile with increased security and enable better use of RAN Slicing with QoS so that enterprise-related apps can work even during network congestion.

Some security-sensitive apps, such as mobile banking, can also benefit from different routing mechanisms of the traffic enabled by URSP. For instance, the banking app would not need to send its traffic to the internet and then to the app server as it does today. Instead, it could go straight to the app server and avoid the routing through internet. With the shortest route by connecting to a defined slice, users could reduce the risk of being attacked by hackers.

In their technical whitepaper on Network Slicing, Samsung explains: 

Along with the concept of network slicing and features in the RAN and Core network, UE Route Selection Policy (URSP) is introduced as a way to manage network slice information for the UE. URSP is a network slice feature enabled by the PCF which informs the network slice status to the UE via the AMF. In 4G network systems, it was near impossible to install new services in the network for a UE. But through the URSP feature, 5G network operators can easily configure new service for a UE. Figure 12 (top of this blog post) shows the difference in network slice selection in 4G and 5G Network. In 5G network, slice selection policy can be configured dynamically through URSP, while slice selection policy is pre-defined and cannot be changed dynamically in 4G network.

URSP contains OSId, AppId, IP descriptors to define the application and Single-Network Slice Selection Assistance Information (S-NSSAI), Data Network Name (DNN), Session and Service Continuity (SSC) mode information for the application and network slice mapping.

The S-NSSAI identifies each network slice service and provides information to properly assign network slice/functions. An S-NSSAI is comprised of:

  • A Slice/Service type (SST), which refers to the expected network slice behavior in terms of features and services;
  • A Slice Differentiator (SD), which is an optional information that complements the Slice/Service type(s) to differentiate amongst multiple network slices of the same Slice/Service type.

3GPP allows the use of the Slice Differentiator (SD) field that can build customized network slices. The SD field can be used to describe services, customer information and priority.

Here is a short video from Mpirical explaining 5G UE Route Selection.

It it worth reminding here that this feature, like many of the other 5G features, is dependent on 5G Core. We hope that the transition to 5G Standalone Networks happens as soon as possible.

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