Three UK’s cloud core plans

Three has a shiny new 4G and 5G NSA core that it says will give it the ability to differentiate the customer 5G experience, as well as the ability to upgrade quickly to a full 5G Core.

Three UK has announced that it will have all its consumer customers migrated to an all new 4G and 5G NSA core, built on a distributed cloud platform, from September. The cloud core network will handle 5G NSA core functionality for Three customers in time with Three’s 5G launch in August. Three has already begun connecting 4G customers to the new core, and will step that up so that the cloud core is handling all its customers before the end of September.

Three has built a greenfield cloud core solution, with the project being managed by Nokia, which is also supplying most of the core network elements and cloud management.

The operator said the new build gives it far greater capacity and reliability, and also greater business and operational flexibility. It also enables it to reduce its go to market timescales on new products and services.

Three has rolled out its core in hosted cloud data centres at 20 sites across the country, as opposed to the prior arrangement of three centralised data centres that it managed and owned itself.

Mike Eales, Head of Network Services Strategy and Architecture, Three UK, said that the 20 new data centre sites break down into three types. Three larger sites handle control plane functions and subscriber data, a mid tier handles peering connections at sites where Three is co-located with those partners, and then sites further out to the edge provide core functions in an aggregated manner to clusters of cell sites to optimise backhaul costs. The edge sites are hosted datacentre sites, and not deployed within Three’s own estate or Central Office-type locations.

Across its cloud base it has deployed about 50 Virtual Network Functions (VNFs) so far. The software has been architected to be cloud native – that is, the functions can all be deployed on common infrastructure, and services access functions within a service based architecture. As yet, the functions themselves do not access a common abstracted data layer; Subscriber Data Management has not yet been ported to the cloud platform. But that is the plan as soon as that capability is available from Nokia, according to Tim Boyd, Director of Business Transformation, Three UK.

That would enable the stateless operations that many identify as a true cloud-native capability. Boyd added that the introduction of decomposed functions, deployed as microservices across the common, distributed architecture, is also on the roadmap. “We must walk before we run,” he said, “even if we are going at a swift walk.”

Boyd also said that the operator was still maturing towards having an overall orchestration capability that manages virtualised resources in its common cloud in an automated manner. Boyd: “The ability to have an OSS layer on top of the network that orchestrates something downwards and spins up new capacity as required and so on… we are on a path to that level of maturity. In any case the use cases are not there on day one. Although having said that, inside the core we already have some use cases on failover scenarios, for example.”

Three’s existing 4G core from Samsung will be decommissioned entirely, but some elements of its 3G core will be maintained until the operator has switched off 3G. The pace of that switch off will be in part dictated by the device base supporting VoLTE – so that the operator no longer needs to provide a circuit switched voice layer. Already, as the operator upgrades its cell sites, it is refarming 10MHz of its 15MHz 3G spectrum for 4G, leaving just the 5MHz carrier for 3G legacy.

Three’s Cloud Native core set-up

Three is using Nokia’s Nuage for its SDN control, Nokia CloudBand for its cloud management, and Nokia’s implementation of Red Hat’s OpenStack distribution for the virtualisation layer.

Although Nokia is the lead partner and provider, Affirmed Networks is providing a traffic management function within the core, Mavenir a messaging function, Mycom is providing cloud-based service assurance and EXFO an analytics and monitoring function.

That means that to some extent the operator is managing a multi vendor environment, with functionality from three core VNF vendors, and assurance and monitoring from others, aside from Nokia’s overall integration and technology provision. The other VNF providers deploy to the cloud platform using Nokia APIs that are a customised version of ETSI NFV ISG specifications, Boyd said. “It’s not impossible, at all,” Eales said.

As the company migrates from its NSA 5G core to a 5G or ngCore that can enable Standalone mode, it retains the ability to deploy 5G core functions from a variety of vendors. “We’ll talk soon about Standalone,” said Boyd, “but being open is a real advantage for us because we will not have to re-architect the network. And any vendor that works with us will have to be open.”

One element that doesn’t look very “cloud native” is the commercial relationship between Nokia and Three. Boyd didn’t want to get into any specifics, but he did say, “We haven’t adopted a cloud payment model.”

Fran Heeran, Senior Vice President, Core Services & Care, Nokia, was on duty as Nokia spokesperson at a press event in London. Before joining Nokia, Heeran had been heading up Vodafone’s move to a cloud platform at Group Level. At Vodafone he had previously expressed frustrations at the slowness of the industry to get to true cloud native support in software, versus vertical software instance virtualisation. 

So how does he see what Three is doing compared to what he was trying to achieve at Vodafone? 

Heeran said that cloud native capability has “dramatically improved” from 18 months ago, when he admitted his frustration at the inability of telco vendors to “play in a cloud environment”. Now he is back at a telco vendor, he said he thought that things had got better partly as a result of industry standards maturing, but also an improvement in the business cases for vendors to re-architect their software.

Heeran said, “Without going into specifics about Vodafone, in a more general context one of the biggest industry challenges has been to move from an application-centric view of silos into the horizontal, cloud native way of working. Making that leap from scratch and building a fresh cloud is something we see larger carriers doing… but not many.”

Boyd said that the decision to go for a greenfield deployment rather than a migration of the existing core was in part a result of low investment in the 4G core over the past 2-3 years, meaning that a full scale overhaul was a valid option.

5G use cases

Boyd said that the demographics of Three’s customer base meant that it had to be ready to support cloud gaming early.

“We are the data network and our customer base is gaming focussed. What we have deployed allows us a way to manage that and give a great experience. It could be the first example of our differentiation,” he said.

He also identified private networks – provided with a slice of the core network – as a good candidate use case for a cloud core that can enable network slicing. That could be deployed alongside mmWave rollouts that Boyd said may happen “sooner than people are expecting”.