In early 2020, as COVID-19 was limbering up and Huawei-bashing was all the rage, Deutsche Telekom boss Timotheus Höttges told analysts that he was ejecting the Chinese vendor from the cockpit of his German network. "We are working towards a Chinese-free core network infrastructure," he said during the operator's earnings call for its first quarter.

The move was identical to the decision taken by the UK's BT to remove Huawei and switch to a core network provider deemed safer by security watchdogs. Yet while BT eventually outed Ericsson as its new vendor, the identity of Deutsche Telekom's substitute remained undisclosed. Confidential sources pointed to Mavenir, a US software developer, but Germany's biggest operator politely declined to comment.

Figure 1: Deutsche Telekom CEO Timotheus Höttges has been aiming for a 'Chinese-free core.'
(Source: Deutsche Telekom)

Confirmation of Mavenir as a likely Huawei replacement in Germany finally came this week. According to a statement issued by Mavenir, its technology will be used to power a new "standalone" version of 5G that Deutsche Telekom is currently deploying. Pointedly described as a "converged" core, it will also be capable of supporting older 4G services as well as the "non-standalone" 5G services that Deutsche Telekom has already launched.

This could be a big deal for Mavenir, which is typically portrayed as a vendor of open RAN software but seems likely to generate most of its roughly $600 million in annual revenues from other activities. It would probably have faced competition for the Deutsche Telekom work from giant telecom vendors such as Ericsson and Nokia, not to mention the array of IT firms and smaller specialists touting for jobs in a market worth approximately $8 billion in annual sales. As Europe's biggest telco, Deutsche Telekom is a customer that Mavenir would be eager to show off.

No easy migration

What is not said in Mavenir's statement is how quickly Deutsche Telekom might shift to the new core. Deploying standalone is not straightforward, according to executives at BT and Vodafone, especially if an operator is designing its network to be fully "cloud-native." This appears to be the case with Deutsche Telekom, which is to run Mavenir's core on top of a Kubernetes platform, an orchestration system based on open-source code.

BT, which is embracing cloud-native technology as it deploys a standalone Ericsson core, does not think it will be able to switch off the old Huawei core until next year (the UK government deadline for removing any core network products supplied by Chinese vendors). With millions of mobile customers in the UK, BT has currently migrated only about 1 million of them to the Ericsson platform, the company acknowledged during a press conference last week.

On standalone, Deutsche Telekom looks even further behind. Currently, it is using Mavenir's technology only in what a spokesperson calls "friendly user trials." Having commissioned its first standalone 5G site (in Garching, near Munich) as recently as last year, it does not intend to launch commercially before the customer benefits are more obvious and "enough devices" can support standalone technology.

But Mavenir is not the only non-Chinese core network vendor in the mix. Quizzed by Light Reading, Deutsche Telekom named Ericsson as its "main partner" on 4G and 5G core technology, suggesting it has already made some progress on replacing Huawei. "As Deutsche Telekom is pursuing a multi-vendor strategy, this means the new 5G SA [standalone] core is built together with other US and European partners as well," said a spokesperson via email. "So, we are dealing with new 5G SA core and an existing 4G/5G core. Both will converge in the future."

Slicing and security

In its most recent annual report, Deutsche Telekom noted that its standalone 5G site in Garching integrates the core with the radio access network (RAN). Dispersing the core across various locations in this manner should help to reduce latency, which might otherwise disrupt more advanced applications like virtual-reality gaming. More prosaically, but no less importantly, standalone would also remove the need for a device to connect to 4G as well as 5G, freeing up resources.

Standalone also promises features like network slicing, which should (in theory) allow an operator to reserve capacity for specific applications or user groups and provide quality-of-service guarantees. It is a controversial technique. For one thing, it appears to clash with more rigorous interpretations of net neutrality, the somewhat hazy principle that all Internet traffic be treated equally. Nor is the analyst community entirely sold on its usefulness.

"I am less convinced about slicing as a mechanism to segregate traffic by quality-of-service levels," said Ruth Brown, an analyst at Heavy Reading, in a recent article for Light Reading. Traffic flows could have bit rate or latency guarantees without slicing, even though it could help to isolate critical and security-sensitive services, Brown argues.

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Deutsche Telekom, nevertheless, is talking up an initial network slicing use case that would target live video broadcasting. "Our services are developed in accordance with legal requirements and comply in particular with the provisions of the TSM Regulation (Telecom Single Market Regulation)," said Deutsche Telekom's spokersperson.

Another plus for the operator is the automation that standalone would support. A platform that can automatically synchronize resources and do configuration with "changes expressed in code" would be less prone to human error, according to the operator.

It could bring a different set of challenges, though. "Human error is a big source of problems, but hacked software is also a big source of problems, so you are trading one for the other," said Karsten Nohl, a German security expert who thinks the open-source code used in highly automated, cloud-native networks provides an opportunity for cybercriminals. Security Research Labs, Nohl's company, is hired by organizations to hack their networks and expose vulnerabilities before any real damage can be done.

Deutsche Telekom's annual report commentary about integrating the 5G core with the RAN could also prompt security concerns. While he has been phasing Huawei out of the core, Höttges has no apparent plans to scrap the Chinese vendor's RAN technology. According to estimates by Strand Consult, a Danish advisory firm, Huawei's 4G radios have historically been used across about two-thirds of Deutsche Telekom's German mobile sites. Swapping those would be a much costlier job than replacing Huawei in the core.

UPDATE: This story has been modified since it was first published to incorporate feedback from Deutsche Telekom.

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— Iain Morris, International Editor, Light Reading