If there was an award for the technology with the highest ratio of hype to reality, cloud-native network functions would be a contender.

Network functions will inevitably make the transition to lightweight, agile containers that run in clouds. But that transition has been slow, because the technology isn't ready yet.

Few telcos have actually implemented containerized network functions (CNFs).

But you wouldn't know that from vendors, who churn out a torrent of press releases, white papers, PowerPoints, blog posts, videos and conference panels touting CNFs.

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The disparity between hype and reality could lead a telco exec to channel the spirit of Elvis Presley, crying out for "a little less conversation, a little more action please."

The Linux Foundation is looking to close the gap between conversation and action with new reference implementations to make it easier for carriers and vendors to deploy network functions in the cloud.

To understand containerized network functions, you need to first understand network functions virtualization (NFV). NFV replaces network hardware appliances with software -- including virtual network functions (VNFs) -- that runs on virtual machines (VMs) running on commodity hardware.

CNFs are like VNFs, but they run on lighter-weight containers, providing greater agility and ease of deployment compared with VMs. That lightweight implementation is useful throughout the network, but particularly so for edge applications and 5G network slicing.

Last year, an alliance of telcos and vendors launched the Common NFVi Telco Task Force (CNTT) for the purposes of simplifying NFV standards. The CNTT exists under the auspices of the Linux Foundation in partnership with the GSMA. The CNTT's mission is to ease the transition to NFV, and beyond NFV to CNFs, for network operators.

The CNTT plans to release a reference architecture for NFV Infrastructure (NFVi), running on virtual machines, in April, and follow up with a reference architecture for CNFs in October.

The NFVi reference architecture due in April will be dependent on OpenStack. "OpenStack is very stable and the vast majority of telecoms have a heavy investment in it," says Beth Cohen, Verizon cloud technology strategist, who is active on the CNTT. "They're not giving it up because it works. Telecoms are very conservative, and they're very dependent on working technology. We know OpenStack works."

And OpenStack will continue to have a future as CNFs gain ground. Containers can run on an OpenStack infrastructure, and vice versa; OpenStack can run on containers, notes Rabi Abdel, network virtualization and SDN/NFV lead architect at Vodafone Group, who is active on CNTT. "Containers and OpenStack aren't mutually exclusive. You can leverage both," he says.

Containers were designed for enterprise applications, and are widely deployed there. But they need to be more mature to be ready for telco networks, says Abdel. Containers need support for high network throughput, security, isolation and other telco needs.

Vendors are stepping up with one-off solutions to those problems, but these need to become widespread and standardized. The CNTT is developing those standards and implementations in partnership with the Open Platform for NFV (OPNFV) project, as well as the Cloud-Native Computing Foundation, both groups part of the Linux Foundation.

While reports of NFV's death are exaggerated, adoption has not been rapid. Instead, it's been slow but steady since NFV was proposed by a telco alliance more than seven years ago. Meanwhile, industry needs have changed, says Heavy Reading analyst Jennifer Clark. "It became clear working with virtual machines in NFV was not really going to work in a 5G environment, and where they really needed to go was toward containers, and cloud-native Kubernetes to manage those containers."

She adds, "Cloud-native is a requirement with 5G. When you move to a 5G core, it's cloud-native core. Especially as you start implementing network slicing and machine-to-machine communications."

While cloud-native telco adoption is slow, it's not sitting still. Most notably, AT&T is building its 5G network on OpenStack with a Kubernetes foundation, in a deal with Mirantis reported -- by Mirantis -- at eight figures in value.

Telefónica said nearly three years ago that it was implementing a microservices architecture -- synonymous with containers -- for its OnLife Networks, providing networking services, based on open source, for Spanish customers.

More recently, Mavenir demonstrated automated deployment of a cloud-native 5G core at MWC LA in October.

AT&T and Dell announced plans to collaborate on cloud-native network development in August, based on container lifecycle management software called "Airship."

And Verizon and Ericsson are partnering on cloud-native technology for live wireless core networks.

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— Mitch Wagner Executive Editor, Light Reading