Deploying distributed units at scale in a disconnected environment

Telco edge computing presents extraordinary challenges with managing hundreds to tens of thousands of clusters in hundreds of thousands of locations. These challenges require fully-automated management solutions with, as closely as possible, zero human interaction.

Zero touch provisioning (ZTP) allows you to provision new edge sites with declarative configurations of bare-metal equipment at remote sites. Template or overlay configurations install OKD features that are required for CNF workloads. End-to-end functional test suites are used to verify CNF related features. All configurations are declarative in nature.

You start the workflow by creating declarative configurations for ISO images that are delivered to the edge nodes to begin the installation process. The images are used to repeatedly provision large numbers of nodes efficiently and quickly, allowing you keep up with requirements from the field for far edge nodes.

Service providers are deploying a more distributed mobile network architecture allowed by the modular functional framework defined for 5G. This allows service providers to move from appliance-based radio access networks (RAN) to open cloud RAN architecture, gaining flexibility and agility in delivering services to end users.

The following diagram shows how ZTP works within a far edge framework.

ZTP uses the GitOps deployment set of practices for infrastructure deployment that allows developers to perform tasks that would otherwise fall under the purview of IT operations. GitOps achieves these tasks using declarative specifications stored in Git repositories, such as YAML files and other defined patterns, that provide a framework for deploying the infrastructure. The declarative output is leveraged by the Open Cluster Manager for multisite deployment.

One of the motivators for a GitOps approach is the requirement for reliability at scale. This is a significant challenge that GitOps helps solve.

GitOps addresses the reliability issue by providing traceability, RBAC, and a single source of truth for the desired state of each site. Scale issues are addressed by GitOps providing structure, tooling, and event driven operations through webhooks.

You can install a distributed unit (DU) on a single node at scale with Red Hat Advanced Cluster Management (RHACM) (ACM) using the assisted installer (AI) and the policy generator with core-reduction technology enabled. The DU installation is done using zero touch provisioning (ZTP) in a disconnected environment.

ACM manages clusters in a hub and spoke architecture, where a single hub cluster manages many spoke clusters. ACM applies radio access network (RAN) policies from predefined custom resources (CRs). Hub clusters running ACM provision and deploy the spoke clusters using ZTP and AI. DU installation follows the AI installation of OKD on a single node.

The AI service handles provisioning of OKD on single nodes running on bare metal. ACM ships with and deploys the assisted installer when the MultiClusterHub custom resource is installed.

With ZTP and AI, you can provision OKD single nodes to run your DUs at scale. A high level overview of ZTP for distributed units in a disconnected environment is as follows:

ACM deploys single-node OpenShift, which is OKD installed on single nodes, leveraging zero touch provisioning (ZTP). The initial site plan is broken down into smaller components and initial configuration data is stored in a Git repository. Zero touch provisioning uses a declarative GitOps approach to deploy these nodes. The deployment of the nodes includes:

You use zero touch provisioning (ZTP) to deploy single-node OpenShift clusters to run distributed units (DUs) on small hardware footprints at disconnected far edge sites. A single-node cluster runs OKD on top of one bare-metal host, hence the single node. Edge servers contain a single node with supervisor functions and worker functions on the same host that are deployed at low bandwidth or disconnected edge sites.

OKD is configured on the single node to use workload partitioning. Workload partitioning separates cluster management workloads from user workloads and can run the cluster management workloads on a reserved set of CPUs. Workload partitioning is useful for resource-constrained environments, such as single-node production deployments, where you want to reserve most of the CPU resources for user workloads and configure OKD to use fewer CPU resources within the host.

A single-node cluster hosting a DU application on a node is divided into the following configuration categories:

Site planning for distributed units (DU) deployments is complex. The following is an overview of the tasks that you complete before the DU hosts are brought online in the production environment.

Low latency is an integral part of the development of 5G networks. Telecommunications networks require as little signal delay as possible to ensure quality of service in a variety of critical use cases.

Low latency processing is essential for any communication with timing constraints that affect functionality and security. For example, 5G Telco applications require a guaranteed one millisecond one-way latency to meet Internet of Things (IoT) requirements. Low latency is also critical for the future development of autonomous vehicles, smart factories, and online gaming. Networks in these environments require almost a real-time flow of data.

Low latency systems are about guarantees with regards to response and processing times. This includes keeping a communication protocol running smoothly, ensuring device security with fast responses to error conditions, or just making sure a system is not lagging behind when receiving a lot of data. Low latency is key for optimal synchronization of radio transmissions.

OKD enables low latency processing for DUs running on COTS hardware by using a number of technologies and specialized hardware devices:

Distributed unit (DU) hosts require the BIOS to be configured before the host can be provisioned. The BIOS configuration is dependent on the specific hardware that runs your DUs and the particular requirements of your installation.

Before you can provision distributed units (DU) at scale, you must install Red Hat Advanced Cluster Management (RHACM), which handles the provisioning of the DUs.

RHACM is deployed as an Operator on the OKD hub cluster. It controls clusters and applications from a single console with built-in security policies. RHACM provisions and manage your DU hosts. To install RHACM in a disconnected environment, you create a mirror registry that mirrors the Operator Lifecycle Manager (OLM) catalog that contains the required Operator images. OLM manages, installs, and upgrades Operators and their dependencies in the cluster.

You also use a disconnected mirror host to serve the FCOS ISO and RootFS disk images that provision the DU bare-metal host operating system.

Before you install a cluster on infrastructure that you provision in a restricted network, you must mirror the required container images into that environment. You can also use this procedure in unrestricted networks to ensure your clusters only use container images that have satisfied your organizational controls on external content.