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Use zero touch provisioning (ZTP) to provision distributed units at new edge sites in a disconnected environment. The workflow starts when the site is connected to the network and ends with the CNF workload deployed and running on the site nodes.

Provisioning edge sites at scale

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 in a far edge framework

About ZTP and distributed units on OpenShift clusters

You can install a distributed unit (DU) on OKD clusters at scale with Red Hat Advanced Cluster Management (RHACM) 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.

RHACM manages clusters in a hub-and-spoke architecture, where a single hub cluster manages many spoke clusters. RHACM 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 each cluster.

The AI service handles provisioning of OKD on single node clusters, three-node clusters, or standard clusters running on bare metal. ACM ships with and deploys the AI when the MultiClusterHub custom resource is installed.

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

  • A hub cluster running Red Hat Advanced Cluster Management (RHACM) manages a disconnected internal registry that mirrors the OKD release images. The internal registry is used to provision the spoke clusters.

  • You manage the bare metal host machines for your DUs in an inventory file that uses YAML for formatting. You store the inventory file in a Git repository.

  • You install the DU bare metal host machines on site, and make the hosts ready for provisioning. To be ready for provisioning, the following is required for each bare metal host:

    • Network connectivity - including DNS for your network. Hosts should be reachable through the hub and managed spoke clusters. Ensure there is layer 3 connectivity between the hub and the host where you want to install your hub cluster.

    • Baseboard Management Controller (BMC) details for each host - ZTP uses BMC details to connect the URL and credentials for accessing the BMC. ZTP manages the spoke cluster definition CRs, with the exception of the BMCSecret CR, which you create manually. These define the relevant elements for the managed clusters.

The GitOps approach

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 (OCM) 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.

Zero touch provisioning building blocks

Red Hat Advanced Cluster Management (RHACM) leverages zero touch provisioning (ZTP) to deploy single-node OKD clusters, three-node clusters, and standard clusters. The initial site plan is divided into smaller components and initial configuration data is stored in a Git repository. ZTP uses a declarative GitOps approach to deploy these clusters.

The deployment of the clusters includes:

  • Installing the host operating system (RHCOS) on a blank server.

  • Deploying OKD.

  • Creating cluster policies and site subscriptions.

  • Leveraging a GitOps deployment topology for a develop once, deploy anywhere model.

  • Making the necessary network configurations to the server operating system.

  • Deploying profile Operators and performing any needed software-related configuration, such as performance profile, PTP, and SR-IOV.

  • Downloading images needed to run workloads (CNFs).

How to plan your RAN policies

Zero touch provisioning (ZTP) uses Red Hat Advanced Cluster Management (RHACM) to apply the radio access network (RAN) configuration using a policy-based governance approach to apply the configuration.

The policy generator or PolicyGen is a part of the GitOps ZTP tooling that facilitates creating RHACM policies from a set of predefined custom resources. There are three main items: policy categorization, source CR policy, and the PolicyGenTemplate CR. PolicyGen uses these to generate the policies and their placement bindings and rules.

The following diagram shows how the RAN policy generator interacts with GitOps and RHACM.