While working with Cloud Networks Automation, Network Function Virtualization (NFV) and Cloud deployment it very common to come across terms like Day-0, Day-1, Day-2, and Day-3. These terms are widely used but not well defined many times creates confusion. We writing this blog post to arrive at an common understanding and definition of these terms considering Cloud-RAN (C-RAN) Deployment.
Network Functions Lifecycle Management (LCM)
These Day-0, Day-1 and Day-2 and so on configuration are used to manage the lifecycle (LCM) of Network Functions (NFs). Following picture provides a high level understanding for the same.
As per above diagram we can have following definitions.
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- Day-0 Configuration and Operations: This configuration contain the information required for Installation of Physical Network Functions (PNFs) e.g. Radio Unit (RU) configuration with FQDN and Container/Vritual Network Functions (CNFs/VNFs) Instantiation configuration.
- Day-1 Configuration and Operations: Day-1 included pushing the working configuration to the PNFs and CNFs and activiating them for service and operation.
- Day-2 Configuration and Operations: Day-2 includes applying optimization configuration to the Network Functions (NFs)
- Day-3 Configuration and Operations: Day-3 includes upgrading the NFs to new softwares, patching for bugs and scalling up or scaling down NFs based on SLAs.
Cloud RAN Architecture and Day’s Configuration Relation:
Following figure show a detailed network architecture for Cloud-RAN based on containers and relationship for Day-0, Day-1 and Day-2 configurations.
Before going to details of Day-0, 1 and 2 lets get familiar with the Cloud-RAN architecture. In above diagram, we can the Conatiner based C-RAN, where DU, CU (CUCP & CUUP) CNFs are hosted on k8s worker nodes. The k8s worker nodes cluser is managed by an Orchestrator for Installation and Termination of CNFs. The Orchestrator connects to Registry (ECR, Harbor are some examples for Registries) which stores container images, Helms charts and yaml files.
There is another network element named as Configuration management which manages Day-1 and Day-2 Configuration inside the Operation Support System (OSS). The Day-1 and Day-2 configuration is pushed to CNFs using Netconf protocols.
- Day-0 Configuration: The Day-0 configuration refers to the instantiation of the NFs and the infrastructure setup that will be needed later in the onboarding process. On top level Day-0 Configuration includes CSAR files, Helm Charts and Value.yaml files.
- Day-0 configurations are stored in Registry or Orchestrator depening on design
- Cloud Service Archive (CSAR) filese are the initial build packages compliant to TOSCA standards and generated using network descriptors (VFD/CNF). It includes the basic configurations for the interconnections of pods/containers or VNFc.
- CSAR package also integrate the cloud-init scripts in the descriptors for primary configurations needed to build up a network service like the OS boot requirements, setting up a hostname, adding SSH keys, configuring network devices and users.
- Day-0 also configure the virtualized infrastructure or worker nodes capabilities in the descriptors like Hugepages, CPU pinning, SR-IOV, or any other data accelerated features based on the functional requirements.
- Day-1 Configuration: Day-1 configuration pushed by Configuration Manager service resides with OSS or part of Orchestration platform. Day-1 configuration provide configuration that is very essential to the operation. Considering a Cloud RAN example, we can the Day-1 is consist of two type of parameters Gold Parameters + Planning Parameters
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- Golden Parmeters is list of parameter which does not change individual site e.g. Core network IPs, PLMNs, QoS configuration
- Planning Parameters are site specific e.g PCI, Frequency, Bandwidth, Cell Identities etc.
- Taking both as an input Configuration Manager generates the individual site configuration and push the PNFs/VNFs/CNFs (RUs, DUs, CUs) using Netconf protocols to make it operational
- Day-1 Configuration also includes Licesnse Activiation, configuring Fault Management, Performance Managements end point IPs, protocols (SNMP, Kafka etc)
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- Day-2 Configuration: Day-2 configuration is related to on-going configurations pushes on the NFs for day-to-day operation to optimize the network e.g. handover mobility parameters. The recommandation for day-2 configuration can be provided by manaul operation by optimizations engineers or there can be an automative process using AI/ML.
- Day-3 Configuration: Day-3 configuration also know as Day-N configuration and it includes information/policies required for operations like upgrading the NFs softwares, patching container/pods for bugs instead of upgrading the complete network service, scalling up/down the container/pods in a network service based network loads.
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