1. Introduction

The ONAP project addresses a rising need for a common platform for telecommunication, cable, and cloud operators—and their solution providers—to deliver differentiated network services on demand, profitably and competitively, while leveraging existing investments.

Prior to ONAP, operators of large networks have been challenged to keep up with the scale and cost of manual changes required to implement new service offerings, from installing new data center equipment to, in some cases, upgrading on-premises customer equipment. Many are seeking to exploit SDN and NFV to improve service velocity, simplify equipment interoperability and integration, and reduce overall CapEx and OpEx costs. In addition, the current, highly fragmented management landscape makes it difficult to monitor and guarantee service-level agreements (SLAs).

ONAP is addressing these problems by developing global and massive scale (multi-site and multi-VIM) orchestration capabilities for both physical and virtual network elements. It facilitates service agility by providing a common set of Northbound REST APIs that are open and interoperable, and by supporting YANG and TOSCA data models. ONAP’s modular and layered nature improves interoperability and simplifies integration, allowing it to support multiple VNF environments by integrating with multiple VIMs, VNFMs, SDN Controllers, and even legacy equipment. This approach allows network and cloud operators to optimize their physical and virtual infrastructure for cost and performance; at the same time, ONAP’s use of standard models reduces integration and deployment costs of heterogeneous equipment, while minimizing management fragmentation. ONAP exists to instantiate and operate VNFs. Typical operator networks are expected to support multiple instances of hundreds of different types of VNFs. ONAP’s consolidated VNF requirements publication is a significant deliverable to enable commercial development of ONAP-compliant VNFs.

The ONAP platform allows end user organizations and their network/cloud providers to collaboratively instantiate network elements and services in a dynamic, closed-loop process, with real-time response to actionable events. In order to design, engineer, plan, bill and assure these dynamic services, there are three major requirements:

  • A robust design framework that allows specification of the service in all aspects – modeling the resources and relationships that make up the service, specifying the policy rules that guide the service behavior, specifying the applications, analytics and closed-loop events needed for the elastic management of the service.
  • An orchestration and control framework (Service Orchestrator and Controllers) that is recipe/policy-driven to provide automated instantiation of the service when needed and managing service demands in an elastic manner.
  • An analytic framework that closely monitors the service behavior during the service lifecycle based on the specified design, analytics and policies to enable response as required from the control framework, to deal with situations ranging from those that require healing to those that require scaling of the resources to elastically adjust to demand variations.

To achieve this, ONAP decouples the details of specific services and technologies from the common information models, core orchestration platform and generic management engines (for discovery, provisioning, assurance etc). Furthermore, it marries the speed and style of a DevOps/NetOps approach with the formal models and processes operators require to introduce new services and technologies. It leverages cloud-native technologies including Kubernetes to manage and rapidly deploy the ONAP platform and related components. This is in stark contrast to traditional OSS/Management software platform architectures, which hardcoded services and technologies, and required lengthy software development and integration cycles to incorporate changes.

The ONAP Platform enables product/service independent capabilities for design, creation and lifecycle management, in accordance with the following foundational principles:

  • Ability to dynamically introduce full service lifecycle orchestration (design, provisioning and operation) and service API for new services & technologies without the need for new platform software releases or without affecting operations for the existing services.
  • Carrier-grade scalability including horizontal scaling (linear scale-out) and distribution to support large number of services and large networks.
  • Metadata-driven and policy-driven architecture to ensure flexible and automated ways in which capabilities are used and delivered.
  • The architecture shall enable sourcing best-in-class components.
  • Common capabilities are ‘developed’ once and ‘used’ many times.
  • Core capabilities shall support many diverse services and infrastructures.
  • The architecture shall support elastic scaling as needs grow or shrink.

Figure 1: ONAP Platform

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2. ONAP Architecture

The platform provides the common functions (e.g., data collection, control loops, metadata recipe creation, policy/recipe distribution, etc.) necessary to construct specific behaviors. To create a service or operational capability, it is necessary to develop service/operations-specific service definitions, data collection, analytics, and policies (including recipes for corrective/remedial action) using the ONAP Design Framework Portal. Figure 2 provides a high-level view of the ONAP architecture and microservices-based platform components, including all ONAP projects.

Figure 2: ONAP Platform components with projects (Beijing Release)

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In Figure 3 below, we provide a functional view of the architecture, which highlights the role of key new components:

  1. The Beijing release standardizes and improves northbound interoperability for the ONAP Platform using the External API component (1)
  2. OOM provides the ability to manage cloud-native installation and deployments to Kubernetes-managed cloud environments.
  3. ONAP Common Services now manage more complex and optimized topologies. MUSIC allows ONAP to scale to multi-site environments to support global scale infrastructure requirements. The ONAP Optimization Framework (OOF) provides a declarative, policy-driven approach for creating and running optimization applications like Homing/Placement, and Change Management Scheduling Optimization.
  4. Information Model and framework utilities have evolved to harmonize the topology, workflow, and policy models from a number of SDOs including ETSI NFV MANO, TM Forum SID, ONF Core, OASIS TOSCA, IETF and MEF.

image2 Figure 3. Functional view of the ONAP architecture

3. Microservices Support

As a cloud-native application that consists of numerous services, ONAP requires sophisticated initial deployment as well as post-deployment management. It needs to be highly reliable, scalable, secure and easy to manage. Also, the ONAP deployment needs to be flexible to suit the different scenarios and purposes for various operator environments. Users may also want to select part of the ONAP components to integrate into their own systems. To achieve all these goals, ONAP is designed as a microservices based system, with all components released as Docker containers.

The ONAP Operations Manager (OOM) is responsible for orchestrating the end-to-end lifecycle management and monitoring of ONAP components. OOM uses Kubernetes to provide CPU efficiency and platform deployment. In addition, OOM helps enhance ONAP platform maturity by providing scalability and resiliency enhancements to the components it manages.

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OOM is the lifecycle manager of the ONAP platform and uses the Kubernetes container management system and Consul to provide the following functionality:

  1. Deployment - with built-in component dependency management (including multiple clusters, federated deployments across sites, and anti-affinity rules)
  2. Configuration - unified configuration across all ONAP components
  3. Monitoring - real-time health monitoring feeding to a Consul GUI and Kubernetes
  4. Restart - failed ONAP components are restarted automatically
  5. Clustering and Scaling - cluster ONAP services to enable seamless scaling
  6. Upgrade - change-out containers or configuration with little or no service impact
  7. Deletion - cleanup individual containers or entire deployments

OOM supports a wide variety of cloud infrastructures to suit your individual requirements.

The Microservices Bus (MSB) component project provides some fundamental microservices support such as service registration/discovery, external API gateway, internal API gateway, client software development kit (SDK), and Swagger SDK to help ONAP projects evolve towards the microservice direction. MSB is integrated with OOM to provide transparent service registration for ONAP microservices, it also supports OpenStack(Heat) and bare metal deployment.

4. Portal

ONAP delivers a single, consistent user experience to both design-time and run-time environments, based on the user’s role. Role changes are are configured within a single ONAP instance instance.

This user experience is managed by the ONAP Portal, which provides access to design, analytics and operational control/administration functions via a shared, role-based menu or dashboard. The portal architecture provides web-based capabilities such as application onboarding and management, centralized access management, and dashboards, as well as hosted application widgets.

The portal provides an SDK to enable multiple development teams to adhere to consistent UI development requirements by taking advantage of built-in capabilities (Services/API/UI controls), tools and technologies. ONAP also provides a Command Line Interface (CLI) for operators who require it (e.g., to integrate with their scripting environment). ONAP SDKs enable operations/security, third parties (e.g., vendors and consultants), and other experts to continually define/redefine new collection, analytics, and policies (including recipes for corrective/remedial action) using the ONAP Design Framework Portal.

5. Design-time Framework

The design-time framework is a comprehensive development environment with tools, techniques, and repositories for defining/ describing resources, services, and products.

The design time framework facilitates reuse of models, further improving efficiency as more and more models become available. Resources, services, products, and their management and control functions can all be modeled using a common set of specifications and policies (e.g., rule sets) for controlling behavior and process execution. Process specifications automatically sequence instantiation, delivery and lifecycle management for resources, services, products and the ONAP platform components themselves. Certain process specifications (i.e., ‘recipes’) and policies are geographically distributed to optimize performance and maximize autonomous behavior in federated cloud environments.

Service Design and Creation (SDC) provides tools, techniques, and repositories to define/simulate/certify system assets as well as their associated processes and policies. Each asset is categorized into one of four asset groups: Resource, Services, Products, or Offers.

The SDC environment supports diverse users via common services and utilities. Using the design studio, product and service designers onboard/extend/retire resources, services and products. Operations, Engineers, Customer Experience Managers, and Security Experts create workflows, policies and methods to implement Closed Loop Automation/Control and manage elastic scalability.

To support and encourage a healthy VNF ecosystem, ONAP provides a set of VNF packaging and validation tools in the VNF Supplier API and Software Development Kit (VNF SDK) and VNF Validation Program (VVP) components. Vendors can integrate these tools in their CI/CD environments to package VNFs and upload them to the validation engine. Once tested, the VNFs can be onboarded through SDC.

The Policy Creation component deals with polices; these are rules, conditions, requirements, constraints, attributes, or needs that must be provided, maintained, and/or enforced. At a lower level, Policy involves machine-readable rules enabling actions to be taken based on triggers or requests. Policies often consider specific conditions in effect (both in terms of triggering specific policies when conditions are met, and in selecting specific outcomes of the evaluated policies appropriate to the conditions). Policy allows rapid modification through easily updating rules, thus updating technical behaviors of components in which those policies are used, without requiring rewrites of their software code. Policy permits simpler management / control of complex mechanisms via abstraction.

The Closed Loop Automation Management Platform (CLAMP) provides a platform for designing and managing control loops. CLAMP is used to design a closed loop, configure it with specific parameters for a particular network service, then deploy and decommission it. Once deployed, a user can also update the loop with new parameters during runtime, as well as suspend and restart it.

6. Runtime Framework

The runtime execution framework executes the rules and policies distributed by the design and creation environment.

This allows for the distribution of policy enforcement and templates among various ONAP modules such as the Service Orchestrator (SO), Controllers, Data Collection, Analytics and Events (DCAE), Active and Available Inventory (A&AI), and a Security Framework. These components use common services that support logging, access control, and data management. A new component, Multi-Site State Coordination (MUSIC), allows the platform to register and manage state across multi-site deployments. The External API provides access for third-party frameworks such as MEF, TM Forum and potentially others, to facilitate interactions between operator BSS and relevant ONAP components.

Orchestration

The Service Orchestrator (SO) component executes the specified processes by automating sequences of activities, tasks, rules and policies needed for on-demand creation, modification or removal of network, application or infrastructure services and resources. The SO provides orchestration at a very high level, with an end-to-end view of the infrastructure, network, and applications.

The External API Northbound Interface component provides a standards-based interface between the BSS and and various ONAP components, including Service Orchestrator, A&AI and SDC, providing an abstracted view of the platform. This type of abstraction allows service providers to use their existing BSS/OSS environment and minimize lengthy, high-cost integration with underlying infrastructure. The Beijing release is the first of a series of enhancements in support of SDO collaborations, which are expected to support inter-operator exchanges and other use cases defined by associated standards bodies such as MEF, TM Forum and others.

Policy-driven Workload Optimization

In the Beijing Release, ONAP Optimization Framework (OOF) provides a policy-driven and model-driven framework for creating optimization applications for a broad range of use cases. OOF-HAS is a policy-driven workload optimization service that enables optimized placement of services across multiple sites and multiple clouds, based on a wide variety of policy constraints including capacity, location, platform capabilities, and other service specific constraints.

In the Beijing Release, ONAP Multi-VIM/Cloud (MC) and several other ONAP components such as Policy, SO, A&AI etc. play an important role in enabling “Policy-driven Performance/Security-aware Adaptive Workload Placement/Scheduling” across cloud sites through OOF-HAS. OOF-HAS uses Hardware Platform Awareness (HPA) and real-time Capacity Checks provided by ONAP MC to determine the optimal VIM/Cloud instances, which can deliver the required performance SLAs, for workload (VNF etc.) placement and scheduling (Homing). The key operator benefit is realizing the true value of virtualization through fine grained optimization of cloud resources while delivering the performance/security SLAs. For the Beijing release, this feature is available for the vCPE use case.

Controllers

Controllers are applications which are coupled with cloud and network services and execute the configuration, real-time policies, and control the state of distributed components and services. Rather than using a single monolithic control layer, operators may choose to use multiple distinct Controller types that manage resources in the execution environment corresponding to their assigned controlled domain such as cloud computing resources (network configuration (SDN-C) and application (App-C). Also, the Virtual Function Controller (VF-C) provides an ETSI NFV compliant NFV-O function, that is responsible for lifecycle management of virtual services and the associated physical COTS server infrastructure. VF-C provides a generic VNFM capability but also integrates with external VNFMs and VIMs as part of a NFV MANO stack.

In the Beijing release, the new Multisite State Coordination (MUSIC) project records and manages state of the Portal and ONAP Optimization Framework to ensure consistency, redundancy and high availability across geographically distributed ONAP deployments.

Inventory

Active and Available Inventory (A&AI) provides real-time views of a system’s resources, services, products and their relationships with each other. The views provided by A&AI relate data managed by multiple ONAP instances, Business Support Systems (BSS), Operation Support Systems (OSS), and network applications to form a “top to bottom” view ranging from the products end-users buy, to the resources that form the raw material for creating the products. A&AI not only forms a registry of products, services, and resources, it also maintains up-to-date views of the relationships between these inventory items.

To deliver the promised dynamism of SDN/NFV, A&AI is updated in real time by the controllers as they make changes in the network environment. A&AI is metadata-driven, allowing new inventory types to be added dynamically and quickly via SDC catalog definitions, eliminating the need for lengthy development cycles.

7. Closed-Loop Automation

The following sections describe the ONAP frameworks designed to address major operator requirements. The key pattern that these frameworks help automate is:

Design -> Create -> Collect -> Analyze -> Detect -> Publish -> Respond.

We refer to this automation pattern as “closed-loop automation” in that it provides the necessary automation to proactively respond to network and service conditions without human intervention. A high-level schematic of the “closed-loop automation” and the various phases within the service lifecycle using the automation is depicted in Figure 3.

Closed-loop control is provided by Data Collection, Analytics and Events (DCAE) and one or more of the other ONAP runtime components. Collectively, they provide FCAPS (Fault Configuration Accounting Performance Security) functionality. DCAE collects performance, usage, and configuration data; provides computation of analytics; aids in troubleshooting; and publishes events, data and analytics (e.g., to policy, orchestration, and the data lake). Another component, “Holmes”, connects to DCAE and provides alarm correlation for ONAP, which depicts the topological relation between different alarms raising either from different layers of VNFs or from different VNF entities that are distributed all over the network.

Working with the Policy Framework and CLAMP, these components detect problems in the network and identify the appropriate remediation. In some cases, the action will be automatic, and they will notify Service Orchestrator or one of the controllers to take action. In other cases, as configured by the operator, they will raise an alarm but require human intervention before executing the change.

Figure 5: ONAP Closed Loop Automation

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8. Common Services

ONAP provides common operational services for all ONAP components including activity logging, reporting, common data layer, access control, secret and credential management, resiliency, and software lifecycle management.

These services provide access management and security enforcement, data backup, restoration and recovery. They support standardized VNF interfaces and guidelines.

Operating in a virtualized environment introduces new security challenges and opportunities. ONAP provides increased security by embedding access controls in each ONAP platform component, augmented by analytics and policy components specifically designed for the detection and mitigation of security violations.

9. ONAP Modeling

Adopting the model-driven approach, ONAP provides models to assist the service design, development of various ONAP components and improve the interoperability of ONAP.

Models are essential part for the design time and run time framework development. The ONAP modeling project leverages the experience of member companies, standard organizations and other open source projects to produce models which are simple, extensible, and reusable. The goal is to fulfill the requirements of various use cases, guide the development and bring consistency among ONAP components and explore a common model to improve the interoperability of ONAP.

In the Bejing Release, ONAP supports the following Models:

  • A VNF Information Model based on ETSI NFV IFA011 v.2.4.1 with appropriate modifications aligned with ONAP requirements;
  • A VNF Descriptor Model based on TOSCA implementation based on the IM and follow the same model definitions in ETSI NFV SOL001 v 0.6.0.
  • VNF Package format based on ETSI NFV SOL004 specification.

These models enable ONAP to interoperate with implementations based on standard, and improve the industry collaboration. Service models, multi-VIM models and other models will be explored and defined in the Casablanca and future releases.

10. ONAP Use Cases

The ONAP project tests blueprints for real-world use cases to enable rapid adoption of the platform. With the first release of ONAP (“Amsterdam”), we introduced two blueprints: vCPE and VoLTE. Subsequent releases test additional functionality and/or new blueprints.

Virtual CPE Use Case

In this use case, many traditional network functions such as NAT, firewall, and parental controls are implemented as virtual network functions. These VNFs can either be deployed in the data center or at the customer edge (or both). Also, some network traffic will be tunneled (using MPLS VPN, VxLAN, etc.) to the data center, while other traffic can flow directly to the Internet. A vCPE infrastructure allows service providers to offer new value-added services to their customers with less dependency on the underlying hardware.

In this use case, the customer has a physical CPE (pCPE) attached to a traditional broadband network such as DSL (Figure 1). On top of this service, a tunnel is established to a data center hosting various VNFs. In addition, depending on the capabilities of the pCPE, some functions can be deployed on the customer site.

This use case traditionally requires fairly complicated orchestration and management, managing both the virtual environment and underlay connectivity between the customer and the service provider. ONAP supports such a use case with two key components – SDN-C, which manages connectivity services, and APP-C, which manages virtualization services. In this case, ONAP provides a common service orchestration layer for the end-to-end service. It uses the SDN-C component to establish network connectivity. Similarly, ONAP uses the APP-C component to manage the VNF lifecycle. Deploying ONAP in this fashion simplifies and greatly accelerates the task of trialing and launching new value-added services.

In the Beijing Release, the vCPE use case supports Policy-driven Workload Optimization, which is supported by OOF, Multi-VIM/Cloud, Policy, SO, A&AI and other ONAP components.

Figure 6. ONAP vCPE Architecture

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Read the Residential vCPE Use Case with ONAP whitepaper to learn more.

Voice over LTE (VoLTE) Use Case

The second blueprint developed for ONAP is Voice over LTE. This blueprint demonstrates how a Mobile Service Provider (SP) could deploy VoLTE services based on SDN/NFV. This blueprint incorporates commercial VNFs to create and manage the underlying vEPC and vIMS services by interworking with vendor-specific components, including VNFMs, EMSs, VIMs and SDN controllers, across Edge Data Centers and a Core Date Center.

Figure 7. ONAP VoLTE Architecture

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ONAP supports the VoLTE use case with several key components: SO, VF-C, SDN-C, and Multi-VIM/ Cloud. In this use case, SO is responsible for VoLTE end-to-end service orchestration. It collaborates with VF-C and SDN-C to deploy the VoLTE service. ONAP uses the SDN-C component to establish network connectivity, then the VF-C component completes the Network Services and VNF lifecycle management (including service initiation, termination and manual scaling which is composed of VNFs based on the unified VNFD model) and FCAPS (fault, configuration, accounting, performance, security) management. VF-C can also integrate with commercial VIMs in the Edge and Core datacenters via abstract interfaces provided by Multi-VIM/Cloud.

Using ONAP to manage the complete lifecycle of the VoLTE use case brings increased agility, CAPEX and OPEX reductions, and increased infrastructure efficiency to Communication Service Providers (CSPs). In addition, the usage of commercial software in this blueprint offers CSPs an efficient path to rapid production.

Read the VoLTE Use Case with ONAP whitepaper to learn more.

ONAP Blueprint Enrichment

The ONAP Beijing release includes four functional enhancements in the areas of manually triggered scaling, change management, and hardware platform awareness (HPA). These features required significant community collaboration as they impact multiple ONAP projects. These features are applicable to any use case; however, to showcase them in a concrete manner, they have been incorporated into VoLTE and vCPE blueprints.

Manually Triggered Scaling

Scale-out and scale-in are two primary benefits of NFV. Scaling can be triggered manually (e.g., by a user or OSS/BSS) or automatically via a policy-driven closed loop. An automatic trigger allows real-time action without human intervention, reducing costs and improving customer experience. A manual trigger, on the other hand, is useful to schedule capacity in anticipation of events such as holiday shopping. An ideal scaling operation can scale granularly at a virtual function level (VF), automate VF configuration tasks and manage the load-balancer that may be in front of the VF instances. In addition to run-time, this capability also affects service design, as VNF descriptors need to be granular up to the VF level.

The Beijing release provides the initial support for these capabilities. The community has implemented manually triggered scale-out and scale-in in combination with a specific VNF manager (sVNFM) and demonstrated this with the VoLTE blueprint. An operator uses the Usecase UI (UUI) project to trigger a scaleing operation. UUI communicates with the Service Orchestrator (SO). SO uses the VF-C controller, which in turn instructs a vendor-provided sVNFM to implement the scale-out action.

We have also demonstrated a manual process to Scale Out VNFs that use the Virtual Infrastructure Deployment (VID), the Service Orchestrator (SO) and the Application Controller (APPC) as a generic VNF Manager. Currently, the process is for the operator to trigger the Scale Out action using VID, which will request SO to spin up a new component of the VNF. Then SO is building the ConfigScaleOut request and sending to APPC over DMaaP, where APPC picks it up and executes the configuration scale out action on the requested VNF.

Change Management

NFV will bring with it an era of continuous, incremental changes instead of periodic step-function software upgrades, in addition to a constant stream of both PNF and VNF updates and configuration changes. To automatically deliver these to existing network services, the ONAP community is creating framework to implement change management functionality that is independent of any particular network service or use case. Ideally, change management provides a consistent interface and mechanisms to manage complex dependencies, different upgrade mechanisms (in-place vs. scale-out and replace), A/B testing, conflict checking, pre- and post-change testing, change scheduling, rollbacks, and traffic draining, redirection and load-balancing. These capabilities impact both design-time and run-time environments.

Over the next several releases, the community will enhance change management capabilities in ONAP, culminating with a full CI/CD flow. These capabilities can be applied to any use case; however, specifically for the Beijing release, the vCPE blueprint has been enriched to execute a predefined workflow to upgrade the virtual gateway VNF by using Ansible. An operator invokes an upgrade operation through the VID interface. VID drives SO, which initiates a sequence of steps such as VNF lock, pre-check, software upgrade, post-check and unlock. Since virtual gateway is an L3 VNF, the specific operations are carried out by the SDN-C controller in terms of running the pre-check, post-check and upgrade through Ansible playbooks.

Hardware Platform Awareness (HPA)

Many VNFs have specific hardware requirements to achieve their performance and security goals. These hardware requirements may range from basic requirements such as number of cores, memory size, and ephemeral disk size to advanced requirements such as CPU policy (e.g. dedicate, shared), NUMA, hugepages (size and number), accelerated vSwitch (e.g DPDK), crypto/compression acceleration, SRIOV-NIC, TPM, SGX and so on. The Beijing release provides three HPA-related capabilities:

  1. Specification of the VNF hardware platform requirements as a set of policies.
  2. Discovery of hardware and other platform features supported by cloud regions.
  3. Selection of the right cloud region and NFV infrastructure flavor by matching VNF HPA requirements with the discovered platform capabilities.

While this functionality is independent of any particular use case, in the Beijing release, the vCPE use case has been enriched with HPA. An operator can specify engineering rules for performance sensitive VNFs through a set of policies. During run-time, SO relies on the ONAP Optimization Framework (OOF) to enforce these policies via a placement/scheduling decision. OOF determines the right compute node flavors for the VNF by querying the above-defined policies. Once a homing decision is conveyed to SO, SO executes the appropriate workflow via the appropriate controller.

Conclusion

The ONAP platform provides a comprehensive platform for real-time, policy-driven orchestration and automation of physical and virtual network functions that will enable software, network, IT and cloud providers and developers to rapidly automate new services and support complete lifecycle management.

By unifying member resources, ONAP will accelerate the development of a vibrant ecosystem of VNFs around a globally shared architecture and implementation for network automation–with an open standards focus– faster than any one product could on its own.