Contents

Summary

The OOF plans to provide optimization capability as a service for ONAP R2 and beyond. OOF uses a typical optimization construct:

• Objective: Maximize/minimize a metric, measured by appropriate key performance indicators (KPIs)

• Technology and operating constraints, such as:

  • Parameter change limits (such as power)

  • Frequency of changes permitted

  • Number of parameters that can be changed simultaneously

  • Data latencies (typically in percentile)

  • DC compute, network, storage, energy capacity

  • Location based and time based energy cost

The objective metrics could be throughput (maximize), interference levels (minimize), accessibility/retainability (maximize), cost (minimize) etc. KPIs could be infrastructure utilization statistics provided by ONAP-MC.

The OOF is developed based on the following core ideas:

1. Most optimization problems can be solved in a declarative manner using a high-level modeling language.

2. Recent advances in open source optimization platforms allow the solution process to be mostly solver-independent.

3. By leveraging the library of standard/global constraints, optimization models can be rapidly developed.

4. By developing a focused set of platform components, we can realize a policy-driven, declarative system that allows ONAP optimization applications be composed rapidly and managed easily

   1. Policy and data adapters

   2. Execution and management environment

   3. Curated "knowledge base" and recipes to provide information on typical optimization examples and how to use the OOF 

5. More importantly, by providing a way to support both "traditional" optimization applications and model-driven applications, we can provide a choice for users to adapt the platform based on their business needs and skills/expertise.

The OOF aims to realize these via a set of initial applications for ONAP use cases that are being developed collaboratively across a broad team.

Rationale and Motivation

Traditional Optimization

Traditionally, optimization applications are tailor-made for specific requirements, and the process for developing an optimization application often involves substantial application-specific "custom code". Any changes in the problem (e.g. new optimization constraints, objectives, or data sources) requires development effort involving code changes in various components of the application. These changes can span aspects such as (a) Optimization Model Specification, (b) Request Handler, (c) Adapters for data and parameters, (d) Application Configuration, (e) Code in custom solver, etc., and involve long development cycles even for simple changes in requirements.

Declarative, Policy- and Model-Driven Architecture for Optimization Applications

The goal of the Optimization Framework is to drastically reduce the amount of such code changes by providing platform-level functionality.

Features and Utility of OOF

The main features of the ONAP Optimization Framework (OOF) are:

1. It provides a robust, scalable optimization framework for rapidly developing new optimization applications independent of how the underlying optimization modules are implemented.

2. It enables reusability of optimization engines, addresses problems arising due to different applications using custom optimization codes, adapter libraries, and configuration logic. This is achieved via a policy-driven configuration system, and a library of generalized optimizers that can be configured via policies.

3. OOF-based solutions can be quickly on-boarded onto ONAP, linked to various data collectors, databases, and microservices in ONAP/DCAE, and can dynamically be scaled at run-time.

4. Overall, the OOF eliminates software redundancy and inconsistencies arising from variations in quality and configurability of different optimizers. The unified approach of OOF reduces the overhead associated with managing different optimization applications.

Advantages of the Unified Approach of OOF

1. OOF is policy driven.

   1. OOF provides mechanisms to specify optimization constraints as policies that are configurable by service designers or operators. In contrast, legacy optimization applications include such information inside configuration files and sometimes in the code.

   2. Constraints and other policies are available for multiple uses, which encourages reusability. This reduces inconsistencies in constraints or policies across services, and helps reduce duplication of effort for common tasks.

2. OOF provides reusable, model-driven adapters for data sources and external systems

   1. Data formats and API calls are model-driven in OOF, so likely errors are identified very early in the request-response sequence. OOF provides adapters to different data sources (DCAE as well as external systems), which can be directly reused.

3. OOF is agnostic towards service, application, and optimization engine technology/language

   1. Optimizers that can be chained together in a technology and programming-language agnostic manner (e.g. general purpose mathematical solvers such as GLPK and CPLEX can co-exist with custom-implementations of algorithms). New optimization solutions can be composed by chaining existing optimizers (e.g. by linking placement, networking, and licensing optimizations).

4. OOF provides a dynamically scalable, fault-tolerant environment with resource pooling

   1. Runtime environment is based on ONAP/DCAE's Hadoop/Yarn technologies (and can be easily adapted to other cluster technologies such as kubernetes).

   2. OOF uses a queue-based system with independent ``workers'' processing optimization tasks. These workers can be dynamically scaled and jobs are picked up by the next available worker if a worker container fails.

Contributors

Overall Architecture/Design: AT&T, VMWare, Intel

Core OOF Components (Adapters, architecture, seed code): AT&T

Underlying optimization platform: Code developed by University of Melbourne and Monash University

Packaging and verification of OOF System: VMWare, NetCracker, AT&T

Policies and interpretation: Intel, AT&T 

Homing and Allocation Service: AT&T, Intel

CI/CD and Test Coverage: NetCracker, AT&T

Modification of Adapters: Huawei, AT&T, VMWare

Functional Architecture

Technology Choices

Minizinc provides an open source constraint modeling language/platform for specifying optimization applications. It contains direct interfaces to COIN-OR CBC, Gurobi and IBM ILOG CPLEX. Additionally, many optimization projects support minizinc via FlatZinc interfaces. The Minizinc standard library provides a subset of constraints form the  global constraint catalogue as a high-level abstraction that have efficient algorithms implemented by several solvers.

Components of the Core Framework

An overview of the components of the core optimization framework. The OOF utilizes the open source project Minizinc, which has a solver-independent modeling language and has interfaces to various open source and commercial solvers. One of the additional benefits of this approach is that by developing a focused set of ONAP-related components, we can utilize ongoing advances in optimization technologies, as well as adapt other currently available extensions to Minizinc and related projects. The OOF project aims to build these components with a focus on minimal viable product for Beijing Release in order to support initial applications and use cases, with subsequent focus on expanding the platform.

Data Adapter Library

The OOF will provide a library of adapters for common ONAP systems. These can be directly used in data specification templates of the applications. In the initial release, these will include adapters to Policy, A&AI, Multi-Cloud, and SDC (additional "stretch goals" for this release include SDN-C, Microservice Bus). As new use cases are implemented, this library will be augmented by new adapters to other services. 

Translation Modules

The OOF will provide modules for translating policies into constraints for the optimization environment. When an underlying minizinc model is used for optimization, it is translated into a minizinc constraint (either via a data specification template or directly from policy). For custom optimizers, these constraints will be translated to the input format expected by the optimizer via the data specification template. The Homing and Allocation Service (HAS; described in the next section) uses a custom optimization module and hence uses the data specification template approach.