According to a survey conducted by McKinsey Global, because of the COVID-19 crisis, companies have accelerated their digital transformation the equivalent of 3 or 4 years in a few months [1]. Communications service providers (CSP) are protagonists of the digital transformation of the rest of the sectors since they feed them by providing an important enabler of digitization: communications services. That is why CSPs have had an increase in business volume that has challenged the limits of communications infrastructures.
Let’s take a look at the main challenges CSPs are currently facing:

Picture 1 Most significant difficulties faced by CSPs
The essential challenge for CSPs is to face a market with a disruptive competition and with a changing demand from its customers. This demand for communications services is growing exponentially, but between the fierce competition, and the demand for cheaper prices from customers plus the frequent investments necessary to meet the demand, leave a limited margin for maneuver for CSPs to organic growth and innovation.
To cope with the strong demand and increasingly agile competition, CSPs need to change their business model and processes, transforming agility in decision-making, culture, way of working and systems that support them. In other words, they need a digital transformation that allows them to evolve from providers of traditional connectivity products towards an “as a service” product
model that allows them to go further and become digital service providers (DSP).
An example of a digital service is the concept of Connectivity as a service (CaaS). Being able to obtain customized communication services at the click of a button is something that is getting closer and closer and will be demanded by customers as technologies such as 5G gain traction. In a hyper-connected world like the one that is coming, connectivity as a service can be as temporary as the live broadcast of a football match in 8k with very specific quality needs tailored to the event. How can a CSP achieve such a thing?
How does the industry face the challenges of OpenAPIs?
A large part of the players in this industry are gathered through TM Forum, an alliance of more than 850 companies that work together to break the barriers between the main “players” in the sector. Its members include digital and communications service providers, telephone companies, cable operators, network operators, cloud providers, digital infrastructure providers, software providers, equipment providers, system integrators, and management consultancies.
The key is that TM Forum helps build an ecosystem between CSPs and solution providers so that they can work and be more efficient in helping the industry meet its challenges. Among other things TM Forum helps to:
- Plan and manage the way to transformation using tools, such as the Digital Maturity Model.
- Solve problems quickly by using the collective intelligence of Telco and providers to create widely adopted tools and frameworks, such as Open APIs, that drive transformation execution.
- Accelerating innovation through fast proofs of concept such as Catalyst Programs and serving as a meeting point for the collective development of reference implementations.
The most notable tools for this transformative journey are agile, Open API and cloud-native methodologies.
Open APIs as enablers of interoperability and automation

Picture 2 OpenAPIs foster innovation [2]
APIs (Application Program Interfaces) are key tools for all types of businesses and industries. From a technical point of view, they allow interoperability between different systems or applications and, therefore, organizations. That is why APIs are feeding a new wave of innovation focused on digital services that catalyze the collaboration and association of companies to put together true digital ecosystems.
The word Open API is synonymous of Open API Specification. The Open API Specification defines a standard, language-agnostic interface for HTTP APIs, which enables both humans and machines to discover and understand the capabilities of a service without the need to access source code, documentation, or inspection of traffic [3].
The Open API Specification is defined and governed by The Open API Initiative (“OAI”), which is a consortium of industry experts who have recognized the immense value of standardizing the way APIs are described. [4]
Following the Open API Specification, it is possible to describe a REST API including the following information:
- Endpoints and their operations (GET / user, POST / users)
- Input output parameters for each operation
- Authentication methods
- Contact information, license, terms of use, etc …

Picture 3 Basic structure of an Open API definition [5]
An Open API description can then be used by automated tools (such as Swagger [6]) to generate documentation, code for servers and clients, code for tests, and many other use cases.

Picture 4 The benefits of Open API-led development [7]
TM Forum Open APIs as an enabler of digital ecosystems
In the age of digital ecosystems, TM Forum Open APIs are a valuable tool to break down the integration barriers that block the digital transformation of CSPs.
TM Forum Open APIs are a suite of +50 APIs, collaboratively developed by TM Forum members, to enable digital ecosystems. These allow managing digital services from the beginning to the end of their life cycle in an environment in which there are multiple partners involved in the provision of the service. The APIs are based on strongly established industry design patterns that allow for rapid implementation.
The key to its success is its clear practical orientation providing specifications, reference implementations and conformance testing. This facilitates rapid API implementation that helps build agile and cost-effective solutions.
It is very interesting to explore the TM Forum Ecosystem API Portal [8] that serves as a guide for the adoption and implementation of these APIs. Particularly valuable, for anyone who wants to adopt a similar standardization initiative in other domains, is the API TMF630 Design Guide [9]. Also, the documentation of each API in the Open API table can lead to the adoption of one of these APIs or serve as a source of inspiration for others in similar fields.

Picture 5 Open API table [8]

Picture 6 Mechanisms of adoption of Open API by CSPs [8]

Picture 7 Signatories of the Open API & Open Digital Architecture manifesto [10]

Picture 8. Open APL Dashboard (11)
Apart from the multiple benefits that the adoption of Open APIs brings, they pave the way towards a microservices architecture as the first step to transform CSP systems into cloud-native, and thus facilitate the migration to a cloud-based model.
“Cloud Native” technologies empower organizations to build and run scalable applications in modern dynamic environments, such as public, private or hybrid clouds today. Topics such as containers, service meshes, microservices, immutable infrastructure and declarative APIs are examples of this approach. These techniques allow creating low-coupling systems that are resilient, manageable, and observable. Combined with solid automation techniques, it enables engineers to make frequent and predictable high-impact changes with minimal effort. “[12] As CSPs will increasingly offer cloud-based products and services it makes perfect sense that systems that allow them to provide such products and services are also cloud-based.
The continuous improvement process for migration includes stages where refactoring the information systems to a cloud-native model using Open API is a fundamental part. Furthermore, Open APIs enable CSPs to acquire or manage their information systems in a SaaS (Software as a Service) model.
Picture 9 Continuous improvement process for migration to the cloud [12]
Open digital architecture to complete the transformation
As we have already seen, the adoption of Open API by providers and CSPs will make interoperability between different software components from multiple providers or other CSPs possible. This will transform the way of dealing with integrations and customizations of a strict model, with high economic and temporary costs, and many times a single provider with a strong dependence on the supplier of products and services, which makes it not possible to replace it without facing substantial costs “Vendor lock-in” towards a flexible multi-vendor model that allows for trial and error and encourages innovation. This flexible model combined with the cloud-native character that software solutions are increasingly adopting leads to a Marketplace-type model where CSP can acquire solutions according to the SaaS model.
To move from a set of Open API to a Market pace of components in which CSPs can acquire and configure their components in an agile and simple way, TM Forum took the step in 2018 by betting on the definition of an architecture that shapes those components . This architecture is the Open Digital Architecture (ODA).
Open Digital Architecture defines an architecture framework, common language, and design principles. The foundations of this architecture are interoperable software components organized in domains that expose business services through Open API. The anatomy of an ODA component is as in the following picture.

Picture 10 Anatomy of an ODA component [13]