As part of their digital enablement and transformation initiative, telcos need to expose their APIs to support interoperability between industry standards for seamless services. The two leading standards for APIs in telecoms are TM Forum and MEF. In October 2020, they expanded their long-standing collaboration by announcing the alignment of their API standards – TM Forum Open APIs and MEF LSO Sonata APIs – to support the automation of B2B services and provide end-users with a similar experience as buying from cloud providers.

While the alignment was a most welcome step, currently telcos must still build and expose two sets of APIs with different swagger specification for respective standards. This is challenging in terms of turnaround times for integration, conformance, with different standards and managing multiple versions of the same set of APIs.

The situation becomes more complex when it is necessary to develop multiple standards plus managing two APIs for the same process but different payloads, increases operational costs.

The key criterion in successfully adapting the interoperability process using APIs is to reduce the turnaround of exposing a single API, securely that can handle TM Forum Open APIs and MEF payloads.

A group of telcos, along with Torry Harris and other participants, initiated a TM Forum Catalyst project to progress this work.

Business Benefits

  • Enabled provisioning of inter-carrier service request and global carrier interoperability for TM Forum and MEF standards.
  • The effort involved in API development fell by 50% as Coupler did the mapping and reverse mapping between TM Forum Open APIs and MEF standards automatically.
  • As Coupler is a no-code/low-code platform, the team implemented and demonstrated a complete end-to-end, interoperability working model within a week.

As Karthik T S, Head of the Centre of Excellence for Torry Harris Integration Solutions, explains, “The TM Forum Open API program aligns well with our approach of helping enterprises extend the power of digital access through the adoption and use of API-driven opportunities. Open APIs facilitate standardization across group companies and help us add value to our customers by fostering interoperability across different industry players.

The intended outcome was to create an API orchestration and composition layer that securely exposed API endpoints for provisioning of inter-carrier services and global carrier interoperability.


The Catalyst team deployed Coupler as a business orchestration layer and DigitMarketTM API Manager to provide the service exposure layer.

It allowed customers to:

  • Expose a unified API for TM Forum Open APIs and MEF;
  • Use a single API Swagger specification; and
  • Enable service Interoperability

DigitMarketTM API Manager provided built-in security and provided a single place to manage all the configuration and management activities.