Ribbon Communications Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

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Ribbon Communications Inc.

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Dear Fellow Stockholders,

We started 2025 in a strong position following a record fourth quarter of 2024, with an improved balance sheet, and deeper and broader customer relationships. This momentum continued throughout the first half of 2025 with both sales and earnings increasing significantly year over year and improving performance across our portfolio.

However, in the second half of 2025, several significant ongoing projects were impacted by macro factors including the U.S. Government shutdown and significant restructuring activities implemented by our largest Service Provider customer. While we believe these issues will be temporary in nature, and the broader industry backdrop remains strong, we have reduced our growth expectations in 2026 particularly in the first half.

As we progress in 2026, we remain optimistic about the outlook for our business as the need for secure high-performance communication infrastructure continues to grow, highlighted by record levels of product and professional services bookings in the fourth quarter of 2025.

2025 Highlights and Key Accomplishments

Our business with Global Service Providers was the highlight in 2025 with sales growing 5% year over year. This included a very strong year in India with sales growing 40% as compared to the prior year. Sales to Enterprise and Critical Infrastructure customers grew 2%, while sales to Government and Defense agencies declined 23%, primarily due to delays and reduced spending associated with the U.S. Government shutdown. Despite this transitory headwind, we continue to believe the broad Government and Defense market segment is an excellent growth opportunity for Ribbon across our entire portfolio.

Revenue for 2025 was $845 million, an $11 million increase compared with the prior year. Both our Cloud & Edge and IP Optical segments contributed to the growth in revenue but were below the targets we established at the beginning of the year. Adjusted EBITDA was $107 million (See Appendix A for a reconciliation of this non-GAAP measure), generating $51 million in operating cash flow, year-end cash of $98 million, and net leverage of 2.3x.

An increasing number of customers initiated voice modernization projects in 2025 — across

multiple market segments including Service Providers, Enterprises, and Government agencies resulting in significant backlog growth in the fourth quarter of 2025. We believe there is a strong return on investment attached to these investments and they help address a growing technology and human capital obsolescence issue. Verizon continues to be one of the strongest proponents of this strategy as we continue to execute together on a large multi-year project resulting in a 26% increase in sales to Verizon in 2025.

The strong demand for our IP Routing and Optical Transport solutions in India allowed us to overcome the drop in sales in Eastern Europe starting in the second quarter of 2024, resulting in overall sales growth of 1%. Excluding Eastern Europe, IP Optical sales grew 9% across all other regions.

2025 was a year of progress — but did not translate into the level of stockholder returns we are seeking. We recognize this and are focused on improving stockholder returns by further broadening our customer base, better defining our strategic positioning and differentiation, and improving our execution.

Industry Trends and Market Focus

There are several key industry trends that drive investment in Ribbon’s solutions and our strategy across multiple markets.

A key area of focus continues to be the modernization of legacy voice and data networks. Ribbon’s expertise in this area is unparalleled, and we believe there is a compelling business case for Service Providers and Enterprises to adopt modern cloud-based platforms to reduce network operation costs and drive revenue growth. This also complements the growing use of unified communications platforms such as Microsoft Teams and Zoom where Ribbon plays a crucial role in securing network boundaries and ensuring highly scalable and fault tolerant services.

Demand for high-capacity fiber and IP networks continues to grow across multiple market segments and applications, with higher levels of security and resiliency. The continued exponential growth in data traffic along with the need to extend connectivity to underserved regions aligns well with Ribbon’s IP and Optical

​ product portfolio. Vendor diversification and trusted supply chains are also an increasing factor in purchase decisions.

Secure private networks is a specific area of differentiation and growth for Ribbon with many types of critical infrastructure providers — energy producers and distributors, transportation, public safety, defense — emphasizing the importance of security and resiliency.

These industry trends extend across multiple end markets — Telecom Service Provider, Medium and Large Enterprise, and Government and Defense. Market and geographic diversity is a key tenant to our strategy to gain scale and improved financial visibility and performance.

The AI Opportunity

In addition to adopting an increasing number of AI solutions within Ribbon to accelerate development, improve quality and customer service, and lower operational costs, there are three specific market opportunities in focus for us in 2026.

We have recently launched a new AI-powered automation platform called Acumen that is an important growth initiative, building on our widely deployed machine-learning Ribbon Analytics and Muse element management solutions. Acumen enables end-to-end observability, automation, and agent development using multiple large language model (LLM) integrations across multi-vendor networks with the goal of accelerating the transition to autonomous networks.

Beyond AIOps, as the adoption of agentic AI platforms continues to grow, we see a great convergence opportunity with our cloud-centric secure voice portfolio to seamlessly integrate AI with a human voice interface. In partnership with AWS, we recently launched the industry’s first carrier-grade cloud-native voice session border controller solutions to accelerate the integration of voice capabilities into AI platforms.

And finally, as the proliferation of AI-related data centers continues and processing demand moves closer to the edge of the network, there is a great opportunity for many of our service provider and critical infrastructure customers to leverage their fiber networks to provide data center interconnect services using our portfolio of IP and Optical solutions.

The Path Ahead

As I have just outlined, the underlying industry fundamentals are strong and there are multiple positive long-term drivers supporting our business, and it is imperative for our customers to invest. However, we are proceeding cautiously as we manage several near-term factors, including the timing of U.S. Government spending and significant M&A consolidation within the U.S. Telecom Service Provider ecosystem. As a result, our 2026 outlook reflects a more conservative set of assumptions, particularly around timing of business in the first half of the year.

In addition to our core strategy, our recent tax planning has created an opportunity to generate more cash over the next several years that can be used to strengthen our balance sheet, as well as to potentially accelerate innovation and expansion into new immediately adjacent markets.

Ultimately, the success of our business is tied to our people and the common focus we have on our mission to become a recognized global technology leader. I can’t thank the Ribbon team enough for their dedication and perseverance, adapting and overcoming all obstacles.

I would like to thank you for your continued support and investment over this last year. Our stockholders are instrumental in our journey of growth and success, and I remain dedicated to enhancing stockholder value.

Your participation in the annual meeting of stockholders is invaluable, and we encourage you to exercise your voting rights bypromptly voting your proxy. Your input and feedback are essential as we strive to continue to increase stockholder value for all investors in 2026.

Sincerely,

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NOTICE OF 2026 ANNUAL MEETING

OF STOCKHOLDERS

A complete list of our stockholders as of the Record Date will be available for examination by any stockholder during the ten days prior to the 2026 Annual Meeting for a purpose germane to the 2026 Annual Meeting by sending an email to ir@rbbn.com, stating the purpose of the request and providing proof of ownership of Company stock. The list of stockholders will also be available during the virtual meeting after you enter the virtual meeting using the 16-digit control number you received with the Notice of Internet Availability of Proxy Materials, proxy card or voting instructions for the 2026 Annual Meeting. For additional information, see “How can I attend the meeting?” in the section entitled “Information about the Annual Meeting” in the Proxy Statement.

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Whether or not you expect to attend the 2026 Annual Meeting, we urge you to vote your shares as promptly as possible to ensure your representation and the presence of a quorum at the 2026 Annual Meeting. If you send in your proxy card, you may still decide to attend the 2026 Annual Meeting and vote your shares electronically. Your proxy is revocable in accordance with the procedures set forth in the accompanying proxy statement.