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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of
the Securities Exchange Act of 1934 (Amendment No.          )

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RIBBON COMMUNICATIONS INC.
4 Technology Park Drive
Westford, MA 01886

April 25, 201929, 2020

Dear Fellow Stockholders:

              On behalf of the board of directors, we want to thank you for your investment and trusting us to manage the long-term success of Ribbon Communications Inc. In light of the current global pandemic, our hearts go out to all those impacted during these extraordinary times. We are especially grateful to the medical personnel and all those on the front lines helping those in need. Our principal attention is on the health, safety and well-being of our global workforce, their families and the communities in which we operate.

              Our board of directors and the management team have substantial experience in successfully navigating challenging conditions. We remain confident about the importance of Ribbon's role in our industry and the long-term positive future of our business that we believe will benefit all stakeholders—our employees, our communities, our customers, our partners, and you—our stockholders.

              We cordially invite you to the annual meeting of stockholders at 10:00 a.m. on Wednesday,Tuesday, June 5, 2019, at2, 2020. Due to the officespublic health impact of Latham & Watkins LLP, located at 200 Clarendon Street, Boston, MA 02116. We look forwardthe novel coronavirus pandemic and to personally greeting thosesupport the health and well-being of our stockholders, who arethis year's annual meeting will be held in a virtual meeting format only. You will be able to be present atattend the meeting. However, whether2020 annual meeting online and submit your questions during the meeting by visitinghttp://viewproxy.com/RBBN/2020/vm.

              Whether or not you plan to attend in person,the annual meeting virtually, it is important that your shares be represented and voted at the annual meeting.voted. Therefore, I urge you to promptly vote andyour proxy. You may submit your proxy by signing, dating, and returning the enclosed proxy card in the enclosed envelope, which requires no postage if mailed in the United States, or provide voting instructions to your broker, bank or other nominee. However, in light of possible disruptions in mail service related to the COVID-19 pandemic, we encourage stockholders to submit their proxy via the telephone or online. If you decide to attend the annual meeting, you will be able to vote in person,electronically, even if you have previously submitted your proxy. Every stockholder's vote is important.

              Thank you very much for your continued trust and confidence in Ribbon. Please remember to vote your shares at your earliest convenience.

Sincerely,

Franklin (Fritz)Bruce W. HobbsMcClelland
President and Chief Executive Officer

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NOTICE OF ANNUAL MEETING OF STOCKHOLDERS OF
RIBBON COMMUNICATIONS INC.

Record Date: You can vote electronically at, and are entitled to notice of, the annual meeting if you were a stockholder of record on April 15, 2019.6, 2020.

If you are attendingA complete list of our stockholders as of the meeting, yourecord date will be askedavailable for examination by any stockholder during the ten days prior to presentthe Annual Meeting for a valid, government-issued photo identification,purpose germane to the 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 via a secure link in the chat box after you enter the virtual meeting using the password you received via e-mail in your registration confirmation. Such list of stockholders will be protected and cannot be downloaded and/or printed and access to such as a driver's license, as describedlist will expire immediately after the Annual Meeting ends. For additional information, see "How can I attend the virtual meeting?" in the section entitled "Information about the Annual Meeting" in the Proxy Statement.

You may attend the webcast of the meeting via the Internet athttp://viewproxy.com/RBBN/2020/vm by entering the event password you received during your registration process. Whether or not you expect to attend the annual meeting electronically, we urge you to vote your shares as promptly as possible to ensure your representation and the presence of a quorum at the annual meeting. If you send in your proxy card, you may still decide to attend the annual meeting and vote your shares electronically. Note that, in light of possible disruptions in mail service related to the COVID-19 pandemic, we encourage

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stockholders to submit their proxy via telephone or online. Your proxy is revocable in accordance with the procedures set forth in the accompanying proxy statement.

		By Order of the Board of Directors,
Westford, Massachusetts April 25, 201929, 2020		Justin K. Ferguson Executive Vice President, General Counsel and Corporate Secretary

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

              The accompanying Proxy Statement contains "forward-looking statements" within the meaning of the U.S. Private Securities Litigation Reform Act of 1995, which are subject to a number of risks and uncertainties. All statements other than statements of historical fact contained in the accompanying Proxy Statement, including statements regarding the receipt of the requisite approval from the Committee on Foreign Investment in the United States ("CFIUS") in connection with our acquisition (the "ECI Merger") of ECI Telecom Group Ltd. ("ECI"); our future results of operations and financial position, business strategy, plans and objectives of management for future operations and plans for future product offerings, development and manufacturing, are forward-looking statements. Without limiting the foregoing, the words "anticipates", "believes", "could", "estimates", "expects", "intends", "may", "plans", "seeks", "projects", "will" and other similar language, whether in the negative or affirmative, are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Forward-looking statements are based on our current expectations and assumptions regarding our business, the economy and other future conditions. Because forward-looking statements relate to the future, they are subject to inherent uncertainties, risks and changes in circumstances that are difficult to predict. Our actual results could differ materially from those anticipated in these forward-looking statements as a result of various important factors, including, but not limited to: risks related to the ongoing COVID-19 pandemic; failure to obtain CFIUS approval in connection with the ECI Merger in a timely manner or at all; risks that the ECI businesses will not be integrated successfully or that the combined companies will not realize estimated cost savings; failure to realize anticipated benefits of the ECI Merger; potential litigation relating to the ECI Merger and disruptions from the integration efforts that could harm our business; our ability to recruit and retain key personnel; reductions in customer spending; a slowdown in customer payments and changes in customer requirements, including the timing of customer purchasing decisions and our recognition of revenues; the potential impact of the consummation of the proposed transaction on relationships with third parties, including customers, employees and competitors; conditions in the credit markets, credit risks and risks related to the terms of our credit agreement; risks associated with assumptions the parties make in connection with the parties' critical accounting estimates and legal proceedings; the parties' international operations, which are subject to the risks of currency fluctuations and foreign exchange controls; ability to attract new customers and retain existing customers in the manner anticipated; reliance on and integration of information technology systems; changes in legislation or governmental regulations affecting the companies; international, national or local economic, social, health or political conditions that could adversely affect the companies or our customers; our successful integration activities with respect to our acquisitions; our ability to realize benefits from other mergers and acquisitions; the effects of disruptions resultingdisruption from acquisitions, making it more difficult to maintain relationships with employees, customers, business partners or government entities; unpredictable fluctuations in quarterly revenue and business partners;from our existing customers; failure to compete successfully against telecommunications equipment and networking companies; failure to grow our customer base or generate recurring business from existing customers; consolidation in the timing of customer purchasing decisions and our recognition of revenues; economic conditions; our ability to recruit and retain key personnel;telecommunications industry; difficulties supporting our strategic focus on channel sales; difficulties retaining and expanding our customer base; difficulties leveraging market opportunities; the impact of restructuring and cost-containment activities; litigation; actions taken by significant stockholders; difficulties providing solutions that meet the needs of customers; market acceptance of our products and services; rapid technological and market change; our ability to protect our intellectual property rights;rights and obtain necessary licenses; our ability to maintain partner, reseller, distribution and vendor support and supply relationships; our negotiation position relative to our large customers; the limited supply of certain components of our products; the potential for defects in our products; higher risks in international operations and markets; the impact of increased competition; increases in tariffs, trade restrictions or taxes on our products; currency fluctuations; data privacy and cyber security risks; changes in the market price of our common stock; and/or failure or circumvention of our controls and procedures. Important

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procedures; and the important factors that could cause actual results to differ materially from those in these forward-looking statements are discussed in the "Risk Factors", "Management's Discussion and Analysis of Financial Condition and Results of Operations", and "Quantitative and Qualitative Disclosures About Market Risk" sections in our Annual Report on Form 10-K/A10-K for the year ended December 31, 20182019 and our other filings with the U.S. Securities and Exchange Commission. Forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements. We therefore caution you against relying on any of these forward-looking statements. Also, any forward-looking statement made by us in the accompanying Proxy Statement speaks only as of the date of the accompanying Proxy Statement. Factors or events that could cause our actual results to differ may emerge from time to time, and it is not possible for us to predict all of them. We undertake no obligation to publicly update any forward-looking statement, whether as a result of new information, future developments or otherwise, except as may be required by law.

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RIBBON COMMUNICATIONS INC.
PROXY STATEMENT

Summary Information

              To assist you in reviewing the proposals to be acted upon at our 20192020 annual meeting of stockholders (the "20192020 Annual Meeting"), Ribbon Communications Inc. would like to call your attention to the following information about Ribbon's 20182019 financial performance, key executive compensation actions and decisions, and corporate governance highlights. Please note that the following description is only a summary. For more complete information about these topics, please review our Annual Report on Form 10-K/A10-K for the year ended December 31, 20182019 (the "20182019 Annual Report") and this proxy statement ("Proxy Statement"). This Proxy Statement and our 20182019 Annual Report will be first mailed to our stockholders of record on or about April 25, 2019.29, 2020.

              Effective October 27, 2017, we completed thea merger (the "GENBAND Merger") of Sonus Networks, Inc. ("Sonus"), GENBAND Holdings Company, GENBAND, Inc. and GENBAND II, Inc. (collectively, "GENBAND"). Because the GENBAND Merger occurred on October 27, 2017, the information reported in this Proxy Statement for the period prior to that date principally relates to Sonus, our predecessor entity. Unless the content otherwise requires, references in this Proxy Statement to "Ribbon," "Ribbon Communications," "Company," "we," "us" and "our" and "the Company" refer to (i) Sonus and its subsidiaries prior to the GENBAND Merger and (ii) Ribbon Communications Inc. and its subsidiaries upon closing of the GENBAND Merger, as applicable.

              Effective March 3, 2020 (the "ECI Closing Date"), we completed the ECI Merger with ECI. On ECI Closing Date, we entered into a First Amended and Restated Stockholders Agreement (the "Stockholders Agreement") with JPMC Heritage Parent LLC ("JPMC"), Heritage PE (OEP) III, L.P. (together with JPMC, entities affiliated with the Company's largest stockholder, JPMorgan Chase & Co. (collectively with any successor entities, the "JPM Stockholders")), and ECI Holding (Hungary) Kft ("Swarth").

Business Overview

              We are a leading provider of next generation software solutions and services to telecommunications, wireless and cable service providers and enterprises of all sizes across industry verticals. With the March 3, 2020 completion of the merger with ECI, we now also provide optical and packet networking products and software-defined solutions to service providers and critical infrastructure sectors, like utilities, government and defense. With over 1,000 customers around the globe, including some of the largest telecommunications service providers, enterprises and enterprisesutilities in the world, we enable service providersour customers to evolve and enterprises to modernize their communications networks through software and providepacket optical networking infrastructures with innovative state-of-the-art solutions. By enabling highly secure, real-time communications solutions to their customers and employees. By securing and enabling reliable and scalable Internet Protocol ("IP") and packet optical networks and applications, we help service providers and enterprisesour customers adopt the next generation of software-based virtualizedsoftware, cloud and cloud communicationsedge-based technologies for service providers to drive new, incremental revenue, while protecting their existing revenue streams.streams and significantly reducing operating costs. Our software solutions provide a secure way for our customers to connect and leverage multivendor, multiprotocol communications systems and applications across their networks and the cloud, around the world and in a rapidly changing ecosystem of IP-enabled devices, such as smartphones and tablets. In addition, our software solutions secure cloud-based delivery of unified communications ("UC") solutions—both for service providers transforming to a cloud-based network and for enterprises using cloud-based UC.unified communications. These networks support the ever increasing demand on network infrastructure created by IP traffic growth as well as the expected increase in traffic from 5G applications and devices. We sell our software solutions through both direct sales and indirect channels, globally, leveraging the assistance

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of resellers, and we provide ongoing support to our customers through a global services team with experience in design, deployment and maintenance of some of the world's largest IP software networks.

(1)

As of March 31, 2020

(2)

Leadership Ranking Source: IHS Research Q3'19. Market share data for past 12 months. See Appendix section "TAM and Market Share References"

              We completed our acquisitionFollowing the March 3, 2020 completion of Edgewater Networks, Inc., a market leader inthe ECI Merger, Ribbon now also provides optical and packet networking, Software Defined Networking and Network Edge Orchestration for the distributed enterpriseFunctions Virtualization portfolio of products and UC market, on August 3, 2018, making us a software market leader in enterprise Session Border Controllers and allowing us to extend Edgewater software solutions internationally while expanding our cloud offerings and entering the SD-WAN market. In addition, on February 28, 2019, we acquired the business and technology assets of Anova Data, Inc., a provider of advanced analytics solutions to reinforceservice providers and extend our strategycritical infrastructure sectors like utilities, government and defense. These solutions support the increasing demand on network infrastructure created by ongoing internet protocol traffic growth and the forecast demand and buildouts to expand into network optimization, securitybe created by increased traffic from 5G applications and data monetization via big data analytics and machine learning.

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20182019 Financial Highlights

•

GAAP total revenue was $577.9$563 million, compared to $329.9$578 million in 2017.



•

Non-GAAP total revenue was $612.0 million, compared to $353.2 million in 2017.2018.



•

GAAP net loss was $76.8$130 million, compared to $35.3$77 million in 2017.2018.



•

Non-GAAP net income was $51 million, compared to $39 million in 2018.



•

GAAP loss per share was $0.74,$1.19, compared to $0.60$0.74 in 2017.2018.



•

Non-GAAP diluted earnings per share was $0.58,$0.47, compared to $0.51$0.37 in 2017.2018.



•

Non-GAAP Adjusted EBITDA was $84.0$86 million, compared to $40.9$62 million in 2017.2018.

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              Please see the reconciliation of non-GAAP to GAAP financial measures, and additional information about non-GAAP measures, inAppendix A.

Cash Flow From Operating Activities		Improving Profitability Margin
Operating Cash Flow of $56M in FY19, up $66M(1)		Record Adjusted EBITDA Margin(2)(3) of 27% in Q419, up 10 ppts(4) Adjusted EBITDA(3) of $86M in FY19, 39% increase, up 5 ppts(1)

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Executive Compensation Highlights

              In 2018,2019, we engaged in a thorough review of our compensation programs and practices in connection with the establishment of a unified Ribbon executive compensation program for our executive officers. We believe that the new program's adoptionour compensation program has established a strong foundation to support the continued growth of our business and the attainment of key synergies and other goals of our business. The ongoing compensation programs and practices are governed by effective and strongsound pay practices as set forth below.

What We Do
		Strong pay-for-performance philosophy
		Independent compensation committee and compensation consultant
		Annual market-based review of compensation levels and peer groups
		Annual risk assessment of compensation plans and policies
		Share ownership guidelines for our executives and board members
		Formal clawback policy with respect to incentive compensation
		Insider trading policy that prohibits hedging, pledging and other similar actions by our executive officers and directors
What We Don't Do
		No gross-up provisions
		No pension plans or other post-employment benefit plans
		No base pay severance multipliers in excess of two
		No multi-year guaranteed incentive awards for executives
		No liberal share recycling

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Board of Directors and Committees

Annual Meeting Proposals

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INFORMATION ABOUT THE ANNUAL MEETING

              Our Board of Directors (our "Board") is soliciting proxies for the annual meeting of stockholders of Ribbon to be held on Wednesday, June 5, 2019, and at any adjournments, continuations or postponements thereof. This Proxy Statement contains important information for you to consider when deciding how to vote on the matters brought before the meeting. Please read it carefully.

Important Notice Regarding Availability of Proxy Materials for the Stockholder Meeting to be held on June 5, 2019: This Proxy Statement and the 2018 Annual Report to Stockholders are available for viewing, printing and downloading atwww.proxyvote.com.

Why am I receiving these materials?

              You have received these proxy materials because our Board is soliciting your vote at the 2019 Annual Meeting. This Proxy Statement includes information that we are required to provide to you under the rules of the U.S. Securities and Exchange Commission (the "SEC") and that is designed to assist you in voting your shares.

When and where is the meeting?

              The 2019 Annual Meeting will be held on Wednesday, June 5, 2019 at 10:00 a.m., Eastern time, at the offices of Latham & Watkins LLP, located at 200 Clarendon Street, Boston, Massachusetts 02116.

Who may vote at the meeting?

              Stockholders of record at the close of business on April 15, 2019, the record date, or holders of a valid proxy, may attend and vote at the meeting. Each stockholder is entitled to one vote for each share of common stock held on all matters to be voted. As of the close of business on April 15, 2019, an aggregate of 111,390,821 shares of our common stock were outstanding, including 867,834 unvested shares of restricted stock. A list of our stockholders will be available for inspection at our corporate offices at 4 Technology Park Drive, Westford, Massachusetts 01886, beginning no less than ten days prior to the meeting.

How many shares must be present to hold the meeting?

              A majority of the 111,390,821 shares of our common stock that were outstanding as of the record date must be present at the meeting in order to hold the meeting and conduct business. This is called a quorum. For purposes of determining whether a quorum exists, we count as present any shares that are properly represented in person at the meeting or that are represented by a valid proxy properly submitted over the Internet, by telephone or by mail. Further, for purposes of establishing a quorum, we count as present shares that a stockholder holds and that are represented by their proxy even if the stockholder does not vote on one or more of the matters to be voted upon. If a quorum is not present at the scheduled time of the 2019 Annual Meeting, the chairperson of the meeting is authorized by our by-laws to adjourn the meeting, without the vote of stockholders.

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What proposals will be voted on at the meeting?

              There are four proposals scheduled to be voted on at the meeting:

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The election of the eight nominees for director named in this Proxy Statement to hold office until the 2020 annual meeting of stockholders of the Company (the "2020 Annual Meeting") (Proposal 1);



•

The approval of the Ribbon Communications Inc. 2019 Incentive Award Plan (Proposal 2);



•

The ratification of the appointment of Deloitte & Touche LLP to serve as the Company's independent registered public accounting firm for the fiscal year ending December 31, 2019 (Proposal 3); and



•

The approval, on a non-binding, advisory basis, of the compensation of our named executive officers (Proposal 4).

How does the Board of Directors recommend that I vote?

              Our Board recommends that you vote your shares:

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"For" the election of each of the nominees to our Board named in this Proxy Statement (Proposal 1);



•

"For" the approval of the Ribbon Communications Inc. 2019 Incentive Award Plan (Proposal 2);



•

"For" the ratification of the appointment of Deloitte & Touche LLP to serve as our independent registered public accounting firm for the fiscal year ending December 31, 2019 (Proposal 3); and



•

"For" the approval, on a non-binding, advisory basis, of the compensation of our named executive officers (Proposal 4).

What vote is required to approve each matter and how are votes counted?

              Election of Directors (Proposal 1).    In an uncontested election, such as the election of directors at the 2019 Annual Meeting, to be elected, each of the nominees for director must receive more votes "For" such nominee's election than "Against" such election (with abstentions and broker non-votes not counted as a vote for or against). With respect to each nominee, you may vote "For," "Against," or "Abstain." Abstaining will have no effect on the outcome of the election.

              Approval of Our 2019 Incentive Award Plan (Proposal 2).    The affirmative vote of a majority of the shares of common stock present or represented at the 2019 Annual Meeting and entitled to vote on this proposal will be required to approve this proposal. You may vote "For," "Against", or "Abstain" from voting on this proposal. Abstaining from voting on this proposal will have the effect of a vote against the approval of this proposal.

              Ratification of the Appointment of Deloitte & Touche LLP to Serve as the Company's Independent Registered Public Accounting Firm for the Fiscal Year Ending December 31, 2019 (Proposal 3).    The affirmative vote of a majority of the shares of common stock present or represented at the 2019

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Annual Meeting and entitled to vote on this proposal will be required to approve this proposal. You may vote "For", "Against", or "Abstain" from voting on this proposal. Abstaining from voting on this proposal will have the effect of a vote against this proposal.

              Approval, on a Non-Binding, Advisory Basis, of the Compensation of Our Named Executive Officers (Proposal 4).    The vote on the compensation of the named executive officers is non-binding, as provided by law. However, our Board and its Compensation Committee will review and consider the outcome of this vote when making future compensation decisions for our named executive officers. The affirmative vote of a majority of the shares of common stock present or represented at the 2019 Annual Meeting and entitled to vote on this proposal will be required to approve this proposal. You may vote "For", "Against", or "Abstain" from voting on this proposal. Abstaining from voting on this proposal will have the effect of a vote against this proposal.

              For the proposals relating to the election of directors (Proposal 1), the approval of our 2019 Incentive Award Plan (Proposal 2), and the approval, on a non-binding, advisory basis, of the compensation of our named executive officers (Proposal 4), please note that if you are a beneficial owner of our common stock and your stock is held through a broker, bank or other nominee (in "street name"), under stock exchange rules a broker, bank or other nominee subject to those rules is not permitted to vote your shares on these three proposals without your instruction. Therefore, if a beneficial owner of our common stock fails to instruct such a broker, bank or other nominee how to vote on Proposals 1, 2 and 4, that beneficial owner's shares cannot be voted on these matters—in other words, your broker, bank or other nominee's proxy will be treated as a "broker non-vote," which is explained in the following question and explanation.

What are broker non-votes and what is the effect of broker non-votes?

              Brokers, banks and other nominees have the discretion to vote shares held in "street name"—a term that means the shares are held in the name of the broker, bank or other nominee on behalf of its customer, the beneficial owner—on routine matters, such as the ratification of the appointment of our independent registered public accounting firm, but not on non-routine matters. Generally, broker non-votes occur when shares held by a broker, bank or other nominee for a beneficial owner are not voted with respect to a non-routine matter because the broker, bank or other nominee has not received voting instructions from the beneficial owner and the broker, bank or other nominee lacks discretionary authority to vote the shares because of the non-routine nature of the matter. The election of directors (Proposal 1), the approval of our 2019 Incentive Award Plan (Proposal 2), and the approval, on a non-binding, advisory basis, of the compensation of our named executive officers (Proposal 4) are "non-routine" matters for which brokers, banks and other nominees, under applicable stock exchange rules, may not exercise discretionary voting power without instructions from the beneficial owner, and therefore broker non-votes will not affect the outcome of the vote on these proposals. The ratification of the appointment of our independent registered public accounting firm (Proposal 3) is a "routine" matter for which brokers have discretionary authority to vote. Therefore, we do not expect any broker non-votes in connection with this proposal. Broker non-votes are counted as shares present for purposes of determining the presence of a quorum. Your vote is very important, whether you hold directly or through a broker, bank or other nominee. We encourage you to read this Proxy Statement and the 2018 Annual Report carefully and if you are a beneficial owner, please be sure to give voting instructions to your broker, bank or other nominee.

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What happens if an incumbent director nominee fails to receive more "For" votes than "Against" votes?

              Our Corporate Governance Guidelines require that as a condition to being nominated by the Board for re-election as a director, each incumbent director must deliver to the Board an irrevocable resignation from the Board that will become effective if, and only if, both (i) in the case of an uncontested election, such nominee does not receive more votes "For" his or her election than votes "Against" such election, and (ii) the Board accepts such resignation. The Board will decide (based on the recommendation of a committee of the Board) whether to accept the director's resignation within 90 days after the election results are certified.

              An incumbent director who does not receive the required vote in an uncontested election will continue to serve as a director while the Nominating and Corporate Governance Committee and the Board decide whether to accept or reject such director's resignation. If the Board accepts such resignation, the Board may fill the remaining vacancy or may decrease the size of the Board in accordance with our by-laws. Our Corporate Governance Guidelines are posted on our website atwww.ribboncommunications.com.

How can I vote my shares in person at the meeting?

              Shares held directly in your name as the stockholder of record may be voted in person at the meeting. If you choose to attend the meeting, please bring the enclosed proxy card and a valid, government-issued photo identification, such as a driver's license, for entrance to the meeting.

              If you hold your shares in street name, please bring the enclosed voting instruction form you received from your broker, bank or other nominee and proof of identification for entrance to the meeting. You must also request a legal proxy from your broker, bank or other nominee and bring it to the 2019 Annual Meeting if you would like to vote at the meeting.

How can I vote my shares without attending the meeting?

              If you are a stockholder of record, you may vote by proxy in any of the following ways:

•

Submit your proxy by mail.  You may complete, date and sign the proxy card and mail it in the postage-prepaid envelope that you received. The persons named in the proxy card will vote the shares you own in accordance with your instructions on the proxy card you return. If you return the proxy card but do not give any instructions on a particular matter described in this Proxy Statement, the persons named in the proxy card will vote the shares you own in accordance with the recommendations of our Board.



•

Submit your proxy over the Internet.  If you have Internet access, you may vote over the Internet atwww.proxyvote.com by following the instructions set forth on your proxy card. If you submit your proxy over the Internet, it is not necessary to return your proxy card.



•

Submit your proxy by telephone.  If you are located in the United States or Canada, you may vote by telephone by calling 1-800-690-6903 and following the instructions set forth on your proxy card. If you submit your proxy by telephone, it is not necessary to return your proxy card.

              The ability to vote by telephone or over the Internet for stockholders of record will be available until 11:59 p.m., Eastern Daylight Time on June 4, 2019.

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              If your shares are held in the name of a broker, bank or other nominee, please follow the voting instructions on the forms you received from such broker, bank or other nominee. The availability of submitting your voting instructions by telephone or over the Internet will depend upon their voting procedures.

Who is serving as the Company's inspector of elections?

              Broadridge Financial Solutions, Inc. has been engaged as our independent inspector of elections to tabulate stockholder votes for the 2019 Annual Meeting.

How can I change my vote?

              You may revoke your proxy and change your vote at any time before the polls close at the meeting. You may do this by signing and submitting a new proxy card with a later date, submitting a proxy by telephone or submitting a proxy over the Internet (your latest telephone or Internet proxy is counted), by giving written notice of revocation to our Secretary prior to the 2019 Annual Meeting or by attending the meeting and voting in person. If your shares are held in street name, you may change or revoke your voting instructions by following the specific directions provided to you by your bank or broker. Attending the meeting by itself, however, will not revoke your proxy unless you specifically request it.

What are the directions to the meeting?

              The meeting is being held at the offices of Latham & Watkins LLP, 200 Clarendon Street, Boston, Massachusetts 02116. Please call (617) 948-6000 if you need directions.

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PROPOSAL 1 — ELECTION OF DIRECTORS

              OurThe Board has nominated eight directorsthe following nine director nominees for election atto the 2019 Annual MeetingBoard to hold office until the next annual meeting2021 Annual Meeting and the electionuntil his or her respective successor is duly elected and qualified:

              All of the nominees are currently directors. Each agreed to be named in this Proxy Statement and to serve if elected. All nominees are expected to attend the 20192020 Annual Meeting.

              In connection DESIGNATION RIGHTS

              On the ECI Closing Date, we entered into the Stockholders Agreement with the Merger, SonusJPM Stockholders, and GENBAND agreed onSwarth. Pursuant to the selection of directors to serve onStockholders Agreement, the initial Board of Directors of Ribbon upon the closing of the Merger as follows: Kim S. Fennebresque, Bruns H. Grayson, Franklin (Fritz) W. Hobbs, Kent J. Mathy and Richard W. Smith were designated by GENBAND, and Beatriz V. Infante, Richard J. Lynch, and Scott E. Schubert were designated by Sonus. Upon the closing of the Merger, we entered into a principal stockholders agreement (the "Stockholders AgreementBoard") with Heritage PE (OEP) II, L.P. and Heritage PE (OEP) III, L.P., entities affiliated withis required to consist of (i) three individuals designated by the Company's largest stockholder, JPMorgan Chase & Co. (collectively with any successor entities, the "JPM Stockholders"). The JPM Stockholders, (ii) once CFIUS approval has been obtained, three individuals designated by Swarth, (iii) our Chief Executive Officer, and (iv) a number of other individuals designated by the Nominating and Corporate Governance Committee sufficient to ensure that there are no vacancies on the Board. Our Board consists of nine directors. The authorized number of directors is determined from time to time by the Board, subject to the requirements of the Stockholders Agreement. Until the first anniversary of the date of the Stockholders Agreement, no member of the Board appointed by either the JPM Stockholders or Swarth will be removed from the Board, regardless of any sell down of Ribbon common stock by the nominating stockholder.

              Each of the JPM Stockholders and Swarth owned 44.83%34.50% and 17.82%, respectively, of Ribbon's common stock as of April 8, 2019.6, 2020. Under the Stockholders Agreement, the JPM Stockholders have designated Kim S. Fennebresque, Bruns H. Grayson, Kent J. MathyR. Stewart Ewing, Jr., Krish A. Prabhu and Richard W. Smith for election to our Board. Swarth cannot designate directors to serve on our Board until we obtain the required approval from CFIUS in connection with the ECI Merger. As of April 29, 2020, we have not yet received the requisite approval. For additional information regarding Swarth's designation right and the anticipated composition of our Board of Directors following our receipt of CFIUS approval, should such approval be received, see the section of this Proxy Statement entitled "Swarth Designees Following Receipt of CFIUS Approval for ECI Merger" and "Board Composition and Stockholders Agreement" in the section entitled "Corporate Governance" below.