SD

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM SD

SPECIALIZED DISCLOSURE REPORT

RIBBON COMMUNICATIONS INC.

(Exact Name of Registrant as Specified in its Charter)

DELAWARE	001-38267	82-1669692
(State or Other Jurisdiction	(Commission File Number)	(IRS Employer
of Incorporation)		Identification No.)

6500 Chase Oaks Blvd, Suite 100, Plano, TX 75023

(Address of Principal Executive Offices) (Zip Code)

Patrick W. Macken, Executive Vice President, Chief Legal Officer and Secretary

(978) 614-8100

(Name and telephone number, including area code, of the person to contact in connection with this report)

Check the appropriate box to indicate the rule pursuant to which this form is being filed, and provide the period to which the information in this form applies:

x  Rule 13p-1 under the Securities Exchange Act (17 CFR 240.13p-1) for the reporting period from January 1 to December 31, 2021.

Section 1 — Conflict Minerals Disclosure

Item 1.01. Conflict Minerals Disclosure and Report

Ribbon Communications Inc. (the “Company” or “Ribbon”) has determined that some of the products that it manufactured or contracted to manufacture through the end of reporting year 2021 (“Ribbon Products”), include gold, columbite-tantalite (coltan), cassiterite and wolframite, including their derivatives, tantalum, tin and tungsten (collectively, “Conflict Minerals”). The Company has further determined that these Conflict Minerals are necessary to the functionality or production of the Ribbon Products.

The Company conducted a Reasonable Country of Origin Inquiry (“RCOI”) to determine whether any of the Conflict Minerals in the Ribbon Products originated in the Democratic Republic of the Congo or an adjoining country (“Covered Country”) and whether the Conflict Minerals are from recycled or scrap sources.  Based on its RCOI, the Company knows or has reason to believe that some of the Conflict Minerals in the Ribbon Products originated in the Covered Countries and are not from recycled or scrap sources.  The Company therefore engaged in due diligence on the source and chain of custody of the Conflict Minerals in the Ribbon Products that originated or may have originated in the Covered Countries, as described in its Conflict Minerals Report filed herewith as Exhibit 1.01, and available on the Investor Relations — Corporate Governance section of the Company’s website at http://investors.ribboncommunications.com/governance.cfm.

Item 1.02.  Exhibit

In accordance with Rule 13p-1 under the Securities Exchange Act of 1934, the Company is filing as an exhibit to this Form SD the Conflict Minerals Report required by Item 1.01.

Section 2 — Exhibits

Item 2.01. Exhibits

The following exhibit is filed as part of this Form SD:

Exhibit 1.01 Conflict Minerals Report for the year ended December 31, 2021, as required by Items 1.01 and 1.02 of this Form SD.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: May 31, 2022	RIBBON COMMUNICATIONS INC.
	By:	/s/ Patrick W. Macken
		Patrick W. Macken Executive Vice President, Chief Legal Officer and Secretary

EX-1.01

Exhibit 1.01

® RIBBON COMMUNICATIONS INC. CONFLICT MINERALS REPORT PURSUANT TO RULE 13P-1 UNDER THE SECURITIES EXCHANGE ACT OF 1934 ®

Ribbon Communications Inc. Conflict Minerals Report 2021 2021 Summary.................................................................................................................................3 Introduction......................................................................................................................................4 Company Overview...........................................................................................................................4 Conflict Minerals Policy....................................................................................................................4 Products Overview...........................................................................................................................4 Supply Chain and Reasonable Country of Origin Inquiry................................................................4 Due Diligence Process.....................................................................................................................5 Due Diligence Measures...................................................................................................................5 Establish Strong Company Management Systems.........................................................................5 Identify and Assess Risk in the Supply Chain.................................................................................6 Design and Implement a Strategy to Respond to Identified Risks.................................................7 Carry Out Independent Third-Party Audit of Supply Chain Due Diligence......................................7 Report on Supply Chain Due Diligence............................................................................................7 Due Diligence Results.......................................................................................................................8 Risk Mitigation Steps to Be Taken for 2022 Due Diligence.............................................................9 Audit................................................................................................................................................10 Annex A List of Smelters................................................................................................................11 Annex B List of Countries...............................................................................................................18 CONTENTS RIBBON COMMUNICATIONS INC. (“RIBBON”) presents this Conflict Minerals Report for the reporting period of January 1, 2021 to December 31, 2021 pursuant to Rule 13p-1 under the Securities Exchange Act of 1934 and associated guidance issued by the Securities and Exchange Commission. This document represents Exhibit 1.01 to Form SD, the Conflict Minerals Report. 2

Ribbon Communications Inc. Conflict Minerals Report 2021 * Conflict Minerals Reporting Template ** Democratic Republic of the Congo 2021 SUMMARY 78 Suppliers completed CMRT in 2021 66% Of manufacturers are DRC Conflict Free 11% Of manufacturers are not affected 23% Of manufacturers are DRC Conflict Undeterminable 100% Of smelters who completed a CMRT filed an independent Form SD 27% More suppliers in scope for CMRT requests compared to 2020 19% Increase in the number of suppliers providing CMRTs in 2021 compared to 2020 100% Of smelters who completed a CMRT maintain a responsible minerals sourcing policy and conduct due diligence with their suppliers Representing 100% of in-scope suppliers requested to complete Conflict Minerals Reporting Template (CMRT) 858 Total suppliers 3

Ribbon Communications Inc. Conflict Minerals Report 2021 4 Introduction This report for the year ended December 31, 2021 has been prepared by Ribbon Communications Inc. (the “Company”, “Ribbon”, “we,” “us,” or “our”) to comply with Rule 13p-1 (the “Rule”) under the Securities Exchange Act of 1934, as amended. The Rule imposes certain disclosure and reporting obligations on companies that report with the SEC and which manufacture, or contract to have manufactured, products containing conflict minerals that are necessary to the functionality or production of those products. Conflict Minerals are defined as cassiterite, columbite-tantalite, gold, wolframite, and their derivatives, which are limited to tin, tantalum, tungsten, and gold (collectively, “Conflict Minerals”). Ribbon has determined that some of the products that it manufactured or contracted to manufacture, and which continue to be manufactured or contracted to manufacture by Ribbon through the end of reporting year 2021 (“Ribbon Products”) include Conflict Minerals. Company Overview Ribbon Communications (Nasdaq: RBBN) delivers communications software, IP and optical networking solutions to service providers, enterprises and critical infrastructure sectors globally. We engage deeply with our customers, helping them modernize their networks for improved competitive positioning and business outcomes in today’s smart, always-on and data- hungry world. Our innovative, end-to-end solutions portfolio delivers unparalleled scale, performance, and agility, including core to edge software- centric solutions, cloud-native offers, leading- edge security and analytics tools, along with IP and optical networking solutions for 5G. Ribbon maintains a keen focus on our commitments to Environmental, Social and Governance (ESG) matters and report to our stakeholders through our annual Sustainability Report. To learn more about Ribbon, please visit rbbn.com. Conflict Minerals Policy Ribbon has adopted a Conflict Minerals Policy and communicated such policy to its suppliers. This policy is available on the Investor Relations-Corporate Governance section of the Company’s website at https://investors. ribboncommunications.com/static-files/79ec23fd- 657e-4d9b-8d90-5e2daec9c183. Products Overview This report covers the following Ribbon Products that were manufactured in 2021 (the “2021 Ribbon Products”): SBCs, DSCs, Voice over IP (VoIP) trunking solutions, policy/routing servers, media and signaling gateways, including the GSX 9000 High-Density Media Gateway, Neptune, MSPP, Access, Apollo, Muse, Qualitech, Cyber, CESR, and network analytics tools. Supply Chain and Reasonable Country of Origin Inquiry Ribbon has determined that Conflict Minerals are necessary to the functionality or production of Ribbon Products manufactured or contracted to be manufactured during 2021. We utilize an outsourced supply chain model pursuant to which our contract manufacturers procure materials on our behalf. Our supply chain is multi-tiered, global and complex, and we outsource the manufacturing of our hardware products such that we are many steps removed from the mining and smelting or refining of Conflict Minerals. Therefore, we rely upon our suppliers to provide information on the

Ribbon Communications Inc. Conflict Minerals Report 2021 5 origin, source and chain of custody of the Conflict Minerals contained in product components and materials. Some of these suppliers may themselves purchase from lower tier suppliers and not directly from a miner, smelter or refiner. The Company conducted a Reasonable Country of Origin Inquiry (“RCOI”) to determine whether any of the Conflict Minerals in our 2021 Ribbon Products originated in the Democratic Republic of the Congo (“DRC”) or an adjoining country (collectively, the “Covered Countries”) and whether the Conflict Minerals are from recycled or scrap sources. Based on our RCOI, we know or have reason to believe that some of the Conflict Minerals in our 2021 Ribbon Products originated in the Covered Countries and are not from recycled or scrap sources. Ribbon’s RCOI measures included conducting a supply-chain survey with in-scope suppliers using the Responsible Minerals Initiative (“RMI”) Reporting Template (the “Template”). The Template was developed to facilitate disclosure and communication of information regarding smelters that provide material to a company’s supply chain. It includes questions regarding the supplier’s conflict-free policy, engagement with its direct suppliers, and a listing of the smelters the company and its suppliers use. In addition, the Template contains questions about the origin of Conflict Minerals included in the company’s products, as well as supplier due diligence. The Template was designed to provide companies with sufficient information regarding their suppliers’ practices with respect to the sourcing of Conflict Minerals to enable such companies to comply with the requirements of the Rule. Due Diligence Process In accordance with the Rule, Ribbon undertook due diligence on the source and chain of custody of the Conflict Minerals in the 2021 Ribbon Products that originated or may have originated in the Covered Countries. The Company’s due diligence measures were designed to conform, in all material respects, to the internationally recognized due diligence framework in The Organization for Economic Co-operation and Development (“OECD”) Due Diligence Guidance for Responsible Supply Chains of Minerals from Conflict-Affected and High-Risk Areas (“OECD Guidance”) and the related supplements. Due Diligence Measures Ribbon performed the following due diligence measures in accordance with the OECD Guidance and the Rule: OECD Guidance Step 1: Establish Strong Company Management Systems Ribbon’s Conflict Minerals compliance efforts are overseen by the Company’s Vice President, Manufacturing, Operations and Supply Chain and its manufacturing department, and supported and sponsored by the Company’s engineering, audit and legal departments. Ribbon employees who are responsible for Conflict Minerals compliance have received training regarding Conflict Minerals compliance. The team was structured to ensure critical information, including our policies related to this subject matter, reached relevant employees and suppliers. To the extent red flags or other issues are identified in the supplier data acquisition or engagement processes, these issues and red flags will be addressed first by the responsible individuals within the engineering, audit and

Ribbon Communications Inc. Conflict Minerals Report 2021 6 legal departments, and, if deemed necessary, will then be reported to and reviewed by the Audit Committee (the “Audit Committee”) of the Board of Directors at regularly schedule meetings on an annual basis. Ribbon also engaged SiliconExpert Technologies, a provider of electronic component data and BOM Management software to the electronics industry (“SiliconExpert”), to assist with its Conflict Minerals compliance efforts. Frequent status meetings are held between Ribbon’s Conflict Minerals support team and SiliconExpert, with Ribbon management receiving status updates on progress and due diligence efforts on a regular and timely basis. In addition, Ribbon has a Conflict Minerals Policy and communicates such policy to its suppliers, which is available on our Investor Relations — Corporate Governance section of our website at https://investors.ribboncommunications. com/static-files/79ec23fd-657e-4d9b-8d90- 5e2daec9c183. To the extent any employee, officer or director has concerns or grievances about the Company’s potential use of Conflict Minerals, such individual is urged to contact his or her manager, the Company’s Chief Financial Officer, the General Counsel or other member of senior management, the Employee Hotline (which can be used on an anonymous basis) or the Audit Committee. Ribbon established documentation and record maintenance mechanisms to ensure the retention of information relevant to the Company’s Conflict Minerals Policy electronically. OECD Guidance Step 2: Identify and Assess Risk in the Supply Chain Ribbon reviewed the information reported on the Template by its suppliers and followed up with any additional questions. To the extent an in- scope supplier had follow-up questions, Ribbon responded with all requested information, including part numbers and manufacturing lots to identify how the supplies were used in the Ribbon Products. Untimely or incomplete responses as well as inconsistencies within the data reported by suppliers were addressed directly with respective suppliers to provide the required and/ or revised responses. Ribbon utilizes a series of escalating responses to address the failure of a supplier to provide the information required by the Template. Ribbon’s engineering, audit and legal departments manage the collection of information reported on the Template by its suppliers. Ribbon collected a list of smelters/processors that are in our supply chain for the Ribbon Products using the Template and reconciled this list to the list of smelter facilities designated by the Responsible Minerals Assurance Process (“RMAP”). Ribbon has provided that list in this report. Ribbon, through SiliconExpert, followed up with suppliers that did not respond initially to our requests to complete the Template.

Ribbon Communications Inc. Conflict Minerals Report 2021 7 OECD Guidance Step 3: Design and Implement a Strategy to Respond to Identified Risks Ribbon adopted and used the Template to monitor and mitigate supply chain risk and took the steps described above. Ribbon worked with certain suppliers to better educate them on the Conflict Minerals process. Members of the Conflict Minerals team periodically report to senior management as well as the Audit Committee on program developments and progress. OECD Guidance Step 4: Carry Out Independent Third-Party Audit of Supply Chain Due Diligence Given that we do not generally have a direct relationship with the smelters and refineries that process the Conflict Minerals that are present in our Ribbon Products, we rely on the RMI to conduct audits of and validate the conflict-free status of smelters and refineries that source from Covered Countries. We have not relied on supplier representations concerning the conflict status of their smelters, but have required industry certification such as through the RMAP before concluding that a smelter or refinery is conflict free. We understand that this program is continuing to audit smelters and refineries to add to its Conflict-Free Smelter List. OECD Guidance Step 5: Report on Supply Chain Due Diligence As required by the Rule, we have filed a Form SD and a Conflict Minerals Report as an exhibit thereto for the 2021 calendar year reporting period. In accordance with OECD Guidance and the Rule, this report is available on our Investor Relations-Corporate Governance section of our website at: https://investors.ribboncommunications.com/ corporate-governance/governance-highlights Due Diligence Results Ribbon contacted 100% of a total of 858 in-scope suppliers (excluding distributors and service providers) for the 2021 Ribbon Products and received some degree of a response all of them. Ribbon Supplier Outreach Overview: 2021 Total in-scope suppliers contacted 858 Manufacturers responding with latest CMRTs (6.2,6.01 or 6.10) 594 Manufacturers responding with earlier CMRTs (5.12 and older) 75 Manufacturers not providing CMRT responses 189 Overall response rate (all CMRT responses) 78% Approximately 78% of in-scope suppliers provided responses to the survey. The large majority of the completed responses received provided conflict mineral data and a declaration at a “Company Level” (supplier/ company declaration represents all the supplier’s products) or “Divisional Level” (supplier/company declaration represents all the supplier’s products from a division of the company). As a result, we are unable to determine whether any of the Conflict Minerals reported by the suppliers were contained in specific components or parts supplied to us with regard to Ribbon Products. Further, while our suppliers for the Ribbon Products identified certain of the smelters and refineries that provided Conflict Minerals, the responses did not provide specific information regarding the smelters or refineries of the Conflict Minerals in the particular components used in the 2021 Ribbon Products. Due to this lack of information, Ribbon is unable to determine with specificity the facilities used to process those necessary Conflict Minerals or their country of origin for the 2021 Ribbon Products.

Ribbon Communications Inc. Conflict Minerals Report 2021 8 Over the years, Ribbon has increased the pool of in-scope suppliers as business has expanded. Ribbon’s ability to secure responses from a greater number of suppliers is the result of consistent efforts to work effectively with suppliers to gain the required information. MANUFACTURERS PROVIDING CMRTS 499 467 486 560 669 2019 2018 2019 2020 2021 Given the higher number of suppliers, however, in 2021, the challenge of following up all details effectively with all manufacturers was significant. Therefore, the overall response rate dipped in 2021, but with continued efforts, Ribbon expects to increase this rate in the future. In 2021, the total number of in-scope manufacturers responding to Ribbon’s CMRT request increased by 19% versus 2020, and by more than 30% over the past five years. OVERVIEW OF CMRT OUTREACH AND RESPONSE RATE 531 508 546 675 858 2019 2018 2019 2020 2021 94% 92% 89% 83% 78% Based on the responses we received from our suppliers, however, we believe the facilities used to produce the Conflict Minerals in the 2021 Ribbon Products may include the smelters and refineries listed in Annex A. In addition, based on the supplier responses, we believe the countries of origin of the Conflict Minerals in the 2021 Ribbon Products may include those listed in Annex B.

Ribbon Communications Inc. Conflict Minerals Report 2021 9 SMELTER LOCATIONS China 25% Japan 13% Indonesia 8% USA 8% Rest of World (36 countries) 46% LOCATION OF MINES Europe 28% Asia 18% Rest of World 24% Africa 30% SMELTERS BY METALS MINED Tantalum 16% Gold 42% Tungsten 18% Tin 24% Smelters in our supplier base 238 40 Total smelters or refiners Countries from Risk Mitigation Steps to Be Taken for 2022 Due Diligence Ribbon intends to take the following steps, as appropriate, during the next compliance period to further improve our due diligence process and results and to further mitigate the risk that our necessary Conflict Minerals benefit armed groups in the DRC or adjoining countries: Continue to focus on additional ways to improve quality and quantity of supplier response rates; Continue to work with suppliers to better educate them on the process; Continue to compare survey results to information collected via independent conflict free smelter validation programs such as the RMAP; Work with our Contract Manufacturers to understand which suppliers they are purchasing from in a given year and use this data to more accurately use our resources when collecting CMRT Data;

Ribbon Communications Inc. Conflict Minerals Report 2021 10 Continue to adhere to the OECD Guidance; and Seek to work with suppliers who use appropriate due diligence methods and have continuous monitoring of both the direct and indirect supply chain to avoid procurement or use of Conflict Minerals. Audit An independent private sector audit was not required for reporting year 2021. Important Information Regarding Forward-Looking Statements The information in this report 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 facts contained in this report, including statements in the section “Risk Mitigation Steps to Be Taken for 2022 Due Diligence,” are forward- looking statements. Without limiting the foregoing, the words “anticipates”, “believes”, “could”, “estimates”, “expects”, “expectations”, “intends”, “may”, “plans”, “seeks”, “projects” 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. Ribbon therefore cautions readers against undue reliance on any of these forward-looking statements. Any forward-looking statement made by Ribbon in this report speaks only as of the date of this report. Additional information regarding these and other factors can be found in the Company’s reports filed with the Securities and Exchange Commission, including, without limitation, its Form 10-K for the year ended December 31, 2021. Ribbon undertakes 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. Documents Incorporated by Reference Unless otherwise stated herein, any documents, third party materials or references to websites (including Ribbon’s) are not incorporated by reference in, or considered to be a part of, this report unless expressly incorporated by reference herein.

Ribbon Communications Inc. Conflict Minerals Report 2021 11 Annex A List of Smelters We present in this report a list of smelters or refineries provided by those suppliers who completed the smelter list on our Template, to the extent reasonably determinable, and that may have provided Conflict Minerals in any of the 2021 Ribbon Products. The table below includes only facilities, to the extent known, that have been validated by the RMI as facilities that are certified Conflict-Free or are listed on the Template as a “known smelters or refineries”. Metal Smelter Name Smelter Country Gold (Au) 8853 S.p.A. ITALY Tungsten (W) A.L.M.T. Corp. JAPAN Tungsten (W) ACL Metais Eireli BRAZIL Gold (Au) Advanced Chemical Company UNITED STATES OF AMERICA Gold (Au) Agosi AG GERMANY Gold (Au) Aida Chemical Industries Co., Ltd. JAPAN Gold (Au) Al Etihad Gold Refinery DMCC UNITED ARAB EMIRATES Gold (Au) Almalyk Mining and Metallurgical Complex (AMMC) UZBEKISTAN Tin (Sn) Alpha UNITED STATES OF AMERICA Tantalum (Ta) AMG Brasil BRAZIL Gold (Au) AngloGold Ashanti Corrego do Sitio Mineracao BRAZIL Gold (Au) Argor-Heraeus S.A. SWITZERLAND Gold (Au) Asahi Pretec Corp. JAPAN Gold (Au) Asahi Refining Canada Ltd. CANADA Gold (Au) Asahi Refining USA Inc. UNITED STATES OF AMERICA Gold (Au) Asaka Riken Co., Ltd. JAPAN Tantalum (Ta) Asaka Riken Co., Ltd. JAPAN Tungsten (W) Asia Tungsten Products Vietnam Ltd. VIETNAM Gold (Au) Aurubis AG GERMANY Gold (Au) Bangalore Refinery INDIA Gold (Au) Bangko Sentral ng Pilipinas (Central Bank of the Philippines) PHILIPPINES Gold (Au) Boliden AB SWEDEN Gold (Au) C. Hafner GmbH + Co. KG GERMANY Gold (Au) CCR Refinery - Glencore Canada Corporation CANADA Gold (Au) Cendres + Metaux S.A. SWITZERLAND Tantalum (Ta) Changsha South Tantalum Niobium Co., Ltd. CHINA Tin (Sn) Chenzhou Yunxiang Mining and Metallurgy Co., Ltd. CHINA Tin (Sn) Chifeng Dajingzi Tin Industry Co., Ltd. CHINA Gold (Au) Chimet S.p.A. ITALY Tungsten (W) China Molybdenum Tungsten Co., Ltd. CHINA

Ribbon Communications Inc. Conflict Minerals Report 2021 12 Metal Smelter Name Smelter Country Tin (Sn) China Tin Group Co., Ltd. CHINA Tungsten (W) Chongyi Zhangyuan Tungsten Co., Ltd. CHINA Gold (Au) Chugai Mining JAPAN Tin (Sn) CRM Synergies SPAIN Tungsten (W) Cronimet Brasil Ltda BRAZIL Tantalum (Ta) D Block Metals, LLC UNITED STATES OF AMERICA Gold (Au) DODUCO Contacts and Refining GmbH GERMANY Tin (Sn) Dowa JAPAN Gold (Au) Dowa JAPAN Gold (Au) DSC (Do Sung Corporation) KOREA, REPUBLIC OF Gold (Au) Eco-System Recycling Co., Ltd. East Plant JAPAN Gold (Au) Eco-System Recycling Co., Ltd. North Plant JAPAN Gold (Au) Eco-System Recycling Co., Ltd. West Plant JAPAN Tin (Sn) EM Vinto BOLIVIA (PLURINATIONAL STATE OF) Gold (Au) Emirates Gold DMCC UNITED ARAB EMIRATES Tin (Sn) Estanho de Rondonia S.A. BRAZIL Tantalum (Ta) F&X Electro-Materials Ltd. CHINA Tin (Sn) Fabrica Auricchio Industria e Comercio Ltda. BRAZIL Tin (Sn) Fenix Metals POLAND Tantalum (Ta) FIR Metals & Resource Ltd. CHINA Tungsten (W) Fujian Ganmin RareMetal Co., Ltd. CHINA Tungsten (W) Fujian Xinlu Tungsten Co., Ltd. CHINA Tungsten (W) Ganzhou Haichuang Tungsten Co., Ltd. CHINA Tungsten (W) Ganzhou Huaxing Tungsten Products Co., Ltd. CHINA Tungsten (W) Ganzhou Jiangwu Ferrotungsten Co., Ltd. CHINA Tungsten (W) Ganzhou Seadragon W & Mo Co., Ltd. CHINA Gold (Au) Geib Refining Corporation UNITED STATES OF AMERICA Tin (Sn) Gejiu Non-Ferrous Metal Processing Co., Ltd. CHINA Tin (Sn) Gejiu Yunxin Nonferrous Electrolysis Co., Ltd. CHINA Tin (Sn) Gejiu Zili Mining And Metallurgy Co., Ltd. CHINA Tantalum (Ta) Global Advanced Metals Aizu JAPAN Tantalum (Ta) Global Advanced Metals Boyertown UNITED STATES OF AMERICA Tungsten (W) Global Tungsten & Powders Corp. UNITED STATES OF AMERICA Gold (Au) Gold Refinery of Zijin Mining Group Co., Ltd. CHINA Tin (Sn) Guangdong Hanhe Non-Ferrous Metal Co., Ltd. CHINA Tantalum (Ta) Guangdong Rising Rare Metals-EO Materials Ltd. CHINA Tungsten (W) Guangdong Xianglu Tungsten Co., Ltd. CHINA

Ribbon Communications Inc. Conflict Minerals Report 2021 13 Metal Smelter Name Smelter Country Tantalum (Ta) H.C. Starck Hermsdorf GmbH GERMANY Tantalum (Ta) H.C. Starck Inc. UNITED STATES OF AMERICA Tungsten (W) H.C. Starck Tungsten GmbH GERMANY Gold (Au) Heimerle + Meule GmbH GERMANY Tantalum (Ta) Hengyang King Xing Lifeng New Materials Co., Ltd. CHINA Gold (Au) Heraeus Germany GmbH Co. KG GERMANY Gold (Au) Heraeus Metals Hong Kong Ltd. CHINA Tungsten (W) Hubei Green Tungsten Co., Ltd. CHINA Tin (Sn) HuiChang Hill Tin Industry Co., Ltd. CHINA Tungsten (W) Hunan Chenzhou Mining Co., Ltd. CHINA Tungsten (W) Hunan Chunchang Nonferrous Metals Co., Ltd. CHINA Tungsten (W) Hunan Shizhuyuan Nonferrous Metals Co., Ltd. Chenzhou Tungsten Products Branch CHINA Tungsten (W) Hydrometallurg, JSC RUSSIAN FEDERATION Gold (Au) Inner Mongolia Qiankun Gold and Silver Refinery Share Co., Ltd. CHINA Gold (Au) Ishifuku Metal Industry Co., Ltd. JAPAN Gold (Au) Istanbul Gold Refinery TURKEY Gold (Au) Italpreziosi ITALY Gold (Au) Japan Mint JAPAN Tungsten (W) Japan New Metals Co., Ltd. JAPAN Tungsten (W) Jiangwu H.C. Starck Tungsten Products Co., Ltd. CHINA Gold (Au) Jiangxi Copper Co., Ltd. CHINA Tantalum (Ta) Jiangxi Dinghai Tantalum & Niobium Co., Ltd. CHINA Tungsten (W) Jiangxi Gan Bei Tungsten Co., Ltd. CHINA Tin (Sn) Jiangxi New Nanshan Technology Ltd. CHINA Tungsten (W) Jiangxi Tonggu Non-ferrous Metallurgical & Chemical Co., Ltd. CHINA Tantalum (Ta) Jiangxi Tuohong New Raw Material CHINA Tungsten (W) Jiangxi Xinsheng Tungsten Industry Co., Ltd. CHINA Tungsten (W) Jiangxi Yaosheng Tungsten Co., Ltd. CHINA Tantalum (Ta) JiuJiang JinXin Nonferrous Metals Co., Ltd. CHINA Tantalum (Ta) Jiujiang Tanbre Co., Ltd. CHINA Tantalum (Ta) Jiujiang Zhongao Tantalum & Niobium Co., Ltd. CHINA Tungsten (W) JSC "Kirovgrad Hard Alloys Plant" RUSSIAN FEDERATION Gold (Au) JX Nippon Mining & Metals Co., Ltd. JAPAN Gold (Au) Kazzinc KAZAKHSTAN Tantalum (Ta) KEMET de Mexico MEXICO Tungsten (W) Kennametal Fallon UNITED STATES OF AMERICA

Ribbon Communications Inc. Conflict Minerals Report 2021 14 Metal Smelter Name Smelter Country Tungsten (W) Kennametal Huntsville UNITED STATES OF AMERICA Gold (Au) Kennecott Utah Copper LLC UNITED STATES OF AMERICA Tungsten (W) KGETS Co., Ltd. KOREA, REPUBLIC OF Gold (Au) KGHM Polska Miedz Spolka Akcyjna POLAND Gold (Au) Kojima Chemicals Co., Ltd. JAPAN Gold (Au) Korea Zinc Co., Ltd. KOREA, REPUBLIC OF Tungsten (W) Lianyou Metals Co., Ltd. TAIWAN, PROVINCE OF CHINA Gold (Au) L'Orfebre S.A. ANDORRA Gold (Au) LS-NIKKO Copper Inc. KOREA, REPUBLIC OF Gold (Au) LT Metal Ltd. KOREA, REPUBLIC OF Tin (Sn) Luna Smelter, Ltd. RWANDA Tin (Sn) Ma'anshan Weitai Tin Co., Ltd. CHINA Tin (Sn) Magnu's Minerais Metais e Ligas Ltda. BRAZIL Tin (Sn) Malaysia Smelting Corporation (MSC) MALAYSIA Tungsten (W) Malipo Haiyu Tungsten Co., Ltd. CHINA Gold (Au) Marsam Metals BRAZIL Tungsten (W) Masan High-Tech Materials VIETNAM Gold (Au) Materion UNITED STATES OF AMERICA Gold (Au) Matsuda Sangyo Co., Ltd. JAPAN Gold (Au) Metal Concentrators SA (Pty) Ltd. SOUTH AFRICA Tin (Sn) Metallic Resources, Inc. UNITED STATES OF AMERICA Tin (Sn) Metallo Belgium N.V. BELGIUM Tin (Sn) Metallo Spain S.L.U. SPAIN Tantalum (Ta) Metallurgical Products India Pvt., Ltd. INDIA Gold (Au) Metalor Technologies (Hong Kong) Ltd. CHINA Gold (Au) Metalor Technologies (Singapore) Pte., Ltd. SINGAPORE Gold (Au) Metalor Technologies (Suzhou) Ltd. CHINA Gold (Au) Metalor Technologies S.A. SWITZERLAND Gold (Au) Metalor USA Refining Corporation UNITED STATES OF AMERICA Gold (Au) Metalurgica Met-Mex Penoles S.A. De C.V. MEXICO Tin (Sn) Mineracao Taboca S.A. BRAZIL Tantalum (Ta) Mineracao Taboca S.A. BRAZIL Tin (Sn) Minsur PERU Tin (Sn) Mitsubishi Materials Corporation JAPAN Gold (Au) Mitsubishi Materials Corporation JAPAN Tantalum (Ta) Mitsui Mining and Smelting Co., Ltd. JAPAN Gold (Au) Mitsui Mining and Smelting Co., Ltd. JAPAN Gold (Au) MMTC-PAMP India Pvt., Ltd. INDIA

Ribbon Communications Inc. Conflict Minerals Report 2021 15 Metal Smelter Name Smelter Country Tungsten (W) Moliren Ltd. RUSSIAN FEDERATION Gold (Au) Nadir Metal Rafineri San. Ve Tic. A.S. TURKEY Gold (Au) Navoi Mining and Metallurgical Combinat UZBEKISTAN Gold (Au) NH Recytech Company KOREA, REPUBLIC OF Tungsten (W) Niagara Refining LLC UNITED STATES OF AMERICA Gold (Au) Nihon Material Co., Ltd. JAPAN Tantalum (Ta) Ningxia Orient Tantalum Industry Co., Ltd. CHINA Tin (Sn) Novosibirsk Tin Combine RUSSIAN FEDERATION Tantalum (Ta) NPM Silmet AS ESTONIA Tin (Sn) O.M. Manufacturing (Thailand) Co., Ltd. THAILAND Tin (Sn) O.M. Manufacturing Philippines, Inc. PHILIPPINES Gold (Au) Ogussa Osterreichische Gold- und Silber- Scheideanstalt GmbH AUSTRIA Gold (Au) Ohura Precious Metal Industry Co., Ltd. JAPAN Tin (Sn) Operaciones Metalurgicas S.A. BOLIVIA (PLURINATIONAL STATE OF) Gold (Au) PAMP S.A. SWITZERLAND Tungsten (W) Philippine Chuangxin Industrial Co., Inc. PHILIPPINES Gold (Au) Planta Recuperadora de Metales SpA CHILE Tantalum (Ta) PRG Dooel NORTH MACEDONIA, REPUBLIC OF Gold (Au) PT Aneka Tambang (Persero) Tbk INDONESIA Tin (Sn) PT Artha Cipta Langgeng INDONESIA Tin (Sn) PT ATD Makmur Mandiri Jaya INDONESIA Tin (Sn) PT Babel Inti Perkasa INDONESIA Tin (Sn) PT Babel Surya Alam Lestari INDONESIA Tin (Sn) PT Bangka Serumpun INDONESIA Tin (Sn) PT Bukit Timah INDONESIA Tin (Sn) PT Cipta Persada Mulia INDONESIA Tin (Sn) PT Menara Cipta Mulia INDONESIA Tin (Sn) PT Mitra Stania Prima INDONESIA Tin (Sn) PT Prima Timah Utama INDONESIA Tin (Sn) PT Rajawali Rimba Perkasa INDONESIA Tin (Sn) PT Rajehan Ariq INDONESIA Tin (Sn) PT Refined Bangka Tin INDONESIA Tin (Sn) PT Sariwiguna Binasentosa INDONESIA Tin (Sn) PT Stanindo Inti Perkasa INDONESIA Tin (Sn) PT Timah Tbk Kundur INDONESIA Tin (Sn) PT Timah Tbk Mentok INDONESIA

Ribbon Communications Inc. Conflict Minerals Report 2021 16 Metal Smelter Name Smelter Country Tin (Sn) PT Tinindo Inter Nusa INDONESIA Gold (Au) PX Precinox S.A. SWITZERLAND Tantalum (Ta) QuantumClean UNITED STATES OF AMERICA Gold (Au) Rand Refinery (Pty) Ltd. SOUTH AFRICA Gold (Au) REMONDIS PMR B.V. NETHERLANDS Tin (Sn) Resind Industria e Comercio Ltda. BRAZIL Tantalum (Ta) Resind Industria e Comercio Ltda. BRAZIL Tantalum (Ta) RFH Yancheng Jinye New Material Technology Co., Ltd. CHINA Gold (Au) Royal Canadian Mint CANADA Tin (Sn) Rui Da Hung TAIWAN, PROVINCE OF CHINA Gold (Au) SAAMP FRANCE Gold (Au) Safimet S.p.A ITALY Gold (Au) SAFINA A.S. CZECHIA Gold (Au) Samduck Precious Metals KOREA, REPUBLIC OF Gold (Au) SEMPSA Joyeria Plateria S.A. SPAIN Gold (Au) Shandong Gold Smelting Co., Ltd. CHINA Gold (Au) Shandong Zhaojin Gold & Silver Refinery Co., Ltd. CHINA Gold (Au) Sichuan Tianze Precious Metals Co., Ltd. CHINA Gold (Au) Singway Technology Co., Ltd. TAIWAN, PROVINCE OF CHINA Tin (Sn) Soft Metais Ltda. BRAZIL Gold (Au) Solar Applied Materials Technology Corp. TAIWAN, PROVINCE OF CHINA Tantalum (Ta) Solikamsk Magnesium Works OAO RUSSIAN FEDERATION Gold (Au) Sumitomo Metal Mining Co., Ltd. JAPAN Gold (Au) SungEel HiMetal Co., Ltd. KOREA, REPUBLIC OF Gold (Au) T.C.A S.p.A ITALY Tantalum (Ta) Taki Chemical Co., Ltd. JAPAN Gold (Au) Tanaka Kikinzoku Kogyo K.K. JAPAN Tantalum (Ta) TANIOBIS Co., Ltd. THAILAND Tantalum (Ta) TANIOBIS GmbH GERMANY Tantalum (Ta) TANIOBIS Japan Co., Ltd. JAPAN Tungsten (W) TANIOBIS Smelting GmbH & Co. KG GERMANY Tantalum (Ta) TANIOBIS Smelting GmbH & Co. KG GERMANY Tantalum (Ta) Telex Metals UNITED STATES OF AMERICA Tin (Sn) Thai Nguyen Mining and Metallurgy Co., Ltd. VIETNAM Tin (Sn) Thaisarco THAILAND Tin (Sn) Tin Smelting Branch of Yunnan Tin Co., Ltd. CHINA Tin (Sn) Tin Technology & Refining UNITED STATES OF AMERICA

Ribbon Communications Inc. Conflict Minerals Report 2021 17 Metal Smelter Name Smelter Country Gold (Au) Tokuriki Honten Co., Ltd. JAPAN Gold (Au) TOO Tau-Ken-Altyn KAZAKHSTAN Gold (Au) Torecom KOREA, REPUBLIC OF Tantalum (Ta) Ulba Metallurgical Plant JSC KAZAKHSTAN Gold (Au) Umicore Precious Metals Thailand THAILAND Gold (Au) Umicore S.A. Business Unit Precious Metals Refining BELGIUM Tungsten (W) Unecha Refractory metals plant RUSSIAN FEDERATION Gold (Au) United Precious Metal Refining, Inc. UNITED STATES OF AMERICA Gold (Au) Valcambi S.A. SWITZERLAND Gold (Au) Western Australian Mint (T/a The Perth Mint) AUSTRALIA Tin (Sn) White Solder Metalurgia e Mineracao Ltda. BRAZIL Gold (Au) WIELAND Edelmetalle GmbH GERMANY Tungsten (W) Wolfram Bergbau und Hutten AG AUSTRIA Tungsten (W) Woltech Korea Co., Ltd. KOREA, REPUBLIC OF Tungsten (W) Xiamen Tungsten (H.C.) Co., Ltd. CHINA Tungsten (W) Xiamen Tungsten Co., Ltd. CHINA Tantalum (Ta) XIMEI RESOURCES (GUANGDONG) LIMITED CHINA Tungsten (W) Xinfeng Huarui Tungsten & Molybdenum New Material Co., Ltd. CHINA Tantalum (Ta) XinXing HaoRong Electronic Material Co., Ltd. CHINA Gold (Au) Yamakin Co., Ltd. JAPAN Tantalum (Ta) Yanling Jincheng Tantalum & Niobium Co., Ltd. CHINA Gold (Au) Yokohama Metal Co., Ltd. JAPAN Tin (Sn) Yunnan Chengfeng Non-ferrous Metals Co., Ltd. CHINA Gold (Au) Zhongyuan Gold Smelter of Zhongjin Gold Corporation CHINA

Ribbon Communications Inc. Conflict Minerals Report 2021 18 Annex B List of Countries Countries of origin of the Conflict Minerals in the 2021 Ribbon Products are believed to include:. Location of Mines: 108 countries Afghanistan Egypt Luxembourg Slovakia Åland Islands England Madagascar Solomon Islands Albania Eritrea Malawi South Africa Andorra Estonia Malaysia South Korea Angola Ethiopia Mali South Sudan Argentina Finland Mauritania Spain Armenia France Mexico Sudan Aruba Georgia Mongolia Suriname Australia Germany Morocco Sweden Austria Ghana Mozambique Switzerland Azerbaijan Guinea Myanmar Taiwan Belgium Guyana Namibia Tajikistan Bolivia Hungary Netherlands Tanzania Brazil India New Zealand Thailand Bulgaria Indonesia Niger Togo Burkina Faso Ireland Nigeria Tunisia Burundi Israel Panama Turkey Cambodia Italy Papua New Guinea Uganda Canada Ivory Coast Peru Ukraine Central African Republic Japan Philippines United Arab Emirates Chile Kazakhstan Poland United Kingdom China Kenya Portugal United States of America Colombia Kyrgyzstan Russian Federation Uzbekistan Czech Republic Laos Rwanda Vietnam Democratic Republic of the Congo Liberia Saudi Arabia Yemen Djibouti Liechtenstein Sierra Leone Zambia Ecuador Lithuania Singapore Zimbabwe