X0306 4 2019-11-15 0001708055 Ribbon Communications Inc. RBBN 0001720721 Marmurek Eric S C/O RIBBON COMMUNICATIONS INC. 4 TECHNOLOGY PARK DRIVE WESTFORD MA 01886 0 1 0 0 Principal Accounting Officer Common Stock 2019-11-15 4 S 0 1102 2.99 D 30748 D The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 instruction letter previously adopted by the Reporting Person and represent shares required to be sold by the Reporting Person to cover tax withholding obligations in connection with the vesting of Restricted Stock Awards (RSAs). Excludes 36,338 shares of common stock (the "Excluded Shares") underlying an award of Restricted Stock Units granted on April 15, 2019 (the "RSU Award"). The RSU Award was inadvertently reported on Table I instead of Table II of the Form 4 filed by the Reporting Person on April 16, 2019. As a result of this administrative error, the Excluded Shares were erroneously included in the Table I, Column 5 totals of the Forms 4 filed by the Reporting Person on April 16, 2019 and May 17, 2019. Eric S. Marmurek 2019-11-19