X0306 4 2019-04-15 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 2019-04-15 4 A 0 36338 0 A 69297 D Performance-Based Restricted Stock Units (PSUs) 2019-04-15 4 A 0 36338 0 A 2021-12-31 Common Stock 36338 36338 D The restricted stock units vest over a three-year period as follows: one-third of the shares shall vest on April 15, 2020, and the remaining two-thirds of the shares shall vest in four equal increments semi-annually thereafter through April 15, 2022. Each PSU represents a contingent right to receive one share of the Issuer's Common Stock, based on the Issuer's total shareholder return (TSR) compared to pre-established relative TSR goals, based on the TSR of the Russell 2500 Telecommunications Sub Sector Index, that were set by the Compensation Committee (the Compensation Committee) of the Issuer's Board of Directors. The aggregate number of shares issued may range from zero (0) shares to 200% of the target number of shares reported in columns 5, 7 and 9 of Table II. The number of PSUs reported in columns 5, 7 and 9 of Table II reflects achievement at the target level of performance. Between zero (0) and 200% of one-third of the PSUs will vest, if at all, as determined by the Compensation Committee after the TSR performance period, commencing on January 1, 2019 and ending on December 31, 2021. Eric S. Marmurek 2019-04-16