X0306 4 2020-04-15 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 SVP and CAO Common Stock 2020-04-15 4 M 0 12113 A 42861 D Common Stock 2020-04-15 4 S 0 3422 2.9197 D 39439 D Restricted Stock Units 2020-04-15 4 M 0 12113 0 D Common Stock 12113 24225 D Restricted stock units (RSUs) convert into common stock on a one-for-one basis. 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 RSUs. The RSUs vest over a three-year period as follows: one-third of the shares vested on April 15, 2020, and the remaining two-thirds of the shares will vest in four equal increments semi-annually thereafter through April 15, 2022. Eric S. Marmurek 2020-04-16