X0306 4 2020-06-15 0001708055 Ribbon Communications Inc. RBBN 0001615890 Riley Kevin W. C/O RIBBON COMMUNICATIONS INC. 4 TECHNOLOGY PARK DRIVE WESTFORD MA 01886 0 1 0 0 EVP and CTO Common Stock 2020-06-15 4 M 0 6666 A 200245 D Common Stock 2020-06-15 4 S 0 1972 3.88 D 198273 D Restricted Stock Units (RSUs) 2020-06-15 4 M 0 6666 0 D Common Stock 6666 13333 D Restricted stock units 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 restricted stock units. 40,000 RSUs were granted to the Reporting Person on June 15, 2018 and vest over a three-year period. One-third of the RSUs vested on June 15, 2019, one-sixth vested on December 16, 2019, one-sixth vested on June 15, 2020 and the remainder of the RSUs will vest in two equal, semi-annual installments thereafter through June 15, 2021. Kevin Riley 2020-06-17