X0306 4 2020-05-15 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 2020-05-15 4 S 0 1095 3.2408 D 38344 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. Justin Ferguson, Attorney-in-Fact 2020-05-19