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                                                                    EXHIBIT 99.1

                           CERTIFICATION PURSUANT TO
                            18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                 SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

    In connection with the Quarterly Report of Avaya Inc. (the "Company") on
Form 10-Q for the period ending June 30, 2002 as filed with the Securities and
Exchange Commission on the date hereof (the "Report"), I, Donald K. Peterson,
Chairman and Chief Executive Officer of the Company, certify, pursuant to 18
U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley
Act of 2002, to my knowledge, that:

        (1) The Report fully complies with the requirements of Section 13(a) or
    15(d) of the Securities Exchange Act of 1934; and

        (2) The information contained in the Report fairly presents, in all
    material respects, the financial condition and result of operations of the
    Company.

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/s/ DONALD K. PETERSON
- -------------------------------------------
Donald K. Peterson
CHAIRMAN AND CHIEF EXECUTIVE OFFICER
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August 14, 2002