Exhibit 4.3

                                 FIRST AMENDMENT
                                     to the
                            IPC COMMUNICATIONS, INC.
                            1999 STOCK INCENTIVE PLAN



        Pursuant to a resolution of the Board of Directors ("Board") of IPC
Communications, Inc. (the "Corporation") adopted in connection with the approval
by the Board of the Agreement and Plan of Merger dated as of February 22, 2000
among Global Crossing Ltd., Georgia Merger Sub Corporation, the Corporation, IPC
Information Systems, Inc., Idaho Merger Sub Corporation and IXnet, Inc., the IPC
Communications, Inc. 1999 Stock Incentive Plan (the "Plan") has been amended
effective February 22, 2000, by adding the following to the end of Section 5(c)
thereof:

        "Notwithstanding the above or anything in this Plan to the contrary,

        (i)     only 50% of the number of unvested Options held by any
                individual signatory to the Agreement dated as of February 22,
                2000 among Global Crossing Ltd. ("Global Crossing"), the
                Corporation, IXnet, Inc. ("IXnet") and fourteen (14) individual
                signatories (each, a "Holder') ("Option Limitation Agreement," a
                copy of which shall be appended to this Plan as Appendix A
                hereto), determined in the order in which such Options otherwise
                would vest, will become vested and exercisable upon the Change
                in Control (as defined herein) arising in connection with the
                transactions contemplated by the Agreement and Plan of Merger
                Dated as of February 22, 2000, among Global Crossing, Georgia
                Merger Sub Corporation, the Corporation, IPC Information
                Systems, Inc., Idaho Merger Sub Corporation, and IXnet ("Merger
                Agreement");

        (ii)    such Change in Control shall not constitute an event requiring
                vesting with respect to the remaining Options held by such
                Holders;

        (iii)   all Options, both vested and unvested, held by such Holders at
                the time of Mergers (as such term is defined in the Merger
                Agreement) shall be converted into options to acquire shares of
                common stock of Global Crossing ("Rollover Options"), upon the
                terms and conditions set forth in the Merger Agreement;

        (iv)    all Rollover Options held by a Holder that do not vest in
                accordance with (i) above, shall vest over a three (3) year
                period, as follows: one third on the first anniversary of the
                Closing Date (as such term is defined in the Merger Agreement);
                one third on the second anniversary of the Closing Date; and
                one third on the third anniversary of the Closing Date; and


        (v)     in the event of the death or Disability (as defined herein) of a
                Holder, or in the event of the termination of the Holder's
                employment without Cause (as defined herein) or by the Holder
                for Good Reason (as such term is defined in the IXnet Option
                Plan Grant Certificate for Executive Officers, except for such
                changes as are necessitated by reason of the Corporation, IPC
                Information Systems, Inc. or IXnet no longer being a publicly
                held company), or in the event of a change in control (as such
                term is defined in the standard option agreement for executive
                officers issued under the 1998 Global Crossing Ltd. Stock
                Incentive Plan as Amended and Restated as of December 7, 1999),
                all of such Holder's Rollover Options shall immediately vest and
                become exercisable, and the transfer restriction set forth in
                Paragraph 4 of the Option Limitation Agreement annexed hereto as
                Appendix A shall cease to apply to such Holder."